Hi !
We recently had a Summer camp with teenagers. We had prepared many stirling motor kits using an engine similar to the one of this page : http://www.internetbestsecrets.com/2010 ... ngine.html. The teenagers just had to assemble the pieces. However, what happened was that only one of their motors was actually working. We have been looking for the cause of that during the last month (part time). All our previous tests with such motors were working very well. Our conclusion is that the soda cans we use are now built differently, here in Canada. It turns out that the only motor working among those built by the teenagers was the one using our oldest type cans, the same we used with our test motors. All the others were using more recent cans.
Our tests reveal that these new cans make smoke when we heat them, and this smoke creates a compression that prevent the motor from working. We first though there was a new coating inside the can. However, after removing all possible forms of coating, it still produces smoke when we eat it, as if the metal itself was slowly burning or emitting some product. We did try different brands of cans, but we think that they all somehow come from the same manufacturer. Did somebody else have the same problem before ? Thanks.
Soda can Stirling Motor smoke problem
Re: Soda can Stirling Motor smoke problem
Hi,
this is my engine design. I have built over 800 can motors using a variety of cans, I don't believe than any of the cans
have a problem with the coating (although, I don't live in Canada, I see no reason for the cans to be constructed differently.
They all seem to be coated and they all smoke, if heated to sufficiently hot enough.
I had the same problem as you, on about 50% of the engines, it feels as though there is too much pressure in the engine for it to turn over.
The best solution I found was to fit a small piece of flexible wire that is about 0.5 - 1mm in diamter under the edge of the diaphragm to allow a small
amound of air to escape continously. This relieves the pressure and allows it to turn freely. I used 0.55mm fishing line under the diaphragm. I think
the pressure comes from their being too much dead space in the engine, possibly from the density of the wire wool ? I never found a definitive reason
for why some of these engines worked easily and others needed the fix above. Anyway I hope that fix works for you.
this is my engine design. I have built over 800 can motors using a variety of cans, I don't believe than any of the cans
have a problem with the coating (although, I don't live in Canada, I see no reason for the cans to be constructed differently.
They all seem to be coated and they all smoke, if heated to sufficiently hot enough.
I had the same problem as you, on about 50% of the engines, it feels as though there is too much pressure in the engine for it to turn over.
The best solution I found was to fit a small piece of flexible wire that is about 0.5 - 1mm in diamter under the edge of the diaphragm to allow a small
amound of air to escape continously. This relieves the pressure and allows it to turn freely. I used 0.55mm fishing line under the diaphragm. I think
the pressure comes from their being too much dead space in the engine, possibly from the density of the wire wool ? I never found a definitive reason
for why some of these engines worked easily and others needed the fix above. Anyway I hope that fix works for you.
http://www.scraptopower.co.uk My web site, Stirling engines and AE stuff.
Re: Soda can Stirling Motor smoke problem
Great! Thank you very much for your answer. We will certainly try your fix and I will tell you the result.
Re: Soda can Stirling Motor smoke problem
We did try your solution and it works! Sincere thanks. The teenagers will be happy to see their engines running. I believe your answer will also help others with the same problem.