We all know how a conventional internal combustion engine works, with a piston and a crankshaft. But that’s by no means the only way to make an engine, and one of the slightly more unusual ...

but now the “upside down” DeltaHawk engine has arrived. The company announced Thursday that its DeltaHawk DHK180 piston powerplant—set to run on jet-A—has gained FAA type certification ...

However, [Attila Blade]’s version of a free-piston type Stirling engine is simple enough to be built in a matter of minutes. To build the engine you only need a test tube, steel wool ...