Stirlingengineforum.com

What do you mean by suction? The displacer does not "do" suction, all it does is move the air back and forth in the displacer chamber which is heated at one end, and cooled at the other. The hot air expands pushing the power piston/diaphragm, and if all is going well the cooling air is contracting, allowing the piston to return.
Ian S C

Hi, thanks for the correction. I tried pressurizing the system and found a leak. I was only able to increase the internal pressure to 5 PSI and I can hear the leak. Working on sealing the system. Thanks again.

Found the leaks, working on sealing the system.

How flexible is the diaphragm, it only needs to be something like a party balloon, or surgical glove, thin rubber sheet call a dental dam is useful.
Ian S C

Hi, I am working on adding a water jacket. I am using a inner tube.


The idea is from other youtube projects. I also will add a weight to the flywheel to neutralize the diaphragm resistance. I am rebuilding the project and correcting all the mistakes. Thanks for the help and I will post results when available. Thanks again.

Hi burnit. Just some random thoughts. Some sort of adjustable balance spring might serve better than a balance weight to overcome the diaphragm tension and/or varying levels of pressurization. The spring could hook to the rod so as to balance the forces before they add to friction loads at the rod and main bearings. Also, maybe you could shorten the stroke enough to eliminate that initial "pop" of the plunger at the top of its action. Maybe you could make the shape under the plunger match its compressed form, so as to minimize dead space. I agree with Ian about the thickness of the plunger material inducing more hysterisis type friction, but as you say, it will be able to stand a bit of pressurization that might make up for it. It'll be interesting to see how it goes.
Bumpkin

http://stirlingengineforum.com/viewtopic.php?f=1&t=2000

Hi, thanks for the suggestions. Basically I am looking at differences between the working projects posted in the link above and my project and the major difference is a water jacket. Thanks again. It should be about a week before I can test again.

You can't use pressure above atmospheric unless it is pressurised on both sides of the diaphragm/piston, have not heard of a pressurised diaphragm engine, reason the diaphragm has a short life, and would entail stripping the engine often to fit a new one.
Ian S C

The pictures and text are frustratingly puzzling, but It looks like a toilet plunger; purpose-built to induce more pressure on one side than the other. I think the mentioned 5 psi would be possible before the s hits the fan. Certainly other diaphragm designs and materials like truck air brakes commonly work at up to 120 psi difference and can last for decades before a quick and easy service. For my purposes, I've seen as many useful diaphragm Stirlings as piston Stirlings: I'm still looking for one, so I try to keep my eyes open and encourage experimentation - particularly when it's someone else's expense.

Bumpkin

[youtube]https://youtu.be/rGFiaL_gYhU[/youtube]

Hi, here is project using a truck brake diaphragm with great results. Thanks for the info.

[youtube]https://youtu.be/HqdoCzNAzHM[/youtube]

Completed updates. Adding a second power diaphragm, interior and exterior water jacket, and a u shaped displacer.

This is all experimentation.

I found a new material to try for the displacer. Grill cleaning blocks from the kitchen supply store. I think it is ceramic. It is similar to Styrofoam, light weight and it should not melt. It should help keep the cold side, cold for a greater temperature differential.

Can it be turned or other wise formed into a suitable shape, and is it strong enough not to break up.
Ian S C

Hi, all I can say at this time is it low cost. I can easily push my thumb nail into it. I will know more in a few days.

Ian S C wrote:Can it be turned or other wise formed into a suitable shape, and is it strong enough not to break up.
Ian S C

Hi, I did some test cuts with a cooping saw and it works well. It is very easy to shape but thin pieces are very brittle. I plan to use a high temp epoxy to glue the blocks together, then shape, and then coat the surface with the high temp epoxy for strength. When you crush a small piece it turns to powder. It should allow me to make a correct size displacer.