Hi,

I have been trying to make a thermoacoustic engine, but I don't seem to be able to get the thing to run at a sensible speed (from what I've read on the internet, it should be approx 1000rpm). I'm getting maybe 60rpm.

I've tried 12mm (100mm long) and 16mm (150mm long) test tubes, with steel wool and kettle de-furrer as regenerator materials. The cylinder is aluminium with a 5mm hole between the cylinder and the test tube.

The bore is just a shade under 12.7mm (1/2" ) so that only a light polish of the 1/2" graphite rod is required to get a good fit (and plenty of compression). The stroke I have varied between 10 and 14mm (aiming for a roughly square bore/stroke engine). The position of the cylinder is adjustable so that I can get the piston to just kiss the end of the cylinder wall for max efficiency.

The flywheel is solid 50mm aluminium, 12mm thick, running on two ball bearings from a 120mm DC fan (like you get in PC cases) , 3mm shaft.

The crank is a piece of 2mm thick aluminium sheet. It runs on a 1mm pin through the back of the piston and has a phosphor bronze bush at the flywheel end.

I have tried heating it with a tealight, gently with a blowtorch, and not so gently with the blow torch.

I can only get it to run at any significant speed with the glass on the verge of metling.

What am I doing wrong?

Edited By Oliver Lindley on 16/04/2013 20:14:37

Edited By Oliver Lindley on 16/04/2013 20:14:58

Edited By Oliver Lindley on 16/04/2013 20:15:17