Author: Luke Ronne

I really enjoy speaking to the visitors at the Rand Society of Model Engineering (RSME) club. If you want me to carry on for ages just keep the conversation technical and away from what the latest celebrity did to make the headlines. I had a gentleman ask me where the trains come from, to which I replied “the members generally build them”.  He then asked “but where do you get the parts?” I realized I should have said they make the trains; adding credence to the expression “scratch built loco”.

Back to the build at hand; with most of the components made and the sub-assemblies tested and fitted I could start with the final assembly, and painting.

General assembly

Most of the assembly is straight forward and not worthy of much mention, other than one point- I leave the copper pipework for last (after everything has been painted) due to the sheer number of different pipes. Most of them are bent into place on the job and that’s where they stay. I have a home-made tube bender for the stainless tubing and the more complex tight bends but the sheet metal forming machine works really well for large radius bends like on the front of the smoke-box.

Large stainless steel bend for the blower line in front of the smokebox
Figure 1: Large stainless steel bend for the blower line in front of the smokebox

Space is very limited for assembly and it is not uncommon to modify spanners or even make special tools for assembly. I never buy expensive spanners; my spanner turnover is too high. A tip on tightening: the further away from the bolt or nut you hold the spanner, the more torque you apply, (for a given force). This is why larger bolts require longer spanners to tighten properly. If you are in a habit of stripping bolts, hold the spanner closer to the bolt.

Once everything has been fitted it’s time to strip for painting. I like to paint in batches, with the frames the first batch and then the remainder of the train.

Painting the Loco

I would like to state categorically I am no expert in painting, and the following is only how I go about it. I normally apply a self-etch primer to the bare metal, then a 2k surfacing primer and finally a 2k top coat. The 2k seems to handle the heat and cleaning reasonably well. For this loco I used the RB-10 high heat self-etch primer on the smoke-box and boiler but after the first steam it bubbled in certain places so I have yet to find a self-etch primer that can handle the boiler temperature. In future I will probably stick with the 2k primer and avoid the etch primer in the high heat areas altogether.

Figure 2: The main frame primed and ready for the next coat
Figure 2: The main frame primed and ready for the next coat

I have found that filling the compressor the day before and clearing the lines helps with any moisture that would otherwise damage a perfect spray job. It’s essential to have a filter and water trap in line and the compressor needs to be sized correctly for the amount of spray painting you intend doing. I carefully measure and mix the paint in another container, and pour the paint through a stocking into the gun. After every spray session the gun is thoroughly stripped and cleaned with thinners and blown dry with clean compressor air. It’s pointless straining the paint if there’s debris in the gun left over from cleaning. I’ve found that if I’m pedantic with the above I generally get a decent finish.

Figure 3: Front part of tender, painting completed
Figure 3: Front part of tender, painting completed

Now for the bit that’s out of our control. Budget for some extra paint because the last coat on the final component is bound to be struck by a kamikaze miggie, or a hair from an overeager best friend that requires a pat. Apparently it is unacceptable to convert the spare room into a spray booth, so the best we can do is watch the time of day spray painting is done, and avoid wind. Generally, I have found early morning is a good time.

As for mixing, number of coats, sanding, etc. the best is always to follow the manufacturer’s instructions and ask for the data sheet when buying paint. The sales guys are also generally knowledgeable for the more common applications. Failing that, there are a couple of good books on spray painting techniques. Mixed 2k lasts a day in the fridge for touch-up; avoid domestic unrest by placing it in a sealed container to stop last night’s quiche tasting a little tangy.

This specific loco required substantial lining which added to the complexity of painting. All boarders were black with either a white or red line. I managed to do this with fine line tape available from the automotive paint shop; it can be removed after the paint has cured leaving a clean line unlike masking tape. The thin white and red line was drawn on using paint in an open syringe with the needle rounded on the end. For thinner paint the needle needs to be longer, and thicker paint the needle shorter. This works on a similar principle to an art pen just much cheaper and it holds far more paint.

Figure 4: Lining on the tender frames and tank
Figure 4: Lining on the tender frames and tank

The stickers were then applied and coated with 2k clear coat to seal them in and for protection against cleaning and handling.

Some woodwork

Originally these locos had wooden footplates, and it would be a shame to do something different with the model.  I generally shy away from woodwork, even pattern making is a chore, but my Gran gave me a piece of sleeper wood that my Great Grandfather had in his workshop that I thought would do. To cut the thin strips reliably I bought a table saw, and when I cut the outer edges off the block I found the most beautiful teak hiding below the degraded skin. I managed to cut 5mm X 20mm strips (in fact I managed 3mmX16mm for a smaller loco as well), with a fine blade – no sanding – just some linseed oil, but enough said; let the picture speak for itself.

Figure 6: Footplate floorboards
Figure 6: Footplate floorboards

Posing for the camera

The loco was tested on air, and then tested on steam. Surprisingly everything worked well without major issues. So before the loco gets scratched and dirty from going round the track at RSME I thought it prudent to take some pictures. To keep it interesting I’ve linked them with what few pictures I have of either the same class or similar locos.

Figure 7: The old loco in all its glory and the model
Figure 7: The old loco in all its glory and the model
Figure 8: The tender
Figure 8: The tender
Figure 10 The chimney
Figure 10 The chimney
Figure 11: The front of the loco
Figure 11: The front of the loco
Figure 12: The reversing handle
Figure 12: The reversing handle
Figure 13: The safety valve cover
Figure 13: The safety valve cover
Figure 14: Back wheel and breaking system
Figure 14: Back wheel and breaking system

The conclusion

Subsequent to the photo-shoot the loco has been to the RSME club to put it through its paces. Day one was a disaster and I’m not ashamed to say I didn’t get the loco to work the first day on the track. The loco steamed really well with every mechanical system working as expected, other than it wouldn’t stay on the rails! The smallest curve would have it derailing. It turned out that the flexibles between the engine and tender were too tight not allowing enough movement, and once this was addressed the loco and I flew around the track without any issues.

It’s an interesting loco to run; because of the size of the loco there are delays with everything that runs off steam like the regulator and steam breaks (just like the real loco, I might add). It is rewarding seeing how efficient my boiler design is; I kept the fire door open for most of the day to stop the safety valve from blowing off unnecessarily, and I was never short of steam.  It ran on anthracite with the firebox less than half full, in retrospect I could have moved the fire door down further. For those familiar with steam trains this loco hasn’t got a steam dome. Regardless, with my regulator design and super heaters in place I have yet to get priming.

The following table has a few statistics that might be of interest.

My Model
Total number of Engine parts excluding fasteners/ rivets380 est
Total number of Tender parts excluding fasteners/ rivets132 est
Number of unique patterns36
Total dry weight of Engine140Kg
Total dry weight of Tender44Kg
Boiler volume8.26L
Boiler pressure (design)100Psi (6.9Bar)
Piston diameter38mm
Piston stroke82.6mm
Project timelineJune 2015-Dec 2017
Largest castingMain wheel 4Kg
Smallest castingSteam beak valve 52g
Smallest valve (ball size)Whistle 2.5mm
Largest valve (ball size)Safety valve 12.7mm
Smallest machined item2mm drain cock shafts
Super heatersRadiant type SS316
LubricationCylinders – mechanical

Other – oil pots

Valve gearStephenson’s link

But enough said, in the last article I promised less babbling and more pics, so here goes…


I would like to thank the following people:

First and foremost my beautiful wife who has more patience and tolerance than I deserve. She never lost it every time she found some container in the fridge that had no rightful place being there, or tools beside the evening meal in the oven. In addition my wife is always willing to proof read my articles, and give me a helping hand with the photos.

To Adendorff for their support in writing these articles, and always willing to go the extra mile for their clients.  Nearly all my machines were supplied by Adendorff and as you can see from the articles they have performed admirably. On the odd occasion when I have needed some assistance the sales guys have always impressed me with their willingness to listen to the problem and help me find a solution.

To everyone willing to take the time to read my articles and share my passion in manufacturing techniques, I hope you enjoyed this series!

To Alwyn Woest for machining the tires. They were the only components that didn’t fit on my lathe and I wouldn’t have trusted anyone else to do it for me.

To Philip van der Meer for all his advice on metallurgy, welding and our long engineering conversations.

To Leon, Uncle Nick and all guys from RSME who are always willing to help solve the latest engineering challenge, and are very generous with their experience and knowledge.

To Gavin Chan Yan for helping me cut the wood for the buffers and checking that the piece of sleeper wood from my Great Grandfather had no steel nails in it.

To Stephen Gwynn-Jones and Salim Essack for the 3D prints.

To Paul Malone, Danny Muller and the guys from TB who pointed me in the right direction with casting.

To all the companies (notably General Profiling, Theo’s metals, Non-ferrous metals, Resistant Materials Services, Lilsales and Hydromobile) who supplied the materials etc. needed to complete this project. The quantities were generally small and the effort on their part was large.

Then finally, to everyone not specifically mentioned that contributed to this project. The smallest contribution moved the idea of scratch building a loco closer to a reality.

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