Flame eater engine modelled and animated in SolidWorks. A flame eater engine is also called a fire eater engine, a fire licker engine, a flame licker engine or simply a vacuum engine, because the piston is pushed into a vacuum by the atmosphere. Personally I prefer the German name Flammenfresser!
The spring loaded cam operates a vent that traps the hot air from the burner in the cylinder, which in turn drives the piston inwards due to a vacuum created when the trapped air cools.
It's all very simple :-)
Original design by Philip Duclos.