MM03 - The THUMPER engine

Technical details
Year of construction 1999
Power piston stroke 16 mm
  diameter 16 mm
Displacer piston stroke 13 mm
  diameter 20 mm
Flywheel  diameter 93 mm
  material aluminum / lead
Idle speed 200 rpm
Energy source alcohol
Mass 760g 


After gaining some initial experience with my first homebrew engines, I embarked on the "Thumper" project, following the idea on Richard Egge's little engine page. The fact that this engine is transparent fascinated me. Piston and cylinder were built from a glass syringe transsected with a diamond wheel (PROXXON Precision drill/grinder) and ground with wet abrasive paper. Displacer cylinder and piston consist of a test tube and a cigar tube as in MM02. The stroke of the displacer piston was experimentally adjusted after, on the first idling test, the piston had damaged the cylinder at the dead center positions despite rubber washers which were supposed to act as dampers. I built the flywheel using a horizontally mounted electric drill as a makeshift lathe (as of that time, I did not own a real lathe). 
To increase the moment of inertia, I filled drill holes in the flywheel with lead.