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Content Updated Fri, 25 Feb 2011 by John G. Richardson ‘Cubcoman’
Formatting Updated Sun, 03 May 2020 by Joe Richardson

Based on the construction of my scratchbuilt model of Kerr Stuart loco ‘ Pixie ‘ surveyed at Leighton Buzzard NG Railway.

For illustrations and brief description of construction see the page Pixie’s Background.

Pixie

Foreword by Mr Ted Jolliffe, Editor of the Magazine ‘ Model Engineer ‘
Introduction by John G. Richardson ‘Cubcoman’

The attractions of model engineering, locomotives and narrow-gauge in particular. An outline of the approach to model engineering in the book.

Contents:

• Chapter 1: Choice of prototype. Space, weight and scale considerations. Location of track. Haulage and handling considerations.
• Chapter 2: Establishing detail. Research. Manufacturers drawings. Commercially available designs. Value of the model press, exhibitions and club membership.
• Chapter 3: Going it alone. Surveying a prototype. Equipment for the survey. A system of working. Ongoing visits. The database. Use of photographs, transparencies and prints.
• Chapter 4: Workshop, tools and equipment. Practical aspects of heating, lighting and ventilation. Workshop practice for the model engineer. The logbook.
• Chapter 5: Materials. Sources of supply. Organised storage and the scrap box. Modifying available materials. An introduction to simple pattern making.
• Chapter 6: Planning. Model engineering with pencil and paper. Machining sequence. Fabrication vs. castings. Use of models, mock-ups, jigs and templates.
• Chapter 7: Frames, stretchers, horns and axleboxes. Wheels, axles, crankpins and quartering.
• Chapter 8: Coupling rods and bearings. Brake hangers and blocks. Lubricator and mounting plate. Coupling blocks. Footplates, support brackets and angles.
• Chapter 9: Patterns and castings. Smokebox saddle. Cylinders, ports, passages, covers and glands. Pistons and piston rods.
• Chapter 10: Motion work. Motion plate. slide bars and crossheads. Valve gear, weigh shaft and reversing gear. Valve setting. Brake standard.
• Chapter 11: Smokebox and and smokebox door, hinges and rings. Wet header, steam, blast and petticoat pipes. Blower ring.
• Chapter 12: Boilers. Home built vs proprietary supply. Construction techniques. Location. Firehole door. Cleading.
• Chapter 13: Pumps. pipework, valves and gauges. Sandboxes and gear. Clacks and dummy injectors.
• Chapter 14: Fittings. Regulator, regulator gland and lever. Chimney. Steam Dome. Safety valves. Retro-fitted pump eccentric. Cylinder drain cocks.
• Chapter 15: Platework, tanks and bunkers. Saddle tank. Weather board/spectacle plate. Roofs and backs. Footplates. Ashpan. Cutting, bending and riveting plates.
• Chapter 16: Erection, smokebox, boiler, reversing lever, regulator, steam and exhaust pipes. Pumps. Platework. Makers plates.
• Chapter 17: Painting. Workplace and equipment. Types of paint. Preparation.
• Chapter 18: Test track and a simple driving trolley. Materials. Driving position and access to controls. Braking.
• Chapter 19: Steaming the locomotive. A simple blower. Raising steam and driving. Safety aspects.
• Chapter 20: Some useful tools and attachments from materials in the scrapbox.
• Conclusion: Conclusion and model engineers nostrums (? nostra)

Foreword

( This was written when the book was first published on 2 Floppy disks !…..John )

I have, over the last few years, had the pleasure of watching Pixie grow, from a design concept through to a finished locomotive. this has been thanks to occasional personal contact, and largely through the occasional articles submitted to MODEL ENGINEER magazine detailing progress to the latest stage.The author is a meticulous craftsman, with a well developed and organised workshop, each feature being installed as a result of considerable thought. That he has chosen to set out this account of his activities, revealing both the triumphs and difficulties encountered in the construction, is a tribute to his meticulous recording of his work.

Of all the books that I have read concerning the building of small locomotives, this one adopts a novel approach, taking as a starting point the actual workroom or other premises which are to be used for the work. Very often this is a facet of locomotive building which is neglected; leading to considerable problems later.

I like the attention to detail, the account of the research needed to bring the product to fruition, the novel approach to pattern making, and the authors somewhat novel approach to gleaning much of the material needed.This is a very readable account of the building of a well detailed locomotive and, as importantly, the many hints and tips of a practical nature passed for the benefit of other constructors by the author.

One can only applaud his industry in making the volume available in this fashion, I for one wish the volume every success.

Ted Jolliffe. Editor
Model Engineer Magazine. Hemel Hempstead. 2nd November 1994

Preparing PIXIE for transport to the Model Engineering Exhibition

Back to Contents

Chapter 1

Choice Of Prototype

Why Narrow Gauge?

Choice of prototype. Space, weight and scale considerations. Location of track. Haulage and handling considerations.

Narrow gauge locomotives and rolling stock, as we in the United Kingdom know them, have a flavour of their own, quite removed from the nature of those of standard gauge railways. Historically narrow gauge lines, essentially light railways, have been quaint and often slow moving yet, in their own way efficient servants of the community. They and their dedicated staff have traditionally provided a personal, if somewhat erratic service, perhaps running in fits and starts, sometimes even stopping for an individual passenger at a field gate. History also records instances where the traveller has been required to assist in re-railing a piece of stock or in fetching water for the boiler!

Narrow gauge lines have a history of running on uneven, occasionally weed overgrown track. They take acute bends and steep gradients in their stride, rarely travelling at speeds exceeding 20 m.p.h. The locomotives are picturesque, often of short wheelbase, sometimes with with small boilers, tall chimneys, intricate weather plates and other interesting items of equipment. In some instances narrow gauge locomotives are festooned with ‘Victoriana’ in the form of sandpots, polished plumbing and literally all manner of bells and whistles. Having said all that, we have to remember that on most continents there are narrow gauge (narrower than standard gauge that is) locomotives working over hundreds of miles of mountainous and inhospitable countryside. Such for example are the metre gauge railways of India and Malaya, and the South African and Ecuadorian Railways of 3 foot 6 inch gauge. In this book we concern ourselves with the narrower gauges and the smaller locomotives which have come to regarded in this country as the ‘Norm’ for narrow gauge.

There is a wide range of prototypes from which to make a selection. Firstly there are the conventional locomotives, often carrying out the duties of standard gauge locomotives over difficult terrain. Then there are tram locomotives, which worked in the industrial or urban environment, many of these are notable for their shrouded wheels and motion and controlled emissions of smoke and steam. They would be designed to be controlled from each end of the footplate, also hand and steam brakes would be compulsory. A number of tram locomotives were built with vertical boilers, an added touch of interest in model form. Vertical boilered locomotive models provide the builder with an opportunity to incorporate some previously built essay in model engineering, such as a Stuart Turner engine into their model. De Winton locomotives with vertical boilers and cylinders were virtually an engine platform with water tank, bunkers, reversing lever and brake standard. Inside and outside frame configurations were employed, also inside and outside drive, the latter by lay shaft and crank. R.A.S Abbot in his book on the topic describes how some locomotives carried the chimney directly above the boiler to avoid the formation of condensation and some locomotives were fired by sliding the fuel down chutes into the firebox located between the frames, plenty of scope here for the freelance modelmaker ! In an article in MODEL ENGINEER Vol 163 No.3859 October 1989, Phil Atkinson gave the reader food for thought in his description of ‘ Coffee pot locomotives ‘ outshopped from Head Wrightsons Works in the late 1800’s, with their heavily riveted vertical boilers and substantial wheelsets, these little locomotives would present a challenge, and a reward for the builder. A surprising feature of the locomtive was a one piece, cast iron frame incorporating main side members, buffer beams, the fuel bunker, all foot plates and the stiffening ribs, the whole described by Phil as a fine piece of the Victorian designers, pattern makers and iron founders art. No. 16 by the same builder even sports a rudimentary roof although one which would afford little protection to the driver !

For added spice, builders may turn their attention to innovative locomotives such as LOCOMOTIVE NO. 1 of the Listowel & Ballybunnion Railway, straddling an early monorail. Double-bogied types such as those of the Festiniog Railway would present a challenge, or perhaps the modeller would wish to undertake a model of one of the the SHAYS or HEISLERS of the American short lines scene. Ken Swan’s series on ‘KOPPEL’ a rack locomotive in ENGINEERING IN MINIATURE could prompt the modeller to produce, for instance, a model of Locomotive Number 7 on the Snowdon Mountain Railway, although track construction would present a major challenge. Those seeking a simpler prototype would do well to build the locomotive Ross Harrison described commencing in ENGINEERING in MINIATURE, issue of September 1982, a convincing model in 5” gauge based upon ‘EDWARD THOMAS’, Kerr Stuart ‘Tattoo’ Class locomotive built in 1921 for the Corris Railway, later moved to the the Talyllin Railway, a model full of atmosphere.

For something really different the modeller might turn to the locomotives of a Dublin Brewery, designed by Samuel Geoghegan. These 1 foot 10 inch gauge locomotives with cylinders and motion placed ABOVE the boiler were used in conjunction with haulage trucks into which they were hoisted for working the 5 foot 3 inch gauge. In this role the wheels of the locomotive rested on grooved rollers which propelled the trucks. Contractors locomotives make interesting prototypes and many model engineers have built ‘SWEET PEA’, designed along these lines by Jack Buckler. Some of these models exhibit remarkable modifications and there is scope for innovation. This locomotive would make an ideal test-bed for the model engineer who likes to experiment with features of his own design. Contractors locomotives provide a range of prototypes suited to modelling and it is a salutary thought that narrow gauge locomotives such as the Bagnall locomotive ‘EXCELSIOR’, a delightful little 0-4-0, were employed in much industrial construction as well as civil engineering works for railways.

A series of articles by Martin Evans in MODEL ENGINEER commencing in 1980 described a free lance narrow gauge 0-4-0 Saddle Tank Locomotive, ‘CONWAY’. This again was a blow-by-blow description and, as with all Martin Evans designs, examples of the completed model have been seen performing credibly on a many occasions.

The modeller fortunate enough to locate the Armley Industrial Museum in Leeds can find there the beautifully preserved Hunslett narrow gauge locomotive ‘JACK’, resplendent in scarlet livery, lined in yellow and black. Built in 1898 for employment in a fireclay works near Burton-on Trent, ‘JACK’ is outside framed, has Baguley valve gear and masses of brass and copper in the steam dome and plumbing, with brass lubricators mounted on the smokebox. On top of the boiler are twin sand boxes and the loco has some nice details such as the hinged lights on the weather board and the drain pipes from the cylinders passing through the front beam. Running like a Rolls Royce it is a wonderful sight and one to make any model engineers pulse skip a beat. ‘JACK’ featured on the cover of MODEL ENGINEER Vol 158, No. 3798 April 1987 and a description of the locomotive appeared in that journal of October 1984

Lest it be thought that narrow gauge locomotives are mainly of simple design there are many examples way and beyond 0-4-0 configuration as regards complexity. These will present just as much of a challenge as a standard gauge locomotive. For example there are the Manning Wardle & Co. 2-6-2 side tank locomotives and the 2-4-2, Baldwin, ‘LYN’ of the Lynton and Barnstaple Railway. (‘LEW’ of this railway is, at the time of writing, being described in a construction series for 3 1/2 inch gauge in ENGINEERING IN MINIATURE.) For the really adventurous constructor there are of course the 2-6-2 + 2-6-2 Garrats of the South African and Indian railways.

Decisions, decisions….!

The writer’s decision to model PIXIE the Kerr Stuart ‘ Wren’ Class locomotive KS4260 / 1922 was based upon several factors. First and foremost was the impression that the sight of the little locomotive as it coasted into Pages Park Station on the Leighton Buzzard Narrow Gauge Railway one spring afternoon. It seemed incredible that a locomotive, produced initially for work on the installation of a sewer in 1922, should 60 years later be found running like a Rolls-Royce and doing useful work in a domestic setting. Enquiries revealed a little of the history of the locomotive, the fact that after the completion of the Barkingside sewer contract it had for some years worked in the Wilmington Road Quarry of Devon County Council, eventually being purchased by the Industrial Locomotive Society and brought to Leighton Buzzard in the late 1960’s. The locomotive has an overall length of something over 10 feet, it weighs 3 Tons 7 cwt empty, and 4 tons 3 cwt in working order. The inside framed locomotive has Hackworth valve gear and is resplendent in an attractive livery of black, green and gold.

Here was a locomotive that was mechanically quite simple for a relative beginner to construct, It would be accessible for survey and was in the hands of friendly folk who were prepared to assist with provision of information. The railway was within 25 miles of home base, so that the survey could be staged over a series of visits. Above all, the locomotive had an atmosphere and charm which appeared to the writer to convey the very essence of narrow gauge railways. The decision has never been regretted and has, over the past ten years, opened up a whole new interest in the mechanical engineering of railways and of narrow gauge railways in particular.

At this stage the modeller intending to work in narrow gauge has to come to terms with the fact that just as much work will be involved in producing his chosen model as in producing one to run on standard gauge. Pixie was ten years in the building, through choice. Some things are too good to hurry and although one is always keen to get one’s first locomotive onto the track, later efforts can be savoured, and perhaps greater attention paid to detail. In some instances such as for instance if a decision was made to model ‘MERDDYN EMRYS’, of Festiniog Railway fame, far more work could be involved. There could however be a saving in unit time in producing duplicate equipment, motion, tanks etc. In practice some builders do make locomotives in pairs and professionals make batches for just this reason.

Size

Although construction of a sizeable standard gauge model locomotive may make excessive demands on the capacity of one’s workshop and equipment, narrow gauge locomotives are generally simpler in design and, at the same scale, work up smaller in model form. ( This fact can be used to advantage by the modeller ‘moving-up’ to a larger scale). The flavour of work and operations on a narrow gauge line can be replicated within a small workshop and in ones own backyard. Model engineering activities along narrow gauge lines’ provide every opportunity for the incorporation into models of the very things that attract us to the prototype, to make and handle the artifacts that would otherwise, unless one works as a volunteer on a preserved line, be literally beyond reach. It should be remembered however that modelled on 5” Gauge quite a small locomotive such as PIXIE, at some 10 feet overall, will be more than 25” long in model form and of such dry weight that it is beyond one (normal) man’s lifting ability! Quite apart from the weight of the model the physical size, 25” long x 11.5” wide by 20” high are dimensions to be reckoned with when it comes to handling in the workshop and between shop and track! These details will not daunt the enthusiast however and ways and means are discussed later in this book.

Scale Considerations

There are many factors to be considered when deciding upon the scale in which to model the chosen prototype. Whilst often one reads a statement that ‘ such and such a scale was chosen because of the equipment available on which to machine the parts’ there is a lot more to be taken into consideration! Even a model of a small locomotive like PIXIE requires space for storage, maneuvering from storage to the track and general handling for maintenance and overhaul. In the case of Pixie it became necessary to build the hoist detailed in chapter xxx to carry out these simple exercises in comfort!

One can comfortably carry out the machining operations for a 5” Gauge narrow gauge locomotive on a lathe in the Myford, ‘ maid of all work’ series, or some similar equipment. In case of need, one can often obtain assistance with larger components from a local engineering works or by enrolling at a local Evening Institute. Many trojans work on 7 1/4” Gauge although here the parts, particularly the boiler assume relatively massive proportions. The enthusiast will tell you that these aspects are offset by the ride-in capability of their models and one can see their point of view. Access to a suitable track for running a 7 1/4” locomotive is however likely to be beyond the reach of many people, depending of course upon geographical location. On the other hand, 3 1/2” and 5” Gauge tracks are generally accessible, the local club probably offers both facilities and one will not require a pantechnicon to get the locomotive there. 3 1/2” gauge locomotives will fit easily into the family car as will some 5” gauge models, although larger locomotives on this gauge may require a purpose-made trailer. Narrow gauge locos for 5” track can be loaded into an estate car, and at a pinch can be manhandled by two strong men. Models scaled to 5” gauge offer sturdiness of components capable of surviving such rigorous handling. There are numerous designs and details available. Over the years, blow by blow descriptions of the construction of such models have appeared in the model press. Narrow gauge on 3 1/2” track can be ideal for a garden railway but for ride-behind fun the larger gauge has more to offer. In the case of a model such as Pixie, 2 1/2” to the foot scale on 5” gauge provides a stable ride, with a locomotive that has heft, and parts that are definitely out of the ‘watchmaking’ class! At this scale too the locomotive is robust, the firehole door whilst small provides a reasonable target for firing on the move and the levers and valves are sufficiently large to convey the feeling of the real thing in use.

Track Location

Of course the ideal track location must be around one’s own garden. Few of us however, are fortunate enough to have sufficient space at our disposal, particularly for anything other than an out-and-back track. Having said that, the out-and-back track has its merits. It can be simple, relatively cheap to construct and lay, as well as providing a useful test facility. Whilst it would be grand to have a railway sweeping round the grounds, there is a lot to be said for 50’ or so of portable track that can be laid down on the lawn or the terrace when required. Such a track avoids problems with landscaping and garden maintenance such as weeding and grass cutting. When the urge to steam a locomotive arises it is a simple matter to fetch the lengths of track from the shed or garage, lay them down, fasten a few fishplates, and be ready to run. One length of such track, carried into the workshop, will prove useful when setting valves and carrying out routine maintenance. Construction of a suitable track system is described and illustrated in a later Chapter.

The more fortunate may have space available which will permit a complete circuit, with perhaps a siding into a storage shed. This is not beyond the bounds of a medium sized backyard and one hears of 0-4-0 locomotives happily negotiating 6 foot radius curves although it has to be said that the larger the radius the better. Certainly a small engine shed could be made to look most attractive and its location on the running ground would avoid a lot of effort that otherwise has to be expended in handling between steamings.

Haulage And Handling Considerations

Where there is sufficient space it is convenient to store the locomotive in the workshop. Failing this, perhaps a corner of the garden shed or garage can be set aside. It will prove helpful if the loco can be kept stored on a small trolley, Pixie’s trolley is of Dexion angle, provided with a length of track and some stops to immobilise her in transit from the track to store and back. The trolley is described in Ch 17. Some splendid trolleys have been described in the model press from time to time. The modelmaker who intends to build up a locomotive stud, and take locomotives to club meets and similar events will do well to construct something similar to facilitate loading into the the car or van. One of the writer’s acquaintances has a purpose-modified road trailer fitted with track on which two sizable locos can sit in transit, secured by bottle screws between strong points on the locomotives frames and the trailer body. Tool and coal storage is provided in the well of the trailer. The locomotives live on the trailer between meets and the trailer is ready for instant coupling to the family car, a good incentive to get out and about to meets and rallies.

As well as trolleys and trailers some ingenious hoists have been described in the model press, one hoist was designed to be coupled to the towing ball hitch on the back of a car for stability whilst lifting. The hoist used for handling Pixie, described later, is used to handle the locomotive in the workshop and at the garden track. It could be rendered more mobile by the insertion of splices in the leg frame to enable it to be transported by car. If this was done the original ‘test load’, two and a half bags of cement would be called into action once again to prove the mechanics. Hoisting a locomotive calls for a custom-built spreader bar to ensure that no damage is suffered in the course of a lift, and time spent getting the correct balance of the locomotive whilst suspended on such a spreader will ensure safety.

Pixie with some of the survey sketches

Back to Contents

Chapter 2

Establishing detail. Research. Manufacturers drawings. Commercially available designs. Value of the model press, exhibitions and club membership.

Establishing Detail

The amount of research required will depend upon whether the modeller chooses to produce an accurate scale model, or a near scale model. In the former case a massive amount of detail will be necessary, to the point of the sometimes derided ‘ rivet counting’ exercise ‘. To embark on a scale model of a locomotive from ‘scratch’ is to commit oneself to many months and perhaps years of work. For the scale modeller every detail has significance, every modification to the original design has be faithfully reproduced and incorporated into the model. The problem here is that the components may prove to be too delicate to stand up to service on the track and there has to be a temptation towards some judicious beefing-up of parts. Fortunately if the choice is a narrow-gauge model on 5 inch gauge track the various components will work up to be quite substantial and durable in use.

The near scale modeller whilst perhaps taking a more relaxed approach to detail has nevertheless to convey the atmosphere of prototype through the parts that he does include. He is fortunate in having the opportunity to make parts a little more solidly than they would be in true scale and thus a little less vulnerable to damage on the track. As we have said before modelling is a very personal process. Whatever the degree of scale accuracy is decided upon, careful research is required. The word ‘ Research ‘ sounds quite impressive. In fact it really describes a process that every enthusiast follows naturally in the course of enjoying his hobby, that of ferreting out detail on a topic which he finds interesting. The sources of information are many and varied, ranging from contact with individuals having personal knowledge of the topic, manufacturers, museum archives, libraries, railway sites, Model Engineering Societies and Preservation Societies. Once one’s mind is set on a particular prototype there seems no end to the sources of information. The only problem is that in the back of one’s mind there is always always the feeling that some source is being overlooked. The modeller may rest assured however, if there is some inaccuracy or anachronism, someone with expert knowledge will probably put him right at time of the models first public appearance!

Manufacturers Drawings And Photographs

We may be fortunate enough to have a sight of manufacturers drawings, if not directly, at second hand. Many of the books on narrow-gauge railways shew illustrations of these drawings which can be worked-up for use as detail in constructing a model. Photographs of locomotives in the outshopped state are an institution. No manufacturer ‘ worthy of his salt’ would have outshopped a locomotive and sent it away to his customer without having it photographed in its pristine state. These photographs are worth their weight in gold to the enthusiastic model engineer who can enlarge detail and glean useful information for model making purposes. Failing works drawings or manufacturers photographs, the authors of many of the series of construction articles published in the model press base their work and the drawings accompanying the text on detail taken from manufacturers drawings.

Some books such as those on narrow-gauge lines noted in the bibliography include, as appendices, quite detailed drawings of the locomotives and stock of the lines they describe. When supplemented by detail derived from the photographic illustrations, these small scale drawings can provide sufficient detail for the model engineer wishing to produce a near scale model. Typical of these, and on the face of things an unlikely source book i s ‘ Narrow Gauge Railway Modelling ‘ by D A Boreham. Intended for workers in 7mm scale this book includes nicely produced general assembly drawings of such locomotives as Locomotives 1 & 2 of the Festiniog Railway and ‘Mary’ by W. G. Bagnall as worked by Cliffe Hill Granite Company. The book ‘ The Lynton and Barnstable Railway 1895-1935’ by L.T. Catchpole includes works line drawings of the three Manning and Wardle locomotives and the Baldwin which reveal essential detail for the modelmaker.

Over the years some excellent, and generally quite accurate, outline drawings have been published in the model railway press devoted to 4mm and similar scale modelling. These drawings provide a basis for an excellent model when used in conjunction with standard details of parts gleaned from the pages of MODEL ENGINEERING and ENGINEERING IN MINIATURE and such standard works as LBSCs ‘ Shop Shed and Road ‘ and Martin Evans ‘ Manual of Model Steam Locomotive Construction ‘. Whilst in the main these books cater for the modeller working on standard gauge, mechanical principles do not vary from those of the narrower gauge. As discussed earlier much of narrow-gauge mechanical engineering is of a simpler design than that of the big stuff but there is no reason why, within the ‘ innards ‘ of a narrow gauge locomotive, one should not employ more advanced methods.

Research

A visit to the local library will reveal a wealth of publications touching upon the subject of narrow-gauge railway operations, locomotives and rolling stock. A brief perusal of the advertisements in the model press will serve to remind us of the considerable number of books available for purchase. A search of the stock on the bookstall at the next model railway exhibition will yield a surprising amount of information which is specific to narrow gauge. In the run-up to commencing a model, it is worthwhile copying or noting for reference material likely to be useful when the work begins. Often one encounters photographs showing useful detail in the most unlikely places. Newspapers, magazines, guide books and holiday advertisements have all yielded useful data in their time. The writer with his interest in sketching and drawing decided to measure from the prototype, meanwhile enjoying the visits to the line and contact with the volunteers working on the stock there. This may not be a feasible approach for many and other means of establishing detail become imperative. Brochures, postcards, and some posters for the Leighton Buzzard Narrow Gauge Railway provided photographs, which were of immense value in confirming detail achieved from survey. The modeller will do well to seek out similar details of his projected prototype.

Researching a model can be tremendous fun. Recent research took the writer to an industrial museum in the Midlands to meet a voluntary archivist. Working in the bowels of the museum this gentleman, a volunteer with years of experience within the engineering industry, specific to locomotive design and construction behind him, spends his time cataloguing works drawings saved from destruction at the time of the demise of an internationally known manufacturer. He has become known to many enthusiasts and is constantly called upon to supply information on requests from correspondents all over the the world. In fact, so busy are he and a colleague, that they cannot publicise their facilities in case excess demand should bring their activities to a halt! Perhaps in the course of research the reader will be fortunate enough to meet similar kind folk.

Commercial Designs

During the past 20 years there have been many series of articles on the construction of narrow-gauge locomotives, notable are those on the construction of CONWAY, a freelance narrow-gauge 0-4-0 Saddle Tank locomotive for 3 1/2 inch gauge by Martin Evans, in MODEL ENGINEER of 1980. Other practical designs are the freelance model ‘ SWEET PEA ‘ mentioned earlier in this book and described in a series of articles in ENGINEERING IN MINIATURE. Whilst such designs are initially prepared for the benefit of the readers of the journal, commercial concerns soon set themselves up to provide the necessary materials and particularly castings for featured locomotives. In this way the modeller gains the advantage of an economic supply of raw materials and is, should he so wish, relieved of the work of producing his own patterns

The model engineer should not overlook designs for which part, or fully machined, sets of parts are available, particularly as these models have been built in large numbers and have proved themselves as runners on tracks throughout the world. Kits of ready machined parts such as those available from Messrs MAXITRACK have served to introduce many modellers to the delights of model engineering. Once having assembled a model from a set of parts, production and assembly of ones own parts seems just a small step to take.

The Model Press, Publications, Exhibitions And Club Membership

As will be evidenced by the frequent references in this book, the writer is an avid reader of a number of model engineering publications. These range from MODEL ENGINEER and ENGINEERING IN MINIATURE to the excellent series of publications by such firms as ARGUS BOOKS and THE OAKWOOD PRESS. Magazines devoted to specialised topics such as small scale railway modelling have information to offer. It is well worth taking time to note articles which contain detail which can prove useful at some later date, a note of the magazine or source made in the diary or logbook can save hours of searching later.

Most of the existing narrow gauge railways have a bookshop at the main depot as do industrial museums up and down the country. Stocks within these shops often contain valuable information for the would-be modeller, most for example have some write-up of the history of the line and its equipment, or in the case of museums a description of a specific locomotive exhibit, containing valuable illustrations. Picture postcards and posters are another source of information and with care can be used to supplement surveys and drawings.

National and Local Exhibitions provide an opportunity for contact with trade suppliers, and other enthusiasts who can provide leads on sources of information. The models exhibited often reveal useful detail, and contact with the producer can assist in extending ones knowledge of methods and techniques. There is often a stand where known experts give demonstrations and provide advice on problems. Bookstalls at exhibitions can provide a useful source of information, on occasions it has been possible to pick up a years back numbers of journals for quite reasonable sums, reasonable when one considers the wealth of information contained therein.

Club membership has a great deal to offer, particularly where the newcomer to model engineering is concerned. There is never any shortage of know-how or advice. Frequently one or other of the members is specialist in or has specific knowledge of a particular railway, having perhaps worked on the line or more recently done voluntary work in preservation. Club membership may well present other advantages such as access to machines and services and sometimes discounted prices on materials from a local supplier. Local club programmes often include talks and demonstrations by visiting speakers, specialist in some branch of model making such as boilermaking, painting and so on, these events are particularly beneficial to the beginner.

Back to Contents

Chapter 3

Going it alone. Surveying a prototype. Equipment. A system of working. Ongoing visits. The database. Use of photographs and prints.

Pixie and Peter Pan at the Leighton Buzzard N. G. Railway

Going It Alone

As we have seen there are many drawings available for narrow gauge locomotives, quite a number of kits of castings and indeed, even sets of parts for home assembly. It is however quite likely that the modeller has a particular prototype in mind, one that has fired his imagination, one that brings back fond memories from the past, or perhaps a locomotive to which access can be gained.

Where the prototype is one of the many that have passed on to the ‘ great engine shed in the sky’ then some research will be required. Indeed, research of some order will be required whatever the reason behind the choice of a specific prototype. We are fortunate that the history of steam and steam railways in particular has been so thoroughly recorded by many devoted writers over the years, these constitute major works and will prompt further reading as a particular topic is followed up.

Surveying A Prototype

The cover of MODEL ENGINEER Vol 158 No 3795 Feb 1987 illustrates ‘Rishra’ and ‘Challoner’ of the Leighton Buzzard Narrow Gauge Railway. The remarks of the Editor of MODEL ENGINEER, Ted Jolliffe who took the photograph are apposite. He writes,’ This shot was taken on one of the best days of last Summer at Pages Park Station, home of the Leighton Buzzard Narrow Gauge Railway. ‘ Rishra ‘ and ‘ Challoner ‘ pose together after double heading a Special Train, a charming sight and one which could well cause many modellers to dash to the railway armed with camera, ruler and sketch pad’ …….. We know the feeling!

If one is fortunate enough to have access to the chosen prototype there are a number of things to consider in achieving sufficient detail for the construction of a convincing model. The locomotive may be sited on a preserved line, in a museum or may even be standing in derelict condition in a scrap yard. The important thing is to secure access. The first step will be an approach to the controller of a preserved line, the curator of a museum or the proprietor of a scrap yard. Permission to survey the prototype is generally given although there may be some stipulations regarding access times and so on. The thing uppermost in the minds of those in authority will be that of safety, both that of the visitor and those who work the line or run the museum. This is understandable in these days when responsibility and the rights of the individual are assuming such importance in life. It is essential that any visitor makes his presence known to those in charge in order that this safety can be preserved in the case of engine, stock or plant movements.

In the case of a locomotive preserved in a museum, one may be fortunate enough to find that drawings already exist, more than likely the curator or some enthusiast will have done some research already and will be prepared provide valuable information. In the case of a preserved locomotive it is likely that the line is in possession of at least some drawings from which copies or at least major dimensions may be taken.

In the case of PIXIE it was decided to make a complete survey, starting from scratch as described in this chapter. Where drawings or key dimensions are available, a lot of what is described can be omitted but in the interests of achieving a model of character it is advisable that, where possible, a visit or visits are made to the prototype for the purpose of achieving accuracy, and observing details that have either resulted from rebuilding or preservation work. Some detail changes are brought about simply by repair of wear and tear, or changes in the demands made upon the loco in service. For example, some small details such as the loops of tow that are used to lubricate the valve rods on PIXIE, the diesel couplers that were mounted for some years, the changes to the rear weather plate and the replacement of the riveted tank by one of welded construction with imitation rivets have been incorporated in the model to good advantage. We did not, however, incorporate the differences between wheels that have resulted from refurbishment over the years!

At an early stage it becomes necessary to decide on a ‘ base date’ for the model. In the case of Pixie this was set as the date on which we first saw the locomotive. As well as the base date, the state in which the model is to be presented has to be determined. It takes a strong character to produce a model locomotive in pristine condition and then render it into a weathered condition! Mostly, we like to see our models in an outshopped state and not exhibiting the ravages of service. I decided to model Pixie as though she had just undergone a face-lift in the paint department but incorporating all the detail that I saw that magic day when I first saw her glide into Pages Park Station on the Leighton Buzzard Narrow Gauge Railway.

Having decided on the prototype it is time to start on the survey. I was fortunate to have the Leighton Buzzard Narrow Gauge Railway ‘ on the doorstep ‘. I had visited this line on a number of occasions and been struck by the friendly manner of all the volunteers who work the line. Not for nothing has the railway won its name as ‘ The friendly little line’. I gathered all the information I could from their publicity leaflets, and obtained some attractive posters, one of which showed my chosen prototype PIXIE the Kerr Stuart ‘ Wrenn ‘ Class saddle tank locomotive, built in 1922. The poster still adorns one wall in the workshop. This illustration and the memory of our first encounter acted as a spur to my efforts over the years.

At the Railway I soon established that the volunteers, among them the taxman, the accountant, the telecom engineer and a number of other interesting characters, were all pleased to help in any way they could. Access to the workshop was given by the Controller. Drivers, firemen and other functionaries took the greatest of pleasure in responding to my sometimes naive questions. I was able to time my visits to coincide with occasions when the locomotive was shedded for normal maintenance and repair, and one notable occasion when the boiler was to be subjected to inspection and test by the Insurance Inspector. Take time to develop a good relationship with the staff of your selected prototypes’ line then you are sure to be accorded the same privileges.

Of course you may be fortunate enough to obtain copies of the works drawings from the manufacturer, or you may have gleaned sufficient information to build your model from your research. In the first case you will only have to scale down the detail, in the second you will need to prepare sufficient detail for construction planning and parts manufacture. In the case of Pixie sketches were produced from site measurements, not finished drawings but simple line drawings to be worked from at the various stages of construction. Examples of these sketches can be seen in the accompanying illustrations.

Plan the survey work. You can only make so many measurements in each session! Sometimes you will need a friend to hold the tape or direct the torch. You can’t always bother the locals who are busy with their maintenance and restoration tasks. It is helpful to pre-prepare sketches from photographs so that you can enter the dimensions as you measure, failing this produce sketches on the spot. Bold outline sketches are best, it is difficult to sketch, measure and insert dimensions all at the same time. It is also difficult to convey to another person just what dimensions you are calling-off, so wherever possible enter the numbers yourself. On return to base, and as working sketches are prepared, make notes of any dimensions that are missing, these will be the first measurements to be taken on the next site visit. Do not be dismayed if on the first visit ( or two ) you miss some details, you will find with practice that you become more observant, and more inquisitive.

Equipment For The Survey

Each individual will have differing ideas on the gear required for the preparation of measured details from a prototype. The equipment used by the author, whilst varying from visit to visit, included the following items;-

Clipboard, pencil (s) and paper, eraser, pencil sharpener or knife, measuring tape, steel rule, torch and a set square, ( on most occasions the edges of the clipboard sufficed)

Camera and flash equipment, preferably a single lens reflex model although todays compact cameras, with their built-in flash and zoom facilities provide excellent photographs. Dare we mention spare film!

Most of these items can be carried in a knapsack or some similar bag, nothing too special should be used as it is likely to accumulate its share of steam oil or grease! Mention of oil and grease brings to mind the need for a supply of ‘ Swarfega ‘ or some similar de-greasant, a bottle of water and an old towel. Not all loco sheds have supplies of such basic needs!

A System Of Working

It is always advisable to phone the site prior to a visit, both to confirm that you may have access to the locomotive and to establish where it is to be found on the day, also what state it will be in. It is also useful to know how to dress for the visit, some days are ‘clean’ days and some decidedly dirty!

Now for taking the actual measurements. It is best to start by making simple sketches of the key items to be measured in the course of a visit, say a front beam, back plate or frame member. It makes good sense to keep groups of details on separate sheets, even at the risk of duplicating some detail. This will make reference to detail of particular parts of the locomotives easier in the workshop when a specific sheet of details can be isolated for reference. This also facilitates filing of the results of the survey, speeding the process of identifying dimensions.

Try to make each sketch to the same proportions as the member to be measured, later this will be facilitated by the use of photographs in producing sketches on which the dimensions can be set out. It is advisable to take running dimensions from a datum point thus avoiding inaccuracies due to the build up of small differences in measurement. In the absence of a helping hand, running dimensions can be taken single-handed by clamping one end of the tape to the feature forming the datum, and reading the tape at each point of interest ( remembering to pull the tape taut as each reading is taken, and ensuring that it is not snagged on some projection! ) Where taking details of groups of items such as bolts or rivets these should be sketched and measured, and the running dimension taken to a key point in the group. The individual rivet heads or bolts positions can then be related to this key point, and set out accordingly when interpreting the sketches back at base. At this stage with the tape in position, a photograph will reinforce the dimensions being noted. When the time comes to translate the detail the photo will serve as a reminder of odd little points which whilst clear on site fade in the mind between whiles. Things that are easily overlooked are material thicknesses, bolt, nut and washer sizes. Whilst measuring the plane surfaces it is also necessary to note such detail as plate thicknesses, pipe diameters, bolt and rivet head sizes and shapes. Where there are details such as cranked plates and coupling rods, dimensions of offsets have to be noted.. Sets in plate, or changes in plane, and similar detail which are critical to the overall appearance and ‘ atmosphere ‘ of the finished model should be noted and ‘ scrap ‘ sketches made for future reference. These scrap or local details are most useful in interpreting the overall picture presented by the dimensioned sketches. Brief notes help too, a note regarding colour, texture or material of some feature will save valuable time at a later date.

Ongoing Visits

After the first visit it may be possible to mark up dimensions onto sketches taken from photographs or from slides, the former by tracing from a large print of a subject set upon a light box, alternatively on a sheet of glass or perspex placed over some suitable form of illumination such as a table lamp. Transparencies can be projected at a suitable size onto a piece of paper taped to the workshop wall and tracings made for use on the next visit to site. Judicious scaling of the projected picture will ensure that sufficient space is available for the insertion of dimensions at site.

At the commencement of a follow-up visit it is essential that outstanding queries are cleared up. This may necessitate further measurement or some discussion with a local, be he a curator, or a volunteer in the case of preserved locomotives. A point of caution here, enthusiasts can be very helpful but…..their memories are tinctured by their personal interests and any two taken together may come up with different opinions regarding when such and such a detail was modified or a particular feature added. In the course of conversations it is worth while listening for local ‘ intelligence ‘ such as a forthcoming ‘ shopping ‘ of the prototype or perhaps a boiler inspection. Visits timed to coincide with such events, with permission, will provide opportunities for examining the inner workings of the locomotive, the valve chests and boiler tube arrangements, blower ring and so on which would otherwise prove difficult when the loco is in service.

When working on the survey it is advisable to visualise how the model parts will be constructed, whether they will be machined from castings or fabricated. Whilst this does not affect the dimensions needed it does assist when the fabrication commences in the workshop.

The ‘Database’

Information achieved at site will form the basis for some months and in some cases, some years of effort in the workshop so that on return to base it becomes necessary to store the details from survey in such a manner that they can be recovered at will. All rough sketches made at site should be retained, possibly in a box file. Photographs and file cards can be stored in boxes and slides filed in the containers in which they are returned from processing. It is advisable, in order to save time later, to segregate details under various headings such as ‘ Backhead’, ‘ Smokebox’ etc. Ideally, general assembly photographs will serve to tie the various items together and indicate the relationships of the individual subsections. During the course of constructing the model of PIXIE more than 180 photographs were taken in the form of transparencies and some 100 pages of notes and sketches were assembled. These are still retained today and act as a reminder when some adjustment or modification becomes necessary. Between visits and when not engaged in making parts in the workshop, some redrawing of details can assist in clarifying detail. It is advisable always to retain original sketches although they may have been superceded by a more recent, perhaps tidier sketch. There is often a need to return to the original to recap on some note or sketch made at the site. In this context it is advisable to make notes of details that present themselves during the survey, Where lock nuts are used, the position of a cotter pin and so on, later in the workshop one does not want to attempt feats of memory to establish what one saw months or years before.

Photographic Records

Now we have digital photography and can wiew the images we take at whatever size is required on computer screen. Archiving is a simple matter and referencing simpler still. It still pays to take addition trouble to include tape and rules to enable sizes to be established back at base and special care over lighting to reveal the inner workings of the machanics of our subject.

Often there are posters and similar material which can yield useful information, as well as postcards perhaps, on sale at a kiosk illustrating our subject in earlier days.

The Internet provides a fund of images of virtually every locomotive that ever existed, simple to download and readily sizable on our computer, and again simple to archive.

It should always be remembered that permission should be sought to photographon site. Safety arrangements have to be observed and also care should be taken regarding copyright of images from the web.

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Chapter 4

Workshop, tools and equipment. Practical aspects of heating, lighting and ventilation. Workshop practice for the model engineer. The logbook.

Old faithful of 30 years… My Myford

Workshop, Tools And Equipment

This chapter ought really to be entitled ‘ Tools, equipment and workshop ‘ because, whilst many books on the topic set out initially to describe in some detail the workshop facilities required, in practice the first requirement is some tools. The next requirement is some mechanical equipment and eventually a workshop, or rather a workplace! Of course it is ideal if one has a dedicated space in which to work, a place where everything can remain undisturbed between sessions, but it is a lucky man indeed who can start with such a space available. A great deal of work has been done in what were on the face of things, quite unlikely situations, in a first floor flat, in a roof space, onboard ship and countless other such awkward or uncomfortable places. At one time the writer made models on a fold-down bench sited, of all places, in the toilet ! Then followed a move to the loft via. the kitchen table and eventually, some years later it became possible to build an extension to the house and set up a formal workshop.

A great deal of useful work can be done simply by using hand tools, small parts being turned in an electric drill. Occasional access to a lathe and drill press, made possible perhaps by enrollment in an evening class or by ‘ chatting- up ‘ the maintenance engineer at one’s place of work can bring the opportunity to progress further in the hobby. Several of the stationary engines which provided the basis of the author’s model engineering experience were fabricated piece-part fashion using such facilities….. ……..Maintenance engineers often turn out to be steam enthusiasts at heart!

The pleasure to be obtained from our hobby can be realised in a number of ways. One of these revolves around pride in possessing the necessary tools for the job, sometimes obtained as a result of some sacrifice such as giving up smoking, or forgoing some other pleasure. There is also the satisfaction to be taken from achieving something which would normally be considered beyond the scope of the simple equipment which we may have acquired. Whilst other delights of model engineering have been touched upon earlier in the book, the challenge of achieving, what once may have seemed to be if not impossible, extremely difficult, using available equipment and facilities still features heavily in the enjoyment stakes!

Tools

Tools are a joy, however acquired either purchased in pristine condition from a first class tool shop or from other sources such as garage or car-boot sales, possibly in need of renovation. The tools that give the greatest pleasure are often those passed on to us from relatives or friends. Tools may have been handed down from departed relatives and considerable pleasure can be obtained as using them prompts remembrance.. Use on the current project prompts thoughts of the original owner, such as the old tool maker who on his retirement made us a present of his micrometer and other measuring tackle. As experience grows the modeller will probably design and make some special tools, these are particularly precious in meeting an identified need and are special to the maker.

It is important to buy the best tools that can be afforded, they will if properly maintained probably outlive us and be passed on to sons (and daughters). Where possible, a workshop set of tools should be maintained as distinct from the general kit used in the garage and on DIY work about the house and garden. When a loan is requested, lend from the general kit! Mainly tools are acquired as the need arises although most of us will have to admit to making purchases on an impulse, particularly at the magical MODEL ENGINEER EXHIBITION where there is the opportunity of making some fantastic purchases. It makes sense to go to the exhibition with a shopping list of items necessary to bring tool stocks up to standard, it offers a grand opportunity for replacing broken small items such as taps and drills. It is very difficult to withstand the urge to snap up bargains and indeed often return with such ‘ bargains ‘, perhaps wondering what prompted the purchase yet secure in the knowledge that they will come in useful one day

Measuring Tackle And Instruments

Apart from the aforementioned micrometer the following equipment, listed in order of aquisition, meets all the requirements of model making on models up to 5” gauge:-

Good quality steel rules in 300 and 150 mm lengths, squares of various sizes, inside and outside calipers, oddleg caliper, 0-150mm vernier caliper gauge, height gauge, mm dial gauge, surface plate ( mine is 250 x 200mm obtained second hand ), magnetic stand for dial gauge also various scribers. Although the sizes are quoted in millimetres the workshop still boasts a set of Imperial equipment and much of the work is carried out in ‘ dear old ‘ feet and inches.

Later additions to the outfit include some inside micrometers, obtained secondhand, a centre finder, a wiggler set for edge and centre-finding, pair of vee blocks and a huge, ex-WD, caliper, purchased for a song in an open market. A dial caliper gauge ( the pride of my life, bought as a bargain at the MODEL ENGINEER EXHIBITION ) is in constant use. As model engineers rather than engineers, much of our work involves working to fits rather than critical dimensions. The dial caliper provides a speedy yet sufficiently accurate means of comparing sizes whether internal, external or depth. The current generation of digital gauges are of course even more dynamic to use and will prove to be worth the ‘ arm and a leg ‘ they may cost. The great advantage is that these instruments can be zeroed at any dimension and thus directly indicate differences between measurements.

A recent aquisition, a magnetic-based holder for a dial gauge, has proved extremely useful. It is used the course of turning, milling and drilling to measure tool feeds. With the base set onto the machine bed and the magnet actuated, a dial gauge can be set to bear against a table or slide such that the travel or depth of feed can be directly read from the gauge as work proceeds. It is far easier in some cases to read the gauge thus set-up, than it is to read the micrometer dial on the machine.

Hand Tools

The number and type of tools that one uses is a very personal thing, excellent models are built by some modellers equipped with what could be regarded as the absolute minimum of tools. It is preferable as far as possible to have the correct tool for the job, sometimes to the extent of ‘overkill’!

Again in the order of aquisition the following tools have permitted the production of a series of models up to 5” gauge:-

An assortment of saws including ‘senior’ and ‘junior’ hacksaws and a coping saw. Hammers, ball pein, claw and pin, also a builders lump hammer for persuasion of heavy sections! An assortment of files and some rasps. A short set of ( expensive ) jewelers files have proved invaluable Pliers of assorted shape also a pair of steelfixers ‘ nips ‘ and two sizes of tin snips, one having curved blades. Chisels, punches of various sizes and an ‘ automatic ‘ centre punch. A wheel brace and an electric drill, later supplemented by the aquisition of a high speed mini-drill and variable speed control. A variety of clamps include ‘ Mole ‘ overlever clamps, ‘G’ clamps and a range of tool makers clamps. A hot-glue gun has proved useful, particularly for locating small or thin parts during machining operations! Screwdrivers include the good old ‘ engineers pattern driver, electrical and watchmakers screwdrivers. Several adjustable spanners are used,for rough work but for actual work on models only good quality open ended, or socket spanners are used. Messrs Proop’s ‘ Doofers ‘ come in useful at many stages.

Drill bitts have been purchased over the years to the stage where number sizes are supported as are Imperial and letter sizes to about 1/2” diameter maximum. Taps and dies have been purchased as the need has arisen and most sizes from 9 BA to 1/2” are held, together with the necessary stocks and tapholders.

Tool Storage

Tools are stored on boards, either wall mounted or, in the case of small tools, fixed as riser boards on the back edge of the benches. The location of tools on these boards is determined by the place in which they are most often used, chuck keys adjacent to the drills, tommy bars adjacent to the mill, small tools adjacent to the clean bench and so on. Tools which see only occasional use are stored in file trays picked up cheaply in a car boot sale. Portable power tools and lathe accessories are sited in cabinets, again wall-mounted, with glass doors to ward off the ever present workshop dust.

Benches

Bench height is a very personal thing, the vices must be at the right height for filing and sawing operations, in the writers case 32 inches from floor level, yet for very fine work it is often necessary to have them higher as does a watchmaker. This is achieved by having a supplementary worktop which rest on the standard bench and can be secured when necessary by clamps, or mounted in the vices.

Within the workshop it seems that one can never have enough benches or worktops. Just as it is sometimes said that ‘ work expands to fill time ‘, so things multiply to fill workspace ! Nearly 2/3 rds of the perimeter of the workshop is allocated to worktops or benches. Some discipline has to be maintained here, one bench is the ‘ dirty bench ‘, one the ‘ clean bench ‘ and the other the light, mobile bench. The first two speak for themselves, although there is a need for strong discipline to keep the clean bench, used for electronics and fine work, really clean ! The dirty bench is for the heavy work of preparing metal for machining.

The mobile bench is a recent production, made from DEXION angle, it is set to match the height of the fixed benchwork and can be used in its own right for light fabrication work, or appended to the fixed benches to accomodate overlong pieces of work. The castors are of the heavy industrial type and are set so that the uprights of the assembly just clear the floor. When any particularly heavy task is to be undertaken it is a matter only of a few seconds work to insert thin wedges to take the strain off the castors. The bench is used for final assembly of clean items and can be sited according to the work in hand, against the lathe as a repository for tools between uses or adjacent to the benches as required. It is useful to have space to ‘park’ small tools in the course of work, to hand yet not cluttering the available worktop. A particular advantage to be gained from a mobile bench is that, sited in the right place in the workshop, it provides a base on which a length of portable track can be mounted for service work, adjustments to the loco and so on. A short length of 3/4 inch plywood is used to bridge between the fixed and mobile benches and access is available all round the ‘island’ so formed.

Vices

Vices are mounted on secondary pieces of benchtop which allow their location to be changed to suit the work in hand. The heavy ply bases for the vices were drilled to template, as were the benchtops and it is a matter of a few minutes work to change things around as required whether for heavy or light work, working in wood, metal or plastics. As well as the normal duties of holding metal for sawing, filing etc. the two metalworking vices mounted in tandem are used for folding and bending plate materials. There is a woodworking vice, this swivels and has the useful facility of reversible jaws which permit gripping material up to 7 inches wide. Cramps include toolmakers, mole, screwclamps as used in woodworking and some excellent clamps which whilst intended to be used as screw clamps can if supplemented by a 3/4” stock bar be used in clamping lengths limited only by the available bar. ‘Grippery’ is competed by a small parts, universal vice built to a design published in MODEL ENGINEER, this is invaluable for small part assembly and the investment of the 2 or 3 hours expended in its construction has been repaid many times over.

Machine Tools

The King of the workshop in these scales is without doubt the Myford 7 series lathe. We graduated to this from a Unimat via a very ancient but extremely trusty Zyto lathe, purchased second-hand which was used in building a series of Stuart Turner stationary engines. The Myford is equipped with 3 and 4 jaw chucks, faceplate, and a swiveling vertical table. Drill chucks to 1/2” and a home- built die holder for the tailstock complete the lathe equipment proper although a number of accessories have been built including boring and knurling tools, wobblers, height gauges and so on from descriptions in MODEL ENGINEER over the years.

The first exercise with the Myford was the construction of a sensitive drill to a design from Messrs Reeves catalogue. The necessary castings and raw metal were purchased from Reeves and provided excellent practice in turning, boring and so on. The parts worked-up into an extremely accurate piece of workshop equipment which allows the use of the smallest number drills without breakages. With small number drills it is important that one gets the ‘feel’ of the drill as it cuts metal, particularly at the critical time just before and at break through, the Reeves drill provides just that feel. One addition ,in the interests of safety was the inclusion of a perspex, ‘ wrap-around ‘ guard for the belt drive which otherwise is running just inches from the users face in course of work. This machine has been replaced in recent years by a ‘cheap and cheerful’ drill press of doubtful ancestry, and recently a small universal milling machine was purchased to suplement the armoury.

A throwback from the days of wooden models is a a small bandsaw. this is invaluable for producing templates and for cutting the odd bit of packing timber. It can be used for light metal cutting which is of course also carried out using a hacksaw and brute force. A ‘nibbler’ has proved useful in cutting thin sheet for cleading and similar purposes.

The Workshop Building

Given the opportunity to have a dedicated building for the workshop there are so many possibilities that a description would fill another volume. We have been fortunate enough to be able to build an extension to the house, brick built, properly heated, insulated and lighted, with power and water available.

The workshop which was described in MODEL ENGINEER Vol 163 No.3853 really is a ‘ quart in a pint pot ‘ as the Editor described it at that time. The best advice stemming from experience must be that one should think of a size, and double it! As with all building work, the finished result always seems smaller than the drawings indicated, and anyway extra space can always be put to good use until filled with that new machine or additional storage shelves.

A well insulated timber building can be used as a workshop, as can the space at the back of the garage, and most of us know model engineers who produce excellent work in such places. A covered access from the house is desirable as in the depths of winter it takes some strength of character to leave the warmth of the house and brave the elements to get to the workshop! In the case of the timber building it is essential to insulate the walls AND THE ROOF. The latter often being overlooked can be responsible for massive heat loss and consequent condensation. The walls should be lined with something smooth to permit ease of cleansing and ideally the floor should have heavy lino or tiles to permit sweeping, thus simplifying the location of those small parts which insist on gravitating to the floor, ( and under the nearest machine or bench ! ) Double glazing, or at the least, secondary glazing of any structure is a further weapon in the fight against condensation as well as retaining such heat as can be introduced by some ‘ dry ‘ form of heating. A centrally heated workplace is of course a luxury. Low wattage tubular heaters have a lot to offer in the smaller or the isolated workshop. A time switch can be a benefit as the heating cycle can then be optimised to suit workshop ‘ hours ‘ whilst maintaining the gentle heat required to preserve tools and equipment.

Services

Plenty of power points at bench height are a must. Provided that substantial cable is used these can be supplemented by extension leads with multiple outlets ( switched and fused ). We have a preference for general fluorescent lighting, local intensity of light being provided by anglepoise or similar fittings. Whilst low voltage lighting is ideal, normal mains voltage equipment has been used for many years without problem or accident, of course these lamps whether free standing, wall mounted or mobile are properly earthed and never mounted on the machines. The use of a circuit breaker is essential where portable power tools are used. On the topic of electricity, one of the most useful pieces of equipment that I possess is a rather ancient meter, this measures current, resistance and other detail to complicated for my ‘ ken ‘ but proves invaluable in checking lamps, earthing of equipment and the like

Access to a sink, adjacent to the workshop yet not in it, is a great asset, providing for the cooling of metal, scrubbing down prior to soldering and so on. A sink which has become too disreputable for normal domestic use is ideal, and an old sink is usually accompanied by some old taps, so that the installation can be carried out by the model engineer with access to appropriate pipes economically and in no time at all !

Ventilation

Many hours are spent in the workshop environment and thought must be given to good ventilation. As some of the operations, such as those of machining cast iron and gunmetal generate a very fine dust we must look after our lungs. A good quality mask will do much to save the respiratory system from attack but the quality of the mask and the suitability of the cartridge to the work in hand is all-important.

The writer’s workshop is ventilated using a very large, Vent-axia fan bought in a car-boot sale, this is mounted in a box INSIDE one of the the fanlights in such a way that the fanlight can be opened and closed in the normal fashion for general ventilation purposes. When a forced draught is required the fanlight is set wide, the fan switched on, and a hinged perspex inner pane is buttoned down to blank-off the fanlight opening beside the fan housing. The fan now produces anything between a mild breeze and a howling gale. Air circulation is also assisted by two smaller fans, as used in cooling computers, set over the lathe and the milling machine. These fans which are attached by clamps can be moved easily, and as they are brushless can also be used to flush away the fumes from any small painting operations carried out in the shop.

The Logbook

As a keen diarist some entry is made in the diary each day. At the same time the hours spent in the workshop are noted, also the activities. This odd quarter-hour or so, each evening is spent noting down details of the way in which things have been assembled, screw and fixing sizes and other details that will prove useful, both when the time comes to take the model down and re-assemble it, and when remaking parts. The information should also prove useful to anyone who may own the models in the future. As well as details of finished work, part of the entries will be sketches of the next component to be fabricated together with a planned sequence of machining operations ( Often in the ‘ heat of the moment t’ in the workshop the sequence may be changed but brief notes ensure an awareness of critical dimensions and intended secondary set-ups ) It is also helpful to note down any items which need to be checked when next visiting the prototype.

It is said that sketch is worth a thousand words, many times now notes have disclosed a detail that had slipped the memory……… after all some models take many years to build and a lot of detail becomes buried as work proceeds. As an example, recently, due to some corrosion around the regulator gland it was decided that the mild steel studs and nuts be replaced by new ones from stainless steel. A few moments spent with the logbook confirmed that 5BA studs and nuts had been used, and not 1/8 inch M.E. as they appeared on first inspection. So, as the result of a few jottings some years ago, as well as valuable time being saved the likelihood of a damaged regulator body was avoided. Other notes made include references to articles in MODEL ENGINEER and ENGINEERING IN MINIATURE for future use when a particular operation is to be tackled. Some notes are reminders, which form a shopping list and ensure that a component cant be produced for lack of the raw material or a particular tool, say a drill, tap or other such item easily forgotten when at the shop.

On completion of a model, with reference to the logbook, it is worthwhile to prepare a set of cards, 150 x 100 index cards are ideal for the purpose. These shew the sequence of erection, fixing and fastening sizes and other detail that a future owner may find useful in running and maintaining the model. These form something like a simplified workshop manual such as one may have for a motorcar. A computer ‘ buff ‘ could set up a useful database in which to record a number of the details mentioned, although this may not prove so accessible to others at a later date.

Indexing 4 tool toolpost mainly from scrap

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Chapter 5

Materials. Sources of supply. Organised storage and the scrap box. Modifying available materials. An introduction to simple pattern making.

Sources Of Supply

Sourcing of material is an important aspect of model making. The writer makes no secret of the fact that a large part of the materials used in modelmaking is scavenged from scrap bins and ‘Biffa’ skips (with permission from the owner of course). We have also benefitted from the miscellaneous selections of ironmongery to be found at road junctions and similar spots where vehicles, waiting for traffic lights to change, shake themselves to pieces. Judging from the range of screws, bolts and miscellaneous metal sections one finds, much of our countries’ transport fleet must be in imminent danger of collapse!

Much of the benchwork and shelving in the workshop, as well as the lighting fixtures and associated wiring have come from skips. Proprietors of the local engineering works are very helpful in this respect, to the extent that, knowing our interests they set aside any particularly useful items of scrap! Once they become aware of ones interest, friends often turn up with interesting bits of metal which can yield useful raw materials. There will be however a number of materials which have to be purchased and much of these will come from the suppliers who advertise in the model press. A good source of materials is the advertiser who puts up packs of useful sizes of bar and rod. A selection of these bundles forms a good basis for a modelmakers stock. Of course not all the materials will have an immediate application in the sizes purchased but a hacksaw and some elbow grease work wonders!

Organised Storage

It is important to be able to access ones stock quickly and simply. Care in segregating materials and storing them in such a fashion that they are not damaged in store is just one further facet of the model engineering hobby. It makes sense to run ones stock in much the way it would be organised in a commercial workshop, noting when stocks are getting low and thus not finding oneself in a situation where materials have to be used wastefully to obtain the particular section required.

Containers suitable for storing small parts and materials are available in a variety of materials, largely steel and plastic. Often job-lots of containers can be purchased at auction. File trays are excellent for the storage of short ends of bar, oddments that prove so useful, provided one can lay hands on the when the need arises. Different materials can be segregated in such trays, mild steel in one, nonferrous in another and so on. A simple wooden or welded steel frame allows such a number of trays to be stacked and reduce the uptake of space. For smaller items plastic icecream containers are useful, honey jars are excellent for small bolts, screws etc. rotate the jar and give it a shake and the bolt screw that you seek will pop into view!

Some simple methods for storing material:-

Medium length pieces of bar, rod and tube can be stored vertically in racks comprising two grillages of steel bar fixed to a wall of the workshop, one to locate the bottom of the stock and the other to support the material 3 foot or so above floor level.

Short pieces of these materials can be stored in lengths of plastic drainpipe. The pipes can be cemented together and banks of such pipes allow both easy access and a quick check on stockholdings. Similar banks constructed from wastepipe and conduit will control stocks of small diameter tubing.

Multiple-draw storage units are available from DIY stores or can easily be manufactured in the workshop. Being wall-mounted they save space. Drawers marked with their contents will save hours of searching.

Drills are best stored in racks, simply made from wood blocks, it will save time too if tapping and clearance sized drills are stored together with the screwing tackle. Draws marked ‘Small number drills’, ‘Small cutting tools’, ‘Centre bitts’, ‘Unions’, ‘springs’, ‘Washers’ and so on, used methodically also save time and avoid frayed tempers.

Jars and ice cream containers are useful for storing small offcuts, nuts bolts and similar items, labeling saves precious minutes of time which will otherwise be expended in searching for an elusive piece!

When seeking space in which to store tools and materials remember to consider the space over, as well as, under that crowded benchwork. With a brick-built workshop and in some cases in timber framed buildings quite substantial loads can be supported in custom-built shelf frames, suspended from the roof members or fixed back to the walls. The shelf frames should be supported in such a way that the majority of the loading is applied to the wall fixings in shear, vertically downwards at the face of the wall. Shelf units placed strategically above the benchwork, leaving adequate working space also permit the installation of lighting units below the shelving providing a good working environment below.

Some of the materials used in the model engineering hobby are quite aggressive, some such as acids and certain paints require special storage. These are best kept in a metal cabinet, locked if there are ‘little people’ about the house. This is another instance where the same care should be taken over storage as is taken in industry.

The Scrap Box

The first port of call when seeking materials for a part of the locomotive will be the scrap box, or that odd corner of the garage or shed where those bits of metal ‘ that may come in useful one day ‘ are stored. That day is bound to come, and provided we weren’t too ruthless the last time we sorted through in the pursuit of space, we will find at least a few pieces that can be pressed into service in our project. The materials may not be exactly what we need and it needs imagination to see how we can use some of the stuff. It may be that, rather than providing material for the locomotive proper, some pieces will provide the basis for jigs or templates to assist in the construction or erection work. Scrap angle steel such as that from an old bedstead whilst being virtually ‘ Monkey metal ‘ could prove to be useful in the manufacture of an erection frame. Dexion angle can be used in mocking-up a driving trolley, scraps of plate may be used as the backplate for the jig on which the horn casting will be machined and so on.

A well-organised scrap box is an important asset. Some time spent in dismantling a defunct television set, a radio, damaged video tape case or virtually any piece of domestic equipment can yield supplies of a range of materials from self-tapping screws to sheet metal bracketry. Admittedly the current trend in commercial manufacture towards ‘ throw away ‘ engineering practice leaves less of a recoverable nature, but there is always some small thing worth keeping.

Modifying Available Materials

Often material of the section or length required for the current component may not be available. With some adjustment either by way of a change of material or method something from stock may be brought into service. Re-cycling, sawing down angle, splitting tube, using chucking pieces saved from castings as bushes and similar dodges can save money and time. Even pieces that were spoiled in some previous operation, and probably thrown into the scrap box in disgust can prove useful when cleaned-up, cut-up and re-machined. Whilst apparently a wasteful process, producing studs by cutting the threaded portion from a bolt can be productive in that one finishes up with a stud, and an embryo bolt albeit one of much reduced length! Conversely, the small threaded offcut that is saved after a bolt has been reduced in length may well be pressed into service as a grub-screw in another application. Keep a few containers marked ‘ Small brass ‘, ‘ Small steel ‘ and so on, and you may be surprised how often you find just the piece of material that suits the current requirement.

It is occasionally possible to find alternative uses for items which would otherwise be considered as domestic or garden hardware. instances of this are small sized hinges which can be reduced for use in a model, studding sold at the ironmongers, again for domestic use which can be brought into service as tie bolts for securing material for machining in the lathe or milling machine. Stores retailing automotive parts sell metal and rubber tube in various sizes and gauges also shim brass and steel and a number of fixings which can be put to use in models. DIY stores stock a number of standard sections of brass, aluminium and plastic which may meet a modelling need at some time. Even the local supermarket will stock polishes, scourers and abrasive materials which can be used in metal finishing. A number of the shops market spun or pressed metal products such as trays, bowl and eggcups, some in stainless steel others in brass. The materials and sometimes the geometric shape of these present possibilities to the model engineer, an example that springs to mind is that of the steam dome cover cut from the bottom of a spun brass vase!. The search for alternative and economic sources of material can be quite fun and may, to some extent, relieve the boredom of a domestic shopping outing.

Simple Pattern Making

There have been many excellent articles, indeed a number of series of articles in the model press on the topic of pattern making. The topic is interesting and one which, given time, could become all-engrossing. Ones time available for model engineering activities is often limited. With such limits there might be some reluctance to spend the time and energy required for the manufacture of the more intricate pattern work required by a project. In this case two courses present themselves. The necessary casting may be obtained, as in the case of the horns for Pixie, by modifying some nearly similar, available casting. Alternatively one may turn-to and make simple patterns which, whilst probably beneath the contempt of the dedicated pattern making modeller, yield castings which can, by careful machining, permit the production of the required part.

Simple patterns may be carved from wood or, in the case of circular work, ‘ horsed ‘ from plaster. Simple wooden patterns need no further description, as long as the resulting castings include the principal detail and enclose the outline of the required part, once the casting has been produced only straight forward machining operations will be required to produce the required component. Of course the amount of machining has to be limited to work that can be carried out with the equipment available in the workshop. Firms producing castings have readily accepted and cast from my simple patterns.

Plaster patterns can be simply produced for the most complicated parts and will provide the one or two uses required for most model casting needs. Regarding the ‘ horsing ‘ of plaster to produce circular work such as wheels, this is an age-old skill yet one which has often been overlooked. The technique which was used for the smokebox rings for Pixie involves the preparation of a sheet metal template of the required section ( plasterers use galvanised material, but for our short-lived requirements any sheet will do ). The template is furnished with a pin which can be inserted into a piece of plate, large enough to accommodate the required pattern. The plate is very lightly oiled and the oil wiped away to leave just a suspicion of greasiness and the plaster laid approximately to the required shape. Judicious ‘ horsing ‘( scraping ) with the template around the pin generates a plaster master which when hard and coated with two or three coats of shellac or paint can be used to produce several castings. In each case the necessary allowances must be made for shrinkage, and it has to be remembered the finished casting will reflect faithfully the standard of finish imparted to the pattern.

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Chapter 6

Planning. Model engineering with pencil and paper. Machining sequence. Fabrication vs. the use of castings. Use of models, mock-ups, jigs and templates.

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Sketches to indicate approach to making axleboxes, hornblocks and dieblock guides for the model of Pixie

Getting Started

With a portfolio of dimensioned sketches and a considerable number of photographs under the belt it is time to make a start on planning the model. This is the time to do some taking-off of materials, not only establishing immediate needs but listing and probably budgeting for, the future. Ours is fortunately a long term hobby, and there are many facets to each project. Once the main equipment has been bought or made or at least a way of accessing equipment has been established, perhaps via a local evening class or community centre, the materials for a model can be bought in step with progress in making the model. This is a major economic ‘ plus ‘, bearing in mind the cost of materials, particularly the more exotic ones, such as stainless steel and phosphor bronze for which there are few serviceable replacements.

It is decision time once again! Looking through our sketches and visualising the model it becomes necessary to determine whether standard castings that approximate to those required for the model are to be used or modified, or whether parts will be fabricated from raw materials. The alternative, and this may be time consuming, is to have castings made from patterns which will be time consuming to produce. Fortunately much of this deliberation can be carried out away from the workshop, in the lounge whilst others watch the television, or during boring business meetings, there is no end to the scope! In practice, a lot of thinking can be done in the workshop or garage where the materials can be handled and their possibilities pondered. Pixie’s chimney was turned from reinforcing steel from a building site, the platework once comprised the instrument panel on a piece of control equipment, the chassis for the driving trolley was in a previous existence part of a steel door, and so on. In many instances a considerable amount of work was required to rework the material and prepare it for the operations that would transform it into a part of the model. Often a whole evening’s modelling time was spent in sawing or shaping ‘ rough stuff ‘ to a stage where marking out and the work of machining proper could be commenced. It adds to the pleasure obtained from the hobby to be economic with materials and be prepared to do some re-cycling!

Pencil And Paper

The scrap pad or the notebook is a vital tool in model engineering. Time spent, pencil in hand will yield immense savings in the time required to produce parts for a model. No matter what our artistic abilities, as long as WE can understand our notes and sketches that is all that really matters! Sketches of the parts required for the model, ideally full size, worked-up from our details and dimensions, will give us a feeling for their eventual shape, size and ‘ heft ‘. With a sensible sketch in hand a start can be made on figuring out the material requirements, and visualising key operations in producing the part. Some of the operations will be those standard operations described so often, and so capably, by the expert writers in the model journals. These replicate to a large degree the actual methods used in the construction of the prototype. In many instances however because of the implications of available equipment or available material we have to be our own method engineer and consultant combined, and devise original techniques. The methods so arrived at may not of course be completely original, modellers have a saying that there is a precedent for everything. Whatever we re-invent however will give us immense satisfaction when successfully put into practice.

Working Details

Whether, or not, to produce scale drawings will depend upon individual preference, The writer works from sketches prepared from the site sketches, often after making several different sketch views of the item as described elsewhere. For detail which is critical mechanically, such as valve gear and motion work, measured drawings are made at the drawing board ( Well actually the pastry board! ), often twice full size. These can be used in conjunction with cut-card components to establish valve events, critical clearances etc.

The amount of drawings prepared will depend upon one’s skill with pencil and paper, and indeed on one’s particular interests. We all tackle jobs differently. In the case of ‘ Pixie ‘ many sketches were made, from all viewpoints. After some time spent in this way the part can probably be drawn from memory . This is very helpful when it comes to the time to decide upon the materials and methods to be employed, also in the course of work in the workshop. Some modellers are happier cutting metal but even they will have to sort out the overall sizes and details to enable the selection of an appropriate piece of stock. Working from the dimensions obtained during the survey each part may be sketched, as near to model size as possible. Some modellers may prefer to use one of the lap-top drawing boards complete with miniature drafting machine, others may even use a computer with a CAD programme. The writer prefers to work in sketch form on a pad of A4 paper, this can be done virtually anywhere, even in the bath!

It is worthwhile making a series of sketches of the part in the various stages of production. In this way the sequence of operations in producing the part can be visualised and suitable chucking or fixing points provided. Choice of a poor sequence of operations can make completion of machining difficult or even result in the production of a substandard finish. Ideally, once a part is set into a chuck or mounted in a fixture it should only be removed once operations critical to concentricity or line are completed. Re-chucking a part causes problems, especially for newcomers in their early days in the hobby. Turned mandrels are often the solution to the problem and the need for these, and suitable jigs to hold small parts for finishing operations, will become apparent on paper as each stage of production is examined in detail.

As an aside, a fixture which the model engineer may like to use as a design exercise is a means of supporting 3 jaw or 4 jaw chucks, and faceplates OFF the lathe. As well as allowing set-ups to be established in comfort on the workbench, such a fitting is useful in holding material whilst setting out and during milling operations. The lathe manufacturer generally offers as an accessory a threaded mandrel replicating the headstock thread and it is a simple matter to attach this to a backplate drilled to match the slots on the top table of the lathe, the milling machine, drilling machine etc. Make a few sketches, dig out the necessary plate from the scrap box, buy, or better still, fabricate a replica of the spindle nose. A suitably threaded nosepiece can cut from a spare intended for use in the tailstock, leaving a useful No 2 Morse taper mandrel which can subsequently be drilled and tapped for use as a backstop when machining thin discs in the 3 or 4 jaw chuck. The result, provided care is taken to ensure accuracy of the fixture, as well as providing an exercise in sketching, simple method engineering and some turning and fabrication work, is a most useful piece of workshop equipment.

Scaling Dimensions - Scaledness

There will be occasions where small adjustments or a compromise has to be made between dimensions established from survey and those to which the model parts are eventually prepared. These adjustments may be required to simplify something which otherwise would be over complicated to manufacture with the means at one’s disposal, to overcome erection difficulties or to ensure that model parts are sufficiently robust to be durable in service. Where a scale 4” axle may be required the writer has no qualms about using the nearest available stock size, in this case, to 2 1/2 inch to the foot scale, 0.875 diameter. This is not laziness, or a reluctance to spend time on a machining operation, rather it constitutes the approach taken in value engineering. Time saved by eliminating the machining operation may well be put to better advantage preparing some other more critical part. Whilst this approach may not suit the purist, it is one that most people will find they can live with !

Instances of compromise made in the course of constructing the model of PIXIE were increased thickness of the plates used for frames and some thinning of parts of the motion. There were one or two other situations such as the axles where, as noted above, stock bar was used rather than material turned to scale diameter. The amount of adjustments made by the individual will be determined by personal preference and standards. At one stage consideration was given to the unprototypical move of splitting the smokebox horizontally, making the top half removable in order to facilitate access for installing the blast pipe, wet header and so on. Even in 2 1/2 “ to the foot scale it is difficult to get fingers and especially spanners to the fittings for the blower and such items within the smokebox. Some thought was given to Martin Evans comments in ‘ Manual of Model Steam Locomotive Construction ‘ where he recommends split smokeboxes, in that instance for 1” scale locomotives. Eventually the decision was taken to use a piece of large diameter steel steam pipe, turned to size, and in the event after much fiddling and bruised knuckles the exhaust pipes were ‘ persuaded ‘ into place. The decision has been regretted since however, as the substantial exhaust pipes and blower ring make it difficult to sweep the boiler tubes. A rebuild would include a split smokebox !

Fabrication vs. Castings

As our working sketches develop we will be better placed to visualise the finished part in model form. as our prototype is a narrow gauge locomotive if we are working in 2 1/2” to the foot scale we are drawing components which are, linearly speaking, approximately 1/6th full size. The finished model parts will be quite substantial and correspondingly weighty. It may well be that if we are constructing a model of an unusual prototype, and one for which there are few commercially available part, we may choose to fabricate components rather than make patterns for our local foundry. The coupling blocks and weighshaft brackets for Pixie were unusual to a degree and it being unlikely that more than two uses would be obtained from patterns, these items were fabricated. Such castings as were bought-in were cast from simplified patterns or, in the case of the horns, were modifications of castings produced commercially for other prototypes. Fabrication allows for economic use of material and in some instances economical use of available time. Pattern making is a time consuming, although enjoyable pastime, offering as it does a change from metal working practice and it does provide another most interesting avenue or aspect of manufacturing technology to be explored. Where club membership provides contact with other enthusiasts it may well prove worthwhile spending time making conventional patterns when the use can be shared with fellow members. Equally if a batch of locomotives were in course of construction then patterns providing multiple casts would be favourite.

Models, Mock-Ups ( And Test Pieces )

The mock-up is an essential stage in automotive, aircraft and many types of full size engineering.Due to small discrepancies in scaling of parts, or the accuracy of our production, it becomes increasingly essential in our model making, . As production of our model parts proceeds models ‘ mock-ups ‘ help us to ensure proper fits in the final erection stage. For ‘ Pixie ‘ a card model was made and superimposed on the general assembly sketch of the frames and cylinder casting to determine acceptable events in the valve settings. A model of the boiler fabricated from stout card was used to ensure that the boiler, as detailed, could be fitted between the frames. A further model of the saddle tank proved the position of the mounting brackets on the boiler, and so on.

On a larger scale, a dexion angle mock-up was made of the driving trolley to ensure a comfortable seating position with access to the controls, this was subsequently translated into the trolley described in Ch xx and has proved to be safe, stable and comfortable in service.

Model assemblies are especially important if, as in the case of the model of PIXIE, parts are being made from a series of sketches rather than a full set of finished drawings. There are however a number of instances such as those quoted where details can be proved ‘ in the round ‘ in mock up form, a task which would account for no little amount of head scratching in the two dimensions of a drawing. Apart from the technical reasons calling for the use of mock-ups there is a great deal of satisfaction to be obtained from the preview of the finished article presented by even the simplest model!

Where some new material or technique is to be employed, time spent on a test piece or pieces is time well spent. instances where tests were performed in the production of Pixie were the trial flanging of the mild steel used for the sandboxes and the saddle tank, particularly the formation of the joggle sketched where the tank plates overlap. Trial rivet formation, used in producing the rivets for the main frame angles, a trial pressing of brass sheet between wooden formers indicated that the technique could be used in making the steam and exhaust pipe covers which have to fit snugly to the steam chests and smokebox. Unusually, in the case of these covers the second trial piece was found to be of sufficiently good standard to be used in the finished model !

Jigs And Templates

Jigs will be required to locate parts for some of the operations such as milling and silver soldering. Time spent in producing a simple jig will be repaid by the ease and speed with which the most difficult operations can be carried out. Jigs, used to locate parts in their correct position, do away with the chancy set-ups which are sometimes attempted, using odd bits of metal or wire to hold pieces for soldering, or the sometimes makeshift clamping arrangements to hold metal during machining. A simple jig permits work to be carried out accurately with the correct application of cutting force or allows brazing to be done whilst avoiding the odd movements whilst the metal is being brought up to heat for jointing.

An example of a simple jig is that used whilst soldering the components of the exhaust pipes for Pixie.

A piece of stock mild steel from the scrap box was marked out to replicate the position of the bolts fixing the exhaust pipe flanges to the cylinder casting. The key points of the set out were transferred using calipers and scribing lines on marking blue. A further piece of mild steel was welded centrally to provide a mounting for a bracket which in its turn secured a piece of studding to locate the junction piece where the two pipes join. The exhaust pipes passed through the flanges and were cut to the correct profile to seat onto the junction block. The whole of the jig was oxydised to prevent the flanges becoming soldered solid with their supports ! The flange bolts and those securing the two parts of the junction block were also oxidised. The exhaust parts were thoroughly cleaned and flux was applied before being assembled into the jig. The assembly was made using the preprepared bolts. The joints were then made with one heating, sure in the knowledge that the flanges of the finished components would match the fixing holes and the assembly would seat properly without strain.

Whilst discussing jigs, ties and packing are worthy of mention. For accuracy, jigs must be securely fixed to the bed of a machine. This will be facilitated if suitable tie bolts and packings are handy. It is well worthwhile assembling an assortment of lengths of studding to match tee-nuts suited to the tee slots in the lathe saddle and vertical slide as well as the bed of the milling machine and rotary table if available. Time will then be saved when securing work for operations such as boring and fly-cutting. Studding for the purpose can be purchased relatively cheaply from the trade, tee-slot material can be bought by the length for machining in the home workshop. Short offcuts of bar should be marked with their size for quick recognition and set aside for use as packings. Marking using a punch on the end of the stock will avoid problems caused by the local ‘ upset ‘ arising from the punching operation. Often trade suppliers sell such offcuts by the kilo containing a range of useful sizes which are ideal for use as packing pieces.

Templates were produced for the machining operations on the horn castings, the drilling of items such as the steam chest covers, the drillings in the steam dome bush, the foundation ring and the cylinder covers. LBSC’s advice was followed in the course of the platework and plumbing. A stiff wire was bent around flanged plates to give the width of plate required. Similarly, wire was also used to establish the route of the pipework and when re-straightened gave the lengths of pipe required. Templates were made for any offhand turning such as that for the cylinder covers, dome, chimney base and so on, ensuring that the required geometry was attained. time spent in thinking through jigging operations and the provision of templates will be amply repaid in ease of operation and the avoidance of scrap.

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Chapter 7

Frames, stretchers, horns and axleboxes. Wheels, axles, crankpins and quartering. Coupling rods and bearings. Brake hangers and blocks.

Pixie’s frames and a start on the motion

Making A Start

So now the time has come, to make a start on machining parts for the locomotive we have so carefully chosen and, on visits to site, measured, photographed and generally fussed over! In the workshop it will be necessary to make constant referance to the database, A plastic folder will hold and preserve the measured sketches from survey and our sketches pertaining to the parts to be tackled. A sheet of perspex in front of a striplight can be used for viewing transparencies which are clipped in place using butterfly clips. It also makes sense to provide some means of retaining photographs of the relevant pieces so that they can be viewed without being handled with ‘ workshop hands ‘. A piece of ply with some criss-cross tapes as used to hold letters in an hotel foyer will enable the photos currently in use to be displayed on the workshop wall.

Whilst your subcontractor is casting the wheels from your patterns it is a good thing to make a start on the frames. Handling the raw steel for a 5 inch gauge locomotive gives a good impression of the eventual size and ‘ heft’ of the finished frames. Our supplier came up with a length of ‘ Black steel ‘. This has an extremely tough surface and is quite difficult to work. Luckily, in this case , a friend undertook to surface-grind the material and it came back shining bright with the hard crust removed. It can prove helpful to carry a small file with you when you visit your supplier, if you are in any doubt about the workability of materials, a few strokes of the file ( on the metal! ) will tell a great deal.

Regarding thickness of frame material, whilst this may be accurately scaled from the prototype it may prove advantagous to beef-up the frames somewhat. Those on Pixie are from material which after surface grinding worked up to just over 5/ 32 inch thick which is in line with Martin Evan’s recommendations for 5 inch gauge locomotives in his ‘ Manual of Model Steam Locomotive Construction’

Marking-Out

The first and perhaps the most critical operation is that of marking-out. The tools for use in marking out frames are basic, a square, a clearly marked steel rule, a good true straight edge and a sharp scriber ( the latter two items can be home produced ). If a marking die which comes as a laquer to be applied by brush is used, the coating thus formed can, with care, be scribed lightly to make an impression without actually marking the steel. Remarkably the lines thus scribed can be ‘ felt ‘ using the tip of a sharp centre punch and will guide the punch to points of intersection where a punchmark is needed. An automatic punch which can be adjusted to make various depths of indentation and accommodate differing surface hardnesses is a useful tool. The blue can be left on the metal until all necessary machining is completed then wiped away with a rag soaked in methylated spirit. Where heat is generated whilst the blue is on metal the marks may require some stronger treatment such as a rub with emery cloth or wire wool.

Marking-out is best carried out using running dimensions, as used in the survey, to mark stations along the frames. Running dimensions are taken from one datum in each case and avoid build-up of dimensional errors and consequent innaccuracy likely to be encountered where a series of discrete dimensions are used. The square is used ( from a true edge of the frame steel ) to mark perpendiculars and then dividers or a calipers to set up offsets from the base line. Perhaps it goes without saying that the initial set-out should be checked for errors, it would be a pity to spoil valuable metal and waste valuable time by errors in setting out.

Care must be taken at this stage to establish the centreline of the axles in their running position, both vertically and longitudinally, centre pops either side of the eventual position of the horn openings will provide a means of establishing the axle position and determining the cylinder location, inclination and so on when the actual centre will have been machined away.

Cutting Metal

Frame steel usually requires cutting to both length and width, a hard job but one made easier by rotating the hacksaw blade through 90 degrees in the frame and mounting the frame material in the vice together with a stock bar to act as a guide.This substantial stock bar inserted into the jaws behind the frame steel acts as both a guide for the saw and a stiffener retaining the long materials Aword here about the number of teeth on the hacksaw blade, and the blade tension, good quality blades generallybear a lael indicatingthe thickness of metal they are designed to cut. Selection of the correct number of tethmakes all the difference to tthe ease, or otherwise of the tsk in hand. Once the blade has been brought to initial tension about three complete turns of the thumbscrew generally suffices to set the correct blade tension. incorrect tension can be recognised when a cut starts townder from the ‘ straight and narrow ‘. One last thought on technique, for years we will have been tutored to use the forefinger of the hand gripping the handle pointed forward, ‘ to guide the cut ‘ in the case of a wood saw. This action courts disaster in the case of the hacksaw, as the finger is liable to be the first point of contact with raw mtall in the case of blade breakage ! Long cuts such as those required for the frame profiles give time to think out the next move as well as providing some exercise to counteract some of the less energetic workshop activities! With the nett length and width established the frames can be cut to profile. A fairly recent alternative to all this hard work is offered by the trade, in the form of laser cut frames. There is an added bonus in this approach as the supplier will spot most of the holes ready for drilling. Accounts in the model press have been extremely complimentary about the prompt an acurate service offered by the one or two lazer-cutting specialists.

The front and back plates follow, again sawn to shape. Where shapes such as those required on the front plate are required, these can be produced by chain drilling and subsequent sawing. The profile of the frame members can be tidied up by draw filing and all is then set for detailed marking out of holes positions for rivets, horns and similar details. The side frame members should be bolted together at this stage using countersunk headed bolts (countersunk to allow the material to be layed flat on the bench for marking out, and more importantly flat on the bed of the drilling and milling machines during subsequent operations )

At this stage the key lines of the motionwork should be established, for this purpose the frames may be coated in marking fluid from behind the front plate to the line of the back axle or some stout paper glued in place. The first line will be that of the axis of the cylinder which will be set to coincide with the centre of the driving axle at its running position. This line established, the location of the cylinder block can be set out and the position of the slide bar indicated. The motion plate fixing holes can now be spotted with the motion plate normal to the slide bars. The critical angle of between the axis of the cylinder and the top of the steam chest can be measured and a template prepared for use in setting up that casting for machining at a later stage. All this is done using dimensions taken during the site survey. Later the critical sizes of the connecting rods, the valve rods and the piston rods will be established.

A Jig For The Wheel Centres

At an early stage in the marking operation it is well worthwhile taking time out to make a simple jig to the dimensions of the wheel centres. This jig can be used to mark the wheel centres on the frames, to locate the wheel bearings and to replicate these centres exactly when making the coupling rods. Having set out the wheel centres and drilled pilot holes in the jig, it should be hardened and set it aside for future use.

Drilling The Frames

With all holes marked out and punched they can be spotted accurately using a centre bitt. This is followed by drilling using a succession of bitts up to the required, final size. Any slight innaccuracies can be corrected at an intermediate stage by drawing wrongly placed holes by centre-punching the edge of the hole on the edge to which the drill bitt has to be drawn during one of the intermediate drilling stages. Often the correct procedure for drilling holes, that of using a series of drills up to the finished size of hole, is omitted. Where this procedure is followed the opportunity for correcting the occasional wrongly positioned hole is forfeited,also the finished hole, unless reamed, is likely to be oversized.. On frames of this size it will be advisable to add further bolts to hold the frames together as work proceeds.

Horn locations can be spotted and opened out by drilling and sawing, finishing with a file or by milling. With only two pairs of horns to cater for in the case of an 0-4-0 filing is not too arduous a process!.

Frame Angles

Whilst standard mild steel angle was used for the frame angles they were trued up by milling along one outer face to render them ‘ die square’ to ensure that once they had been rivetted into position, the joints between frame members came up square. The angles were rivetted to the frames taking care that the top of the angle steel was quite flush with the top of the frame members.

Buffer Beam And Drag Beam

These were cut from the same material as the frames, somewhat overscale but substantial. The positions of the holes for rivets were spotted through from the frame angles whilst the whole assembly, frames and beams were held together by instrument makers clamps. The actual erection / assembly process was carried out on the bed of the lathe to ensure absulute accuracy of plane. On PIXIE as distinct from many standard gauge locomotives, the head of all rivets on the beams are countersunk. This was replicated on Pixie as were the rivet heads described earlier. There are a number of holes in the beams which give witness to various modifications made during service, although surveyed these were ignored at this stage but will be incorporated later to add to the authenticity of the model.

Frame Stays

The frame stays on PIXIE are castings, these are reproduced by fabrication to save the time which would otherwise have been spent in making patterns. The flanges and fillets were shaped, pinned and held together with wire during silver soldering. Having learned the technique,silver solder is generally used to join items where strength is required. A word here about silver soldering. When first starting model engineering great difficulty was experienced in obtaining sound, clean joints.Fortunately however, a friend arranged for a brief training session with a dear old ‘ Gent ‘ in the local engineering works. He emphasized the importance of degreasing the materials to be joined, and the need for an adequate source of heat as well as the conservation of this heat by strategically placed firebricks. “ Watch the flux,” he said, “ When it liquifies, touch the solder to the metal and see it ‘ flash ‘ into the joint! “ Among other tips which he passed on in the course of the brief session was that of making small centre pop marks on surfaces to be joined. The slight raising about the pop mark ensures a minute space between the two parts being joined into which the molten solder is drawn by capilliary action. The solder always flows towards the hottest component in the joint, a point which will prove of assistance when making a difficult joint. For pickle, follow Ted Jolliffe’s advice in MODEL ENGINEER and use a solution of citric acid crystals in water. This is generally as effective as acid pickle and far safer to have about the workshop and safer in disposal. The crystals can be obtained in any shop specialising in home brewing equipment.

Many narrow gauge locomotives have distinctive frame details, in the case of PIXIE it is the stiffening angles at the top of the side frames, attached by prominent, large diameter rivets. Having had difficulty in the past with forming rivets to any degree of consistency, and, realising that the results achieved here would greatly effect the final appearance of the locomotive, it was decided to fabricate the rivets.The formed end and shank of the rivets were turned from mild steel rod. The formed end was held in place using a conventional ‘ Snap ‘ whilst the shank was peened into a countersink formed in the dummy cone head. In the case of the ‘ rivets used to fix spreaders between the frames, these were in fact bolts with their heads turned to rivet profile. The cone head was made seperately, tapped to suit the thread on the shank and the fixing was made by tightening head using a specially made socket spanner, furnished with a pin which registered with a hole in the cone. A miniature tommy bar assisted in the tightening process and prior to final assembly the threads were annointed with locktite ‘ screwfix ‘. Elswhere on the frames, such as at the angles connecting the beams with frame members, standard black iron rivets were used, the shanks being peened into countersunk holes in heads, again produced seperately but drilled and countersunk rather than tapped. on completion of the peening processs, the ends of the shanks were and filed flush with the face of the ‘ heads ‘

Horns

The axles on PIXIE run in heavy, sprung axleboxes, riding in cast horns. Consultation with Peter, a mine of information, at that time major domo at Messrs Kennion, in Hertford, revealed that some gunmetal castings, which they held in stock, would provide suitably shaped material which with further additions by silver soldering and subsequent machining could be made to replicate those on the full size locomotive. These operations were carried out, prior to the aquisition of a milling machine, on the lathe using a simple jig to assist in work holding. It seems that we amateurs do not make enough use of jigs and fittings, so much a feature of full-size practice. Where we need two similar components, and especially where there are four or more items then construction of a simple jig is well worthwhile, not the least from the safety aspect. Record has it that, in the course of machining materials for an earlier locomotive, one part flew out of a makeshift attachment and left the workshop through a ( fortunately open ) window. Jigs and fittings may take time, they can frequently be fabricated from scrap, and set aside, can often be re-used, albeit with some modification, for further work of a similar nature. Some tasks simply cannot be done without jigs or fittings, for example, to attempt turning a wheelset to size without a suitable mandrel would result in failure. Many other jobs will benefit from the time and thought employed in producing similar simple tools.

At this stage a start was made on machining the horns, the worst of the rough texture of the casting having been removed by filing, the outside face of each was cleaned up by facing cuts made using this tool with the horn mounted in the four-jaw chuck. A tungsten carbide tipped tool is kept specially for such operations, it is a rugged tool produced for a lathe much more substantial than the Myford. It is set on packing blocks under the holder intended to retain tools in the Myford ‘ boat ‘ nd is capable of giving castings big licks, provided that is that they are securely fixed! The flat face produced in this fashion was then used as a datum whilst bringing the castings to finished thickness. Centrelines were established and the axlebox openings milled to slightly less thaan drawing size, some work with a fine file squared up the radiussed internal corners left from the milling operation. It was now necessary to solder onto the bottom of each horn a flange piece for later attachment of the hornstay. A jig was made to facilitate the final machining of the horns, it consisted of a backplate which could be mounted on the vertical slide ( those with a milling machine can of course use a similar jig ), fitted with a pad of steel representing the axlebox and having a cover plate which in effect formed a flange retaining the horn in position. Each horn in turn was set onto the jig whilst the bolting face of the horn was machined back by the thickness of the main frame members. The horns were then reversed on the jig and a small diameter end mill used to tidy up the back faces, around the fillets. Each horn was filed to shape and drilled, again on the jig, for the bolts which secure it to the frames. These bolts must have the heads thinned down. Although the slight recess in the back of the wheels provides ample clearance with the axles in their running position it has to be remembered that the completed wheel sets have to be assembled onto the frames and full-sized heads would prohibit this.

Equalisation

Consideration was given to making working springing. It was decided however to use the simple suspension achieved by the use of a hard rubber block as adopted on ‘ Sweet Pea’. Dummy springs were milled from brass block, these were enclosed in a fabricated band of mild steel and the whole drilled with a clearance hole for the tie rods which are screwed into the axleboxes. In practice the rudimentary springing arrangement serves the purpose of keeping all four wheels in contact with the track, at least on my track, described later, which is portable and can thus be packed to a good level when being set out in the garden. The spring mounting brackets were machine from the solid, again by milling in the lathe.

On Milling

Considerable amounts of milling work can be carried out in the lathe. To obtain the best results it is worth investing in a substantial vertical slide, preferably one incorporating a swivel action. Lateral support for the vertical slide can be taken from the tailstock quill and for heavy work the slide can be packed up from the top slide. Even without a vertical slide, a lot of useful milling can be done on materials either secured to the topslide using steel packings and strong clamps or in the case of smaller items clamped in the lathe tool holder. A range of end milling cutters and slot drills will prove useful in forthcoming operations. Contact with a local engineering works may yield a supply of used cutters which although past their useful life in the course of rigourous production work can prove useful in the amateur workshop.

As a result of the ‘ crick in the neck ‘ resulting from time spent viewing the milling cutter at work on material held in a vice on the vertical slide, that the decision was made to purchase a milling machine! A visit to the Model Engineering Exhibition afforded an opportunity to compare machines, and prices. Fortunately for the model engineer the exhibitors often make special offers on equipment and tools at the exhibition , and many are prepared to quote a special price if approached. For the occasional light machining that I was contemplating, a imported machine appeared to fill the bill, and as the price reached after some discussion, and comparison with other suppliers, was within my budget one was duly purchased.

With care in mounting the work, controlled application of cutting force, the use of sharp tools and other simple precautions the machine has proved to be a good investment. I also use it in woodworking, for grooving, routing and so on. It is invaluable as in the construction of hollow masts for model yachts, and similar tasks.The collet chuck is essential in achieving rigidity by reducing the projection of the quill from within the head of the machine. In the absence of an autolock chuck it is advisable to ‘ key ‘ cutters into the collets to avoid draw-out of the bitt during the cutting operation. As in all milling operations on such light machines it is important to avoid step milling, or moving the material being machined in the direction of rotation of the cutter, with the tendency of the cutter to climb onto the work. Either of these actions whilst using a light machine are likely to result in snatch with the possibility of damaged tools or worse! . Purchase of the milling machine called for a rotary table and a kit of parts or completed table which has proved quite adequate for the task is marketted by an advertiser in MODEL ENGINEER. Purchase in the completed form, saved valuable time which I could spend in model engineering, this saving more than outweighed the extra cost of a fabricated table. The table has been a great help in many instances from the finishing of valve spindle forks to simple dividing. When rounding ends of connecting rods and similar operations it is important to hold the work securely, and to rotate the work against the rotation of the cutter, failure to observe this rule can result in snatch and possibly injury.

Axleboxes

The axleboxes were made in two stages, a phosphor bronze bar sufficiently long to yield four individual axleboxes was machined to a tee-shaped section, the main stem of the tee, being a few thou’ wider than the horn openings. The limbs of the tee formed one pair of flanges. The axleboxes were parted off using a slitting saw on a simple mandril in the three jaw chuck. A further phosphor bronze plate was then prepared to form the second, inside flange of each box This method of construction whilst, on the face of things appearing laborious, permits a good fit to be simply achieved in the next operation, that of filing to an individual fit in each hornblock and ensuring a good slide fit between the cheeks of the hornblock. The wearing surface so formed was filed slightly convex to avoid binding when the axleboxes move as the rubber springing blocks become compressed as the locomotive rides innacuracies in the track. The second flange face was now fixed into position using countersunk screws. Each axlebox was next drilled and bored to suit the silver steel used for axles, oilways were cut in each bore and the lubrication holes conveying oill to the axle and to the axleboxehorn surfaces were then drilled.

Wheels

The wheel castings were in grey cast iron, and remarkably free from casting sand which, if not removed, can quickly take the edge off tools. The castings were mounted in the four jaw and the back face turned until the wheel thickness was .03 inch more than the required finished thickness of the wheel at the boss. At this stage the recess in the back of the wheel, noted during the survey, was machined. This recess provides clearance for the heads of the bolts retaining the horns in the frames. With the back turned to profile the central hole in each wheel was drilled, first with a centre bitt then using successively larger bitts to the stage where it could be reamed to final size.

A plate mandrel was now built from materials from the scrapbox, a short length of 1 inch diameter rod and a disc of mild steel slightly smaller in diameter than the flange dimension of the wheels. The rod formed a stout chucking piece to be gripped in the three jaw and was set to protrude through the plate in order to provide a mounting pin for the reamed wheel bores. The mandril having been turned true its outer face was lightly relieved so that the wheels would bear only around the edge. Care was taken to avoid any fillet at the root of the pin, which would have prevented the wheel casting seating properly. The mounting pin was drilled and tapped, using only first and second taps, and slit so that, when a bolt was inserted and tightened to the extent of the thread, the wheel casting would be firmly located and prevented from revolving under the force of the cutting tool.ith some wheel patterns the existence of a through hole, or the space between spokes may allow the insertion of a stud to further prevent the wheel turning on the mandril. After the mandril was inserted in the three-jaw a reference mark was punched on the rim coincident with the centre of No. 1 Jaw. During the following operations a watch was kept on this to ensure that it had not moved. The mandril was not disturbed until further work on all the wheels was finished. The mandril has now joined the various jigs, collets and templates retained for future use.

Each wheel in turn was mounted on the mandril, face outwards, for the flange to be turned and the tread coned. The old chestnut that coning allows for differential travel of wheels on a curve has often been debated, whether it does or not it certainly assists in maintaining an 0-4-0 centred on the track and may well reduce the tendency of the locomotive to yaw. Here we are reminded of report of the Board of Trade Inspector, Captain H W Tyler on the Talyllin Railway of September 1866 regarding the ‘horizontal oscillation’ of the one locomotive available to steam the line. 0-4-0 locomotives, particularly those with short wheelbase and substantial overhangs are likely to ‘oscillate’ and any means which may help to reduce this tendency is welcome. Recent reports in MODEL ENGINEER describe the free running of coned wheels compared with those having parallel treads when set to ‘ freewheel ‘ down a curved gradient, another item of food for thought. Coning completed, the radius between the tread and flange was turned using a tool ground to the correct form, the flanges were rounded by filing, (using a file with a proper handle ) and the chamfer put onto the edge of the tread using a sharp tool. Prior to removing each wheel from the mandril, the retaining bolt was removed and a final light cut was taken over the boss. A line was then lightly scribed across the centre of the wheel and the boss for use in locating the crankpin holes. In order to drill these holes, accurately located and perpendicular to the face of the wheel, each of the wheels were supported on two parallel pieces of stock bar in the drilling machine. A hardened drilling jig with an accurately located guide hole was located onto a fitted steel pin, set into the bore of the wheel and clamped into position with reference to the lines scribed whilst the wheel was on the mandril. Each hole was then drilled in the drill press and subsequently reamed to suit the crankpin, the reaming operation being completed on the same setup.

Axles

It was convenient to use silver steel for the axles, as discussed earlier the stock size selected approximated to the scale dimension. The axles were sawn slightly over length then, after turning to nett length, centres were formed in each end for subsequent turning operations. PIXIE has plain axles with just two shoulders, one bearing against the back of the axlebox, locating the axle transversely, the other acting as a spacer bears against the back the wheel. The shoulders and bearing surfaces were turned and, after re-touching the tools with a stone, brought to a fine finish. As the wheels were to be fixed using retaining fluid, the axle seatings were machined to leave a full thou’ of clearance within the reamed bore of the wheels. Later the joints would be further secured by pins pressed into holes drilled half in the wheel casting and half in the axle

Crankpins

Crankpins are of silver steel with turned shoulders to determine the length of projection. Here a slight departure from prototype was made, the outer end was drilled and tapped to permit a separate retaining flange to be screwed into place. In the case of the model Pixie this permitted the marine type bearings to be made in one piece with a dummy joint face as described later. In service the heads are secured by a touch of retaining fluid on the screw as it is turned home into the crankpin. The crankpins are secured by pins pressed into holes drilled half in the wheels and half in the crankpins. This is particularly important in the case of the crankpins on the rear wheels, to maintain the truth of the return crank setting.

Quartering

A variety of methods for quartering wheels have been described in MODEL ENGINEER over the years and choice must be a personal thing. The wheels for Pixie were quartered using twin plate templates accurately squared-up as a pair, bolted together, and holes drilled and reamed at the axle centres and crankpin positions. Holes were drilled at each corner of the plates for tie bolts used to drive the wheels into position on the axles. These plates were used in conjunction with a turned stub-centre of the same diameter as the wheel bore mounted in the tailstock Jacobs chuck. The centre was located in the tailstock chuck to facilitate access to the tie nuts in the next operation. The crankpins were first fitted into the wheels, using LOCKTITE, the bond being reinforced by a pin fitted into a hole drilled half in the crankpin and half in the wheel casting. One wheel of each pair was set onto its axle using locktite and the joint allowed to cure. The axle with the one wheel ( and with axleboxes installed!) was then positioned within the ‘ jacking frame ‘ formed by the two templates and the four jacking screws. The previously turned centres in the axles engaged on the point of a standard lathe centre at the headstock whilst the tailstock centre was engaged into the previously machined stub centre. At this stage the loose wheel, whilst supported by the stub centre had its bore slightly engaged on the axle end. The bottom edge of each of the templates was packed up, on a common bearing plate, to ensure they remainded correctly aligned in the next operation, that of feeding the wheel into place on the axle. The exposed bearing surface of the axle where the wheel was to seat was annointed with LOCKTITE as far as the shoulder and the nuts on the tie rods were quickly tightened, taking a few turns on each in rotation. The wheel was thus transferred from the stub centre into its correct location against the shoulder on the axles. Accurate quartering was ensured as the crankpins were correctly located by the plate templates which were retained in position by the carefully levelled packings. Once the LOCKTITE had cured each wheel was secured onto its axle by a pin, half in the wheel and half in the axle.

On reflection the work could have been simplified by using a smaller centre slipped into the tailstock sleeve, this would have supported the axle without the need for the roduction of a stub centre. Whilst the first described method worked satisfactorily, it is typical of the model engineering hobby that improvements, or at least modifications of method occur in the course of an operation. This is one of the reasons that the journals devoted to model engineering are so valuable, they form the forum for the transfer of ideas and new improved methods and are akin to the commercial concerns research and development department!

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Chapter 8

Coupling rods and bearings. Brake hangers and blocks. Lubricator and mounting plate. Coupling blocks. Footplates, support brackets and angles.

Motionwork on Prototype

Coupling Rods And Bearings

’ PIXIE ‘ has round-section coupling rods terminating in marine bearings at each end. The coupling rods for ‘ Pixie ‘ are made from lengths of silver steel, shouldered and entered into the bolting flanges at each end. These joints were brazed and the faces cleaned up. The bearings were simulated on ‘ Pixie ‘using blocks milled from mild steel incorporating the profile of the prototype castings. Each block is scribed deeply to represent the joint between the two parts of the bearing and each crankpin hole is fitted with a pressed-in phosphor bronze bush. The length of the coupling rods was checked against the wheel centre template made earlier. Small adjustments were required at this stage, due no doubt to minor differences in dimension at each joint. Adjustment was achieved by turning-off the inner ends of the bearing blocks in the four-jaw chuck. To complete each assembly, matching keeper plates were filed to shape, clamped in place on the coupling rod ends together with the bearing blocks and the whole assembly was then drilled for bolting. mm size bolts were found to be very near to the required diameter and these were used, the heads being turned to the shape of those on ‘ PIXIE ‘. The thread ends were turned away and the bolts drilled for split pins. Oil cups are fitted to each bearing block. For ‘ Pixie ‘ these were machined from brass hexagonal material, which provided the flats by which the cup is screwed into the block. A small form tool ground up from a slip of toolsteel ensured the same ‘antique’ profile to each cup. The cups are topped off by a threaded cap screwed into place, these were reproduced by turning down the heads of BA bolts and knurling the periphery of the resulting head. It was noted at the time of the first survey that any missing caps were replaced by corks, as yet no caps have gone missing from Pixie so this has not been necessary! Each of the upper bearing bolts has a turned groove coincident with the oil cup to allow lubricant to penetrate to the bearing surfaces.

Brake Hangers And Blocks

On ‘ PIXIE ‘, braking arrangements are simple in the extreme, there being only two blocks acting on the front of the rear wheels. The brake hangers are pieces of bar drilled for fixing to the frames, for the brake block pivot pins and attachment to the brake rod. The brake blocks we r e cut from a ring of mild steel turned to match the wheel section internally and externally to a section which could be milled to provide the hanger slot. The hangers pivot on shouldered studs, captive in the frames and backed up by large square washers. The pivot pins securing the blocks to the hangers are fitted with split pins.

Oilboxes

Four brass ‘trays’ or reservoirs for axlebox lubricating oil are mounted on the stiffening angles. The reservoirs and their hinged lids were milled from some anony mous brass from the scrap box, probably parts of electical switchgear dismantled in the ongoing ‘ salvage and alternative uses campaign ! Rubber tubing forming minute pipes conveying oil to the bearing surfaces of the axleboxes was obtained from a suppl i er of laboratory equipment, a useful source of speciality items such as rubber and plastic tube. The pipes are attached to small diameter copper pipes silver soldered into the oil trays. The feed to the bearings is via similar copper bends which are solde red into the axlebox castings. Old fashioned fluffy wire pipe cleaners pushed into these bends stems the flow of oil to ensure a constant flow of the necessary lubrication at the critical points.

Lubricator And Mounting Plate

PIXIE has a mechanical lubricator mounted on a steel plate fixed using two bolts through the right hand frame angle. On the model this is replaced by a proprietary lubricator from Norman Spinks. The lubricator was seen in an advertisement, catching the eye because it incorporates roller clutches rather than a ratchet and pawl mechanism, this allows an infinately adjustable stroke. The oil case is not too unlike that on the prototype, except that it lacks an oil level gauge. On Pixie, as on the prototype, the drive is taken via. a small diameter rod clamped to the valve rod, adjustment to the flow being achieved in the model form by selecting one or other of the holes in the pump actuating lever. The geometry of the action can be adjusted by nuts set on a threaded portion of the actuat ing rod. When first seen PIXIE was carrying diesel coupling blocks, and, as this is how she was to be recorded, diesel coupling blocks were next on the agenda. The dimensions from my survey were set out in sketch form and the scrap box yielded the majority of the small pieces of mild steel required for fabrication. Access to TIG welding equipment provided the opportunity to assemble the parts ‘ in the square ‘ and a session with the angle grinder, used offhand, introduced the necessary geometry. A study of the prototype front plate revealed the fact that a variety of attachments had been made during the life of the loco but currently the blocks are attached by 4 large diameter bolts, these are replicated by BA bolts. The coupling pins were turned fom scraps of mild steel rod. These were cross-drilled whilst clamped onto a vee-block. A line was scribed on the periphery of the head, a centre finder was used to scribe a diameter coinciding with this line. The centre of the cross hole was marked with a punch. The pin with the diameter set vertical was clamped in a vee block and a pointed wiggler used to locate the punch mark below the centre bit in the drill press. An overlever clamp remains on the drill press table at all times providing a simple means of retaining material and jigs during drilling operations. The fact that the clamp is ‘ resident ‘ avoids situations where one might otherwise be tempted to ‘ take a chance ‘ by holding something for a one-off drilling operation, putting ones fingers in jeopary at the time of the drill breaking through when snatch is liable to take place.

Footplates, Support Brackets And Angles

Two support brackets were fabricated from plate and angle steel, these are important as they support the weight of the bunkers. They are rivetted back to the main frames using dummy rivets as previously described. The rails are sections of angle rivetted to the main frames and the drawbeam at footplate level, those supporting the outer plates being at a lower level than for the centre plate. The centre footplate is slotted for the damper handle and provided with a cranked angle which engages in the handle to provide several settings of the damper opening. There is also a checkout for the drain pipe from the water gauge. The rail which trims the outer footplates is cut and bent to form a curve matching that of the bunker later mounted above it. PIXIE’S footplates are replicated in the model by stainless steel plates which are bolted to the angles and rails.

Finishing Touches To The Frames

On top of each of the frame stiffening angles are mounting blocks on which are seated the bearing flanges on the boiler. On the prototype the brackets are fabricated from steel angle, these are reproduced in the model although to ensure that the boiler would sit true to level within the frames, final machining to height was was left until the boiler could be offered up into position and the appropriate dimension established. Cutouts were required in the stay immediately behind the boiler, these provide clearance for blowdown valves, sited just above the foundation ring. Details not to be found on the full-size locomotive are the holes for dumping rods or pins which allow the ashpan to be dropped in case of emergency. Whilst the downward movement of the ashpan is restricted, there is still sufficient room for the grate to drop and the fire to disperse in the event of the pins having to be pulled in case of emergency These details just about c omplete the frames. Of course detail varies from loco to loco and there is a lot of enjoyment to be obtained from identifying details for inclusion in ones model. It may be that a particular prototype has been modified at some time in its life, something added, a piece of plate fixed at a potential crack position or some other ‘ adjustment ‘ made in service. For example, in the case of PIXIE there are some plates bolted to the front of the weatherboard where at some stage the angles have been cut and subsequently rejoined. These are yet to be incorporated in the model. It is well worth while researching such detail which will go a long way to improving the authentic atmosphere of the finished model. On PIXIE there is a small piece of plate attached to the front frame member, this provides a purchase for the bolting attachment of the drain cock return spring. Small details such as this which were perhaps an afterthought on the part of the designer, or an innovation on the part of a restorer, help to promote the atmosphere so beloved of the narrow gauge enthusiast.

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Chapter 9

Smokebox saddle. Cylinders, ports, passages, covers and glands. Pistons and piston rods.

Piston rod gland and slide bar fixing

Smokebox Saddle

The smokebox saddle is a simple casting, produced from a rudimentary pattern which governed the profile with allowances for shrinkage but incorporating no fine detail. The casting was clamped to the topslide and the bolting faces were machined using a fly cutting tool. This useful tool simply produced in the home workshop comprises a substantial section of 2 1/2” diameter bar with a drilled hole for a circular tool and a grub screw set in the perimeter to enable the toolsteel to be set at the correct angle. The mass of metal comprising the body of the tool when CHAPTER NINE gripped in the three jaw chuck serves to induce a ‘flywheel’ action reducing the effect of the intermittent cutting, a feature of flycutting operations. in order to increase the versatility of the attachment it is provided with three further holes which match the centres of the tapped holes in the faceplate on the milling machine quill. This arrangement is always used when heavy cutting / planing operations are carried out in the mill.

The seating for the smokebox and the small rebate which conceals the joint between the saddle and the smokebox were fly-cut whilst the saddle was fastened to the vertical slide, set parallel with the axis of the lathe. When setting a fly cutting tool to radius it is essential to remember that too small a radius will result in metal being cut away from the depth of the concavity, i.e. with too great a rise on the chord. Cutting should be started with the tool set to a slightly larger radius than that finally required, the tool being adjusted inwards, slowly reducing the radius of the cut until the finished radius is achieved! This needs a little thought but a few lines on a piece of paper will soon verify the facts, and may save a valuable casting from destruction!

On completion of the machining operations the small gussets which stiffen the bolting flanges on PIXIE were silver soldered into position, leaving an generous fillet of solder to replicate those on the casting. At this stage a template was prepared for the location of the cylinder / frame fixing bolts The centre line of the cylinder was transferred to this template and the template set aside for later use.

Cylinders

The cylinder castings were made from simple wooden patterns which followed the main outline of the pieces. In view of the writer’s limitations in the pattern making department, it had been decided that such items as seatings for the valve spindle and piston glands would be added after the main machining operations had been carried out. First the top face of the casting was fly cut to the correct inclination. This angle was determined from a trial set out in marking blue on the frame, using the dimensions from survey and the template previously prepared. As well as providing a plane surface to assist in setting out this face would later determine the correct angle for boring the cylinder. The next operation was that of machining the steam chest. PIXIE has the steam chest integral with the cylinder casting, and this called for some massive excavations in the model casting ! A new term was added to the vocabulary at this stage. Conversation with a ‘ real ‘ engineer evinced a description of an operation known as ‘ hogging-out ‘. This elegant term describes the process of making multiple drilled holes within the area which would eventually become the steam chest cavity in the casting, before finally the remaining few pieces of metal were milled out, using an end mill, to leave an accurate cavity. This procedure was duly followed and the resulting steam chests proved to be acceptably accurate.

Having cleaned up the perimeter of the steam chest, attention was then turned to boring the cylinders. This was carried out with the castings secured to the topslide using straps of stock material in conjunction with suitable packings and tie bolts to retain the casting securely during the fairly substantial cuts of the boring operation. A word of warning…… unless ties such as used in this instance are set absolutely vertical, relative to the topslide, with, in this case tapered packings properly anchored into position to provide a firm purchase, they may loosen in the course of boring, with dire results. The tendency is, due to the cutting effort applied together with vibration in the system, for the tie bolts to loosen as they assume a position normal to the topslide and the tee-nuts therein. At this stage the cross travel of the saddle must be locked by tightening the clamp nut. On my lathe I have fitted a short lever here to enable me to exert stronger pressure on the clamp bolt without the need to use a spanner.

Once lined with the axis of the lathe and with the correct inclination determined by the previously fly cut face, the ties checked and the cross-slide secured against movement, a start was made on drilling for the piston rod. PIXIE only has one cylinder cover on the front end of the cylinder, the piston-rod passing through a gland on the the closed end of the casting. Drilling for the piston rod was done using bitts held in a headstock-mounted drill chuck. This operation was started using an end mill to provide a flat land on which the centre bitt could bear without being deflected, after the centre bit a succession of changes of drill size, up to clearance size for the rod, ensured a correctly located and accurately sized hole. The hole was not reamed because reaming to finished size can, in this instance, when the gland nut is inserted, form what is in effect a ‘self locking clutch’. Any misalignment of two reamed holes occurring in the course of taking-up the gland causing the piston-rod to bind.

The cylinder bore was cut using a specially made, short, stiff boring tool set up in the four jaw chuck which in this instance was used as a boring head. On the Myford this required some thought. Finally reference to, would you believe, a page by ‘ Geometer ‘ in the 6th September 1962 issue of MODEL ENGINEER provided the solution ! Two pieces of 1/4” plate were cut and inserted between the jaws. This allowed the boring tool to be moved laterally across the axis of the machine, within the central hole in the chuck, by the amount required to bring the bore to finished size. The metal plates ensured that at all positions of the tool it was still supported by all four jaws. A proper boring head would have simplified the operation but, bearing in mind the few occasions on which such a tool would be used, budgetary considerations determined that other accessories were more important.

In machining bores which are to have a cylinder cover at one end only it is necessary to guard against producing a bell-mouthed bore. This is best achieved by bringing the bore nearly to finished size then taking only very fine finishing cuts. LBSC called this ‘ taking the spring out of the tool ‘.

Cylinder boring completed, the writer encountered a piece in MODEL ENGINEER by Keith Wilson relating to the profile of cylinder bores. Given the benefit of Keith’s experience earlier in the course of building Pixie the cylinder bores would have been made according to his ‘ words and music ‘.

Next the position of the ports was established and the milling machine brought into play to cut them. These were not the working ports, as the port faces were to be in stainless as described earlier. They were cut within the outline of the eventual port positions to a depth which would permit the steam ways to intercept within the metal between the bottom of the steam chest and the cylinder bore. The steam inlet and the exhaust passages from the steam chest terminate on the top face of the cylinder block where the flanged pipes seat. These passages were drilled from the bolting face of the cylinder block and were, after the vertical parts of the passages had been drilled and swarf cleared from the holes, subsequently sealed by small turned and threaded plugs with slotted heads similar to grubscrews. The plugs were anointed with liquid gasket prior to being screwed home. The slotted heads of the plugs enabled insertion using a screwdriver and were of course concealed between the cylinder casting and the frame after erection. No excuses are offered for the use of liquid gasket. Joints do not need to be taken-up too tightly, the synthetic rubber hardens as it cures, excess is easily stripped away with a sharp knife, and a good seal results each time. This technique may not be in line with the practice adopted in the prototype but I feel sure that, had Engineers of yore been given access to liquid gasket, they would have used it. Indeed it is interesting to ponder, given the range of materials available to us today, what the Trevithics and Stephensons would have selected for their constructions were they here to make the choice !

The passages between the valve chest and the cylinder ends were drilled in the drill press, care being taken to achieve the correct inclination by packing and clamping to the drill table. First the open end of the cylinder was prepared with the bevel which allows steam to pass into the cylinder, this was done by filing , using a scrap of brass to shield the bore should the file slip. As well as permitting the passage of steam in service, this bevel allows the hole positions to be spotted with a fine punch to ensure that the smallest centre bitt can be started correctly. LBSC’s tip on grinding the drill bitts used to drill the channels with one lip wider than the other to enable a broken bitt to be extracted is a winner, as was proved in the process ! There is nothing quite like the panic that one experiences when a drill or a tap breaks in an expensive casting, possibly the more valuable because a lot of time has been spent working on that casting up to the stage at which the breakage occurs. I suppose as a last resort spark erosion could be used but fortunately thanks to LBSC this has not yet been necessary.

The inclination of the passage from the port to to the blind end of the cylinder was such that the holes could be drilled using an extended drill from the steam chest. An extended drill was necessary to avoid the drill chuck coming into contact with the bolting face of the steam chest. Extended drills can be simply fabricated by grinding a stepped joint on the drill shank, cutting a matching step on a suitably sized rod, applying flux, binding with soft iron wire and then silver soldering the two together. A collection of various sizes of drill treated in this fashion will build up as work proceeds and provide a useful armoury for future use.

It had already been decided that, as the valve events of the model would in the early stages, prove to be somewhat tentative, the valve port faces would be made replaceable. Stainless steel was used for the faces and this proved to be simple to machine to the required degree of accuracy as it could be set up flat on the bed of the milling machine. Those without access to a mill could equally well machine the piece on the vertical slide. Final fixing was carried out within the steam chest bedding the stainless steel onto ARALDITE and securing the plate using purpose made, stainless steel countersunk screws into tapped holes in the bottom of the steam chest. In the event that subsequent modification to the porting may be required, the ARALDITE bond could be broken down by local application of heat.

Flanges were prepared for the inlet and exhaust pipes. These were used to locate the drilled and tapped holes for their fixing onto the top of the cylinder casting, these were then set aside for assembly onto their respective pipes in due course.

Cylinder Covers

Having bored the cylinders and prepared the steam passages, the next step was to produce the cylinder covers, in the case of PIXIE these are of fairly substantial section with a nice domed centre. Machining this centre called for a lot of knob twiddling, a thoroughly enjoyable business. Achieving the correct profile was aided by the production, on the drawing board, of a card template which could be applied to check the profile between bouts of twiddling. Experience has shown that such profiled surfaces generally turn out to be less than spectacular due to a conservative tendency on the part of the machinist, reluctant to take those last few cuts that would make all the difference to the form of the piece. This springs from the memory of those ‘ last few cuts ‘ taken in the past which have resulted in a scrapped part and lots of rework ! The use of a template as described promotes the development of the striking shapes which are a feature of, and provide much of the charm of, the narrow gauge locomotive.

A glance through any of the books which describe the motive power employed by the various narrow gauge and light railways evidences the fact that engineers in the heyday of steam were quite happy to spend money on ornamentation which would be frowned upon by the ‘ value engineering ‘ oriented designer of today.

The covers were mounted in the three-jaw and the spigot prepared a good fit in the cylinder. The spigot was carefully filed away to provide a clear steamway to, and from, the steam passage. On a previous locomotive this step had been omitted and only remembered when on trial with air, when unbelievably there was no action on switching on the air supply. this was of course simply rectified, once the cause of the problem had been identified, although at the cost of unbolting the cylinder covers and breaking the then carefully made gaskets (that was in the days b.i.g, before instant gasket). Drilling for the studs followed using a template from thin plate material. The hole positions were transferred from the cover clamped into position and then the first hole was drilled and tapped to allow the insertion of a stud to immobilise the cover during the subsequent drilling of the remainder of the holes. The use of a template whilst apparently laborious is a worthwhile precaution as otherwise although the holes for the studs can be set out on the cover and transferred to the cylinder, with a gunmetal on gunmetal joint slip can easily occur. Again harking back to a previous model, the draughtsman had drawn equally spaced studs although with the cover located as drawing, one of the studs would have coincided with the position of one of the steam passages, small errors like this sometimes slip into details and are worth watching for. One cannot help but wonder what is the effect on the modeller following instructions in a periodical when he reads an announcement such as ‘ we regret that owing to a printers error in our last issue etc. etc.!’ Perhaps its advisable to work a few issues in arrears in which case printers errors will have been accounted for by the time work commences on a particular part. In the same vein one magazine, now defunct, published an apology some 16 installments into a series on building a particular model, a note to the effect that they had lost touch with the writer and were seeking someone to complete the series! This must have had disastrous results !

Steam Chest Covers

Next came the preparation of the steam chest covers. This called for a template which was duly produced from a scrap of mild steel. The template was used to drill each cover plate in turn, including the small tapped holes for the metal threads used to break the gasket joint when access was required to the valve chest for maintenance purposes on full size PIXIE.

Once the cover plates were drilled the template was again used to locate the tapped holes in the cylinders, one hole being first drilled and tapped and a bolt inserted to secure the template against displacement whilst the remainder of the holes were spotted through. PIXIE has a union set in the right hand cover providing a take-off for a pipe to a steam chest pressure gauge, this was produced from a chucking piece of material from the scrap box.

The studs securing the steam chest cover are, on PIXIE, set out uniformly about the centre line of the cover. At each end is a small bolt, set into a tapped hole on the centre line. These bolts serve the important purpose of enabling the steam chest / cover joint to be broken when carrying out adjustments to valve settings. It was a delight at the time that the covers were required to be removed to be able to slacken off the lock nuts on these small easing bolts at the ends of the cover, then to break the cylinder/cylinder cover joint by screwing down the bolts. Although on Pixie are they are only 8 BA. they did the job famously. Those old engineers certainly knew their stuff !

Glands

Seatings for the valve rod gland and tail cover on each cylinder casting were milled and shaped from bar stock. They were then silver soldered into place on the cylinder casting, correct location being ensured by the use of short lengths of carbon salvaged from the bushes of a vacuum cleaner, turned to a push fit in each assembly. The carbon resists the solder whilst retaining the correct location and is a good example of the recycling activities which form a part of the writer’s modelling activities! A good fillet of solder was formed at each joint to emulate those on the prototype casting. After the soldering operation each gland was faced up true to the main body of the casting.

The glands for the valve rods were turned up as circular, flanged bushes prior to being sawn and filed to the required shape. The body of the piston-rod gland is interesting, incorporating as it does the seating for the slide bar. Production of the body involved a considerable amount of hand-work, carried out once the the hole for the rod had been drilled and counter bored for the gland. The piston rod gland has an oilway for lubrication and is adjusted by two shouldered studs as is that for the valve rod. Rather than use conventional packings in the glands, ‘ O ‘ rings are preferred as these provide tightness whilst causing minimum friction between the parts.

A nice little detail seen in service is an oil-soaked length of tow which is tied to the easing bolt on the valve chest cover and looped around the valve rod to provide lubrication. Very practical, and a useful bit of ‘ colour ‘ to assist with the narrow gauge image !

Pistons And Rods

Pistons are turned from gunmetal, the piston blanks being mounted in the three jaw, the holes for the rods drilled and tapped with a 1/4” M.E Thread. The thread was cut away using a 1/4” diameter D-bitt for half of the piston thickness to allow the piston rod to be drawn into position by its thread in the later operation of uniting the two parts.

Piston rods of silver steel were set into a simple collet in the three jaw. These collets are home produced from suitably sized slugs of metal by drilling and reaming to the finished diameter of the spindle or rod to be gripped. After marking by centre punch at No. 1 jaw to ensure accurate re-location the collets are then slit with a razor saw. As work progresses a number of useful collets accumulate and are be stored with the tooling ready for re-use as the occasion arises.

The thread for the pistons was cut with extreme care, using an M.E. die and ensuring that at all times the die stock was firmly supported square to the axis of the rod by the nose of the tailstock chuck. A tailstock-mounted die holder is of great assistance in such work and can be manufactured in the home workshop from a proprietary mandrel and some offcuts of round bar. A secondary bush which can be set into the space for the die, and which permits longer adjustment screws to pass, allows the use of smaller sizes of die within the main sliding die holder.

With the rod set in the collet within the three jaw, the ends of the rods were lightly centre drilled prior to oil being placed on their threads and into the the tapped holes in the pistons. The pistons, gripped in a hand protected by rag, were then screwed onto the rods, care being taken that the plain portion of the rod entered well into the smooth, ‘ D-bitted ‘ part of the hole. Once the pistons were secured in this fashion the tailstock centre was engaged in the small centre and the pistons turned to finished diameter with reference to each cylinder bore. Each piston was then marked to ensure subsequent matching of the sets. It is helpful if a uniform system of marking is followed, centre-pops on an unimportant surface will suffice, say one pop for items on the right side of the loco and two on the left, looking forward from the footplate, or perhaps simpler still one pop for one side, and no pops for the other !

With each piston assembly still mounted in the collet and supported by the tailstock centre, grooves for ‘ O ‘ rings were machined using a parting-off tool. Grooves for these rings must be produced to the sizes recommended by the makers, this being critical to achieving a sound seal whilst reducing frictions to a minimum. The edges of pistons and grooves should always be ‘broken’ using a fine file, to avoid damage to the rings as they are installed.

On final assembly, the piston rods are retained in the crosshead bushes by wedges passing through slots in both parts. In the case of Pixie these wedges are, in fact, bolts with the heads filed to simulate the ends of wedges. Holes for these simulated wedges were not drilled until their position could be accurately located at the time of trial assembly of the engines. Builders may wish to replicate the full size arrangement which may call for slotting the piston rod and crosshead and providing appropriate cotters and wedges.

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Chapter 10

Motion plate. Slide bars and crossheads. Valve gear. Weigh shaft and reversing gear. Valve setting. Brake column.

Marine bearings on Pixie

Motion Plate

The motion plates are of course a handed pair, those on PIXIE are quite conventional and those for Pixie were produced by cutting plate to the required profile. Then the flange for fixing to the frame was attached by silver soldering. The lugs which support the trailing end of the slide bars were soldered into place at the same heating. Drilling the holes for the slide bar fixing bolt was left until final erection. The motion plate was trimmed with a half round fillet on the front face, simulating the detail on the prototype, this was attached using soft solder. For the purpose of trial assemblies the slide bar was be held in place using a toolmakers clamp. The location of the motion plate and thus the position of the fixing holes in the frames is best established at the time of setting out the motion work.

Slide Bars

Each engine on ‘ PIXIE ‘ has a single slide bar the front end of which takes support from the body of the piston rod gland on the back of the cylinder casting. The trailing end is bolted to a bracket on the bottom of the motion plate. The slide bar itself is a piece of profiled steel, in the case of Pixie ground gauge plate. This was milled to shape and the fixing holes and countersunk lubrication holes drilled in conventional fashion in the drill press.

Crossheads

On PIXIE the crossheads are substantial steel boxes, assembled around the slide bars. Lining each box is a set of slippers, so shaped as to remain captive once the crosshead assembly is bolted up. The box is fabricated from three plates and a fabricated mounting, assembled by bolting. Incorporated in the bottom plate of the crosshead assembly is the mounting for the piston rod / coupling rod joint. This comprises a flange for the gudgeon pin and a boss into which the piston rod end is secured. The boss was first turned onto a mild steel blank, and was left overlength for subsequent adjustment when the motion was assembled. The crosshead blanks were then milled to profile and section, incorporating the bottom plate of the crosshead. Twelve bolts were prepared. The threads were turned from the ends of the bolts which were then drilled for split pins. In course of erection on PIXIE the leading two bolts of the assembly are entered from above the crosshead, the remainder from below. It was important that the assembly on Pixie replicated that employed on PIXIE, otherwise with all six bolts entered from the top, the projecting ends of the trailing bolts would have interfered with the movement of the coupling rod. Detail such as this must be studied carefully at the time of survey as each locomotive is likely to have some such idiosyncrasy. Omission of such information from the notes made at the time of survey could result in problems at the time of erection or worse, damaged parts at the time of air testing.

The hole for the gudgeon pin was then drilled and a phosphor bronze bush pressed-in. To ensure a good fit the gudgeon pin is machined from silver steel, brought to a high finish in the lathe. As is general practice on PIXIE the ends of the pins are turned down and fitted with split pins for safety purposes.

Slippers

Slippers are of gunmetal and provide a nice exercise in milling, either in the milling machine or the vertical table on the lathe. As with many thin or slender components it is worthwhile soldering, or bonding the material to a more substantial section of metal. This backplate can be more readily gripped in a vice, or if necessary, bolted to a faceplate or bed. In this way machining can be carried out without fear of a nearly finished part moving under the cutting effort and becoming scrap. This technique was adopted for the slippers which were brought to within a few thousandths of the calculated finished size prior to filing and burnishing to fit within the crosshead, ensuring a nice easy action. There is a tendency to make parts too slack a fit at this stage. It must be bourn in mind that the running-in process affects every part of the motion and parts which seem quite tight at first, or trial, assembly soon free-up as the running in process proceeds ( using plenty of lubricant of course! )

Assembling The Slide Bars, Crossheads And Motion Plate

This is a critical part of the construction. Parallelism (if there is such a word) between the piston centre line and the slide bar being most important for free running. Fortunately in the case of Pixie there was an opportunity in the course of the erection process to maintain this parallelity ( ? ) by adjusting the level of the bearing surfaces at the top of the glands and if necessary insertion of shim washers at the bracket on the lower edge of the motion plate.

Valve Gear

PIXIE is fitted with Hackworth valve gear. This gear is sometimes derided by pundits because vertical movement of the axles upsets the valve events to some extent. This has not proved to be too noticeable in the case of Pixie and indeed the Hackworth gear is employed effectively on what must be the hundreds of Sweet Pea locomotives, designed by Jack Buckler, running on club tracks about the country. Jack Butler contributed an excellent article to ENGINEERING IN MINIATURE May 1986, Volume 7, No. 12 examining some of the criticisms and recommending methods of optimising performance. These include adjusting the height of the weighshaft and ensuring the correct ride position of the axle to ensure that the die block pivot moves equally about the weighshaft centre. In a more recent edition of ENGINEERING IN MINIATURE Vol 15 No.1 June 1993 a highly technical article, almost of Ph.D. standard by Nigel Bennet describes the computer simulation of Hackworth valve gear for Edward Thomas and incorporates a lot of useful detail on the motion work for Sweet Pea.

In the case of Pixie the critical dimensions of the prototype were replicated as accurately as possible and in the air trials these worked satisfactorily. no doubt the events could be fine tuned in light of Messrs Bucklers and Bennetts discussions, and maybe they will, when time permits perhaps. Meanwhile Pixie’s performance is quite satisfactory with her replicated sizes incorporated.

Hackworth gear takes its motion from the return crank fixed directly opposite the crank pin i.e. on a line passing through the crankpin and centre of the axle. The vibrating lever attached to the return crankpin connects with a pivot pin on the die block which runs within straight guides set upon the weighshaft. With the guides in line with the centre of the axle the valve rod pivot on the vibrating lever is driven through an oval path of which the length of the horizontal axis equals twice the valve lap plus the lead. Rotating the weighshaft alters the inclination of the guides and changes valve events accordingly.

The size of the components of the valve gear was scaled down from the prototype and cardboard templates were employed at the drawing board to ensure that all would work when assembled onto Pixie. Whilst a spare weighshaft and guides was produced having extended slides for experimental purposes, to date these have not been installed.

One end of the return crank blanks was drilled and bored to match the shouldered crankpin. The other end was drilled for the vibrating lever pivot pin. The blank was milled to shape and the pivot pin set into place using retaining fluid. The return crank itself was secured to the crankpin by a slotted and bolted connection, aided by a further touch of retaining fluid.

The vibrating lever on PIXIE has a small marine type bearing at the lower end, and two bushed holes for the die block and valve rod pivot pins. As with the connecting and coupling rods, the marine bearing permits some small adjustment to be made to the geometry at the time of final erection. The vibrating lever blank was cut from mild steel, the pivot holes drilled and then milled to final shape. When milling bosses, or indeed when shaping the ends of any of the rods or levers by means of an an end mill in the lathe or milling machine with the material set upon a pin, it is important to remember that the material must only be moved against the direction of the cutter. Failure to observe this will result in the cutter attempting to ‘ climb ‘ onto the material, the resulting snatch causing damage to the part or, worse, the operators fingers ! Phosphor bronze bushes were pressed into the pivot pin holes.

Oil Cups And Local Lubrication

Oil cups are fitted at each pivot point and adjacent to the bearings. These oil cups like those on other narrow gauge locomotives add a touch of individualism, they are of brass, of interesting shape and can be polished, and are ‘ perched ‘ somewhat precariously it seems, on the vibrating levers and die blocks. Those on the vibrating lever were milled to shape prior to fitting the tubes which convey oil to the bearings. These tubes are fitted into drilled holes with just a touch of bonding fluid, sufficient to fix them without blocking the tubes. Each cup is topped with a screw plug turned from a BA bolt, the head being brought to profile then knurled prior to the arisses being removed. A small centre bitt was used to drill the countersunk breather holes in each plug.

Weigh Shaft, Weigh Shaft Brackets And Guides

The weigh shaft is of silver steel, shouldered to enter the back plates of the guide assemblies. The shaft is rotated from the reversing lever by a reach rod which is connected to a lug on the bottom of the right-hand guide. The cheeks of the guide are milled from gauge plate, later hardened by heating,and are attached by bolts and a locating pin passing through the backplate and the weighshaft.

The weigh shaft brackets were fabricated from steel angle and plate, the lower section being welded-up. The top plate has small seating pieces sweated into place to accomodate the stud nuts when the two parts are assembled. Once the two parts are assembled the hole for the weigh shaft can be drilled and reamed. The brackets are assembled onto the frames by bolts passing through the frames and the frame angles. Ideally the position of the brackets should be determined when the whole of the motion work has been completed and the valves inserted onto the rods within the valve chest. At this stage the correct location can be established by trial and error with the brackets clamped to the frame angles.

A modification to the guides has been suggested by Jack Buckler in describing ‘ Sweet Pea ‘, ENGINEERING IN MINIATURE. In his redesign the guides are milled from one block of mild steel, a slotted cover plate being attached by countersunk screws onto the front of the guides so formed. This appears to be a simpler form of construction and may commend itself for some models.

Die Blocks

Die blocks are of tee section and have a shouldered pin for connection with the top of the eccentric rod. this pin is entered from the back of the die block, a further shoulder seating in a counterbore in the back of the block. An oil cup is mounted on the top of the die block. With a good sliding fit achieved within the guides, the die block and pin were case-hardened by heating and treatment using ‘ Casenite ‘

Reversing Lever And Sector Plate

The lever was prepared by sawing and filing from a piece of mild steel. The handle, with a pin for insertion into the top of the lever, was turned from a piece of square material and soldered into position. The latch block prepared by filing was soldered into position at the same heating. The latch itself was prepared by soldering a blade onto a square steel shaft with the top milled and drilled for connection to the latch lever. A small spring maintains the latchblade in contact with the sector plate. A good source of high quality springs has been found to be the plastic video tape case. On opening a defunct case one finds a number of small stainless steel springs also some stainless steel rollers as well as several self -tapping screws, all useful candidates for the scrap box !

Slide Valves

The slide valves were machined from gunmetal, heeding LBSC’s advice that dissimilar metals should be used for slide valves and portface. The blocks of gunmetal were turned to overall size in the four jaw, leaving a little on the length for final finishing work. then the cavity for exhaust steam was milled out using an plain end mill and finished with a bull-nozed bitt, care being taken to work within setting-out lines lightly scribed on marking blue.

The slots for the valve rod and the recesses for the collars which are used in place of a buckle were milled then filed to shape, care being taken that the fit permitted the valve to slide freely from end to end of the valve spindle when set in the steam chest and before the locating bushes were installed. The face of the valve was rubbed on a sheet of medium wet-and- dry paper ( used dry ) to impart the minute scratches which, in service, retain a film of oil and assist in maintaining a tight joint under the steam pressure in the steam chest. it is of course important to ensure that the valve block is free to lift from the portface, it is held in contact during service by the valve chest steam pressure but has to be free to overcome any problems with condensate in the early stages of firing whilst the cylinders are cold.

The arrangement of threaded valve rods and nuts with locknuts employed for fixing the valve blocks to the rods on PIXIE is replaced on Pixie by 4 bronze bushes ( 2 per valve block ) machined from hexagonal bronze bar. These bushes were initially secured to the valve rod by mild steel grub screws which whilst proving sound enough in service, started to rust. These have been replaced by 5 BA set screws machined from stainless hexagonal bar. The hexagon head of the set screw permits greater fixing force to be applied once the correct setting has been achieved than was possible with the earlier grub screws. These stainless steel screws are secured in service using a retaining fluid.

A general point regarding grub screws which can save problems with head breakage in the case of smaller sizes is that the body and most of the head of the screw should enter the tapped hole. In this way, when effort is applied using a screwdriver, the lobes at each side of the slot in the head end are supported by the walls of the tapped hole in the bush, wheel or whatever the screw is intended to secure. Where possible, when set screws or grub screws are used, the spindle or axle should have a small flat or dimple on which the tip of the screw can bear when tightened. The use of two screws in a bush permits a small drill to be passed down one tapped hole to form such a location whilst the bush is secured by the other fixing screw.

Dummy Slide Valves

As an aid to determining slide valve dimensions, valve setting and visualising the events of the slide valve assembly the modeller may care to make a pair of dummy slide valves. These can be simply prepared using 1/8” perspex sheet. The exhaust cavity position can be scribed on the base and further piece of perspex cemented vertically onto the ‘ valve ‘. The upright can be drilled for the valve rod and the valve spindle installed in the usual fashion, using grub screws or whatever fixing is favoured. Whatever the final arrangement for securing the actual valves to the spindle, for the dummy assembly two bushes fitted with grub screws allow trial settings. With the dummy valves set in place the engines can be taken through their cycle and, with the length of the valve scribed on the perspex, the valving checked out. This arrangement has proved particularly helpful in the case of Pixie where the motion was constructed to dimensions taken from survey and small innaccuracies arising in construction called for some adjustment of the valve lengths to achieve optimum performance. Where a model is being built to proven details this eventuality should not arise although it is still most interesting to see the valves in motion and to visualise the events.

Valve Spindles

The valve spindles are lengths of rustless steel, their ends terminate in bosses which are turned to shape, drilled and reamed for phosphor bronze bushes prior to being silver soldered into place. After the soldering process the bores are cleaned up by a pass of the reamer and a small bush pressed into place in each. When working on bushes of this size, the bore of the bush is often reduced by this squeezing action and require a pass of the reamer to bring them back to size. Small oil cups are mounted on the top of each bush, a fine hole being drilled to convey the ‘amber liquid’ to the bearing face.

Valve Rods

These are from silver steel with mild steel forks soldered at each end. The forks are profiled by milling and filing. Milling the rounded ends is carried out on a pin mounted in the small 4 jaw chuck attached to a baseplate which can be bolted onto the table of the milling machine. Prior to the aquisition of the milling machine such work was carried out using a pin mounted in a machine vice secured to the vertical table. In each case care has to be taken to avoid climb milling with resulting snatch on the part. Prior to installing the valve rods onto the locomotive the silver steel pins were fitted into the forks and holes for split pins were drilled through fork and pin. A very small drill was used, run at the highest speed obtainable on the drilling machine.

Work of this nature is carried out on a sensitive drill constructed from a set of castings purchased from MESSRS REEVES of Birmingham. The drill formed an exercise in machining and boring and building the drill served to teach many a lesson. The result is a drill with which minute holes of considerable depth can be drilled with confidence, an extended arm controlling the movement of the quill giving a very direct ‘ feel ‘ right to that critical point where the drill breaks through on the underside of the material. One small amendment made to the design of the machine is the addition of a perspex guard around the twin pulleys driving the quill. One’s face is often quite near to this area when concentrating on that last, critical hole in some assembly that represents some hours of work, and a broken drive belt could seriously damage a person’s good looks ! Prior to building the sensitive drill I used an auxiliary drill chuck set in the lathe and used in conjunction with a drill-pad set in the tailstock, feed being achieved by the tailstock handwheel. This is quite an exciting operation, particularly with the lathe turning at top speed to suit the smaller number drills. Drama can result if, with the Super 7 and its self-ejecting mechanism, the drill-pad reaches the point of ejection before the bitt reaches the bottom of the hole !

Valve Setting

Valve setting was carried out at the appropriate stage in the erection process. The best description that we have encountered in any book is that by LBSC in his account of building ‘ TICH ‘. As he always did, old LBSC describes the process in the simplest of terms, and there seems little point in repeating any but the key points here. these are basically that the ‘crack ‘ of the port must occur on each dead centre In the case of the Hackforth valve gear, the inclination of the guides on the weighshaft determine the amount of the port opening. Unfortunately, compared with the Walschaerts’ gear there is no combination lever to hasten the opening of the ports to exhaust, inlet and exhaust taking place at similar pace. This has not proved to be a problem in practice however and the little locomotive has ample pulling power.

Brake Standard

The brake standard was turned from a piece of mild steel reinforcing rod, bored a clearance fit for the rod. The standard is supported by two angle steel straps bolted into the frame supporting the footplate. On Pixie it is set-up on the right of the foot plate although in some previous period it has been sited on the left. At footplate level the standard is based upon an oval plate and incorporates two angle steel supports between this plate and the standard proper. At the top a bracket takes support from the frame of the rear weatherboard. Near the top of the rod and within an enlarged section of the standard is a collar which, being pinned to the shaft, acts as a bearing resisting the thrust as braking effort is applied by rotating the brake handle clockwise. As the force set up by putting the brake off is relatively small, a keeper plate, retained by small round head screws tapped into the top face of the standard, is sufficiently substantial to provide a bearing surface. this is one of the few places in railway mechanical engineering that such screws are encountered.

The rod passes through the footplate into a substantial bush set in the fork of the actuating lever. the thread on PIXIE is of course a buttressed thread, that on Pixie, a ‘ common or garden ‘ Whitworth thread… we did say that Pixie was a near-scale model ! The brakeshaft sits in two bushes bolted to the frames. Actuating rods form a connection between cranks on the brakeshaft and transverse rods passing through clearance holes in the bottom of the brake hangers. The actuating rods are maintained in the correct transverse position by bushes and split pins, some allowance for adjustment to the brake set-up is provided by a series of holes in the back end of the actuating rods.

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Chapter 11

Smokebox and and smokebox door. Hinges, darts and rings. Wet header, steam, blast and petticoat pipes. Blower ring.

Smokebox door, coupling block and location of axle driven pump

Smokebox

The smokebox was turned from a piece of steam barrel, not on first sight a prepossessing piece of material. Turning in the four jaw revealed an immaculate piece of high quality steel however and this was soon brought to the correct diameter and length. Before removal from the lathe, lines were scribed longitudinally onto marking fluid on the outer surface at 90 degrees intervals as a guide for use later in setting out the position of the chimney, the openings for the steam and exhaust pipes, and importantly the holes for the bolts which are used to connect the smokebox to the saddle. This marking was aided by using the simple dividing attachment described later in the book, the lines being scribed using a point tool in the topslide tool holder and traversing the saddle.

The position of the hole for the chimney was next established and marked out, again using marking fluid. The tube was then set on end and clamped to the saddle with packing such that the centre of the hole was on the axis of the lathe. The hole was started using a centre bitt, followed by a succession of drill bits up to the largest available, finally being brought to size using a boring tool mounted in the four-jaw chuck.

Two pieces of ply were bandsawn to the profile of the outer diameter of the smokebox tube. Spaced by a block of wood these permitted the location of the tube, on its side, on the table of the drilling machine. Where just a few operations are to be carried out, such an arrangement, whilst quickly produced is adequate in providing a sound support. If there were a number of similar operations something more substantial would be employed. Apertures for the steam and exhaust pipes were then set out. These openings were formed by chain drilling and some careful work with ‘ junior ‘ hacksaws. The ends of the saws being wrapped with insulating tape to avoid damage to the inside of the smokebox tube. Two saws were used, one the common ‘ junior ‘ saw with the blade parallel to the handle, the other with the frame cranked through 90 degrees enabling the cuts around the perimeter of the tube to be made. The edges of the openings were finished by filing. Holes for the bolts securing the smokebox to the saddle were then set out and drilled, still using the ply cradle to support the tube, these would be subsequently transferred to the top of the saddle casting.

Smokebox Door

A disk of ‘mild steel’ yielded the smokebox door, after a fight that was ! The blank proved to be extremely hard, possibly as a result of some long-past cropping operation. This is a problem sometimes encountered when ones material comes from scrapboxes, breakers yards and similar sources, although a problem which will not be encountered by modelmakers who patronise the trade supplying ‘ bona fide ‘ model engineering materials ! The result was that having taken the edge off, and the temper out of, several tools it became necessary to set up green-grit grinding wheel in a power drill and having protected the lathe bed with rags, applying this to the blank as it rotated in the lathe. Unorthodox as this may have been, it did the trick. Fortunately there was no hard spot in the centre of the piece, and after drilling the blank was mounted on a bolt whilst the inner face was relieved to leave just a small ‘ land ‘ which would ensure a good seal on the front smokebox ring. What LBSC would have described as a ‘ nobby ‘ handle, and what the writer sees as a Victorian cupboard door handle is screwed into the central hole to complete the door. Other prototypes employ darts and crossbars with perhaps keys and locking handles, these provide some exercise in watchmaking. Crossbars to retain the dart are seated into brackets rivetted to the front smokebox ring. These are not needed on Pixie as the door is retained by two angle steel brackets and ball handles

Smokebox Rings

On PIXIE, as on a number of narrow gauge locomotives, the smokebox front is a piece of plate mounted on the firebox by a rolled steel angle. this arrangement is represented on Pixie by using a one-piece gunmetal casting turned to profile. Dummy bolts in the front face represent those connecting the plate and ring of the prototype. Such an arrangement often proves simpler in model form than would fabrication using separate components, in this case it makes the sealing of the firebox easier to achieve.

A plaster pattern had been prepared for the smokebox ring castings. The pattern was ‘ horsed ‘ as described earlier and yielded the two castings which, whilst crude, contained the necessary material. The rings were prepared by first machining the external form with the casting set-up on the reversed jaws of the four jaw chuck. The outer face of the front ring was turned to a snug fit within the smokebox tube, leaving the small projection which simulated the thickness of the front plate where it laps over the front edge of the tube. Set-ups of this type must be approached with care as thermal expansions tend to loosen the grip of the chuck. Frequent checking is essential. With the outer edges machined, the face and inner section of the casting could be brought to profile. This was carried out with the ring gripped within the jaws of the chuck, here again care is required to avoid distorting the now quite slender ring whilst tightening the chuck. The back ring was turned to a neat fit within the tube then set aside until the inside diameter could be ascertained from the boiler.

The front ring was next drilled for the bolts which on the prototype connect the front plate and the annular angle. The twenty bolts are installed nut outside, one shares the duty of supporting the lamp iron at the top in front of the chimney.

Hinge Plate, Lugs, Pins And Catches

Mild steel plate was used for the hinge plate. In order that the back face could be turned to match the form of the door the blank was cut to rough outline and set up on a faceplate. A secure fixing was obtained by using bolts screwed into tapped holes in parts of the hinge plate which would later be machined away. With a good fit obtained between the hinge plate and the outer face of the door, the blank was filed to profile.

To ensure the airtight joint essential to good draughting under steam, care must be taken with the geometry of the hinge points. A few minutes work with pencil and card will reveal that the hinge point must be so placed that the door opens both outwards and away from the front ring of the smokebox. It may be necessary to slightly relieve the edge of the door adjacent to the hinge to ensure clearance. Once the geometry has been resolved the hinge plate can be milled or filed to final profile and rivetted onto the door. The hinge lugs are filed up to shape from square mild steel, set into the four jaw and turned to accept a thread. A bright steel hinge pin is lightly tapered at one end and fitted with a collar. The lugs can be slipped onto the pin which is passed through the hinge plate and the whole offered-up to the front ring. It may prove necessary at this stage to make some small adjustment to the shoulders on the lugs to bring the perimeter of the door into contact with the front plate to ensure the essential airtight joint when the door is closed.

Twin steel angle brackets secure Pixie’s door in the closed position. These are mounted on studs set into the smokebox front ring and are tightened by two ‘ ball headed nuts ‘, which present a nice piece of ornamental turning. This is an example where a note on the survey sketch would have resulted in a more authentic model, these ball handles appear on later inspection to be of gunmetal and not mild steel as reproduced ! The manufacture of these handles was however most a enjoyable exercise. The profiles were generated offhand, using a bar clamped under the MYFORD tool clamp as a tool support. After parting off the blanks with a ball at each end were set into the drilling machine vice, sandwiched between two scaps of steel having countersunk holes to provide a locating grip for the blanks. With the blanks set to the correct angle the larger ball was then drilled ad tappped for the stud which is set into the front face of the smokebox.

Wet Header

The wet header was turned from a piece of gunmetal rod, it sits in a bush soldered into the smokebox tubeplate. Three stainless steel bolts pass through the header into holes tapped into the boiler bush. The steam pipe ( from the regulator ) enters the header and the joint is sealed by an ‘ O ‘ ring. A small diameter pipe from the lubricator delivers oil into the steam at this point. Whilst generally this is done by inserting tees into the steam pipes nearer the cylinders or by means of displacement lubricators mounted on the steam chest covers, the current arrangement appears to be satisfactory and does not lead to priming as the steam ports of the Stroudley type regulator are set high in the steam dome and thus considerably above the level of the outlet at the header.

Steam, Blast And Petticoat Pipes

After careful annealing, the steam pipes were bent to shape and fitted with the flanges to connect with the cylinder casting. The flanges were silver soldered to the pipes and care was required to ensure the correct orientation of these flanges to suit the location of the fixing studs in the cylinder block. The upper ends were then soldered into the wet header during the same heating as the lubricator pipe.

Exhaust steam pipes were formed from 1/2” diameter copper pipe which had to be annealed frequently in the course of producing the reverse bends between the cylinder block and the connection for the blower ring. A jig was prepared replicating the actual position of the holes in the cylinder casting for the blast pipes and the proposed location of the blower ring, determined by the type of ring selected. The connection between the twin exhaust pipes was filed up from two pieces of mild steel, the two halves were clamped together and the holes for connecting bolts drilled. The assembled joint was then drilled and tapped for the installation of the combined blast pipe and blower nozzle and a small slug of metal prepared to fair-in the joint and improve the flow of steam once the joint is assembled. The parts were all assembled into the jig and the flange and connecting block joints were all soldered at one heating. In the case of all flanged connections the flanges are prepared as a pair and then used to spot the holes for the fixing bolts. a centre popped mark ensures that the flanges are used where intended and thus minor discrepancies in hole centres are overcome.

Blower Ring

As the ring on PIXIE is a loop of small diameter tubing and replication in model form would not perhaps have provided a satisfactory draught, a rather more sophisticated type of blast ring was incorporated. This took the form of of a combined blast nozzle and blower with an annular chamber around the nozzle pierced by very small holes to provide the blower jets. The arrangement has been detailed in several articles in the technical press over the years.

Petticoat Pipe

A piece of copper pipe from a recent domestic plumbing job was annealed ready for spinning. The pipe was plugged at one end to avoid distortion in the three jaw, the other end was then spun-up to a push fit in the chimney base using a polished piece of silver steel supported from a piece of stock bar clamped into the tool holder. The first plug was removed and the newly expanded end was plugged then spun. Frequent annealing permitted the eventual achievement of the required form. On erection the petticoat pipe would be fixed using a smear of instant gasket.

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Chapter 12

Boilers. Home built vs. proprietary supply. Construction techniques. Location. Cleading.

A boiler from a proprietary supplier, this one for the Allchin

Boilers - Home Build Vs Proprietary Supply

Tackled systematically and following upon the advice of the masters such as L.B.S.C, Alec Farmer Martin Evans and Keith Wilson the task of boiler construction is within the capability of most model engineers. Where possible the modelmaker will be wise to enlist the assistance of an experienced person in constructing his first boiler, in the case of the writer this person was a dear old gentleman who had for many years been employed in all types of plate fabrication and jointing using welding, brazing and soldering and many different techniques for a range of materials. The following comment arises from experience in building that first boiler, the advice recieved from the aforementioned old gentleman who provided me with the basics of soldering practice. Other people have joined evening classes or attended short courses held during the vacation at various Universities and colleges. Usually these events are organised and staffed by experienced technicians prepared to guide participants through the tricky parts of the operation. They also provide access to that most important ingredient of good boilermaking, the substantial heat source.

The keys to successful boiler building are; a proven design, care in obtaining good fits between parts, absolute cleanliness, and an adequate heat source. Given these essentials together with space and time the beginner can produce what L.B.S.C described as the ‘ kettle ‘ for their locomotive. In the case of Pixie, experience gained in producing the boiler for an earlier 3 1/2” gauge locomotive had convinced the writer of the difficulty of providing sufficient heat using existing equipment, both propane and butane torches. To avoid problems, and economise on time available for model engineering work, the decision was made to sublet the boiler construction.

This proved to be a wise decision and should there be any doubt in the modellers mind as to whether he can afford the equipment or obtain the necessary support and assistance, he would do well to consider obtaining a ready-made boiler from one of the many experts advertising in the trade journals. In this case it may only be necessary to phone several suppliers to obtain a quotation for a boiler for a specific model to a published design. Various well known specialist suppliers spring to mind and one cannot go far wrong in purchasing from any of these. Although there are a few widely known suppliers, prior knowledge passed on by a fellow club member may direct ones choice to another fabricator who although perhaps not so widely known has proved his ability in a previous supply.

Non-standard boilers such as that required for Pixie call for a slightly different approach. Here, whilst the overall dimensions are known, the design of the boiler and its staying is best left to a builder with with a proven track record. After obtaining several ‘ budget ‘ figures it was decided to employ a boilermaker with an excellent record, although the budget price quoted was not the lowest. The fact that the builder had for many years manufactured a range of standard boilers, so much so that his firm had a ‘ household name ‘, generated confidence. As well as being approachable the proprietor was exceedingly knowledgeable and was most helpful in assisting with design input.

Armed with outline details, especially critical dimensions of items such as the location of the tank support brackets, firehole door, steam fountain and dome, arrangements were made for a meeting at the firms stand at the MODEL ENGINEERING EXHIBITION. Here the boilermaker advised upon such matters as the number and location of tubes, size and bore of bushes, desirability or otherwise, in fact otherwise, of superheater and so on. After the meeting these details were transferred to a finished drawing on which the final quotation was to be based. At this stage the builder knew exactly what was expected of him and as a result could provide an accurate quotation of what the cost would be, an essential to a satisfactory business deal. Here it should be bourn in mind that money that we spend on a boiler today would, a few years ago, have purchased quite a reasonable motor car ! Boilers from commercial suppliers come with a boiler test certificate which must not be confused with the certificate required by clubs where the locomotive is to be run. The certificate simply indicates the pressure contained during a raw test, probably before the bushes were drilled out to tapping size. Although the criteria vary from club to club, officials will require more stringent testing, including the efficiency of the safety valves, before they issue a club certificate.

In the event that the model engineer decides to go it alone, it makes sense, in the case of a standard model for which designs have been published, to make use of the ready flanged plate service offered by many suppliers. This will save a lot of time and, whilst costing more than obtaining the raw material and flanging up over hardwood or mild steel formers, can prove more economic in time, and material. The price of flanged plates can be maintained at an economic level because as well as re-using the formers many times in the course of production, the proprietary supplier has a better chance of planning his material usage in the course of a production run. He can work far more economically than does the individual attempting to cut a set of plates from his one piece of sheet copper.

Construction Techniques

A first class boiler, and we must not settle for anything less, demands excellent materials. These will be found in the catalogues of the proprietary suppliers to the hobby. With the materials to hand, the plates must be set out in the most economic fashion. Here paper templates are essential, these can be shuffled around on the raw material to provide a best fit and thus the utmost economy in material. The lines are best transferred to the material using a waterproof overhead projector pen. In this way scribing is avoided at this stage and the lines can be simply erased using a rag soaked in methylated spirits. Where essential the lines can be lightly scribed once the best layout has been achieved.

To cut the plating material obtain the largest pair of snips possible, grip one handle in the vice and slip a piece of pipe of suitable diameter over the other. With this arrangement, not only can considerable force be applied when necessary, but also very small cuts can be made slowly with great precision.

Whilst the platework can be prepared using the range of hand tools owned by most model engineers there are one or two additional tools which can make platework easier. a planishing hammer, a cross faced hammer and a large pair of tongs, mine are in fact medical forceps as used in delivering babies ! Plumbers gland or automotive pump pliers are useful for grasping hot metal. Also overlever wrenches such as the ‘ MOLE ‘ wrench make useful quick release clamps.

When flanging, anneal plate frequently by heating to a medium red then plunging it into cold water. The tendency to take a plate ‘ just a little bit further ‘ before annealing must be avoided as cracks will result due to work hardening of the metal. When preparing the tube holes in the tubeplates, countersink the holes, roughen the edges of the holes and file small nicks in the periphery of the hole to promote the flow of solder into the joint and around the tube.

Where it is necessary to drill copper plate for tubes, bushes and the like, Alec F. Farmer suggests a useful dodge which will be appreciated anyone having experienced the snatch of a drill as it breaks through the material. He recommends that drill bitts for copper plate should be ground in such a way that the tips cut the plate almost in the manner of a trepanning cut and so that the lips of the drill remove a curl of swarf from within this cut. The point of the drill seats within a pilot hole drilled after the centre of the hole has been set-out an positively spotted using a centre punch.

Assembling The Boiler Parts

On the matter of soldering one can do no better than to read ( and view in the series of more than 300 photographs ) the advice of Alec F. Farmer. Not the least of the tips passed on in this treatise, ‘Model Locomotive Boiler Making’ is the mixture that Alec uses when making up flux. He uses 2 heaped TABLESPOONFULS of flux powder, a 1/4 TEASPOONFUL of household detergent and mixes these to a creamy consistency with water. Using this mixture we are told that the detergent breaks down the surface tension of the liquid, ensuring penetration into the joint as well as degreasing the components being soldered, the greases being replaced by flux and then burnt off. As well as adding the detergent to the flux paste, cleaning and degreasing of components, prior to painting on the flux, has been found to provide the best results. With the joint painted with flux and the metal quickly brought to red heat. the flux will be seen to glaze and melt. The solder stick or wire, applied with the metal at this temperature, will melt and flash into joints. If blobs appear these have to be dispersed using a scratch, a wire ground to a point and bent through a right angle at the end. The solder will flow to the hottest parts of the joint and can be drawn along by judicious heating. Once a bright line of solder is apparent along or around the joint the parts can be allowed to cool before immersion in pickle. Final cleaning of soldered joints is best carried out using steel wool or scouring powder, after 1/2 an hour or so in pickle.

Firebricks as a wall around the hearth which is banked up with crushed firebrick maintain all available heat in the soldering process around the parts being worked on. A useful source of firebrick is the redundant storage heater. If it should be necessary to purchase bricks then a local laboratory supply company will generally stock the genuine article.

It is advisable to have a trial assembly of as much of the boiler as possible ‘ dry ‘. Holes can then be drilled, in key positions, for small rivets to hold the parts firmly during the soldering operations that follow. The pundits have always advised the use of differing grades of solder for the ongoing soldering operations to avoid spoiling joints made earlier. Due to the way in which the solder amalgamates with the copper in the course of the soldering process whilst advisable this is however, not essential.

Firehole Door

Arrangements had been made at the time of ordering Pixie’s boiler for the provision of blind bushes for later attachment of the firehole door hinge plate ( Care being taken to ensure that these were set on the correct side of the firehole ring ), also a bush for the spur. The firehole door with its hinge incorporating two shaped gusset pieces was set in place and clamped in the closed position against the firehole ring. With the hinge plate, again fabricated from mild steel located within the projecting gussets the hinge pin position could be marked and the hole for the pin drilled in the door gussets. At that stage the fixing bush positions were transferred to the hinge plate, the plate drilled and the hole positions spotted through to the bushes which were in their turn drilled and tapped. The spur for the latch, profiled from a piece of mild steel, was set into the four jaw for the end to be turned and threaded for insertion into the bush on the boiler. At this stage the latch lever could be cut to shape and brought to thickness, ensuring a good fit in the spur with the door closed tightly. A baffle was then cut to size which allowed it to pass through the firehole ring without binding when mounted, using a small parallel collar to space it from the door proper. On Pixie a small length of chain is used to lift the latch. In practice it is more likely lifted by the fireman’s shovel, however the chain is provided and as on the prototype it terminates in a ring through the small shelf above the firehole door

Cleading

There has been considerable discussion in the model press regarding the insulation values of available materials. For Pixie the asbestos replacement material supplied by the trade has proved successful. The material was easy to cut to pattern, did not stretch or distort in the course of handling and installation and was sufficiently rigid to remain firmly in place until the cleading material was fitted and the boiler bands set in place. In shaping the material the use of patterns is essential, it takes but a few minutes with paper and scissors to produce quite accurate patterns, indeed the lady of the house may well find that this is an area where she can make a contribution ! The material is best cut on a sheet of hardboard using a sharp knife or a scalpel. Prior to installing the cleading the insulation can be held in place around the boiler using soft iron wire or even the plastic coated wire sold for use in the garden. These wires serve as an extra pair of hands and can be snipped away after the cleading is in place.

A further set of patterns are required for the cleading plates. It is important when cutting the plate material to remember to allow for the overlap at the joint. The time honoured method of using snips, with one of the handles secured in the vice and a piece of pipe on the other, makes short work of the straight cuts. A nibbler is fine for this job although it may be worthwhile protecting the metal from scoring by laying sellotape along the line of the cut. For curves and for the formation of the large diameter holes for boiler fittings, chain drilling and a sharp chisel will suffice or, rather more laboriously, a metal cutting blade in the saw frame. Precautions are required to avoid scoring or burring the metal and particularly, forming creases which will prove impossible to remove.

In the case of Pixie a supply of half-hard brass was available, this was used although the pundits advise using thin mild steel Although the material is a kindly one in use and tin snips can be used for cutting it to shape, care has to be taken in installation to avoid a local sharp bend which can produce an irremovable crease in the plate. Attempts to remove such a crease will only emphasize it so it is best left alone, that is if the builder can live with it, otherwise that piece should be set aside for a less visible use and a new plate prepared. In the absence of bending rolls, and few of us are fortunate enough to possess these, a variety of formers can be used to roll the plate, clean scaffold tube, preferably the lightweight variety, even a jam jar has been pressed ( with care ) into service, work being carried out on a piece of carpet to preserve the face of the material.

The boiler bands are fairly straightforward provided that the correct length is first established using a piece of wire wrapped around the cleading which is temporarily held in place by wires, as was the insulation. Small sections of angle steel, drilled for the fixing bolts are rivetted and soldered to the ends of the boiler bands, remembering to leave a tongue of the band projecting beyond one of the angles to maintain the line of the banding. With the bands assembled, the wires temporarily retaining the cleading plating can be snipped allowing the bands to do the job for which they are designed.

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Chapter 13

Plumbing. Gland and union nuts. Union liners and olives. Valve bodies, spindles and wheels. Pumps. Gauges. Sanding gear. Clacks and dummy injectors.

Plumbing

One of the attractions of locomotives large or small is the profusion of pipework, both in copper and brass. Much of this is visible and can be polished, adding to the aura of a model. When preparing runs of pipe, once their routing has been established it is advisable to replicate the pipe using a length, or lengths, of fairly stiff wire. Straightened out, the wire(s) will give an accurate length measurement which would otherwise be difficult to achieve. Many of the pipes on PIXIE have a joiner in mid-run, this is helpful when it comes to erection when the two lengths of a pipe can be installed, sometimes a fiddley job, the joiner inserted and the pipes coupled up.

L.B.S.C. had a lot to say about pipes and unions and there can be little doubt that he was right to ridicule the overlarge unions seen on many standard gauge models on 3 1/2 inch gauge track. His solution was to solder the cone directly onto the pipe thus avoiding union linings which have of necessity to be of such a diameter that the pipe can be entered into them. Size is not such a problem in 2 1/2 inch scale and on Pixie linings incorporating the cone are soldered onto the pipe ends. This soldering is best carried out by applying the heat to the inside of the lining whilst touching the fluxed outside of the pipe and lining with 1/16” diameter rod of silver solder.

Gland Nuts And Union Nuts

Gland nuts for valves will be of standard sizes and a number should be fabricated for stock. A small recess cut with a minute boring tool will form the locating groove for an ‘O’ ring seal adjacent to the butress end of the nut, steam or water tightness can be achieved with just the slightest turn of the nut on the Model Engineer thread.

Gland and union nuts are made from appropriately sized hexagonal brass bar. The bar is first centered from the tailstock then drilled using the appropriate bitt for the thread employed. Model Engineer threads are used universally for fittings and a glance at any catalogue will indicate the appropriate size of threads for specific pipe sizes. It is worthwhile making up a ‘ D ‘ bitt to complete this stage of the work and provide a square face to the buttress. Next drill a few thousandths of an inch larger than the diameter of the pipe is taken just beyond the overall length of the nut. Tapping is carried out with the tap supported by the tailstock centre, finishing with a plug tap. A touch with a a chamfer tool or a smooth file ( with a good handle ) applies the chamfers and the piece is completed by parting-off.

Union Liners

Making liners is an enjoyable job, especially where a four tool turret is available ( and if it isn’ t, now is a good time to make one! ) The angle setting of the chamfer tool forming the cone on the liner can be set from a centre-bitt mounted in the tailstock drill chuck and once set can remain in position until a batch of work is complete. A knife tool is set into another position in the holder. With a parting tool set in the rear tool post production can commence. A length of brass bar of diameter which will just enter the thread to be cut in the union nut is set in the 3 jaw, centred and drilled from the tailstock chuck, using firstly a centre-bitt then a drill of the diameter of the pipe bore. The hole is taken rather deeper than the turned and shouldered length of the lining plus the length of the cone. This is to ensure a through hole after parting-off. Next a drill of the a few thousandths of an inch greater than the outside diameter of the pipe is taken down to the line of the eventual shoulder, this provides a positive stop for the pipe end. The parallel portion of the liner is now turned to a diameter a fraction under that of the hole in the buttress face of the union nut. The chamfer tool is plunged in leaving a short length of the original diameter between the cone and the shoulder. The parting off tool completes the job, bringing the cone to length. If the dial readings are noted as the first component is made then manufacture of a batch of linings becomes almost automatic.

Union Olives

Small cones or olives can be used where it is required to reduce the overall size of a union or connector. From the range of copper tube available it is usually possible to select one that is a sliding fit on the size of pipe to be connected or secured. To obtain the correct cone angle a chamfer tool can be set to a centre bit in the headstock drill chuck. Several cones can be produced in quick succession from the copper tube held in the three jaw chuck. A sharp tool and high speed will be required to avoid distorting the tube, particularly when parting off which should be done leaving a small shoulder. These cones soldered into place on the tube, using the merest touch of solder require very little force on the union nut to achieve a tight joint.

Valve Bodies

Manufacture of valves is quite a time consuming operation and some builders may wish to buy theirs from the trade. It is always difficult to get exactly what is required for a specific prototype however and the following should prove helpful to those who wish, or are forced, to have a go for themselves. Trade suppliers market useful material for the body of valves in the form of tees and double-tee castings. These save the constructor the trouble of building-up bodies from bar or rod.

At this stage a set of tapped bushes will prove to be most useful. Produced in the three jaw, drilled, tapped and marked for number one jaw in a series of Model Engineer thread sizes, these bushes permit bodies to be mounted securely for turning and drilling operations without thread damage. The set of bushes, which should include 3/16, 1/4 and 5/16 sizes as a minimum, can be set aside and re-used, so that time spent in their manufacture will be amply repaid as work proceeds on further models . The valve body casting can mounted in the four jaw, the first end to be threaded centered and lined with the axis of the lathe. This can be achieved by centre punching the approximate centre of the spigot, lodging this on a centre set in the tailstock and then lining-up the body by adjusting the chuck jaws, the tailstock can then be withdrawn. With the body thus set the outside diameter of the body can be machined as far as the intersection of the limbs of the valve. The limb can be brought to length, centre drilled and a hole drilled a slight clearance over the pipe size. A suitable size of centre bit can then be used to form an internal chamfer to suit the liner. The external thread for the gland nut can now be cut, ideally using a tailstock die holder. In the absence of a tailstock die holder the nose of a tailstock drill chuck can be brought along to bear on the back of a standard diestock to maintain the correct line of thread. With the body still mounted in the mandrel the hole for the valve spindle can be drilled to the required depth and the body tapped to suit the spindle. Once one limb of a casting has been threaded externally it is a simple matter to mount it in one of the previously prepared mandrels, set in the three jaw chuck for further turning and completion of the other limb(s) ready for union nuts. With all limbs completed it becomes matter of a few minutes work with a succession of files to complete the body profile. For this operation the valve body, still in the mandrel can be transferred to a vice or the chuck set on the mounting plate described in the chapter on simple tools and attachments.

Valve Spindles

These are generally made from rustless steel and are best made several at a time. A length of material set in the three jaw and fine turned to the appropriate spigot diameter. this may if required be coned using a smooth, flat file. Threading is carried out using the tailstock die holder or a diestock supported from a tailstock drill chuck. The neck of the spindle can then be turned to diameter and, if required, the end filed square for attachment of the valve wheel. An accurate square section can be achieved using the simple indexing attachment described later. After parting off, if the valve wheel is to be fitted permanently, the gland nut should assembled onto the spindle before the end is swaged or punched. Where the wheel is to be threaded onto the spindle sufficient length of thread should be allowed to enable a lock-nut to be fitted.

It is important to ensure that valve spindles remain captive in the body of the valve whilst in their open position. Spindles which unscrew completely from the body of the valve are potentially hazardous in service. Spindles can be rendered captive by reducing the spindle diameter where it passes through the gland nut such that a shoulder is formed beneath the ‘ land ‘ of the nut. When the valve spindle is unscrewed this shoulder bears against the buttress so formed, preventing its complete withdrawal.

Valve Wheels

Those who manufacture their own valves will be faced with the production of valve wheels that convey the spirit of the prototype. There have been several methods suggested in the model press and the following are though to provide convincing wheels. A.G Neville in MODEL ENGINEER Vol 146, No 3644 described a method using six lengths of thick walled tube, silver soldered around the circumference of a central tube. These were held in place for the soldering operation by soft iron wire. Succeeding operations were to part off suitable lengths for individual wheels, lightly countersink the holes and file the rim to required final section.

LBSC describes a method of building ‘ cool ‘ wheels where a coiled wire is soldered around the periphery of a turned brass wheel centre. Requiring considerable care in production this does produce a good looking and effective wheel.

A person coming new to model engineering will do well to buy a few nuts and cones, or even a complete valve to serve as patterns for their plumbing work. From these the general proportions can be gauged rather more easily than from the many drawings that are published in the model press. Of course the fanatic can produce fully scaled models of fittings if they wish, but most of us are happy with conventional model fittings. as has been said before, we set our own standards to suit our purses and the time available.

Pumps

The use of ‘ O ‘ rings for packing pistons and glands ensures that the very beginner can manufacture efficient pumps. In the days of graphited yarn and tallowed hemp, the amount of packing and the tightness of gland nuts was critical, too little and pressure was lost, too much and excessive friction resulted. With careful machining, in accordance with the manufacturers instructions, pistons and glands will be perfectly tight with the least possible amount of friction developing. In the case of piston packings some small pieces of tool steel ground to the correct width for the main sizes of ‘ O ‘ ring will save time in preparing the necessary grooves. For gland nuts, small diameter boring tools, again ground up to the correct profile can be set into the tool holder described later to machine the internal grooves in glands.

Pumps should be located such that the eccentric rod is as long as possible. This reduces the wear on glands as well as cutting out a certain amount of the friction in the system. The length of the ram is also critical in this respect.. In Pixie the pump is mounted behind the front beam, below the saddle, on a block profiled such that the axis of the pump lines with the centre of the front axle. This position was chosen as the available space was limited by the position of the main stretcher spanning between the motion plates. There would also have been insufficient clearance around the back axle for the sweep of the eccentric strap. The mounting block is secured to the front beam by countersunk screws hidden behind the front coupling, the pump in its turn being bolted to the block. This arrangement will permit the pump to be dropped down from between the frames in the event of maintenance being required.

Pump rams are best made of rustless steel, barrels are generally gunmetal castings incorporating the stand and valve box and are readily obtainable from the trade. Rustless steel balls, a suitable sized ‘ O ‘ ring and some hexagon brass bar complete the material requirements. Construction details have been spelled out many times in the model engineering press and there is little point in repeating them here. LBSC gave good coverage in his collection entitled ‘ LBSC’s Shop Shed and Road ‘ which describes several types of pump and their construction. He notes the key points, for efficiency of eccentric driven pumps as being, ‘ fairly large bore and short stroke, ample sized ball valves with restricted lift, minimum clearance within the pump itself, and the water pipes ( especially the suction ) of sufficient diameter not to throttle the flow of water ‘.

A crosshead driven pump has a lot to offer, not the least being accessibility for adjustment and maintenance. Discussing the the advantages of a crosshead-driven feedwater pump in the case of ‘ Rob Roy ‘, Martin Evans rightly states that ‘ such a pump is readily accessible for servicing, if the pump doesn’t function for some reason such as balls sticking or becoming furred-up, it is only the work of minutes to take the whole thing off, strip it right down and clean the valves etc.’

Gauges

There have been some magical articles in the model press, written by wizards who have made their own gauges complete with microscopic Bourdon tubes. The beginner will do well to buy-in his gauges from a specialist supplier. Gauges are not the thing to cut ones teeth on, particularly when dealing with the substantial pressures that our locomotives are capable of producing. Those who have an overwhelming desire to construct their own gauges should study the article in Model Engineer. This will probably prove sufficient to prompt them to start out for the nearest trade supplier of the finished article! The gauges on Pixie were purchased from a suppliers catalogue, one for the boiler pressure, taking its feed from the steam fountain, the other measuring valve chest pressure. The latter is fed from the right hand valve chest via a ‘ tee ‘ incorporating a drain valve complete with a tap reminiscent of that to be found on a antique Samovar, complete with ebony handle, replicated here by a turned, stained and varnished piece of hardwood on a mild steel spindle.

Sanding Gear

Sandboxes are a prominent feature on most narrow gauge locomotives, being especially necessary in the conditions in which narrow gauge locomotives operate. Making the sandboxes on any narrow gauge locomotive should give the builder great deal of enjoyment. Whether mounted on the running plates, on top the boiler or as in the case of the Wrenn Class on the front of the saddle tank, they probably include a degree of geometry. The many patterns can be produced by turning or using a combination of turned parts and barrel or formed sheet. Sandboxes are another of the features which generate atmosphere and care was taken to replicate those on the model. For Pixie the mild steel fronts and backs of the boxes were flanged up over a piece of 1/4 inch plate which was cut to the correct profile, with allowance for the plate thickness to be used, and rounded on one edge. As the flange was to be relatively narrow flanging could be done cold without too much upset to the metal. With the profiled plate sandwiched between the template and a slightly smaller piece of stock steel it was gradually flanged using hammer with a smooth face. Progressing around the plate about 1/8 inch of flange was formed without creases. After removal from the templates the flanges were brought to uniform thickness by filing, paired off and marked in two sets. With the plates set flange to flange, the outside edges were trued locally, again by filing.

A wire was bent around the perimeter of the flange to establish the length of the strips of mild steel infill which were to form the sides, top and bottom of the boxes. The strips were then bent to the required profile and small adjustments made to ensure a neat butt joint. At this stage a small hole was drilled centrally where the flange for the cover would be located. This was thought necessary to avoid any possibility of an explosion as each box was sealed during welding! Now the three pieces of each box were wired together and the welding operation carried out. Welding was only adopted for this assembly as access was available to TIG welding equipment, brazing would have been equally acceptable. After the assemblies had been cleaned-up the filler openings were drilled and bored and flanges for the covers were soldered into place.

With the boxes clamped to the topslide of the lathe the holes for bushes for the operating rod could be drilled. As the rod passes through four bushes, two in each box, the lathe set-up was used in order to ensure that the holes lined correctly, parallel to the faces of the boxes. The bushes for the operating rod were then soldered into place, location aided by turned shoulders, bearing against the sandbox sides and the insertion of a length of rod which had been thoroughly oxidised to prevent it becoming a permanent installation! Now the back of each box was drilled for the fixing bolts which were to engage in the blind, stepped bushes in the front face of the saddle tank. These holes were spotted from the template prepared at the time when the bushes were set-out on the tank. The cone shaped feeders at the bottom of the boxes were shaped and fly cut to radius then through-drilled for the sand flow. Pipe flanges were prepared and drilled at the same time as the feeder cones to ensure a good fit on final assembly.

Filler caps and flanges proved to be simple turning jobs and one of those little tasks that give so much enjoyment in obtaining the correct curves. These are achieved using a graver held on a bar secured under the clamping shoe of the top slide, and finished, dare I say, by filing in the lathe!

The operating lever with a boss at one end and at the other a tapped hole providing a fixing for the pivot bolt connection with the pull rod was prepared from mild steel. The pull rod itself is a length of 1/8 inch diameter mild steel rod terminating in an eye for the pivot bolt at one end and yet another ‘ Victorian cupboard handle ‘ at the other. The travel of this pull rod is limited by a strategically placed split pin which bears against the weather plate in the extreme rearward position. Small cranks and a dart valve inside each box control the flow of sand to the copper sandpipes which extend to the track level and are supported at one spot by pipe brackets bolted to the main frame members.

Clacks And Dummy Injectors

Feed water on Pixie is introduces via clack valves positioned where the prototype injectors are installed. Clacks are efficient and provide trouble free running. Lately time has permitted the production of dummy injectors which fit into the bosses on the boiler and replicate injectors for show purposes. These dummy injectors, whilst outwardly similar to the prototype, are in reality clack valves in disguise. they are soldered up assemblies of pieces filed from gunmetal offcuts from other operations. The screwed cap permits the installation of a spring and ball valve just as in standard valve. At a later date a working injector will be installed under the footplate.

Boiler Feed By-Pass Valve

An extra not to be found on the prototype is a feedwater by-pass valve. On Pixie this is mounted on the left hand frame member in the space between the back of the bunker and the boiler cleading. It is unobtrusive in this position, yet easily accessible. The valve itself is an essential brought about by the axle mounted water pump and the setting has to be monitored in steam to prevent over-feed and priming. That is if the driver wishes to avoid the ‘ hot shower ‘ which will otherwise result!

The Waterworks

Below and at the rear of the saddle tank, feeds are taken to the axle pump located behind the front beam and the hand pump sited in the left hand bunker. From the pumps the feed goes to the boiler, that from the axle pump via the by-pass valve. Sited below the front of the saddle tank is a balance pipe which also serves for emptying the tank. On Pixie this is extended and the shut-off valve is, for convenience, accessed below the level of the main frame member.

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Chapter 14

Regulator block, gland and lever. Chimney. Steam dome. Safety valves. Retro-fitted pump eccentric. Cylinder drain cocks.

Regulator

Steam dome

Regulator Block And Gland

A search through the scrapbox revealed some short lengths of gunmetal, chucking pieces from a previous model, these were to form the body and gland. The machining involved is similar to that for any gland assembly, the body being a slide fit in the large bush on the backhead, secured in place using threaded and shouldered studs. Nuts on the threaded part of the stud tighten the gland into its recess. An ‘ O ‘ ring was installed into a groove behind the flange of the regulator body so as to bear on the boiler bush and ensure a steam tight joint. ‘ O ‘ Rings, whether standard or purpose-made from a kit feature more and more in model engineering and, provided the manufacturer’s limits on groove sizes and fits are observed give trouble-free service.

The regulator rod in rustless steel locates into a hole in the regulator within the dome and is maintained in position by a tiny bush of the same material which, pinned to the rod, bears against the back of the regulator body at the backhead. Some small allowance is necessary to avoid any tendency towards binding due to expansion in service. The gland slides within the block, guided by the threaded studs, here again an ‘ O ‘ ring forms an excellent steam tight joint with little or no effort applied to the nuts.

The regulator lever and handle, ( sometimes seen on the prototype with the handle facing rear-wards and sometimes facing forwards ) is from mild steel and the travel of the lever is limited by an angular shroud fitted with stops at the perimeter of the face of the block. Some experiment was required to ensure that the limits imposed by the shroud allowed the full travel of the actual regulator disc on the Stroudley type regulator within the steam dome

The Regulator

A number of reasons prompted the choice of a Stroudley type regulator, not the least was the straightforward construction and positive action. A further factor was that access for maintenance could be simply achieved via. the steam dome. These considerations have been bourn out in service although the fixing method would be revised in a further model. Being reluctant to drill the boiler to provide a fixing for the regulator the fastening is is made through the steam dome, using stainless steel bolts. This necessitates some juggling at the time of assembly and would, in a rebuild, be modified to the more conventional fixing using a strap screwed to the boiler shell.

Gunmetal was used for the body of the regulator, and the two valve discs. The body was drilled to provide the vertical steamway then sealed with screwed plugs. The fixed disc and two fixing brackets were silver soldered onto the body at one heating. The steamway was drilled through the disc and the hole for pivot stud drilled and tapped. Care was taken to remove the burrs formed in these drilling operations as they would otherwise prevent the valve disc from making a steam tight joint with the fixed disc. A ‘ vee ‘ notch was filed in the edge of the hole in the fixed disc to assist in providing gradual opening of the port as the regulator was opened in service. The hole for the steam pipe was next drilled and tapped. The loose disc was then prepared, being drilled a close clearance on the pivot pin. Holes were drilled and tapped for the linkage bolts. These were threaded such that when fully inserted into the holes in the loose disc they provided ‘ pinch-free fit ‘ when passed through the holes in the actuating rods. All screws and pins are stainless steel and all are drilled and secured using stainless wire to prevent loosening in service. The spring maintaining contact between the valve faces is of stainless wire wound-up around a pin in the 3 jaw, only a light spring is required here as steam pressure does the job in service. The actuating levers are from rustless steel as is the rocker bar. This fits onto a square formed on the end of the regulator rod, being retained by a nut threaded onto the rod. The rod terminates in the rounded spigot which engages in the regulator body.

Chimney

The chimney was turned from a piece of reinforcing steel culled from the scrap heap on a building site. It was set in the 3 jaw, drilled using the largest available drill bit, then bored out. The boring tool used was an adaptation of a design published in MODEL ENGINEER many years ago and described later in this book. This has the advantage that it can be entered into small bores and, when modest cuts are taken, provides a a long reach without chatter. The tool uses small diameter cutters which can be produced from the remains of broken centre bitts. As with all long tools however it is essential that a number of fine finishing cuts are made to counteract inaccuracy resulting from the spring of the shank holding the tool.

The outer taper was turned in several stages, setting the top slide to the required angle and moving the saddle and locking it at each intermediate position. A small rebate was formed at the top of the piece to locate the cap, and, prior to parting-off to finished length, a similar rebate formed to seat into the chimney base. The cap and base castings were next machined to the required profile with the necessary rebate and projection to ensure a good register between the parts at the time of soldering the joints.

The chimney cap was turned from a piece of gunmetal, set in the 3 jaw. It was bored and the joggle formed for the joint with the chimney body. The curved surfaces were shaped offhand, using a tool supported by a piece of stock bar set in the tool post. Once bored and profiled the cap was then parted off. The bottom casting was turned, again with a joggle for locating the chimney body and the plain portion above the flair turned circular. The part was then set on the vertical slide for fly-cutting to match the radius of the smokebox. This was facilitated by using a washer and one of the medium Myford tee bolts set into the slot in the vertical slide. as in all such operations the slide was packed from the topslide to eliminate movement and avoid chatter. Finally the flair was ground and filed to shaped. Enthusiasts may wish to produce their parts by spinning or raising them from gilding metal. This is, it seems, an aquired art and presents a rather daunting prospect to the tyro.

The three parts were joined by silver soldering and the base drilled for the bolts to fix it in position onto the smokebox. As is the case when soldering boiler tubes, several small nicks in the joining surfaces will assist the flow of solder into the joint.

The petticoat pipe was spun-up from a piece of copper pipe, an offcut from the last plumbing job carried out in the house. Frequent annealing permitted the lower end to be expanded to a profile in line with the recommendations in ‘The manual of Model Locomotive Construction’ by Martin Evans. The upper end is a push-fit into the chimney and stays secure with the aid of a dab of instant gasket. Whilst on the face of things this may seem to be a pretty tenuous means of fitting it permits the petticoat pipe to be withdrawn when access is required to the otherwise congested smokebox.

Steam Dome

The steam dome on any locomotive is a joy to produce. Whether turned from a casting, from solid material or spun to shape by the more adventurous and proficient model engineer the dome has to be a thing of beauty. The fortunate model engineer may find a suitable casting in the stocks of his local supplier. He may through perusing the details in articles in the model press find a dome casting that nearly matches his requirements and can be doctored to provide the required form. It was Henry Moore the celebrated sculptor who pointed to a massive piece of material and said that the form he wanted was ‘ in there somewhere ‘ ! The dome on PIXIE has been fabricated from thin sheet metal and fortunately there is a joint in the material just below the convex curve at the top. In the case of Pixie this permits a turned dome being produced in two pieces, the lower from an offcut of steel of unknown parentage, probably a cropping from a stockists scrapbox, the upper a cast piece of gunmetal. Assembly from two pieces of material also facilitated the cutting of the opening for the base of the safety valve assembly.

A length of bar for the lower dome was cut by hand from the billet of steel…. blood and sweat ! The length required was determined bearing in mind the flare which fits over the cleading. This was then set in the 3 jaw chuck and a length slightly less than the dimension from the top of the flair to the top of the parallel portion of the dome was turned to finished diameter. A small rebate was formed in the end to provide a location for the dome top section. The blank was then turned in the chuck, gripped by the reduced section and the remainder turned to to the diameter of the finished flair. The body was then bored out to clear the inner dome.

Whilst means of producing the flair by milling alone have been described by Martin Evans, the tyro will find that the simplest solution to the somewhat knotty problem of the geometry involved will be to turn the upper, external concave shape which is viewed in the side elevation of the finished dome, fly cut the seating to match the boiler cleading ( NOT the boiler itself ) then mill away the evidently surplus material before finally finishing up with a succession of files. Ideally the edges of the flare should be very thin to replicate the prototype, this is easier said than done and the individual must work to HIS predetermined standard. Again a template will assist in achieving the correct profile.

Following the sequence described above, the base of the dome was fly-cut to the profile of the cleading. The part-machined blank was mounted on the vertical slide using bolts passed into the tee grooves via a washer fitted into the inner dome recess. In instances such as this where material is to be machined whilst attached to the vertical slide, particularly where there is any amount of overhang, some packing should be used to augment the support provided by the bolts or clamps. A piece of stock bar and some small blocks secured between the piece to be machined and the top slide will provide such support This precaution will be appreciated when for example the heavier of the intermittent cuts of a fly cutter are experienced. Once again, a reminder …. when fly cutting, first set the cutter to describe a radius greater than the required finished radius and then slowly reduce the radius of the cut, whilst advancing the piece, until the eventual diameter is achieved. Frequent checking against a template will ensure a good fit.

With the seating shape generated, the excess material was milled away and the final form achieved by filing, taking care not to remove too much material in any one place at a time. The filing operations were eased by mounting the dome blank onto a mandrel secured in the vice at the workbench. Final polishing produced an acceptable lower dome ready for drilling for the various valves which adorn the prototype.

Pixie’s upper dome was produced by straightforward turning, finished freehand using a tool bearing upon a length of stock bar set in the toolpost. The part was then set, protected by paper at each jaw in the 3 jaw for the inner profile and the locating tongue to be turned. Later the plan profile of the the safety valve base was set out on the top of this piece using lines scribed in marking blue and the opening milled for final filing to fit at the time of erection.

Safety Valves

The safety valves on PIXIE sit on top of the steam dome. This arrangement is replicated in Pixie by two valve bodies, containing the valve seatings, which pass through a shaped block into bushes in the top of the inner steam dome. A turned pillar which provides the fulcrum for the spring retaining beam is mounted on the block. When the valves lift, exhausting steam is directed away above the roof of the locomotive by two polished brass pipes slotted to fit over the retaining beam. These pipes seat upon a shoulder turned onto the valve seat bushes and are supported by a mild steel bracket bolted to the roof.

Where two safety valves are fitted, and this is recommended, they should be set to blow at the same pressure. Failing this the higher of the two may never be actuated and may seize-up.

In Pixie the valves are phosphor bronze balls drilled and tapped to accept stainless steel spindles. The seat for the balls was formed in the manner described by LBSC, a blow with a heavy hammer on a steel ball set onto the embryo seating. To avoid thread damage during this somewhat brutal procedure each valve bush in turn was screwed, as far as its shoulder, into a tapped hole in a substantial piece of bar. Valve springs were wound from stainless steel wire and were tested using a simple loading rig as described in an article by ‘ Laurie ‘ Lawrence on ‘ SAFETY VALVES AND A FEW OTHER SAFE ODDS AND ENDS ‘ in Model engineer Vol. 162 No.3847 of May 1989

Retro-Fitted Pump Eccentric

The axle driven pump is, of course, quite unprototypical in the case of Pixie, although as with most things connected with locomotion, there are prototypical examples of the use of axle pumps. However, in view of often encountered comments regarding substandard performance of injectors with ‘ warm ‘ water an axle driven pump is mounted behind the front plate. Later experiments may result in this being discarded in favour of an injector. With subsequent removal of the pump in mind, and as the wheels are bonded onto the axles, the pump eccentric is clamped and pinned to the leading axle.

The standard pump is mounted on a pair of tapered blocks behind the front plate using countersunk headed screws. The inclination of the blocks lines the pump with the axle. A blank for the eccentric tumbler was first produced from a piece of stock bar, this was left oversize for eventual finish turning and the machining of the locating groove for the eccentric sheave. A length of bar of sufficient section to incorporate the clamping bolts was squared-up on all four faces. This block was drilled for clamping bolts. One of the faces was ‘raised’ by centre pop marks to ensure full penetration of the solder into the joint, and the block then silver soldered into position on the tumbler disc with regard to the approximate axle centreline. The assembly was then split by sawing, the sawn faces lightly cleaned up and the whole re-assembled to enable the axle hole to be drilled then bored. With the hole bored a thou or so undersize, the assembly could now be clamped onto a stub of material of the same diameter as the axle, mounted in the four jaw, offset by the throw of the eccentric. Now the eccentric was machined to final shape including the projecting guide. Later, during erection, the eccentric assembly was pinned to the axle using a short length of silver steel, this was inserted into a hole drilled through the clamping block. The eccentric thus produced works efficiently and can be removed when an injector is fitted in due course.

The eccentric strap was a standard casting intended for another locomotive. The lugs were drilled for the assembly bolts, the assembly sawn into two parts, re-assembled then faced and the inner radius and guide groove bored, to match the tumbler which was frequently offered up to ensure a nice fit. The strap was then clamped onto a stub of stock material for the other face to be machined. Provision of an oil cap on one lug and milling the halved joint for the eccentric rod completed the part. Binding between the tumbler and the completed strap was eased by some judicious application of grinding paste then metal polish followed by a good wash and scrub with scouring powder and detergent !

LBSC’s words and music provided the basis of the method used to produce the drain cocks. The principle operation here was not that of machining the valve bodies but rather the manufacture of a tapered reamer for forming the valve seatings. The technique involved setting the top slide to the correct inclination and turning not only the tapered plugs but also a reamer in silver steel for forming the seating within the body of the valve. The reamer was then filed to shape and tempered. The cross hole in the body of the valve was drilled undersize and then reamed to what must then to be the correct taper for the plug. The ‘ thin ‘ end of the plug was then threaded for the retaining nut and washer and the ‘ thick ‘ end squared-up for the attachment of the operating lever. A little ‘ running-in ‘ with a small amount of grinding paste ensured a tight valve although all traces of the paste had to be removed using scouring powder then detergent. On Pixie very small diameter tubes are superglued into the valve outlets to direct the wet steam away from the loco with the drain cocks in the open position.

Steam Actuated Cylinder Drain Valves

When first encountered PIXIE was fitted with steam actuated drain cocks. These are operated from the footplate by a valve similar to that found on the outlet of Victorian tea urns, a valve of character ! The actuating cylinder is mounted behind the front beam, the piston rod connecting to the cockshaft via a link and lever. The bar connecting the drain cocks on the right hand side of the locomotive has a tension spring which keeps the cocks open / closed according to the setting of the valve on the weather plate.

A short stub of gunmetal was turned then bored for the cylinder, quite fun as it is only just about an inch overall. A cylinder cover was turned to suit and bored for the piston rod. The piston and rod were prepared all as those for the engines, and the whole assembled using 8 BA bolts. The cylinder is mounted behind the front beam on an angle bracket, forked around the steam inlet union, again using small bolts. The crank, pivot and lever connecting to the cock provided some watchmaking experience, the lever being pinned to the cockshaft which is set in tiny bearing bosses on the frames.

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Chapter 15

Platework, tanks and bunkers. Tank mock-up. Building the saddle tank. Tank mountings. Weather board / spectacle plate. Scale roof and back. Driving roof and back. Footplates and footplate supports. Ashpan. Cutting, bending and rivetting plates.

Saddle tank cover with access panel on model

Platework, Tanks And Bunkers

The saddle tank dimensions having been established from the survey of the prototype a start was made by constructing a card and plywood mock-up. Plywood end panels, 3/8” thick, generated the curves of the platework which in this mock-up was represented by thick cardboard. One of the plywood dummy ends was later used as a template when cutting a piece of 3/8” mild steel plate to be used as a flanging plate. Provision of the mock-up enabled an early trial fit to be made to confirm that the finished tank constructed to the measurements taken at site would seat properly on the components of the model erected so far.

Blocks of wood set upon the frame angles to simulate the tank-support angle brackets enabled dimensions to be established for the location of angle brackets which would eventually be brazed to the boiler shell. The position of the curved steel angle support connecting the tank to the smokebox could likewise be established. Messrs. Reeves’ asbestos-free lagging material was to be used in conjunction with cleading and boiler bands of brass sheet. The mock up confirmed that there was sufficient space between the underside of the tank and the boiler for these items. With key dimensions of the model components established, work could be commenced on the tank proper.

Flanging The Plates

It was decided to use mild steel plate for the tank rather than brass sheet which would have been the alternative. By making a few trial sections of flanges which included both convex and concave curves it was established that, with care, 16 gauge mild steel could be flanged cold without loss of flatness of the plane parts of the platework. This could be achieved provided that, whilst flanging, the plate was sandwiched between the 3/8” template and a stiff piece of plate slightly smaller than the flat part of the template. As the flanges were formed it became necessary to snip out excess material from the flange at the convex corners in order to avoid cockling and to provide a smooth land for the wrapper plate. A touch of weld-metal sealed the flange at these points. With care the metal could be spread sufficiently to accomodate the concave curves where the tank sits over the smokebox and boiler cleading.

In the prototype, due to the riveted construction and the lapping of plates, it was necessary to form a joggle in the flanges to accommodate the extra layer of plate at the lap joint adjacent to the bottom corner of each side. This was also necessary in the model, it was achieved by setting the plate into the twin vices , and using two substantial backing bars together with two offcut pieces of plate of thickness equivalent to that of the tank plating. With the offcut pieces of plate positioned either side of the tank plate, above and below the position of the joggle, the vices were tightened in unison and the offset or joggle in the tank plate thus formed as it would be in a press. A considerable amount of ‘ presswork ‘ can be carried out in the vice although of course the bigger the vice, the better for such applications. When folding or pressing, the workpiece should always be supported using quite heavy backing bars, in this way twist and distortion will be avoided.

Sandbox Fixings

At this stage fixings for the sandboxes were inserted into the front flanged plate, these consisted of brass bushes of ‘top-hat’ configuration in which blind holes were tapped to receive bolts which would be passed through the back of the sandbox. These bushes, as well as providing a secure fixing for the sandboxes served to space the sandbox from the front plate. The holes for the fixing sockets were drilled to template, the template then set aside for future use in drilling corresponding holes in the sand boxes, a small note was scribed on the templates as a ‘ reminder ‘ to reverse the templates when applied to the back of the boxes !

Wrapper Plates

The tank wrapper plates were formed using suitably sized bars from stock set in the twin vices at the dirty bench. Packings sitting on the bed of the vice located two bars, one the radiussed bar which actually formed the bend, the other a square section bar to maintain the flatness of the plate. Timber drifts used driven by a builders ‘ lump ‘ hammer persuaded the plate to take up the right form. The certain way to generate blemishes in folded platework, when not using a folding tool, is to use too light a hammer when bending or flanging. Blemishes are also formed if the face or edge of a hammer is allowed to come into contact with the plate. It is essential that clean barstock, free from blemishes is used for the formers, otherwise blemishes will be transferred into the plate being folded. A hardwood block should always be interposed between the plate and the hammer as the metal plate is bent. The combination of hammer blows and pressure applied to the plate by the free hand ensures the desired curve being generated. With some steels, particularly stainless steel, it will be necessary to over-bend the plate slightly to allow for elastic recovery although care is needed to avoid forming a local kink beyond the freshly formed curve.

Difficulty can be experienced in correctly gauging the width of plates which are to be folded to fit into, or around, concave or convex flanges. It it is advisable to start with an overwide piece of plate which can be trimmed to size on completion of the folding operation. The approximate width of such plates can be established by bending a piece of fairly stiff wire around the flanged plate, straightening it, then making some small allowance for the effects of the bends to establish the cutting width. With the folding operation completed any excess can be cut away. In the course of forming wrapper plates frequent checking against the flanged plates is necessary to ensure a good fit. It is important to make index marks on the flanged plates and wrapper to ensure that the wrapper is located in the same place each time a trial fit is made. Temporary marks of this nature are best made with a ‘ Permanent ‘ grade of pen as used for overhead projectors. The marks can be removed using methylated spirits and a scrap of rag. Trial fits should be made against each end plate as, when using rolls, particularly when using makeshift ‘ bending rolls ‘ lacking control of parallelity, there may be some small difference between the two ends of the wrapper plates.

Tank Assembly

The tank currently mounted on PIXIE has been fabricated by welding, with dummy rivets, a grand job it is too! However, as locomotive was to be modelled as it was the first time it coasted into Pages Park Station on the Leighton Buzzard Narrow Gauge Railway, it had to be a fully riveted assembly on Pixie! In order that the rivetting process could be carried out on all visible joints it was decided that a closing plate would be introduced into the curved underside of the tank. When all had been riveted up this plate was to be inserted and secured by countersunk screws into tapped holes in butt straps along the joint. Being on the underside of the tank these would not be visible in the finished model.

Rivetting was carried out commencing with the installation of the tank front. Fortunately, in the prototype the flange on the backplate of the tank is located rearward-looking and these rivets can be inserted and formed last. Soft iron rivets were used, a dolly being set in the vice to enable the innermost rivets to be reached. As with all riveted joints it is essential that the plates being joined are held tightly together to avoid the rivet shanks distorting and actually spacing the plates apart. Rivet holes should be marked by a scribed line and set out along the line using dividers. Apart from satisfying the ‘ rivet counting brigade ‘, accuracy of line and spacing have a considerable effect on the appearance of the finished model, and any inaccuracy on the tanks or bunkers which form a prominent feature of many narrow gauge locomotives can detract from otherwise good quality workmanship. Once the holes in the wrapper are drilled the flanged plate can be set into position and two holes transfer-drilled from the wrapper. Two small bolts through these holes will then hold the plates in the correct location whilst the remainder of the drilling is carried out.

The reconstructed tank on the prototype has an access panel let into the tank top. In the model advantage was taken of this feature to enable access for lining the tank with Fiberglass for durability purposes. When laying up the fibreglass in the tank BONDAGLASS pre-wetted glassfibre tape was used to ensure a good fit into the corners Pre-wetting avoids a problem well known to laminators, that of air becoming trapped between the composite lining and the base material at angles. Entrapped air makes it difficult to fully ‘ wet out ‘ the glassfibre. At this stage a baffle was glassed into position across the tank below the filler opening to prevent water in the tank surging backwards and forwards when the model is started and stopped in service.

Filler Cap And Pipe Flanges

The tank filler cap flange was turned from gunmetal as was the cover. The cover was made a push-fit on the flange to avoid problems in service. These activities are great fun, especially the reproduction of detail such as the very domesticated knob on the filler cap ! After fixing the filler cap flange by rivetting the underside of the panel was primed and painted. The panel was then secured by screws into flanges fixed to the underside of the tank top.

Balance pipe and feed pipe connection flanges were fixed into position on the wrapper using countersunk screws into tapped holes, a seal being achieved using Araldite. Once the Araldite had cured, the holes in the flanges guided the drills used to penetrate the tank . Where a mating flange is required, for the feed pipes for example, good matching fits can be achieved if these items are prepared at the same time as those for the tank. Pairs of flanges drilled and, if necessary, tapped at the same time ensure an accurate fit when they are eventually fixed together when the plumbing is installed. Flanges pre-prepared in this fashion should be marked according to location ( and orientation ) and stored safely for later use.

Tank Mountings

The tank is located and fixed at the smokebox using a radiussed steel angle, connection being made by bolts passing through the tank front and through the top of the smokebox. Attempts to form this by heating a piece of angle then bending it around a former failed, due to distortion of the section. This problem was solved by producing a simple plaster pattern from which a local foundry produce a suitable casting. This casting was set on the lathe faceplate and turned to finished section and radius. The angle is quite prominent on the model and, whilst this solution amounted to the ‘ use of a sledge-hammer to crack a nut ‘, the correctly shaped mounting enhances the overall appearance of this part of the locomotive. An alternative would have been to rough-saw the shape from the solid and then turn it to final form. On the model only two bolts are actually used in fixing the angle to the tank front, the rest are simulated by nuts run onto studs set in the angle. Similarly only two bolts actually penetrate the smokebox, the remainder being dummies. In the case of this fixing, as in many instances encountered in model making, absolute replication of fixings and fastenings is unnecessary for the purposes of strength and may even complicate final assembly and later maintenance.

The rear of the tank is located and retained by studs set into mounting plates on the underside of the tank, these pass through holes in the brackets on the boiler shell, these holes are slotted to cater for movement as the boiler heats and cools. The plates on the underside of the tank were fixed using countersunk screws into the wrapper plate, the joint being anointed with Araldite before the mounting was fixed. The fixing studs project downwards through hardwood blocks, which exist for insulation purposes. Teak blocks are used on the model and these allow a small amount of adjustment to overcome inaccuracies in the level of the tank assembly measured at the time of erection.

Two holes were drilled in the upper flanged joint at the rear of the tank. These are required for bolts fixing the stay-rods to the weather board, or as it might be termed on other locomotives, the spectacle plate! These two holes are coincident with the pitch of the rivets at this point.

Priming

It is most enjoyable to see a model develop in gleaming raw metal, be it steel, cast iron or gunmetal, and there is always a reluctance to follow what is perhaps the more usual sequence of priming, undercoating and painting parts as the work of production and erection proceeds. It has to be admitted however that there is little worse than entering the workshop and finding that surfaces, which the previous evening had exhibited a satisfying shine, are marred by embryo rusty fingerprints ! It is difficult enough to prepare metal around rows of rivets for priming, without having to remove such evidence. In view of the mild steel construction it was decided to prime the finished tank before storage. Accordingly, the tank was spray coated with a rust preventative paint, ‘ BONDAPRIMER ‘; this is a resin based paint containing zinc which has good covering powers and dries quickly to a uniform matt finish. This was a drastic step as painting a model is not something to be attempted lightly ! Experience has proved that this was the right course to adopt, the primer warded off the dreaded rust and provided a hard base for subsequent coatings, although they were applied many months later. More about the painting process anon!

Coal Bunkers

The coal bunkers presented another folding job. This time a flanging plate was produced to the dimensions of the inside of the main face of the bunker. Two suitably sized pieces of stainless steel plate were prepared to the correct height of the bunker. The plate to be folded was sandwiched between the flanging plate and a substantial piece of plate from stock, this was cut just slightly smaller than the flat on the flanging plate. This ‘ sandwich ‘ was then gripped in the vice and force applied via. a hardwood block. Care was taken when applying the force to start close to the stock plate to achieve the necessary tight bend. To overcome difficulty experienced in gripping the small amount of plate projecting from the sandwich this was held between two further pieces of stock held by a ‘ mole ‘ wrench which allowed hand pressure to be applied. With the bends completed a check was made on a true surface to ensure that the whole assembly sat flat and that the back and front were perpendicular to the base. Any slight twist in the formed plate was adjusted at this stage before the back and front edges of each bunker was trimmed to the correct length.

The top edge of each bunker is trimmed by a beading. A length of 5/16” diameter rod was milled filed to the correct ‘D’ section ( filing would have sufficed ), bent to match the top edge of each bunker and then riveted into position. The openings at the bottom of each bunker were chain drilled and sawn to shape prior to fitting steel angles at the edges which would abut the back plates. Similar angle was fixed to the bottom edge of each folding and to the back plates for use in fixing the bunkers to the footplates. Before rivetting these joints, plates were cut to the correct profile to fit into the bunkers. It was decided to mount the boiler feedwater pump in the left hand bunker and that plate was slotted accordingly. The left hand bunker was chosen for the pump location as this would free the right hand for the ticklish work of stoking through the dimunitive firehole door ! Later a hole would need to be drilled for the feedwater pipe although at this stage in construction the exact position of the hole was not known. As stainless steel had been used in constructing the bunkers these could be left in their pristine, shiny state until the time came for the final paint job . A word here about working stainless steel. Many are the broken bitts that testify to difficulties encountered in drilling ( not to mention tapping! ) stainless steel. The secret appears to be that any tool used to fashion stainless must be kept cutting at all times it is in contact with the metal. Considerable heat is developed the moment the tool rubs rather than cuts, and the temper is lost or the tool jams with dire results in case of the small drills we use. Hundreds of rivet holes in stainless plate have proved the wisdom of using an anti-scuff paste as a lubricant. This combined with working the tool hard by applying plenty of force to the feed avoids tool wear, heating and damage

The Weather Board / Spectacle Plate

The platework forming the front of the rather spartan cab provides some interesting work in shaping the plate itself and fabricating the angle steel supporting frame. This is mostly straightforward, fashioning material prepared according to measurements from the survey into model form. The angle supports presented a problem as far as bending the metal without distorting the section. The difficulty was ovecome in this instance by cutting a disk of plate of the scale thickness of the angle and turning from this a complete circle of material of angle section. Segments of this section were then cut as required to meet the geometry of the support frame. The roof bearer was of sufficiently large radius to be bent cold in the vice. The curved segments, uprights and the roof bearer were clamped to a ply template and silver soldered. After this the plate could be clamped into position and the whole assembly drilled and bolted up.

The Scale Roof And The Driving Roof

Two roofs were made, one for exhibition purposes, the other for use when the locomotive is working. the latter has an opening which permits a good view of the ‘works’, the gauges and access to the firehole door and the regulator. Stainless steel plate was used here, with rectangular section bar stiffeners riveted at all edges, using the right number of rivets ! Correct curvature was achieved using blocks of wood, a clean length of scaffold tube and foot power. The plate was set upon the blocks cut to the correct rise on the chord and the scaffold tube applied ‘ rolling pin fashion ‘ by the sole of the shoe. Heath Robinson as this may seem, both roofs fit comfortably onto the roof bearer for bolting into position, and both roofs are completely interchangeable ! Provision was made in each case for the two bolts to which the support plate for the two brass columns of the safety valves was to be attached.

The Scale Back And The Driving Back

As with the roofs, two backs were fabricated, one for driving purposes and the other for exhibition. The scale back or rear spectacle plate ( which, due to in service modifications to the locomotive, may not replicate the back currently fitted to the prototype ), was built to the dimensions achieved from the survey soon after I first saw the locomotive. It comprises a framework of angles and a curved roof bearer, silver soldered together and clad with plate. Holes for the glazing were trepanned from the plates whilst they were mounted on the vertical slide, absolute care being taken to ensure that the face of the slide was set dead square to the lathe axis. This was ensured by placing one edge of a steel rule against the chuck face and bringing the face of the vertical slide tight against the other prior to tightening the bolts securing it to the topslide. A suitably shaped tool was ground-up for the fly cutting tool holder providing the nearest radius to the required opening. Bearing in mind the maxim that the tool must be kept cutting at all times the saddle was fed towards the cutter, propelled by the tail stock quill. In such an operation it is advisable to tighten the saddle locking bolt slightly, and essential to interpose a piece of hard plywood between the metal being worked and the topslide.

The glazing is secured within the platework of the scale back by two turned rings, one pair cut from brass bar and the other from steel. These are of course of such size that when fixed, using small screws, they provide a rebate into which perspex glazing material can be fitted. The driving back is a simple open structure, again silver soldered with just side plating added to aid with rigidity along the main axis of the locomotive. A small angle provides a fixing for the brake standard.

Footplates

On PIXIE the footplates are quite rudimentary. There is a plate which bears on angle steel brackets attached to the inside of the frames and two outer plates which are supported on brackets on the drag beam and cantilever brackets riveted to the outside of the frames below the bunkers. Stainless steel plate is used on the model, more drilling ! Angle steel stiffeners run around below the edge of the outer plates. The rather tight bend below the front of the bunkers can be formed by cutting a 90 degree ‘ vee ‘ from the flange and bending the material cold. Care is required here to ensure that bolting faces of the angle remain flat, this can be checked on a true surface as the bend is formed. The cantilever support brackets may be cut from angle steel or fabricated, I chose the latter course, adding the smaller angle for the footplate connection as on the prototype.

The plate between the frames has an opening for the damper lever and a small cranked plate that engages with this lever to locate the damper in the required position. It is advisable to leave the cranking process until the correct angle can be be gauged to the slots in the lever. Small checkouts will be required in each of the footplates to accomodate the angle brackets at the junction between the drag beam and the main frame members. In the central plate the drain pipe from the water gauge and fixings for the brake standard have also to be accommodated.

The ashpan and damper are important parts of the firing system. In Pixie they are constructed of stainless steel sheet and mild steel angle. The angles sit below the foundation ring of the boiler, located by stainless steel dowels set into tapped holes in the ring. The upper edge of the ashpan projects slightly into the firebox and thus provides support for the grate which is cut from a section of proprietary stainless steel grate material supplied by Messrs Spinks. A length of mild steel was milled, drilled and filed to shape and cut into four pieces to provide the hinge blocks into which a stainless steel hingepin is slipped.

The damper is controlled by a lever projecting through the central footplate and retained by a small, joggled piece of plate. Any of three checkouts in the lever locate on this to provide three settings, one fully closed and two sizes of opening…high tech ! In service the position of the damper does make quite a difference to the state of the fire, closed down it allows the engine to simmer comfortably.

A Small Preview !

At this stage a ‘mini-erection’ can be carried out ! The cantilever brackets supporting the outer footplates can be installed and the outer footplates set into position and bolted into place. Next the bunkers can be positioned and the fixing holes drilled through from the fixing angles. Then the weather board and the backplate can be set up. The weather board bolts to the bunker front and the back to the drag beam. Now the roof can be installed and it is time to step back and admire the fruits of our labours so far!

Back to Contents

Chapter 16

Erection, frames and motion, weighshaft and valve gear, reversing lever, valves and setting. A trial run on air. Smokebox, boiler, steam and exhaust pipes and blower, regulator, safety valves, brake gear, ashpan and grate, saddle tank, superstructure, makers plates.

Motionwork on Prototype

Note

As this chapter proceeds the text describes the work in erection. Although this book is not of the ‘ words and music ‘ type produced by illustrious writers such as LBSC, Martin Evans, Keith Wilson and other extremely experienced model designers and builders, it is written with an understanding of the problems that face the newcomer. It is hoped that the approach adopted will assist newcomers to model locomotives in their efforts.

Whilst the reader may be building a model of another prototype the principle procedures stand.

Erection

This is perhaps the most enjoyable part of the construction process, when at last the fruits of one’s labours take finished form. The work of erection will be eased if the builder has access to both sides of the locomotive. Many builders employ an erection frame at this point in construction and there have been a number of examples in the various model publications. If the modeller intends to go along that route it is worthwhile making a frame that can be adjusted for use in subsequent maintenance operations, and indeed for further locomotive erection. End frames set upon an angle steel base can provide adjustment for length of locomotive, the ends being slid along the angles and clamped into position as required. A frame that permits the locomotive to be rotated and locked in any position is obviously going to be an asset although provided that the end frames are of square form and large enough to clear the projecting part of the locomotive this will permit access to the locomotive whilst the frame is set on its side or inverted.

Mr J Bowman described a useful building stand in MODEL ENGINEER Vol 159 No 3805, August 1987, this was built using two scrap car jacks obtained from a breakers yard. Pivoted clamps provided attachment to the front and back beams of the locomotive. The jacking screw arrangement can be used to elevate the model to the required working height, as the designer says, opening-up useful bench space beneath the model.

Frames And Motion

With the frames inverted the axle sets are be dropped into position, including any springs or rubber parts of the suspension. The hornplates are installed, their bolts being anointed with a spot of fixing fluid. At this stage it is convenient to install an axle pump if one is to be fitted, the bolts connecting the parts of the eccentric strap again being given a touch of securing fluid. The cylinder blocks can be attached to the frames, remembering to insert insulation between the back of the block and the frame, where required. The motion plates are next, the bolts, or dummy rivets in the case of Pixie being inserted and taken up tight. The slide bars can then be installed between the seatings on the piston rod glands and the lug on the motion plate, not forgetting to install the crossheads, the correct way round. At this stage the geometry of the engines should be checked out. Careful measurement of the distances between the piston rod and the slide bar(s) at the extreme ends revealing whether the two are parallel. This adjustment is carried out on a full size locomotive by sighting through the centre-line of the cylinder or establishing the centre line using a taut wire then taking measurements in the same fashion. Any minor adjustments can be made by insertion of shim washers where the slide bars are attached to the motion plates.

At this stage the cock shaft for the cylinder drain valves can be installed, as can the small steam actuating cylinder and cranks. The cylinder bolts behind the front plate on the right hand side of the locomotive. The straps linking the cocks can be installed. that on the right hand side of the locomotive having an extension for a return spring which is secured to an eye bolt through a plate projecting from below the front beam.

Coupling rods, with marine bearings in the case of Pixie, are next. Some anti-scuff paste assists in sliding them home onto the crankpins. In the case of crankpins constructed incorporating the retaining flange, scale marine bearings can be split on the centreline of the crankpin and bolted-up. With dummy marine bearings, the leading end of the coupling rod can be secured by a countersunk cap sized to replicate the head of the crankpin. A nice detail in Martin Evans book ‘ Model steam locomotive construction ‘ shows the use of either a cap threaded onto the crankpin, or the use of a cap secured by an ‘ 0 ‘ BA Allen screw. Whichever is chosen, securing fluid ensures that the caps do not come loose in service. In the marine bearing the upper bolt must be that having the groove for lubricant. Each bolt has a full nut, half nut as a locknut and a split cotter pin for safety. With the rear coupling rod bearing assembly completed, the crossheads can be installed on the slide bars, including slipper plates as appropriate, and the piston rod / crosshead joint made using a cotter or bolts.

The connecting rods can be positioned and gudgeon pins installed. On Pixie it is possible to drop the connecting rod by rotating the wheels to a position where the crosshead clears the wheel allowing the the gudgeon pin to be withdrawn from the back of the crosshead, this is helpful when it comes to routine maintenance. The gudgeon pins have single large nuts on the threaded portion, again safety split cotterpins are inserted.

With the coupling rods installed, connecting rods secured within the crossheads and the cylinder drain cocks open and plenty of machine oil on all the moving parts the motion should turn over sweetly. In the event of any binding the bearings can be slackened one by one to find the offender when a touch with a fine file or insertion of a piece of shim stock sorts the problem.

Weighshaft And Valve Gear

The weighshaft brackets on PIXIE are fixed by bolts through the stiffening angles on the main frame and through the frames themselves. In the case of Hackworth valve gear the position of the centre of the weighshaft relative to the remainder of the motion is critical to the valve events and these have to be checked out prior to finally fixing the position of the weighshaft brackets. A check was made prior to constructing the valve gear by making a twice scale sized model in card, set up on the drawing board. The location of the brackets on Pixie is exactly as established from the survey and fortunately the positions and sizes of components thus determined provided, in conjunction with scale sized components, sufficient valve travel.

The return is crank set on the rear crankpin, lined with the axle centre and both the bolts tightened. A spot of securing liquid assists in maintaining the correct position although with a well fitted, reamed hole in the return crank the locking bolts provide a remarkably strong connection. A variety of methods are employed to fix return cranks, ranging from pinned and bolted, slotted and bolted and simply bolted connections, each has its merits. That employed on Pixie is straightforward to make and effective in service.

With the die blocks installed in their guides the vibrating lever can be set into place, the top secured by the pivot bolt in the die-block and the bottom by a cap with a countersunk screw. Next comes the installation of the valve rod. Here it should be mentioned that wherever a connection is made with a simple pivot pin, the pin should be retained by a split cotterpin. Holes for minute split pins tend to wander in the course of drilling through the fork and the pin, and some time can be expended in attempting to reinsert split pins after a service or routine maintenance. A small punched mark made when holes for such minute split pins are drilled through the forks and pins will identify the resident pins with the forks and also the correct orientation of those pins within the forks.

Reversing Lever

On many locomotive the reversing lever and sector plate can be assembled independent of any part of the superstructure. On Pixie this is not the case as the sector plate depends for support at each end from bolts through the inner face of the right hand bunker. To facilitate access and valve setting a temporary bracket was fabricated to provide support at these points and the lever and reach rod installed. The front end of the rod pivots on a stud secured into a lug on the bottom of the slide. The rear end of the rod, forks over the reversing lever which in turn, pivots on a fulcrum bolt on the bunker side, replicated on the the temporary bracket. There are occasions such as this when a temporary arrangement allows access for adjustment which would be difficult to make with everything permanently in place. This time the use of the temporary bracket permitted the notches for the latch to be marked before the stage of final erection. The notches were actually cut after removal of the bracket and final erection of the sector plate and bunker assembly onto the bunker side.

Valves And Valve Setting

The slide valves were dropped into place in the valve chest. The gland nuts were threaded onto the valve spindles which were inserted into the glands on the valve chest, not forgetting to insert the ‘ O ‘ ring packings. The rod was then passed through the first of the retaining collars, the slot in the valve, the second collar and then into the tail guide. Now the valve rod could be installed and the pins inserted. Valve setting followed the normal procedure of adjusting the position of the slide valve on the valve spindle, locking the collars when the optimum position had been established.

It has to be remembered that the collars must allow the spindle freedom in the vertical direction such that steam pressure in the valve chest forces the valve onto the port face. Now the weighshaft brackets can be fixed into their final position, also the position of the notches on the sector plate can be marked in full forward and full reverse.

In the event of a need to modify valve arrangements it is a great help if a set of perspex ‘ slide valves ‘ are produced. These can be simply made from 1/8” perspex sheet, joined by using plastic solvent. The exhaust recess can be scribed and coloured-in using marking blue. The dummy valves can be threaded onto the valve spindle and the events viewed as the locomotive is moved back and forth along a short length of test track.

With the valves set the valve chest cover can be installed, it is advisable that all the studs should be inserted and the cover checked for location prior to finally inserting the gasket and tightening down the nuts. This will avoid the situation sometimes encountered where, due to minor inaccuracies in hole location, the cover binds on one of the many studs and fails to seat down properly ! For the cover / valve chest joint, liquid gasket has proved satisfactory in service, and certainly saves a considerable amount of work otherwise required in the manufacture of traditional gaskets.

A Trial Run On Air

At this stage it is more than likely that, with the the engines attached to the frame and with the motion work installed, the builder will want to have a trial run. This can be carried out at the bench on compressed air with the frames set upon packing. The writer felt the urge at this stage to prove the work to date. In the absence of a length of track Pixie’s first run was on the floor of a local garage. The frames complete with motion and a temporary steam inlet pipe were taken to the garage, the only source at that time of an adequate supply of air. To the amazement of two young mechanics, who whilst having intimate knowledge of the workings of motor car engines were apparently ignorant on the working of steam, the ‘ mechanism ‘ shot twenty feet across the workshop floor on the end of the air line, like a scalded cat. Remarkably too, on resetting the reversing lever and opening the regulator it shot back again. The power developed by the small engines had to be seen to be believed.

Such excitement! After more than seven years and much figuring and speculation as to the effects of scaling down parts of the valve gear, its geometry, the steam chest dimensions and the dozen or so components of each engine, the thing worked, and powerfully too. In retrospect the whole proposition of a concrete engineer manufacturing such a complex mechanism in miniature, and one that worked as intended on first trial, seemed as unlikely as the prospect of the construction industry, as we know it, putting a man into space!

Smokebox

The smokebox can be secured onto the saddle, here stainless steel bolts are advisable. These can be turned up from stainless steel hexagon stock of the appropriate size. It is a good thing to hold a stock of the common sizes of hexagon material in stainless for bolts, and brass for unions. When there are a few minutes to spare between other jobs, or when only a limited time can be allocated for the workshop, a few unions can be turned up or the odd bolt prepared without too much upheaval and without too much effort in setting up machinery.

Boiler

Boiler installation will render the space between the frames rather less than accessible so that it makes sense to insert any pipe runs and make-up any joints in those pipes before finally locating the boiler into the smokebox ring and seating it onto the bearing brackets on the frames. First attempts at boiler installation onto Pixies frames involved considerable sweat and no little amount of personal injury ! Despite the fact that the boiler matched the dimensions from the survey in every detail, ( indeed the accuracy achieved was a great credit to the builder ), the boiler just would not seat into position…… Enter Giant Despair ! ……Several cups of tea and a breather later however, on resuming what until then had been a struggle, the boiler suddenly slid into position as it has indeed on subsequent occasions. There may have been ‘ Gremlins ‘ in the workshop on the occasion of the first attempts at installation, although more likely the interference was caused by some rogue rivet head or overlong bolt, eased-in in the heat of subsequent operations.

With the boiler installed a check should be made to see that the firebox end is free to move as everything heats up and the boiler expands. Holes in the bearing brackets need to be slotted to allow this movement as will those in brackets providing support for a saddle tank. The level of the boiler, relative to the frames, can also be checked and if necessary packings inserted at the bearing brackets. At this stage also, sufficient clearance can be established around blowdown valve(s) and if necessary any openings in stretchers adjusted as required.

Steam Pipe, Exhaust Pipes And Blower

Now the steam and exhaust pipes can be installed,. Some juggling is likely to be necessary to persuade these items into position through scale size apertures in the lower quarters of a smokebox ( Later thought was given to this and perhaps in a subsequent model, where some detail of the prototype is concealed in the model then some licence may be taken with sizes ! ) Eventually with such Chinese puzzles solved, the wet header can be bolted into place on the boiler bush ( not forgetting the ‘O’ ring seal ). The joints between the steam and exhaust pipe and the cylinder block can then made. Liquid gasket was used to seal these joints on Pixie and has proved perfectly effective in service.

With the blower ring installed the plumbing can be completed. The parts of the pipes between apertures in the smokebox and the connections with the cylinder blocks are enclosed in a sheet steel cover, secured by tiny screws into tapped holes in the smokebox tube. To render the apertures airtight small quantities of modelling clay can be smoothed around the pipes from inside the smokebox using one of Messrs Proops ‘ Doofers ‘. These can be obtained from a MODEL ENGINEER exhibition stand and although they convey a fearsome reminder of time spent in the dentists chair will prove immensely useful about the workshop!

Regulator And Regulator Block

The regulator can be mounted within the steam dome, using stainless steel screws into the lugs on the regulator body. A check should be made at this stage to ensure that the screws on the actuating rods are wired to prevent them coming loose in service. Stainless steel wire is a must.

With the regulator rod inserted into the regulator handle and the rod passed through the gland, the small bush can be set onto and secured to the rod by a stainless steel grub screw. This bears against the back of the body block, retaining the rod in its correct position within the regulator proper. The complete assembly can now be passed through the regulator block bush, the leading end being located in the back of the regulator body within the steam dome.

Safety Valves And Header Pipes

In the case of pixie, once the regulator and the regulator block and rod had been installed it was time to install the safety valve block and safety valve bodies. The block is in fact retained by the screwed portions of the valve bodies so that it became necessary to enlist the aid of the plastic gasket material once again. The fulcrum bracket which retains the safety valve balance beam screws into the safety valve block. The beam itself is mounted using a bolt as a pivot, the ends of the safety valve spindles move freely within bushes at the ends of the balance beam. Adjustment of the valves is achieved by screwed bushes set into those at the ends of the balance beam. Assembly of these items takes less time than is needed to write the description, although with such an important part of the ‘ works ‘ care has to be taken to ensure freedom of action of the parts.

Platework

There are three running plates on PIXIE. The two outer, low level plates take support from brackets rivetted to the main frame members and rails which are bolted to the drag beam. These plates provide seatings for the side bunkers, and importantly, the brake standard. These items are each in turn clamped into position and the location of the fixing screws transferred to the plates using a centre punch. If the platework is of stainless steel the holes for the fixing screws has to be drilled using a freshly sharpened bit with sufficient pressure to ensure that the bitt cuts metal all the time. As has been noted elsewhere, the slightest rubbing action will heat the bitt and spoil its temper.

Once the lower running plates and the left-hand bunker are erected, the positions of the holes for the feedwater pipes from the hand pump in the left hand bunker can be established. Here pieces of stiff wire to replicate the pipes facilitates the marking process. The holes drilled the the pump can be installed on a mild steel block of sufficient height to bring the operating handle clear of the bunker ends at the extremes of the pump stroke. The brake standard is positioned on the right hand, lower running plate ( where it was located at the time of the survey, although there is evidence in the form of a set of mounting holes, that it has been set on the opposite side at some time in the locomotive’s history ) and the fixing holes and the hole for the brake spindle spotted and drilled.

The middle, upper footplate will require trimming to fit around the frame angles, also slotting for the damper lever. this is another situation where it is advisable to produce a strong card template and carry out a trial fit prior to cutting metal. Clearance for the angles joining the drag beam to the frame members is easy to arrange by pure measurement. To avoid wasteful errors in positioning the slot, the template can be slotted on the known line of the lever. Inserted into position, the card can be marked to indicate the position of the ends of the slot and the footplate marked and cut accordingly. A small metal catch is bolted to the plate to engage in, and retain, the damper lever. This was bolted into position on the footplate and with marking blue and a scriber the correct angle and depth of the three slots in the lever were established. Provision of one last slot for the drain pipe from the water gauge permitted the plate to be dropped into place.

Brake Standard, And Brake Gear

The main brake shaft with just the fixing bushes in place, was offered up and clamped into position, square across the frames and level. This allowed the cut-outs necessary to allow the bushes to seat onto the frame members to be determined, marked out, then cut and filed. The brake nut was then threaded onto the brake spindle and the handle rotated until the brake shaft complete with actuating arm, two bushes and two drop arms could be bolted into place. With the hangers and blocks installed by bolting to the frames, the pull rods could be inserted and the rods which serve as brake beams with their retaining bushes threaded into position. With all assembled the holes for the split pins which secure the bushes in place were drilled and the minute split cotterpins set into place. This size of split pin has extremely sharp ends, so beware!

At the running plate two bolts pass through support angles on the standard downwards into the angles supporting the floor member. The screwed portion of the brake shaft can be engaged in the bush within the brake fork below the running board and the handle turned until the foot of the column contacts the floor when the fixing bolts can be installed. At the top, the brake standard takes support from the cab backplate support angle and is bolted into position using a shaped strap, reminiscent of a gutter bracket.

Ashpan And Grate

At the time of final erection the ashpan was set into position, clamped and blocked to prevent movement whilst the holes for retaining pins were drilled. After a lot of careful measurement, small diameter pilot holes were drilled through the mainframes and the ashpan sides. During the drilling of the holes a colleagues assistance was saught to sight the drill and ensure that the holes were put through horizontally. Transverse accuracy was obtained by lining the drill with a try-square set against the frames. The ashpan is located by two stainless pins, cross drilled for tommy bars at one end and tapered at the other to facilitate insertion. The pins themselves are retained by ‘ O ‘ Rings slipped into position once the pins are engaged. In the event of an emergency the grate can be dumped by withdrawing the pins when the ashcan will drop as far as the sleepers, spilling the fire.

Saddle Tank

With the boiler seated into position and the boiler / smokebox joint made, the fastening angle for the front of the saddle tank can be installed. Although there are a number of bolts through the angle and the smokebox tube, only two of these are in fact bolted connections, the rest are dummies, this to reduce the amount of work when dissembling for maintenance in future. On Pixie, the rear of the saddle tank rests on two brackets supported from the boiler casing and the front takes its support from the aforementioned bracket. Studs projecting from stiffening plates which also serve to reinforce the delivery pipe connection points from the tank, pass through timber blocks into the boiler brackets. the timber blocks are for insulation purposes. again the holes in the mounting brackets have to be slotted to permit expansive movement of the boiler.

Superstructure

After the arduous work of boiler and tank installation, the erection of the superstructure affords time to relax and enjoy ! The rather elementary weather plate is supported on angle steels which in their turn take support from the backs of the bunkers. The back of the cab, again platework on angle framing takes support from the drag beam. The weather board and cab back plating support the roof which is bolted to the curved angle steels forming the top of the superstructure framing.

Makers Plates

At this stage it was time to mount the makers plates ( which had been prepared earlier ! ) Mounted on each of the bunker sides these proclaim ‘ Kerr Stuart etc……” Plates such as these are essential in conveying the atmosphere of the model and some thought was given to their production. The method eventually adopted was first to choose a photograph of one plate from the reference shots on transparency film. This slide was then projected onto a sheet of paper set on the workshop wall and the image drawn-over using indian ink to approximately five times the size of the required plates. These were photographed by a friend, to provide the required image size, using a film having high contrast negative emulsion. The negative was then sent to Messrs Reeves for the production of etched plates. The detail was etched onto brass plate of the required thickness. All that was then necessary was to saw and file these to profile, polish the edges and drill for the fixing bolts. A coat of enamel was applied overall, the plate was lightly filed to expose the letters then polished. With the availability of Digital Cameras this process can be simplified, and a dic with the appropriate photograph sent to the engraver the size being simply adjustable as required.

Ron Acock described the use of brass punched letters, obtainable commercially, for constructing nameplates. His article in MODEL ENGINEER Vol 161 No.3833 October 1988 will be found most helpful for the modeller taking that route.

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Chapter 17

Painting. Workplace and equipment. Types of paint and preparation. The finishing coats.

Spray cabinet for small parts from scrap, computer fans and drier hose.

It is quite pleasing to leave the locomotive unpainted as long as possible, the parts that won’t rust that is. Unfortunately fingerprints on polished mild steel may rust overnight so that items such as the mild steel platework have to be painted on completion. Otherwise all the stainless, rustless, and gunmetal parts can be left unpainted so that one can enjoy the appearance of the raw metal. Some parts can be decorated, up to the time of painting, using the age-old technique of a split dowel in the lathe or the drill, with a piece of wet and dry paper set into the slotted end. this can be set to revolve at speed and the part then applied systematically to the ‘ tool ‘ This imparts a finish akin to that from milling, although on a much finer scale. It looks good in the raw and, according to the strength of paper used, provides a nice key for a priming coat later.

Workplace And Equipment

Whatever finish is selected, the results achieved will depend to some extent on the temperature of the workplace. An even temperature and a dust free environment are two key aspects to be considered when painting. Probably the worst place for the operation is the workshop as there is almost always a film of dust from machines and equipment which can easily be disturbed by the smallest draught. Good work can be carried out in in a greenhouse or in a spray booth set up temporarily using polythene dust sheets from the local D.I.Y store. Small parts have been sprayed in a sink in the utility room, the water set running over the back surface of the sink by a piece of card, simulating the wet back in some commercial spray booths. In the writer’s early days of modelmaking, a good sized cardboard box for a booth, with a larger box placed overall whilst the paint dried, yielded quite satisfactory results. Latterly a simple ‘ spray booth ‘ for small parts has been fabricated from a steel box, using one of Messrs Proops brushless fans and a length of spin-drier hose to take away the overspray.

Regarding equipment, the range is enormous, from simple spray guns to sophisticated airbrushes. Expensive equipment does not guarantee good results, choice is likely to be based upon one’s budget and, provided preparatory work has been carefully carried out, good work can be achieved with simple equipment. With sound preparation a combination of simple tools used skillfully and ongoing care taken in rubbing down and finishing, an excellent paint job will result.

Spray guns and airbrushes require a satisfactory air supply. Cans of propellant are expensive and are soon used up in the course of coating the many parts of a locomotive. For economy, a small electric tyre pump can be used to provide an air supply via an inner-tube as a reservoir, ( the writer once re-sprayed a motor cycle using only a car footpump ! ). Compressors provide a reliable, consistent source of supply and need not be expensive although a filter must be used to provide a clean supply. There have been several articles in the model engineering press on adapting compressors from refrigerators. One very clear description was that by Steve Ballinger entitled ‘ An Airbrush Compressor ‘ in ENGINEERING IN MINIATURE Vol 2, No.5 October 1980. It is important that some form of pressure regulator is used as varying paint consistency calls for a means of controlling the pressure. The simple ‘ external mix ‘ gun can, with care, provide a good finish although mix adjustment has to be carried out between actuations. The ‘ internal mix ‘ tool is probably more favoured by the professional and expert, providing as it does more immediate control of the air / paint mix at the touch of the trigger. For occasional use an electric, airless spraygun can provide an economic solution and again, excellent results can be achieved with care.

Other equipment includes lint-free cloth, wet and dry paper, rubbing compound, metal polish, masking tape and an endless supply of newspaper. Masking film and masking fluid will be useful to protect polished parts and to mask-off in the course of developing a livery. An out-of-date telephone directory will provide a good source of paper for masking purposes and on which to sit small parts for painting and some stiff wire hooks will be useful for handling and ‘ hanging out ‘ the parts to dry. A turntable such as those used in icing cakes will also prove useful. A good supply of thinners appropriate to the paint system to be used is essential. Where paint and thinners are concerned small tins are wasteful. Both materials will be cheaper if purchased in sensible quantities from a paint supplier. Your local dealer will advise on the type of solvent to be used according to the system selected. Paints will keep in the can for years provided it is properly sealed, the lid firmly replaced and a seal formed by inverting the can before storage.

Spaying small parts is simplified and can be carried out in the workshop if a suitable facility is provided. The simple cabinet illustrated at the top of this chapter has proved effective and useful. The ply box has two fans from defunct computers mounted high at the back. Extracted air and spray is blown into a cone-shaped funnel, which mounts on the ply back, into a length hose from a tumble drier and out of a window. At the front of the box a strip of perspex prevents overspray from escaping. The whole somewhat ‘ Sid Carnow ‘ cabinet can be packed together taking the minimum amount of space in a busy workshop.

Types Of Paint

Firstly a decision is required regarding the type of paint to be used. The choices range from cellulose and acrylic car sprays, through enamels, to special heat resistant paints such as those intended for automotive use. The choice rests with the individual, but whatever system is selected it has to be remembered that sound preparation is critical to achieving a good finish. A colleague calls the painting stage ‘ the spoiling stage ‘ and this it may well prove to be if the preparatory work is hurried or not carried out systematically.

Contact with the suppliers of various types of paint systems reveals an interesting fact. On investigation, the majority of complaints regarding substandard finishes achieved across a wide range of materials result from failure on the part of the user to read, or comply with the manufacturers instructions. Whilst it might be argued that the manufacturer is bound to come up with this conclusion, it has been proved time and time again that similar products have produced differing results in the hands of different people. It seems that when all else fails, when the paint fails to dry, or to provide the required surface, the user turns to the instructions, or complains to the makers!

Preparation

LBSC used to advise washing parts to be painted in petrol, this seems a risky business and today a thorough wash in detergent, a rinse and then drying in a warm spot is probably more effective. The aim here is to remove all traces of oil, grease and cutting fluid which will otherwise prevent the priming coats bonding to the metal. Failure to remove grease will be evidenced by wrinkling of the early coats of primer. Should this be observed then the best course will be to go back to the bare metal, thoroughly degrease and start again.

Whatever paint system is to be used, the same steps are required in preparation of the surfaces for paint. Paint will not mask irregularities of surface, it will not fill joints and it certainly won’t fill holes in castings! Minor defects in castings can be filled with a polyester or epoxy filler and rubbed down to the required form, a rasp will cut away any overfill and a scraper can be used to take the repair to the stage where wet and dry paper will finish the job. Castings and any nonferrous surfaces should be coated with an etching primer, obtainable from any good automotive paint supplier. This should again be cut down using wet and dry paper, recoating and rubbing as necessary to produce a consistent matt surface to accept the selected paint. Filler is next, this fills any minor defects and can be carefully cut back using wet and dry paper until an allover, dead smooth surface results. The paper should always be supported, using small blocks of wood or a hard rubber block to ensure that the thickness of coating is left consistent throughout, and that corners are not exposed, or rounded out. The surface should now be dried. Wiping with a lint-free cloth helps, as does leaving the coated part on a radiator for an hour or two or spend some time using a hair dryer, the latter technique is good as it dries out all the little nooks and crannies in a complex part. Take time, attempt to speed things up and the painting stage will rapidly transform into my colleagues ‘ spoiling stage ‘ !

Next is the priming stage, here we are building the surface which will finally be apparent. The smoothness of finish achieved at this stage determines the appearance of the part after the application of the final coats of paint. This is true whatever paint system is adopted. Any small defect after this stage will be magnified by succeeding ‘ finishing ‘ coats. The use of materials of differing colours up to this stage assists by indicating depressions and local defect. After each succeeding coat is rubbed down, high spots will be shown up by the previous colour, ‘ grinning through ‘ and local depressions retain the colour of the last coat applied. The aim is consistency and a uniform colouration all over the part. Once this stage is reached all is ready for the application of the final finishing coat(s) according to the selected sytem.

Enamel

Provided one is satisfied with the available colours, brushing enamel provides a good durable finish. It is always advisable to warm tins of enamel in a bowl of hot water prior to use. Don’t shake the tin before use, open it and thoroughly stir the contents. Using enamel, applied by brushing, the finish will depend a great deal to the quality of the brushes used. Only brushes from a well known maker should be used, and they should be washed frequently using thinners and finishing with soap and water, as work on any large parts is carried out. This avoids problems and brush damage caused by enamel drying where the bristles are set into the handle. Carefully dry the brush after this cleaning operation, otherwise any moisture remaining in the brush will upset the paint consistency on restarting brushwork. Enamels can be spray applied although absolute cleanliness of the spray equipment is essential, and defects are not easily corrected.

Whilst ideally one coat of enamel should provide a good quality finish, it is sometimes necessary to recoat. Previously coated parts should be set aside for the paint to harden before re-coating. A warm, dust-free spot is desirable, a cardboard box on top of the central heating boiler has proved effective in the past. Before re-coating, the surface should be lightly cut back taking care not to remove paint from the corners and edges of the piece. Work painted using enamel generally benefits from rubbing and buffing using automotive rubbing compound prior to finishing with metal polish, these processes should be carried out over a few square inches at a time, first rubbing, then buffing. A soft brush will be needed when polishing rivetted surfaces, care being taken to avoid exposing the metal of the rivet heads by rubbing too hard.

Heat Resistant Paints

Heat-curing paints can be used to advantage on the smokebox and chimney. These paints, applied from a spray can, are cured either by the heat of operation, by blowlamp or by baking in the oven. Heating parts coated with this material in a very hot oven ( Regulo No. 9 ) for half an hour proved satisfactory in the case of Pixie. The black finish obtained is midway between eggshell and gloss and can be maintained by a light rub with an oily rag. The black heat resisting paint in spray cans so beloved of motorcycle enthusiasts is great for chimneys, smokeboxes and similar items. Oven or gentle heat from a blowlamp will cure it to a satisfying matt finish.

Spray Cans, Guns And Airbrushes

When painting using spray cans, the can must warmed gently before being shaken according to the makers instructions, generally for some minutes after the mixing ball is heard to rattle within the can. The spray should be tested to determine the spray pattern and the distance of the jet from the work by trials on a piece of scrap. With both cans and guns the spray should be started away to one side of the part being coated and carried across the part several times before moving away from the workpiece to stop the spray. In this way the finish will not be marred by blobs of paint which often occur when starting and stopping the paint flow. Before succeeding coats are applied, (some instructions say that the succeeding coats should be applied quite soon, whilst the previous coat is tacky even, others require a dry finish before recoating) the parts should be turned to ensure that all edges are coated. The temptation to build with one coat of spray has to be resisted. A series of thin coats always gives the best results. Building should be done in the course of a series of coats, rubbing down between each coat.

When using an airbrush much better control of the paint and thus regulation of the coating is possible, the most critical aspect here being the cleanliness of the equipment. Paint consistency is important and it is advisable to strain all but the freshest paints. Mix the paint by stirring, not by shaking the can. Always test the consistency of the paint on a piece of scrap before coating any model parts. Most paints also benefit from straining after mixing, strainer material can be obtained from model or automotive spares suppliers. When deciding on the correct mix of thinner and paint, start on a piece of scrap with a 30 - 50 percent thinner content, adding more until the flow is correct. A short blow of air alone will clear the brush if it clogs. Always clean the airbrush using thinners immediately on finishing painting, any minute flake of paint that dries on the tool could spoil the next job to be tackled.

During the coating process the air brush should be kept on the move, using a motion of the hand and arm which maintains the head at a constant distance from the surface and sweeps the piece with spray. Movement of the wrist varies this distance and prevents even coating. Spraying should be started and stopped away from the piece being coated. Runs and pools of paint result when the brush is stationary for even a second. When paint dries too quickly, before reaching the part being coated, a rough texture develops. Ideally the coat should appear to shine as it is applied, rapidly drying as the spray is moved on.

Dealing With Defects

Whatever tools are being used in the painting process, should there be the slightest evidence of a run or ‘ orange peel ‘ surface developing no attempt should be made to rectify things by wiping with a cloth. This action can result in the removal of the current coat of paint and parts of the previous coats which have become softened by the spray. The components should be set aside for the paint to harden completely then the surface can be cut back with successive strengths of wet and dry paper, care being taken not to expose primer at edges and corners. Once a uniform, matt finish is achieved overall, then priming, rubbing down then re-coating can commence.

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Chapter 18

Test track and a simple driving trolley. Driving position and access to controls. Braking.

Pixie with driving roof and back. The driving trolley footrest is stowed.

Test Track

As this was the first 5” gauge locomotive built by the author it became necessary to build a test track. This would later be extended to provide a running facility. Material costs were of course a major consideration and the search began for scrap material which could be recycled ! The track would prove expensive if an attempt were made to replicate narrow gauge practice, for example using 4’ 6” Sleepers of 9” x 4” section at 3’ 0” centres as described on the Ffestiniog Railway of yore. Some more simple trackage was envisaged, probably having randomly spaced sleepers as are sometimes encountered. The solution came in the form of discarded pallets which are fabricated from anonymous timbers and occasionally hardwoods. A kind friend, who is keen on woodworking, ripped down enough of the pallet staves to the appropriate section which were cut to length prior to slotting. The 1” x 3/8” mild steel section used for rails was purchased from a commercial supplier in 6’ 0” lengths. Joints at 6’ centres have not proved to present a running problem provided that they are properly aligned at the time of tightening the fishplate bolts.

The three pieces of equipment on the side of the workshop allocated to drilling and milling operations provide a useful bed for supporting lengthy stock. The drilling machine tables can be set level with that of the milling machine and long stock thus supported at three points in its length. After being brought to a nett 6’ length, the rails were drilled for fishplate bolts in a jig set on the table of the drilling machine. . The jig consisted of a pre-prepared fishplate of 1” x 1/4” material fitted with a stop to accurately position the rail end, holes were positioned to establish the location of a pilot hole drilled using a centre bitt. Clearances were kept to a minimum for 2 B.A. bolts, this resulted in a tight joint. With holes centrally positioned in the height of the rail the heads of the bolts do not interfere with the wheel flanges in service.

Initially a few trial sleepers were slotted on the milling machine to establish the correct depth of slot and to prove the rigidity of the simple sleepering arrangement. Araldite was employed to bond the sleepers and rail and it was found that sleepers spaced at a maximum of 8” centres provided a suitably rigid assembly. Latterly the sleepers have been secured in place by self-tapping screws from below a somwhat tedious job but aided by fences to position the drill in the press central in the rail. the sleeers being positioned laterally by eye.The remainder of the sleepers were slotted in a jig set up on a sawbench, the cut being made with a wobble saw. This was to be a simple straight track and eight 6’ 0” lengths were fabricated and used in the early stages of testing. Subsequently a curved section of track has been built using the same techniques and has performed satisfactorily. For this the rail section was taken to a local works and put through their rolls. When not in use the track is stored on top of a cupboard in the utility room and causes no offence to the domestic authority . The track described can be laid onto a flat path, or onto gravel along a level patch or trench in the garden. Should the powers-that-be demand that the track be removed and stored between uses this can be simply accomplished by means of simple trestles, ladder type arrangements of 75 x 50mm timbers which form the supports for the sleepers. In their turn, short lengths of fence post set into the metal brackets supplied for fencing purposes can be cut and provided with cross members to support the ladder frames. When the track and ladder frames are stored, along the wall inside the garage, hung under the eaves of the garage or in a convenient shed the posts can be removed and, provided the tops of the sockets are set below ground level the grass can be mowed as if the railway line never existed. Such an arrangement would surely satisfy the most demanding indoor authority!

A Simple Driving Trolley

Most of us, with the exception of the ride-on 7 1/4” brigade, will at some time have to build a driving truck. Clubmen have access to club vehicles, but the lone model engineer with a few yards of track in the garden has to have a vehicle from which to drive his pride and joy. Having completed Pixie and run it on air on a short length of track a few times the writer looked around for inspiration. Whilst it was intended that the chosen vehicle should convey the spirit of narrow gauge working, what was needed was something simple and relatively quick to build, ( this a major consideration in view of the length of Pixies gestation period ).

The vehicle which became the final choice was found in one of two volumes of a book on the bookshelf, the excellent history, ‘ The Festiniog Railway ‘ by J. I. C. Boyd, published by The Oakwood Press. The open mineral wagon illustrated therein would be straightforward to build, the wheelbase being such as to permit, with a little licence, manufacture of a near scale vehicle which, whilst not looking out of place behind Pixie, would offer a comfortable driving position.

At the time of completing the locomotive, with driving in mind, a special driving back and roof were built with openings to improve the view of the gauges and allow access to the regulator and brake, Between steamings, when the loco is on show these are replaced by nearer scale components.

Driving Position And Access To Controls

On commencing design of the truck, a mock-up was built in Dexion angle, this was perched on wooden blocks representing the wheels. Set-up behind the locomotive this proved the projected sitting position to be comfortable. It established that the intended design would be stable axially, with drivers ‘ mass ‘ imposed upon the driving seat positioned relative to the proposed wheel centres. Transverse stability was also checked to avoid sideways rock on the proposed track. The mock-up also avoided what would have been a major blunder, production of a vehicle which, whilst looking right would, due to its height, have allowed only limited access for driving and firing the little locomotive. A reduction in the height of just the front of the wagon was found to be necessary to permit good access to the firehole door. The space in front of the drivers seat provides useful storage for spare coal, tools and so on.

Construction Materials

Construction, apart from the wheel blanks bought at Kennions, Hertford, now defunct but who provided excellent service over the past 20 years, is from scrap materials gleaned from rubbish skips. The main frame materials were part of a discarded steel door form, the roller bearings came from worn-out washing machines, courtesy of the service engineer. Whilst these bearings are not in good enough condition for the high speed, arduous requirements of washing machine at ‘ full chat ‘ they are quite satisfactory at the speeds encountered in the model application. The footrest is from gas barrel. Plywood and framing timber are from kitchen cabinets which were replaced and dismantled 20 years ago! The timber is superb, clear pine, the likes of which one would be hard pressed to find even in specialist timber yards today, let alone todays ridiculously pricey Do-It-Yourself stores. A weather eye maintained on rubbish skips about the town, such a source, particularly where shopfitters are working is likely to yield just the stuff our hobby calls for ! Rexine and foam for the luxurious upholstered seat are from a dearly departed lounge suite.

Building The Truck

The frames which are over-scale and extremely robust are constructed as are frames for most locomotives. They are joined using mild steel angle and bolts, great care being taken to maintain the whole assembly in truth. Slots were provided in the frames for the substantial axle assemblies. This allows the complete assembly of bearings, bearing housings and wheels, whilst bonded up solid onto the axles, to be dropped out in the event of a need for maintenance at a later date. In service the absence of any form of springing has been found acceptable and the vehicle runs freely, reducing the work that the locomotive has to do to a minimum.

The wheel blanks were turned on the mandrel previously used in producing the locomotive wheels. Axles were turned between centres to ensure concentricity, a separate bearing being set into the back of one of each pair of wheels to overcome differential rates of rotation on tight curves. We are talking narrow gauge here! A variety of bushes were needed to allow for the assortment of sizes of available, ( inexpensive! ) bearings, four of which were built into simple, turned housings bolted into the slots in the frames. Bonding fluid is used throughout to secure axles, bushes and bearings.

The bodywork was mounted onto timber bearers bolted to the main frames, the edges of the 5/16” plywood being built-up to the scale thickness of the timbers of the prototype. The lines of individual planks were scribed into the ply in accordance with the drawings thoughtfully included in the history book.

1 1/4” and 1/2” x 1/8” strapping was applied to the sides and one end. Whilst these items are somewhat overscale, the extra thickness seems to add character. For the same reason dummy coach-screw heads turned from 3/16” square bar were Araldited to the strapping, square heads were chosen as looking ‘ more interesting ‘ than would the bolt heads of the original. A ‘ liberty ‘ perhaps, but one of those little bits of licence that the near-scale modeller can allow himself from time to time ! Rudimentary strapping is included at the back end to convey the ‘ atmosphere ‘ of the hinged parts of original vehicle.

Painting was carried out using automotive paint in ozone friendly dispensers, expensive in themselves but economic in view of the availability of appropriate colours in the small quantities required. An added bonus obtained by using spray-cans is the reduction in clean-up time after the painting operation.

Coupling to the locomotive is by rigid bar using the scale coupling block on the loco and a fabricated coupler on the trolley. A heavy duty spring slipped over the coupling bar prevents snatch due to take-up in the clearance holes in couplings and coupling bar as the locomotive moves away, reduces rattle and acts as a buffer when the amachine is brought to a halt.

Braking

Driving truck braking, should it prove necessary, will be achieved by disc braking, not the complex automotive type of disc brake but a simple lever operated vee-d block working upon a tapered disc or discs, clamped round and pinned to the axles, between the frames. These discs can be retrofitted using the technique employed in installing the axle pump onto Pixies front axle.

The Finished Truck

The finished result is quite pleasing in appearance, comfortable to ride and economic to produce. Nett cost was in the region of about Fifteen Pounds thanks to the recovered and re-cycled materials employed! The 18 hours of construction time provided a pleasant change from the more exacting work of modelling the locomotive. The next project is the construction of ride-in wagons for passengers, these will be based upon other prototypes as illustrated in ‘The Festiniog Railway’. The search for materials has begun !

Handling Equipment

Even a small, narrow gauge locomotive on 5 1/2” gauge track will prove to be quite weighty. Pixie weighs some 120 lbs dry, that is with the boiler empty and without coal in the bunkers. A model of this weight and proportions is literally ‘ quite a handful ‘. Thought has to be applied to handling the locomotive in the workshop and at the track. For the workshop where routine servicing is carried on, a hoist was built from standard box-section steel, the material came from…yes, a skip! A local builders merchants was discarding racking and enquiries of the manager brought forth permission to acquire the material. Whilst this was a stroke of luck, similar section can often be found at the local scrapyard or, as a last resort, at a steel stockists. The material has good mechanical properties and can be simply sawn and bolted or welded. Where bolting is employed care must be taken to sleeve bolts within the section using fitted lengths of thickwall tube to ensure that they can be properly tightened without the section becoming distorted.

The proportions of the hoist frame to the base were decided by the requirements of stability, also the fact that the equipment was to be used on ground which whilst paved was not level throughout.

The hoist for Pixie is of welded construction, gussets being placed to stiffen the whole assembly, although with a good fillet of weld the whole frame works up sufficiently rigidly to provide a safe lift. The lifting tackle is typical of that available from the local automotive parts stockist being intended for handling car parts, and is fitted with a positive ratchet control over the lifting and the lowering actions. Heavy duty castors were bolted to the bottom fork frame which is of such width that it can be rolled through a 2’ 6” door opening. Where castors are used it has to be remembered that with the wheels swivelled towards each other, inwards, the true base width of the assembly can be very much reduced. In the case of large wheels on a narrow base this may reduce the actual base size to the point of instability

The hoist is used to transfer the loco from the bench to a trolley and vice versa, the trolley is constructed from Dexion angle and has two wheels on an axle placed centrally on the frame also a single fixed trailing wheel, actually a bearing from some long departed piece of machinery. The assembly is similar to that of the trolley used to move upright pianos. Pixie is immobilised upon the length of track secured to this trolley by some removable chocks sitting on the rails. The wheel configuration of the trolley provides absolute maneuverability through doorways and up and down some portable ramps constructed from plywood and the trolley can be turned in its own length.

Spreader Bar

As in full size practice the lifting connection between locomotive and hoist is by spreader bar. This is fabricated from box section with lifting points welded into position. These ensure that the locomotive is correctly balanced in the course of a lift. Where more that one locomotive is to be handled using the same equipment the lifting loop positions can be made adjustable as long as positive location is provided against longitudinal movement. Only good quality slings are used, these are made from climbing rope of guaranteed tensile strength, purchased from the local yacht chandlers. In the short lengths required this rope offers very good value. The knotted ends of the slings are prevented from unraveling by a touch of the blowlamp, not sufficient to burn, but sufficient to melt the rope and allow it to be rolled to a smooth finish.

Testing The Equipment

Although such equipment may be intended for the sole use of the owner, and probably will only be used in the workshop and on private ground away from the public, it is recommended that the equipment is tested. A test should be carried out by a full lift, throughout the range of the gear, of twice the maximum weight intended to be lifted in practice. Bags of cement or shingle provide suitable loads of known weight for the test. The safe working load ( SWL ) thus established should be indicated on the frame and the spreader bar. At no time should anyone be allowed under a suspended load, except where some trestle or benchwork is arranged in such a manner as to prevent the load from dropping in the event of failure. It is unwise and dangerous to attempt to move such a frame under load on bad or uneven ground.

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Chapter 19

Steaming the locomotive. Simple blowers. Raising steam and driving. Safety aspects.

Blast pipes on prototype

Equipment For Firing The Loco

A supply of soft water heads the list of needs, water from a rainwater butt, filtered through an old stocking is ideal. Distilled water is also ideal for the job, although a costly item. Whichever is used, have plenty of water available. The plastic bottles that mineral water comes in are ideal storage containers / dispensers. Coal of the type favoured by your local club will be the best bet. It is not desirable to experiment at this stage ! A quantity of small paraffin soaked sticks will be used to light-up, these are best kept in a plastic box of the ice-cream container type ( LBSC favoured charcoal soaked in paraffin ). A cheap cigarette lighter will save matches. Impatient types may wish to use a gas torch although with care this may prove unnecessary.

For lubricating oil, light standard motor oil will suffice for oiling-round, a good pump-type oil can will ease the application of the lubricant to the motion, eccentrics and so on.

Shell ‘Valvata’ or similar, a sticky steam oil is required for lubrication. The lubricator being filled 3/4 full prior to a run.

A pricker / rake and a firing shovel complete the inventory, except perhaps for a pair of industrial gloves, the small wheels on valves can get quite warm after a time in steam. My pricker is of bent wire pointed at the end and with a loop handle, the rake similar but having a blade in place of the point. My firing shovel is fashioned from a serving spoon, part of the ‘ family silver’ , with the end ground square and the sides turned up. It just enters the firehole door and the handle is just long enough to stay cool. One day it will be treated to a wooden handle !

Two Simple Blowers

When it comes to steaming the loco almost as essential as the supply of coal and water, is a blower. Having a small compressor in the workshop it seemed sense to make up an air powered blower. The principal is described in LBSC’s book on ‘ Tich ‘. A small tube blows air up a larger diameter tube which fits into the locomotive chimney causing the vacuum necessary to draw the fire. The outer tube in the assembly devised for Pixie comprises a length of large diameter copper water pipe and a parallel union. The union has a groove turned around the periphery into which is fitted an ‘ O ‘ ring to ensure a push fit in the chimney and importantly an airtight joint. The small angled tube, which is silver-soldered into the main body about 1” above the level of the chimney cap, is swaged to a point then drilled using a No 70 bitt. The supply end of the small tube is fitted with a Schraeder valve, acquired from a local tyre fitting shop ( collect a handful whilst you are there, they come in for lots of things about the workshop ). The valve permits coupling to the inflator accessory of the compressor.

In use the main tube is inserted into the chimney where it stands firmly fixed by the friction provided by the ‘ O ‘ ring. The tyre inflator is attached to the schraeder valve and the blower is ready for action. An advantage of the air powered blower is that the draught obtained is infinitely variable according to the amount of air allowed to flow through the inflator valve. In practice only a very small blast is required. Too strong a blast makes a hole in the fire and causes embers to clog the tubes. Once the correct draught has been established, a small block of wood wired to the handle of the inflator helps maintain the setting by limiting the trigger travel.

A novel blower for use whether or not a power source is available was illustrated in MODEL ENGINEER Vol 156, No. 3778. 6-19 June 1986. The blower built by Maurice Simmons was based upon a traditional bicycle lamp case. A disc of metal replaced the glass and provided support for a low voltage motor and three small diameter struts supporting a further plate which served as a bearing for the impeller fan. In use, a tube mounted on a further plate below the fan, fitted into the chimney of the locomotive. Mr Simmons replaced the battery in the body of the lamp with a pack containing two re-chargeable batteries for economy. Any model engineer worth his salt would be able to build a similar device quickly and cheaply.

Oiling Round And Filling Up

Check that the mechanical lubricator is filled, work the manual wheel or lever a few times to free the clack, go right round the locomotive with the oil can, oiling bearings, rods, eccentrics and so on, plus fill all oil cups.

Check that the blowndown valve(s) are closed, then open the whistle valve or some other vent to allow air to escape as the boiler is filled with water. Water can be introduced either through the safety valve bush from an external supply, a bottle or can, or from the tank using the hand pump. The latter method will be quite a slow job although it will prove the efficiency of the pump, and the tightness of the unions in the feedwater system. Filling through the safety valve bush, or better still through a bush provided for the purpose on the steam dome, can be speeded-up using a plastic bottle fitted with a small diameter plastic tube, the plastic bottle being squeezed to introduce an element of force feeding! For the more ‘ laid back ‘ a can of water set on top of the cab can be used to feed water siphoned through a small bore tube.

The water level should be checked in the gauge glass. You are aiming for about 3/4 of a glass. It makes sense at this stage to open the water gauge drain valve. As the drain tube is of small diameter the water rises slowly in the glass despite the small quantity draining away. Once the correct level shows in the glass the valve can be closed, the safety valve or the filler plug inserted, and whatever is used as a vent, closed. The saddle tank can next be filled. With both the boiler and the water tank filled, refill the water containers, this will avoid a panic situation when the onboard water supply gets low after some time in steam !

Lighting-Up

Check that the regulator is closed and that the reversing lever is set in mid-gear ! With sufficient of the paraffin soaked sticks in the firebox to cover the grate area ‘ light the blue touch-paper ‘ With care, a breath of blower will fan the sticks into flame. After a while, when they settle to a red glow, put in a few shovel fulls of coal. Close the door and after a few minutes further blowing when the whole fire will be glowing red, add more coal. Soon the air blower can be removed and the locomotives own blower set to work. The pressure gauge will start to register and continued firing will bring the pressure to working level and the safety valves will start to lift. Watch the water level, pumping by hand as required, not too much however.

Getting Under Way

Having built the fire to an all-over incandescence, and topped up with a layer of fresh coal. it is time to start! With the reversing lever in full forward gear and with cylinder drain valves open, open the regulator slightly whilst easing the loco forward a few feet. Steam will drive out any water from the cylinders as well as beginning to heat the pistons and cylinders. During this process the locomotive will be blowing off and using steam so it is essential to watch the gauge glass and pump up as necessary.

There may be a shower of water from the chimney at this stage as the condensate is blown past the slide valve, this will soon cease however and the whole show will settle down ! Close the the drain valves soon as the cylinders are clear and steam alone is issuing from them.

The setting of the safety valves should be checked against the pressure gauge which will have been calibrated against a full size gauge in the workshop. Have the necessary tools to hand at firing-up time. In the case of there being two valves fitted, they both should be set to blow at the same pressure.

Now is the time to set the reversing lever to full forward gear, open the regulator gently, avoiding wheel slip, close the blower down and feel the locomotive surge forward, as surely it will.

Once under way adjust the gear back a notch or so, and enjoy!

Driving

As the beginner soon finds out, firing and driving a locomotive, albeit a model locomotive does not come easy. One has to learn how to best use the controls to maintain a head of steam, and more importantly what to do if the pressure falls off. It is exciting, and even though the first few firings may prove disappointing as far as performance is concerned a lot will be learned and a great sympathy develops for the engine men of the steam era who drove through whatever weather and conditions prevailed, rain, snow, ice and sometimes even, flood. These men ( heros ) took great pride in their work and in their time keeping.

Spare a thought for the engine men of the Ffestiniog Railway of 1876. The Railway Regulations of the day set out a series of fines which were to be levied on unfortunate workers as follows:-

Engine driver for having used greater quantity of Coal or Oil than the fixed lb. per mile Coal 2s 6d. Oil 1s 0d.

Fireman ditto. Coal 6d. Oil 3d.

If reported to have used more than the stipulated quantity, more than three times in six months is liable to dismissal.

THESE RULES to be strictly enforced: none but the most tangible excuse will be accepted in favor of not imposing the fine

We shall have to watch our fuel consumption!

Whilst driving there a lot of things to be remembered :-

• Two of the driver / fireman’s actions result in loss of boiler pressure, those of adding coal to the fire, and adding water to the boiler. These actions should be carried out when the safety valves are blowing.

• Always shut the blower down after opening the regulator. In motion the exhaust is sufficiently strong to draw the fire. Open the blower valve before closing the regulator in order to maintain the draught.

• Adjust the by-pass valve to maintain the water level in the gauge glass, remember that the axle driven pump works flat-out all the time, and with both pumps working one can soon be in for a shower!

• Fire little and often to maintain an incandescent fire whilst avoiding a drop in steam pressure.

• A few droplets of oil around the chimney top are a good sign that oil is getting through the system.

• Make sure to add coal to the front of the fire, use a pricker if necessary to distribute the coal and avoid a choked grate.

• On an ‘ out and back track ‘ add coal when the locomotive is stationary and when the safety valves blow, it’s too late when the fire blackens.

• A layer of coal on an incandescent fire will light and burn, on a black or holey fire it will not.

• It is not necessary to keep the fire up to the level of the firehole door, this is wasteful and leads to a choked fire.

• If the fire does die down, avoid pumping cold water into the boiler, using the blower in short bursts or making the loco work harder, by putting the reversing lever into full forward gear, until the fire comes back.

• In the event that the pressure continues to fall off it will be necessary to open the blower to increase the draught and draw the fire, this is also necessary at the stops and at the end of an out and back track. In the latter circumstances it is all too easy to forget to close the blower valve so be alert and avoid a holey fire!

• Notching-up, shortening the cut-off by moving the reversing lever nearer to mid-gear, saves steam and thus coal and water.

• If on any of the first few runs things appear to be ‘ getting ‘ out of hand, do not hesitate to pull the pins and drop the fire. Better safe than sorry is a good motto where the pressures encountered with model locomotives are concerned.

Shutting Down

The sequence of shutting down after steaming is equally important as that of firing up the loco. The fire should be allowed to burn right down as far as possible whilst retaining sufficient pressure to permit a blowing down. The blowdown valve(s) should be fully opened to permit the sediment that collects about the foundation ring to be ejected.

The firegrate and ashpan can be dropped, and the firebox brushed out. With the smokebox door open and the ash cleared, a blowthrough with compressed air will clear away any debris from the tubes. Later tube brushes will finish of the task.

All valves should be left open and the warmth of the boiler will dry all out. It is best to leave the valves open whilst the locomotive is in store, particularly the regulator. Martin Evans, in ‘ Rob Roy, Building a Caledonian 0 - 6 - 0 Tank locomotive ‘ Argus Books Limited., passes on the helpful tip that ‘ should a regulator or blower valves stick in storage, rather than attempt to force them open, it is better to raise steam when they will almost certainly free themselves with very little persuasion ‘

At this stage the engine drivers friend, the oily rag passed over the paint work will promote that silky, satiny finish so beloved of the railway enthusiast. WD 40 or similar lubricant in suspension will protect the working parts and can be cleaned off using a rag dipped in methylated spirit prior to the next run.

This is a good time to check the locomotive over, tightening any loosened fastenings, replacing lost pins, caps or corks and generally putting things in order so that the next steam-up can be started without hold-ups.

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Chapter 20

Some Useful Tools And Equipment From Scrap

These are illustrated elsewhere on my site. To view click here

Although excellent models can be produced with the bare minimum of equipment there are certain tools and attachments that can be readily fabricated from scrap. The following have proved useful in general model engineering work in fact, without them some parts would have been difficult to produce. The attachments for the Myford noted here can be made from offcuts, or at least from relatively cheap materials found in the odds-and-ends bin at the material suppliers. Whilst the time expended in making them has to be set aside from model making the results will prove useful in constructing the present and many future models.

Rear Tool Holder

The most useful attachment made to date is the rear toolpost used for parting-off. This was machined from two blocks of mild steel, fixed together using socket-head screws. This assembly was then drilled and bored for a clamping bolt passed from the top through into a length of tee nut which fits into any of the slots in the topslide. The clamping bolt is fitted with a lever terminating in a ball handle. The parting tool holder is located, upside down of course, within the toolpost using two further socket head screws. Use of the rear tool post removes the possibility of dig-ins and jamming. This attachment has transformed parting-off from a chore to a pleasure, and all for minimal cost. Used on the front of the top slide it can be used for holding the more substantial boring tools although due to the constant need for a parting-off tool in practice, a further similar tool holder has been produced for this purpose.

Fly Cutting Attachments

A very simple device for use in fly cutting can be made from a length of bar drilled to accept cutters, secured by grub screws. This can be set in the four-jaw chuck and adjusted as necessary by moving the bar within the jaws. Material to be machined is clamped on the saddle or mounted on the vertical slide. For the milling machine a tool holder has been fabricated from a billet of steel obtained from the local scrap yard. This is turned to register with the backplate on the quill of the milling machine and is secured by Allen cap head screws in counterbored holes. The cutters, from silver steel rod, are adjusted and secured by grubscrews. In service, in the light milling machine, the mass of the block provides a ‘ flywheel ‘ effect and also reduces vibration when intermittent cuts are made.

A Boring Tool Holder And Arbour

Boring small and deep holes can be carried out using a simple attachment based upon a design illustrated in MODEL ENGINEER. The body of the attachment is a block of mild steel, cleaned up all round and trued on top and bottom faces by turning in the four jaw chuck. The block is drilled and reamed to match the tool clamp stud on the topslide of the lathe. This completed the block is secured on the topslide in place of the tool clamp assembly ready for drilling and boring for a silver steel bar of 1/2” diameter which forms the tool holder. The hole for the tool arbour is drilled and reamed from the headstock drill chuck, feed being achieved by advancing the saddle. If required, the tailstock can be brought up to the back of the block to provide additional support during these operations. With the hole completed the block is drilled and tapped for two socket headed screws then slotted to form a clamp which secures the tool arbour in service. The arbour is turned down and threaded with a fine thread to accept the coned cap. The cap is cross drilled for the tool, coned, then tapped to suit the thread on the bar, it is provided with a knurled grip for first adjustment and two flats which permit the use of spanners in tightening the the thread to grip the tool. A small slug of phosphor bronze acts as a bearing between the thread end and the tool. Suitable cutters may be ground from circular tool steel (a broken centre bitt will suffice ).

In use, with block set up on the topslide clamp stud and the arbour gripped in the block, the toolsteel is set into the coned head and a spanner used to tighten the grip. With the clamp eased, the arbour can then be rotated to bring the cutting tool to true centre height. The clamping screws are then tightened. The bar can now lined up in the hole to be bored and the lathe clamping stud tightened. Depth of cut within the bore is adjusted by the cross slide feed screw.

Clamping Bolts

Several clamping bolts have been made up. These are from silver steel and match the threads in the Myford tee-slot nuts and also the closer disk for the crosslide anchor plate. Apart from normal duty retaining the various tool holders and the Verdict gauge stand, they can be used, in conjunction with suitable drilled and slotted plates to secure work in course of milling, fly-cutting and so on.

A Simple Dividing Attachment

A lathe attachment which is very simple to construct is a dividing attachment to engage in the bull ring. This is in constant use, in preparation of bolts, nuts, in setting out holes on cylinder covers and operations such as filing carried out in the lathe. The attachment comprises a plate bracket which, attached to the headstock casing using a bolt through the existing hole, supports a spring-loaded plunger engaging in the bullwheel of the backgear assembly. Using the attachment the headstock spindle can be locked in any one of 60 positions and of course multiples of those positions, providing divisions of 60, 30, 20, 15, 10, 6, 4, 3, and 2.

A simple modification, cutting the detent tongue to match the profile of the bull ring teeth increases the divisions that can be achieved. In this role the detent tongue is rotated through 90 degrees to pick up a further 60 positions.

Gauge Blocks

Over the years, whenever offcuts of steel have come to hand, these have been checked out for size, marked accordingly and set aside for use as gauge pieces. One straightforward use for such pieces is in setting the saddle from a saddle stop.

Saddle Stop

This comprises a length of 1/4” diameter bar sliding within two lugs. The lugs are secured to a backplate attached to the headstock of the lathe, using bolts into the tapped holes provided for gearbox fixing. Length of travel is limited using a bolt through a small collar sliding within the lugs. In use the tool is run to its intended eventual position relative to the headstock, a shoulder or thread end. the rod is brought up to contact the edge of the lathe carriage, the collar is slid to contact the rearmost lug, that furthest from the tailstock end, and locked into position. The projecting rod thus governs the travel of the saddle. To set a specific length of cut the cutting edge of the tool is brought to the end of the workpiece, one of the gauge pieces, or a drill shank matching the required length of cut is placed between the stop and the saddle and the bush secured against the backstop. Turning can then commence confident in the knowledge that the saddle stop will determine the correct length of cut. If auto feed is engaged the leadscrew nut should be disengaged a short distance from the stop and the cut completed manually. The little gadget is invaluable when turning to a shoulder and where putting a set length of thread onto a rod held in the chuck.

A Four-Way Toolpost

A four-way toolpost was constructed completely from scrap. A piece of round mild steel was turned to replicate the Myford closer disk for the topslide anchor plate and provide the fixing to the lathe carriage. Three blanks of mild steel were cut to size and squared-up in the four jaw chuck to form the main body of the attachment. The height of the lower block of the three is sized, relative to the centre height of the lathe, to permit either square shank tools or tools set in the Myford tool boat to be used. The three pieces of the body were welded together ( socket headed cap screws could have been used ) and the whole assembly cleaned-up. The upper plate was drilled and tapped for the tool retaining bolts. The Myford closer disk and the circular base of the toolpost were joined using 1/4” B.S.F. Cap screws and the central hole tapped for the clamping bolt. The clamping bolt is a length of 3/8” silver steel threaded each end with a B.S.F thread, the bottom engaging in the base plate, the top terminating in a a length of 1 1/4” diameter mild steel into which the spindle for the ball handle is inserted. A simple detent comprising an externally threaded bush with a plunger actuated by a spring was fabricated, again from offcuts of mild steel rod ready for insertion into a 1/4” reamed hole in the body. With the body, the base and the clamping screw completed the blind holes in the base were drilled by spotting through the 1/4” hole in the body with the toolholder locked in the four required positions. The body was then removed from the base and the spotted holes were completed in the pillar drill with the stop set to avoid breaking-through the plate.

A Knurling Tool

A knurling tool was fabricated to details published in Ian Bradleys book ‘The amateurs workshop’. This is a tool described as a straddle turning tool, comprising a body supporting a yoke retaining two arms, each fitted with a commercially obtainable knurling wheel. The advantage of straddle knurling is that, provided the wheels are adjusted to be diametrically opposite each other when forming the knurl, the forces are contained within the tool and not transmitted to the headstock bearings.

A Tapping Guide

There are a large number of tapped holes in the parts of the average locomotive, many of which are of the smaller sizes, 7 BA, 8 BA and beyond. To ensure the accuracy of the threads and avoid tap breakage, time spent in making a small tapping tool will be amply rewarded. Any flat piece of plate can be used for the baseplate, careful filing will provide the necessary accuracy. The head can be arranged to slide on pillar, a stock length of silver steel of about 1” diameter, secured into the base with retaining fluid. The head, a block of mild steel has two holes which have been drilled and bored in the same set-up on the lathe cross slide. One hole is a nice slide fit on the pillar, a slot enables this to be locked into position by two cap screws. A length of 1/2” diameter bar is set into the other hole, one end prepared to accept whatever chuck is available, the other a knurled head. In service it is helpful if the head is cross-drilled for a tommy-bar. It is advisable that if a thread is used for mounting the chuck it is screwcut on the lathe to ensure concentricity.

A Universal Chuck Mount

A chuck mount is a useful attachment which permits work to be set up away from the lathe. Some second operations can also be carried out on, for example, the milling or drilling machine. Either the four jaw, or the three jaw chuck can be accomodated and mounted on ancilliary equipment such as the vertical table or a rotary table. The basis of the attachment is a standard accessory, a Number 2 Morse taper spindle. this is mounted in the three jaw and the tapered spindle parted off just behind the register. for the chuck. The back of this piece should be lightly relieved to ensure that it beds down fully on the baseplate at the time of assembly. These operations are easy as the material used is extremely free cutting. ( The tapered spindle can be set aside and used for another purpose such as a screw support for use when working on slender discs in either type of chuck ). The threaded portion is then drilled and tapped for two 1/4” cap screws which will be used to secure it to a base plate.

The base plate can be from any piece of plate of reasonable thickness. Ideally it should be of sufficient size to permit of picking up the tee slots in the equipment to which it will be attached, yet small enough to be used on the available surface plate whilst leaving room for the base of a height gauge to be moved about whilst marking out. The plate should be squared-up and turned, or fly cut, to uniform thickness throughout before drilling for the tee bolts and the two cap screws for fixing the nose piece. The holes for the cap screws should be counterbored and the attachment can then be assembled.

Whilst lathe chucks can be mounted on the finished attachment for a variety of operations, heavy milling cuts should be avoided as they could loosen the chuck on the mounting with dire results! It is also essential to remember when using the mount to cut in such a direction that the tool attempts to ‘ climb ‘

A Simple ‘Wobbler’

This device is based upon an article in MODEL ENGINEER Vol 159, No 3811 October 1987 by Mr Cruikshank. The wobbler comprises a length of 2mm diameter rod with pointed ends, floating in a rubber bearing (cut from a car tyre tread), projecting through a 1/8” hole at centre height within a short length of mild steel bar. Any small eccentricity at the pointed end in contact with the part to be set is reflected by a greater movement at the free end. The ratio of the lengths of the two arms of the rod about the bush determine the amount of movement of the indicator end and a ratio of 6:1 seems to be about right for most purposes. In use the pointed end of the rod is located into a centre pop mark on the piece to be set and the chuck jaws are adjusted until the movement of the free end is minimised. When this stage is reached the piece is properly centred.

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