IT ALL started with a Hornby clockwork 0-4-0 and a circle of tin plate track in the 1950s, then 00 gauge electric followed finishing up with an end to end scale layout which filled the lounge and took half a day to set up! My first introduction to live steam followed in the 1980s after a visit to Tom Coopers’ Merlin 16 mm. locomotive factory, situated in a small industrial unit adjacent to Llanfair Cerion station on the Welshpool & Llanfair Light Railway. Here small numbers of 16 mm. gas fired locomotives were being produced; 16 mm. was at this time in its infancy with the only other main suppliers being Archangel and Roundhouse.

Shortly after I purchased my first 16 mm locomotive; this was later converted to radio control, but the novelty of running up and down a three feet long track was soon to become insufficient. An out and back 45 mm. track was laid in the garden, this being followed by a further locomotive and rolling stock, after which I joined the East Midlands 16 mm. Group and attended many garden meets over the years.

Towards the end of the 1990s I must have looked at a copy of Model Engineer magazine and decided I wanted to build something in a larger scale, and because of my love of narrow gauge and the fact I had built a 16 mm scale Kettering Furnaces locomotive, I decided to build a Sweet Pea as the design and numerous successful working examples had been around for a  considerable number of years. It was a basic locomotive that could be built using a Myford ML7 lathe.

On a visit to the M.E. exhibition at Donnington I obtained a set of drawings from Blackgates and also the builders manual by Jack Buckler, published by TEE, with step-by-step instructions; this would later become my bible. However, as my workshop at this time was insufficient and just housed a pillar drill and grinder, I decided a workshop rebuild was required. A small extension was added, all the walls insulated, a new polycarbonate roof fitted plus additional electrics.

When this was completed I obtained a refurbished ML7 lathe from Myford; it is still in use today. With this universal bit of kit and a better working environment I decided a start on the Sweet Pea could be made.

A starter kit for a rolling chassis was purchased from Blackgates, (though not the laser cut frames version), comprising all the steel and castings. As I had decided to add a pony truck and the frames would require modification, a kit for this was also obtained at this time.

I could now make a start; the first section of the hand book had been read so many times and the drawings studied so intently that they were known off by heart. Frames and stretchers were cut and drilled with one problem encountered at this time being the distortion of the frames after removing cut  cuts for hornblocks; this I think was due to stresses within the steel, but after coercion with a hammer and block of wood this was rectified.

I now realized that my first lathe accessory was required and a vertical slide to aid milling of hornblocks and axle boxes obtained. Next a jig, as per the manual, was made for mounting the wheels for machining; I found machining the wheel castings quite a pleasurable exercise, apart from the two I had to have exchanged due to hard spots making them un-machinable. The crank pins were fitted and the wheels were quartered onto the axles using another jig set up, this is where having a manual is a god send when on a very steep learning curve.

I had reached a point at this time of feeling very pleased with myself as I had something to push back and forth on the bench. Next tackled were the weighshaft and die blocks of the simple Hackworth value gear.

It was around this time I started visiting Sweet Pea rallies armed with a digital camera amassing quite a vast collection of photographs, usually of the particular area I was working on at the time. This carried on right throughout the build as I found it invaluable to refer back to these when unsure of certain details.

The time now came for cylinder assemblies to be built which I must admit I approached with much trepidation, being concerned as to my ability to machine these, fully realizing that one small error could ruin work previously completed. All castings were obtained and this section of the manual well digested, and I also found a Sweet Pea build web site with a section on machining the cylinders. They were then machined using techniques gleaned from both this and the manual.

The cylinders were completed successfully with a great deal of care and time taken, they were then mounted to the frames and the exhaust pipe work fitted, followed by slide bars, coupling and connecting rods plus the rest of the valve gear. A milestone had now been reached; I could run on air (hopefully).

Some temporary pipe work was connected between the cylinders with a tee for air connection. A compressor was borrowed from work and with the chassis well oiled and up on blocks with air supply connected, I was ready with everything crossed as I turned on the air supply; it ran smoothly and at a nice slow speed!

At this point I wanted to hang up bunting and tell everybody, it’s a good feeling to know that all those previous hours spent had come to fruition, and I felt more confidence within myself.

It occurred to me by now that I must be about halfway through the build. Almost half the page ends of the manual were grubby.

Fabrication and fitting of the smoke box assembly came next followed by axle pump, hand pump, hand brake and reverser assembly. I had now reached that major stage of the build that I had been thinking about for sometime; the boiler.

The thought of building it myself was very daunting to say the least but at the same time when asked later “did you build the loco all yourself”, I wanted to be in the position to say “yes!” The decision to build a non superheated boiler was made and materials obtained on a trip to Blackgates.

As up to this time I wasn’t a member of Northampton SME, I decided to join and making a visit one Sunday morning, was shown around  and talked boilers with Peter Squire, to learn the requirements for inspection at various stages of construction and testing.

Over the next few weeks all the components of the boiler were machined to length and to fitting tolerances, the ML7 just accommodating the eight inch diameter throatplate and backhead. Although being a marine type boiler rather than locomotive type and as such only involving a fitting of nine stays, I found that a considerable amount of care was  required when assembling. Everything is circular and a clear centre line was needed on every component, particularly throat and back plates, because of their eccentricity.

I constructed a brazing hearth utilizing insulated building blocks. After some very useful advice from Peter Jarman (oxy-propane was used as a heat source) a start was made on soldering the  boiler together, and as work progressed and more components were added I began to realize that background heat was required, as a Sweet Pea boiler is quite large. I used a large diameter propane torch clamped to the bench plying heat to the surrounding area while soldering.

There were a couple of re-heats when I wasn’t entirely happy with the results. However, It was finally completed and a hydraulic test was obtained.

With the boiler now mounted in the frames and smoke box and the steam header pipe work connected to the cylinders, the regulator assembly was built and fitted so as to have steam feed from boiler to cylinders complete. I did make one small modification to the regulator to reverse shut off position to right hand side, which I feel to be better when in use if right handed. 

Next followed cab fabrication using zinc coated steel sourced locally, and brass angle internally for corner joints, with round headed screws with no slots to simulate rivets. The cab was fitted to the footplate and the saddle tank length between cab and smokebox could be determined; I did make the tank slightly longer than the drawing.

I found time well spent constructing a wooden jig upon which to hold the brass tank while soldering. With the tank fitted I moved onto the firebox, the main stainless steel assembly being supplied by Blackgates. I didn’t consider this cheating too much, as I was making and fitting doors, hinges and fire grate etc., also from stainless steel.

This then left the pipe work and boiler fittings. I have a need for pipe work to be vertical, horizontal and parallel, this probably being in built due to my career in plumbing, so a fair amount of time was spent here. I’ve seen many nicely built Sweet Peas sadly let down by what I call A to C pipe work.

In the early part of 2010 the first steaming took  place with the locomotive raised on blocks. Having raised steam successfully, a problem became apparent upon opening the regulator, in as much as after no more than one half turn of the wheels they locked up. However, if left for two or three minutes, they freed up, then the whole sequence of events could be repeated.

After a few failed attempts to resolve the problem I was no nearer to a solution, and it was then that John Tomlinson came to the rescue. After quite a lot of thought, John came up with the idea of finding out which side of the locomotive was the cause of the trouble. At this point we disconnected the connecting rod from the left side and ran again, but no change - still locking. However with left side replaced and right side disconnected it ran correctly on just one cylinder.

It was now apparent that the problem appeared to be the piston seizing in the cylinder and when left a few minutes it was cooling down and freeing up. I had used gunmetal pistons in cast iron cylinders, different expansion rates obviously not helping. With half a thousandth of an inch removed from the piston diameter, the problem was resolved.

The locomotive obtained a steam test and had a  few successful proving runs, and as I had been down the route of not painting during construction, the latter part of 2010 was used to strip the locomotive down to a kit of parts. Then over the winter frames, footplating and all associated parts were painted; I used a single pack etch primer intended for car body work with excellent results. For top coat I sourced a local company that would mix cellulose aerosols to my requirements, this giving a hard wearing finish with the benefit of fast drying, meaning that parts requiring multi-stage painting could be completed in a shorter time.

On the smokebox and cylinders I used barbecue paint, which is good to 425°F, applied direct as no primer was required. It keyed to both brass and cast iron after a light abrading, and after several steamings has performed well (it does what it says on the tin!).

When it came to the bodywork cab tank etc., I had discovered the colour I liked on a visit to the Statfold Barn Railway, where it had been applied to a recently out-shopped locomotive. They kindly supplied the paint code and I was able to source the two pack paint locally. As I realized at this point that I didn’t have the required confidence or spraying equipment to obtain the required finish, I entrusted this work to the ‘Dave Holland Bespoke Coach Works’, and the results speak for themselves.

On re-assembly I was quite surprised how much difference a coat of paint can make to the fit of various components, however some tweaking here and there corrected this. The locomotive is

now completed apart from name and works plates which David Fieldhouse kindly offered to make. A later project will be to fit an injector fed from a tank on the driving truck as a third alternative for boiler water supply.

I would recommend Sweet Pea to anyone who is considering building their first locomotive. I found the drawings relatively straight forward to follow with the added bonus of the construction manual, which gives clear instruction for the various set ups and jigs for machining etc.. It did take me over ten years to complete although it was only worked on over the winter months until I retired, after which a lot of time was spent on it.

Something totally different next, a 3.5 in. gauge 2-6-4 Jubilee tank locomotive to complete; I obtained this part built sometime ago.

Graham Hardwick is a member of the Northampton SME and this article first appeared in the society’s magazine, The Blower.