Heat Source for a Stirling Engine

[dnp101677]

I am in the process of making my first Stirling Engine. I finally got it running, but I had to get it pretty darn hot before it would continue running. Using a propane torch is a quick way to get it that hot, but I was looking for a more mobile way to heat it. I thought an open flame from a candle or something like that would do it - apparently not. I See people using alcohol burners and a variety of other things to heat their stirlings. I will be making a wooden base that I would like to add a compartment for the heat source to. What should I use for a heat source?

As always, that you in advance for your thoughts on this. Also, there is a picture of the engine I am making attached.

Dan

 

[mklotz]

I've built that very engine...

I fire mine with a simple, single-wick alcohol lamp. If you need to use a propane torch to get yours hot enough to run, you need to do some construction refinements. The most likely problems are, not necessarily in order:

Friction - many sources but the bearings and displacer rubbing are good candidates

Leaks - a good power piston fit is essential

Clogged passage between displacer and power chambers

Keep tinkering with it. The basic engine design is a good one and it should prove to be a good runner.

 

[dnp101677]

Wow, yours looks great! Mine is not yet picture worthy, but I will post some as soon as it is. I have good compression with the power piston. Actually it is so air tight that I wonder if it isn't robbing power. The displacer rod has been a pain. I already got rid of the .125 diameter that the plans called for and replaced it with a .1875 dia. It stills rubs sometimes though. Any suggestions for the displacer rod? What did you do for the bearings (Shaft size, bearing ID size, how any bearings, etc.)?

 

[mklotz]

I used ball bearings from my scrap box. Washed throughly in mineral spirits to remove all traces of oil/grease and then lubricated with only a single drop of turbine oil.
(Bearing friction in these flea-power engines is a real no-no.)

Mine has the 1/8" displacer rod. The gland where it enters the displacer chamber was reamed with an "over" reamer - 0.126". A bit of 3-in-1 oil on the gland helps to seal the chamber. (Remember that these engines are producing only tiny pressure differentials.)

Post some pictures. A video would be better and might help in diagnosing why yours needs so much heat to operate.

 

[dnp101677]

OK, the first picture is just to show you the engine. It's not finished yet, but you get the idea. I was considering making a new flywheel that extends past the 1.0" overall thickness to fill the space between the two frame pieces (the areas highlighted in the second picture). It looks like your flywheel may be made from steel. Should I use a material other than aluminum? I was also considering making another hot cylinder. Mine is made of SS, but it has some marks from the parting tool on the back side and they are bother me? What material is your hot cylinder?

What is 3-in-1 oil? What kind of press fit do your bearings have to the shaft? Also, did you make your burner or buy it?

 

[mklotz]

The flywheel is steel and the hot chamber is made of, appropriately, hot-rolled steel.

A stainless hot end should be fine. You want a relatively thin chamber made of something that conducts heat poorly (so it doesn't lose all its heat to the cold end).

3-in-1 is a brand name - can be found in any American hardware store. (You really should put your location in your profile so we don't recommend stuff unavailable in your corner of the world.) Any not-runny-thin oil should do the trick.

I have no idea about the bearing fits. The engine was made maybe twenty years ago and my memory isn't that good.

I made my own alcohol burner.

 

[dnp101677]

Can I see what your burner looks like? Any suggestions or words of advice concerning me making one of my own?

Dan