Making it airtight

[GlennV]

Hello everyone ,

I have build quite some stirling engines , but only a few did work.
The problem always seems to be that somewhere it's not airtight.

A video of my best engine :Video
The main air leaks are at the displacer rod seal.
I've only had succes with a fishing line and a small hole trough a balloon or something.
Whenever I try to make to make it with a rod, the air leaks out too much.
And when I get it airtight, the friction is to great...

How does everyone get it so well air tight and reasonable friction at the same time?

Thanks

[Ian S C]

One way to get enough of a seal for the displacer rod; instead of just a hole, make a guide out of a bit of tube that is a close fit on the rod, make it about 1" / 25 mm long, if you have some machinery you can get a bit fancy, other wise hold it in place with a suitable adhesive. Ian S C

[tomostre]

Hey,

I am with Ian on this, length is the savior here, although I think you can get away with shorter than 25 mm, maybe even half of that. I found that a bicycle spoke makes an ok rod, with the bonus of threads on one side to attach it to something. The nut that goes on the spoke, once you file/drill out the threads, makes an ok gland for the air tightness. If your mechanical part is precise enough, you can add teflon lining to it (extracted, you guessed, from a bicycle cable housing). I also read about folks making a gland from epoxy (just oil your rod so epoxy dont stick to it)

cheers!

[Bumpkin]

tomostre, thanks for the inspiration. The bicycle cable housing might be just the thing for something I'm doing.
Bumpkin