The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and its attached cylinders rotated around it as a unit. Its main application was in aviation, although it also saw use in a few early motorcycles and automobiles.
An 80 horsepower (60 kW) rated Le Rhône 9C, a typical rotary engine of WWI. The copper pipes carry the fuel-air mixture from the crankcase to the cylinder heads acting collectively as an intake manifold.
This Le Rhône 9C installed on a Sopwith Pup fighter aircraft at the Fleet Air Arm Museum. Note the narrowness of the mounting pedestal to the fixed crankshaft (2013), and the size of the engine
Megola motorcycle with rotary engine mounted in the front wheel
An 1897 Félix Millet motorcycle
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is called a "star engine" in some other languages.
Radial engine in a biplane
Master rod (upright) and slaved connecting rods from a two-row, fourteen-cylinder Pratt & Whitney R-1535 Twin Wasp Junior
Continental radial, 1944
Pratt & Whitney R-1340 radial mounted in Sikorsky H-19 helicopter