This is the four-cylinder Stirling engine that putters up to an efficient 2,000 rpm, powered by the expansion and compression of air. Made in Germany from machine-tooled solid brass and stainless steel, its operation employs the thermodynamic principle of a regenerative heat engine—put to its first practical use in 1818 by Robert Stirling. Four alcohol burners resting on a hand-finished birch platform heat four horizontal piston cowlings; a quick flip of its dual brass flywheels sets the engine's displacement and working pistons into motion. The resulting expansion and contraction of heated and cooled air inside the cylinders transforms the 16 connecting rods, eight rocker arms, and crankshaft into a precisely calibrated alternating cycle. It can operate at lower rpms by using only one to three burners. Four full burners of ethyl alcohol (not included) power the engine for up to 10 minutes. 8" L x 6 1/4" W x 6 1/4" H. (5 1/4 lbs.)