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dimensions for displacer on a Stirling engine? Answered

I want to make a low temperature Stirling engine. I was looking at some different designs for them and none really have a set dimension for the displacer. All the ones I see must just be guesswork. I  have a glass tube that I was going to use for the power cylinder about 16mm diameter I will build it like this. I have no idea what size the displacer cylinder and displacer will need to be for it to be effective. can anyone guess for me?

I also need to know how much the piston should move for it to be effective.

Thanks, David.


The displacer can displace more air then the power cylinder holds, the extra will just stay in the displacer cylinder. In some - Low temp for example there is an advantage in displacing a lot of air at once and they usually have a wide shallow displacer cylinder.

The displace should be as light as possible. BUT be able to withstand the temperature of the heat source. I have used crushed aluminium foil - a sort of crude honeycomb aluminium as well as empty cans.

Low temp generally use foam as a displacer because of the very light weight and low temperatures.




There's a page on LTD Stirling engines here: http://diystirlingengine.com/ltd-stirling-engine/

There is good info on that page. At the bottom of the page there is a link to a good book on this topic.

I've read it and it's short and easy to understand a will give a much better perspective on low temperature differential Stirling engines.

Hope this helps.

The displacer cylinder should be the size you can manage - unless you are going to splash out on a custom-made cylinder, you're going to have to use a reclaimed cylinder, like a soda can or a bean tin. Either way, all the displacers I have seen have been around a third the height of the inside of the cylinder.