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I see the cold piston sticking out. Why is that?

Conner, you could try thinning the hot cylinder, at the hot end to say 1 mm to 1.5 mm thick, the thinner it is the easier it is to heat the air inside.
Ian S C

Aviator168 wrote:I see the cold piston sticking out. Why is that?

The Pistons are just shorter than the cylinders, so each one sticks out by 15-20mm at the end of each stroke. I did this to encourage air seal, but I may halve both their lengths in attempt to reduce friction/weight. They're currently about 57mm each.

Ian S C wrote:Conner, you could try thinning the hot cylinder, at the hot end to say 1 mm to 1.5 mm thick, the thinner it is the easier it is to heat the air inside.
Ian S C

Thanks Ian, I'll give this a go.

Hey Connor,

Here's a few suggestions that might be worth considering..

A regenerator might be worth trying. You could fill your tube with material from a s/steel scourer pad, maybe the first clear tube would allow a good fill factor without choking airflow too much.

Experiment with the phase angle, some alpha engines will run better with a phase angle of up to 120 deg, so somewhere from 60 to120 might give you a better output for your particular engine. Play around you never know??

Place a shroud/flue around the hot end to allow the hot gas from your flame to better fully envelop
the cylinder and input more energy/heat.

Use a hotter burning heat source.

Try different lubricant viscosities, and/or lubricant types, have you considered ptfe based lubricants they can have good stability at high temperatures, also maybe your hot and cold side lubricants could be different to each other depending on their operating characteristic requirements.

increase surface area on the cooling side. Maybe place some much larger cooling fins on with thermal glue/paste, or even better braise them on

increase hot side surface area by machining in grooves to the outside of the cylinder

also for interests sake see if it improves with a wet cold cloth wrapped around the cooling side

good luck
vamoose

A good lubricant is the synthetic oil used in aviation gas turbines, if you have an airstrip near by with a maintenance depot, you might be able to scroung a few ml.
Ian S C

I'm a nube, but I think I've developed some book knowledge, so let me try...
Tough to get a sense of scale, but you are looking for a volumetric change relatively similar to the absolute temperature change. http://www.solarheatengines.com/2009/11 ... tor-guide/ So depending on how you computed the displacement of the engine, I think your compression is still a little low due to the volume of the copper pipe. It also doesn't seem like you have a proper regenerator other than the copper tube, so I'd suggest filling part of the copper transfer tube with iron wire or something similar. This would seem reasonably easy, cheap and will raise the compression ratio and give you a better regenerator. I doubt you would be able to plug the pipe, so even if this is a dumb idea, it will be easy to reverse if incorrect.

Mister QED, at least as important in this design would be to replace the copper tube with steel(steel brake tube), this would reduce the heat conduction from the hot cylinder to cold. The outsige of this could have cooling fins similar to those on the transfer tubes between cylinders on multy cylinder compressors.
Ian S C

Hello
Im new to Stirling's and have never built one. I have a idea for an alpha stirling.
I want to use DIAPHRAGMS INSTEAD of PISTONS. I want to put the cold cylinder in a pond and the hot cylinder in a solar trough collector. The question I have is , the pipe that connects the two cylinders has the regenerator, can this be long? Is there a limit to the length?

It can't be very long, it joins the hot and cold cylinders via the shortest route, a longer tube is just waist space.
Ian S C