MM06 - The Can engine

Technical details
Year of construction 1999
Power piston stroke 7,5 mm
  diameter 16 mm
Displacer piston stroke 15 mm
  diameter 64 mm
Flywheel  diameter 60 mm
  material aluminum
Idle speed 100 rpm
Energy source heat from warm hand
Mass 240g 


Since low temperature difference Stirling engines seemed worthwhile and challenging projects, I became excited about building the "tin can engine" described in Dieter Viebach's book "Der Stirlingmotor einfach erklärt und leicht gebaut" ["The Stirling engine -- A simple introduction and straightforward designs"] (Ökobuchverlag Staufen; 2nd edition 1999; ISBN: 3-922964-70-2)
I heeded all hints provided by the author, but the engine still proved troublesome: Although it runs very well and smoothly if put into a cup of hot water, it refuses to function on just the heat of my hands. I may have to rework it once again, i.e. decrease leakage and lower friction by replacing the acetal piston by one made of graphite and by addding a PTFE bushing to support the displacer piston rod.
Or are my hands simply too cold? ;-)