Stirling Engines - Pistons and Cylinders


Here is the video commentary:

This is an actuator I got from It's a free sample I got from their website. Actuators are used for different industrial processes but they are perfect for making stirling engines as well. This little sticker has the model number and some safety warnings. This end of the actuator is pre threaded with a washer and a nut. It's very convenient for attaching the actuator to anything. It's also threaded on the inside of the hole but I remove those threads by drilling a larger hole down the middle. You can see it came with a black rubber sleeve to make it a little less fragile.

This connecting rod has a low friction bushing at the end. You could probably use the bushing they provide for your engines but I like to replace it with a small bearing. The inner diameter of this bushing is 5/32 of an inch, the end of this connecting rod has a quarter inch diameter. I don't need this rubber sleeve so I'll just remove it with a razor blade.

Here it is, a low friction graphite piston inside a pyrex cylinder. This actuator is pretty much friction free and air tight. I haven't been able to make anything of this quality yet. I'm going to cut the end of the cylinder off so I can remove the graphite piston. This will also allow the connecting rod to rotate at greater angles. I do this by wrapping a small piece of the black rubber sleave around the actuator and clamping it into the lathe. This connecting rod needs to be all the way in the cylinder or it could hit something. I'm going to use this Variable Speed Rotary Tool with a Diamond Cut-Off disc. I use a 7 x 10 mini lathe. I'm going to set the lathe to the lowest possible speed which is 200 rpm.

This operation creates a lot of dust so you'll want to wear a mask. This cut is a little rough so I'll sand it a little on some 400 grit sandpaper. After I sand the end of the cylinder I run it under hot water to remove all the dust particles then I dry it thoroughly to keep the steel end from rusting.

This is a glass tube cutter I found online. It's spring loaded and has this small round blade you use to score glass tubing. You are supposed to be able to score the tubing and then snap it along the score line but I had really inconsistent results with it. I found some graphite online somewhere and I got this pyrex tubing from it's actually called Borosilicate Glass, Pyrex is a name brand. Here's one of the cuts I made with the glass tube cutter.

This is a piston cylinder set I made. This Borosilicate Glass I got from does not have a precise inner diameter. This cylinder is narrower near the middle which causes the piston to stick. I need to find some better borosilicate glass tubing.

This is an engine I'm working on that uses brass tubing for the piston and the cylinder. You can find this brass tubing at hobby shops. I'll show you more on this one in a future video.