THUMPER!

12/20/98

Richard's latest is a Ringbom type of Stirling cycle engine.  This engine makes extensive use of Pyrex, high temperature glass, so as to make all of the internal moving components visible. The engine is fascinating to watch!

The displacer cylinder is a standard Test Tube (25 mm OD) and the water jacket surrounding it is a 50 ml Beaker.  Both of these parts required some modification: the Test Tube was cut to a length of 100 mm and the bottom was cut off of the Beaker.   For this I used a 6" dia. diamond cutoff saw mounted on a lathe tool post grinder.  A teflon sleeve protected the glass from the chuck jaws.

tmp1.jpg (13820 bytes)
tmp2.jpg (14613 bytes) The flywheel is made of 3/4" thick Plexiglass.  This proved to be too light so four stainless steel dowel pins were added to provide rotational inertia.    The crankshaft runs on ball bearings. 

The base is hollow as serves as fuel tank for the alcohol (note the brass filler cap).

The power cylinder measures .627" dia.   X .625" stroke. 

The displacer pushrod measures .365" dia. X .500" stroke.

The displacer piston is made from a "Don Diego" aluminum cigar tube. (I can't say anything about their cigars- I don't smoke them- but their 'wrappers' make wonderful engine parts!)   

tmp3.jpg (15194 bytes)
tmp4.jpg (16135 bytes) The power piston is solid except for a clearance hole for the 2-56 screw that attaches the connecting rod. There is no wrist pin, the cylinder 'oscillates'.    The shaft that it oscillates about is tubular and forms the passageway for air to move between both cylinders.

Not quite sure how a Ringbom works? Click here.