Stirlingengineforum.com

I find the hardest part of making a Stirling Engine, when you have not got a metal lathe, is making the power piston. While trying to find something to use for a power piston, I found that the diameter of a one pence piece was just a little bigger then the diameter of 20m plumbers copper pipe. Here is a power piston I came up with, that uses two one pence pieces and a bolt with three nuts. Total cost - around three pence! It is easy and cheap to make, and more importantly, it work very well.

It is on my Hints and Tips page
Roy

http://homepage.ntlworld.com/sheepdog1951/

I used the Haigh Piston. I used the same size brass pipe for my mould, as the cylinder; 2 crimp connectors set in the matrix for the piston pin(plastic removed). Then I knocked it out of it's mould and turned it down on the drill press for a great fit. I used sanding cloth plumbers use for dressing-up joints before soldering, for the "turning process". On the bed of the drill press, I installed a point off of a set of tie tongs used at the railway, and then drove a dowel through a wooden thread spool, applied two sided tape to the face, and used that for a face plate.(chuck the dowel in the drill).I stuck the top of the piston to this assembly, then lowered it onto the point, locked it down and did my turning. Kinda like a vertical lathe I 'spose lol. Worked very well. Belt sand the top of the piston BEFORE you take it out of your mould. As you sand, you'll see you can go by the amount of material removed evenly by the edge of the mould itself.

I have heard a lot of stiring modelers use resin or JB weld to "cast" pistons. I have an idea, how about adding a clump of dry lubricating graphite to the mix? I don't know if it would mix in right but it would be self lubricating? Just an idea.

That, wouldn't work... it would chanche the composition of the material and it even might not harden at all. You can add some grease to do mold to make it easier to unmold though...

Maybe if you "dust" the grease in the piston mold with dry graphite then? I'm finding very large perfomance gains in my engines with tiny amounts of reduced friction. Of course this goes without saying but going back through your running engine is worth doing.