I don't know if it was put together improperly or if it got tossed around by the postal service, but it wouldn't turn over. The cap was set too far in, not giving the displacer enough room to move freely.
Anyway, in taking it apart to see what the problem was, I discovered that this engine had a heavy aluminium displacer.
After reassembling, it seemed, the engine required a rather lengthy pre heating and quite a lot of heat to get going. I thought that likely that aluminium displacer was conducting an awful lot of heat, right through to the cold end of the displacer chamber, before the engine could even get started, largely neutralizing the temperature difference
So, as an experiment, I tried making a wooden displacer
I found these s'mores forks with wooden handles about the right size.
After some sanding and drilling I had a replacement wooden non-heat conducting displacer.
I first ran the engine with a propane torch, as before, to cherry red hot, which resulted in the displacer getting a bit charred, but it seemed to still run just as well as before, if not better.
After that, I wanted to see if the engine would run with less heat than before
I found that the engine ran quite well on considerably less heat; just the glancing heat from a little tea candle was enough to get it going and keep it running.
https://youtu.be/bQ44Rm40unA
But the stainless steel tube used for the hot cap is no doubt also conducting away a lot of heat, so next step is, I'm going to try replacing that with a plastic chapstick tube which seems to be about the right size.
- IMG_20220123_120136459.jpg (158.7 KiB) Viewed 15499 times
I'll also be making a new displacer, out of a longer dowel, or something else, non-heat conducting, but also fire/heat proof, if possible, and may also try adding a regenerator.
Yes, I know, the plastic may melt, but my theory is, with such an efficient engine and so little heat being necessary to run it, the body of the displacer chamber being made of plastic won't be a problem.