Stirlingengineforum.com

Cheers!,

I have got a question, what can I make a displacer piston out of? I have no lathe or prior experience. I tried taking two cans (coors lite and diet coke) and putting the coors inside the coke, that creates a vacuum that I know my engine will not be able to overcome. So are there any other varitaions of the displacer piston. They can be made of pop cans, I know this, but how.

Thanks,
Matt

You need it to be light weight and very easy to move. There should be enough space between it and the walls of the displacer chamber to allow the air to pass without creating vacuum or compression but not too much or you will have air space that does no work (dead air) Styro foam, insulating foam both work well and are easy to shape. I have heard of using wadded tin foil pressed into shape and even hallow paper displacers. With "tin can" Stirling's they usually mention using a smaller can but I see no reason not using foam. I have used insolation foam for my two engines with no problems. Styro foam might have a problem if it gets too hot though.

The purpose of the displacer piston is to move the air from the hot side to the cool side. In order to do so efficiently it, in and of itself, must be air tight, i.e. no leaks can be tolerated. A metal can with the rod secured at each end with one through a packing gland, a piece of foam material, or even balsa wood cut and sanded to shape will work it your construction will not be so hot as tp damage it.
Soft drink cans can be used but there is a problem with two fitting to close.
Just pick out two cans the bigger one taller than the smaller, shorter one which should have a little clearance between itself and the larger.