Dave's "Miser" Stirling Engine

The Stirling Cycle, or "Hot Air", engine was invented by Scottish minister Robert Stirling in 1816.   This was in the age of steam, well before internal combustion engines were developed.   The Stirling cycle uses heat to expand a gas (air in this example) and push a piston.

This model (the flywheel is 5" diameter) was designed by Jerry Howell to work with a low temperature heat source - it will run when sitting on your warm lap!   Dave built it from Jerry's plans, using aluminum, steel and brass plate and barstock, some 6"OD acrylic tubing, a styrofoam disk, a pile of misc and some elusive round tuit.   Tools are just your normal screwdrivers, files, drills, metal lathe and milling machine.

The three most significant parts are: The displacer chamber is sealed except for a passage to the bottom of the power cylinder.  In operation, the bottom displacer disk is heated and the top one cooled.  If the styrofoam displacer is raised to the top disk, most of the air in the chamber is "displaced" to the bottom, and gets heated by the warm bottom disk.  The heated air expands, goes through the passage to the bottom of the power cylinder, pushing the power piston up, pushing the connecting rod and left crankpin, and turning the crankshaft.

When the crankshaft turns, so do the flywheel and right crankpin, which lowers the displacer toward the bottom, warm, displacer disk.  This displaces the air to the top of the chamber and the cooler top disk.  The air cools, contracts, pulls the power piston down, which turns the crank, which raises the displacer, until h__l freezes over.

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