I will have to arrange another photo of the set of parts I have with the general elevation drawing.

This does show the section through the boiler and firebox as I was talking about in the earlier post. Hope this all helps set the scene for this engine.

The plans are hand drawn using a Rotring drawing table, I've played with CAD, but at the end of the day this is a hobby that relaxes me and drawing using an old fashioned board works well. The drawings are progressing and I will make them available, just not sure quite how to do that as yet…might be as pdf's, might be free as long as people send me updates and make the updates free, I thought about charging for them, but think that would just be a token amount to cover some costs – if you have experience of selling plans or giving them away for free then do let me know

Had to share the pair of rear wheels with the bolts riveted over and the spokes soft soldered to the hubs. The alignment is superb as I used a jig to align the hubs and held in place whilst I heat jig and wheel to solder. All of the stages of building these wheels has taken me some time (around 8 weekends worth), but the final result is quite rewarding.

I need to machine the outer face of the spokes on the hub to get a clean, parallel finished surface onto which I can fit the hub cap. I'm a tad nervous of this machining step…..will let you know, Nigel

I've been approximating the amount of fuel used and steam produced, my simple calculation for a boiler fired by methylated spirit and driving an engine at 12mm bore and stroke at 300rpm gives:

1.38g water per minute => 0.26g fuel / minute

the steps are given in more depth here, but wanted to share the high level numbers for this 1/20th scale traction engine.

I now have an input power of 128.7 Watts and an engine output power of 3.3 Watts, the Steam Engine and Boiler Efficiency is a ratio of the output and input:

Steam Engine and Boiler Efficiency = Output Power / Input Power

Miniature Traction Engine Efficiency = 3.3 / 128.7 = 0.0256 = 2.56%

So, my calculated efficiency is 2.56% that feels very high for this small system and I expect a lot more losses when I put this into practice.

I cut the front wheel rims out of a piece of 70mm diameter mild steel

However, they just looked rather large compared to the rear wheels, some this is down to the fact that these are the roughed out rims and when I machine the outer rim to the proper section they will look much lighter.

Overlaid on the image that I'm using to design the traction engine from and they perfectly just cover the front wheel rims.

I'm spending too many hours just looking at the parts I've made so far…..

The rims now have the right cross-section

The front wheels have a single bead and the spokes crossover side to side. Will be making the hub and spokes next, the hubs will be made from PB or brass at the front as they will also be bearings for the front axle.