Apropos Stirling (small), how about this set up in the focal point of a 
solar collector ? :

http://www.bekkoame.ne.jp/~khirata/gallery/special1.gif

from:

http://www.bekkoame.ne.jp/~khirata/english/gallery.htm

If it's not obvious, it is a one-cylinder displacer-less Stirling (or 
Newcomen) engine. The 'displacer' is the shutter that can shield the 
burner flame from the hot part.

Then there are NASA closed oscillating Stirlings (I think that one could 
try to build a low tech version using pistons and cylinders from a car 
engine):

http://www.grc.nasa.gov/WWW/tmsb/stirling.html

(click on the drawing to see the animation)

(off topic: now, who was hating the grassmowing chore ? ;-)

http://www.evatech.net/

Peter

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