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[hittinnb]

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[theropod2]

I think you are adding complexity where it isn't needed and may waste energy by the addition of processes to the whole affair. Every step where the heat is moved without doing work in the engine is potentially wasted.

R

[hittinnb]

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[Ian S C]

hittinnb, I agree with theropod2. And if you follow the instructables design, you will have a very inefficient motor, they use copper pipe for the displacer (defuser) cylinder, this should be steel, and if possible stainless steel, and the displacer its self should also be stainless steel, not aluminium.
The copper tube conducts heat too well, causing the heat to travel to the cold end, bringing the motor to a stop. The aluminium displacer is much the same, it will work, but not the best, and if you get the heat that the motor really should have, aluminium will possibly collapse.
The stainless steel you want is .5 mm or less, down to about .25 mm. The tube for the displacer cylinder might be some thing like an extension tube for a vacuum cleaner.
The displacer cylinder must be sealed at the hot end, all the air you start with is the same air you finish with.
I have run a motor (labelled my second motor in my gallery) on solar power, using a large Freznel lens (about 2ft x 18"). You might need a parabolic mirror of 2ft dia or more.
KISS Ian S C

[hittinnb]

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[Ian S C]

Some indication of the heat developed by a large Freznel Lens, as the sun moved, the focal point on the displacer moved, and as it moved it etched a line on the stainless steel hot cap. The motor had at least as much, if not more power than when run on LPG. Ian S C