Spinning triangle

Most engines today use the piston and crankshaft system. Explosions in the cylinders make the crankshaft turn. Is it possible to construct an engine without a crankshaft? There is one very neat design, the Wankel engine. It doesn't have pistons but instead just one rotor formed like a Reuleaux triangle. This shape is by the way the solution to the second cornfield puzzle. It is a curve of constant width. You can construct such curves from any odd edged equal sided polygon, Britain had some 20p and 50p coins that had these shapes. They had the neat property that slot machines could recognize the width easily while the coins contained less metal than a circular coin of the same width.

The neat thing about the Wankel engine is that intake, expansion,compression and exhaust happens in different parts of the housing allowing the rotor to turn continuously. A gear in the middle of the rotor turn the drive shaft. Mazda seems determined to make it practical and their Renesis engine looks very promising. I hope we will see more development of this beautiful engine in the future.