Thanks for the encouraging replies. I've also had some PMs and a couple of 'phone calls, in one of which I was smacked round the head and told to stop being an idiot. 
The plan is now to take a break and concentrate on the paid for work that is finally coming in. After that, like it or lump it, I'll be back. I will still be reading, and responding to, PMs. The timing may be slow though, as for reasons never explained I no longer get an email to say I have a PM waiting.
I'm not entirely abandoning the traction engines and other engineering. There are three main tasks upcoming:
1. Collect the set of wheels from the rubber tyre company and get the second engine on it's wheels.
2. Re-design the safety valves to be pop types.
3. Understand the maths and see if I can create a 3D CAD model of a spiral bevel gear. If I can model it then I will be able to 3D print and/or machine it.
Andrew