Dear JedRothwell do you know this history ?
I have never heard of this. Wow! It is impressive.
Steam powered cars made more progress than people realize. The final version of the Stanley Steamers were marvelous machines. The early versions took a long time to bring to boil and generate enough steam. The final version had something like a large, shallow boiler. (Something like that . . . I don't recall the details.) Water was injected and flashed into steam quickly, so you could start up in a few minutes. The cars were speedy.
I wonder if a cold fusion heat source will bring about the revival of steam piston or small steam turbine heat engines. It seems like the best approach. More efficient than a Stirling engine. Efficiency will not matter from an economic point of view, but an inefficient engine would take up a lot of space and generate a lot of waste heat. Ultimately, I hope that low cost thermoelectric heat engines can be developed. They have no moving parts, so they last longer. I think they can be made compact, judging from the size of the ones now used to power things like remote railroad crossings. They cost a lot of money per kilowatt of capacity. I don't know how much money. The manufacturers' web sites are unclear about the actual cost.