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Postby imnotaround » Wed Oct 22, 2008 7:04 am

I have a few points to ask...

- what is best, a lightweight power piston or a more heavier power

- can a Stirling engine run if the power piston displacement is only
10 mm considering that there is no air leakage, minimal friction and
displacer displacement is 33 mm? (well im in the process of completing
my home made gamma engine and that is exactly my problem)

- how do you balance the flywheel? where do you balance it to? and
what works well, a heavy flywheel or a light one??

i just hope that someone would comment or reply on this thread cause
im really looking forward to it..
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Postby stan.hornbaker » Thu Nov 06, 2008 7:30 am

It seem that you have undertaken a very ambitious design for a first engine building project.

Look at the drawing at . Notice that the pistons are of the same diameter and have about the same travel distance. The flywheel should have minimum weight and just enough inertia to carry the engine through the cycle and balanced to minimize vibration.

A large number of links to Stirling engine information can be accessed at that may provide you a resource of help.
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Postby longboy4 » Thu Nov 06, 2008 12:21 pm

.......Hi Pete, A few technicals for you, based on the following assumptions in model Stirling construction. Aluminum and graphite most likely choices. Weight of piston with either material will not matter....we're talking Grams here. Model Stirlings from what I build and have seen on "You Tube" seem to revolve around a piston size of a half inch diameter or so, dictating the overall size of the model. Displacement between power & displacer pistons can be vey liberal.......but your 3 to 1 ratio most likely is too extreme and I have not found such an example on the WEB. In your text you say 10 and 33 mm "displacement". These terms do not discribe this. If these are actually piston "diameters", your 10mm piston would have to travel a longer stroke or the 33mm piston a shorter stroke, achieving a more favorable movement of air by ratio between cylinders within your models internal air pathways. You would be miles ahead by building a square up motor, where the cylinders & stroke are the same for both sides of the motor.. .........The consensus on flywheel weight is toward heavy. You have to overcome the dead weight of whatever is connected to it and sustain the reciepricating movement with flywheel inertia. Balancing not critical here as your flywheel would overwelm the weight of a piston and rod and these are low RPM engines. A balance point on a flywheel would start 180 DEG. from where your connecting rod mounts to said flywheel. Have fun, Dave.
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Postby ontuyalex » Wed Feb 18, 2009 7:03 am

Is there a "Golden Ratio" between the displacer diameter and the power piston diameter?

My thought was that the displacer Piston's Total area should equal Half the volume of the total airspace inside the engine. Then when it was near the heat source ALL air would be cooled, and when it was away ALL air would be heated. Is that correct?

My other thought is that the power piston whould Weigh the same as the displacer. That way the Flywheel would spin at a constant speed
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