   thumb|right|master rod (upright), slaves and balances from a two-row, fourteen-cylinder pratt & whitney twin wasp  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" (german sternmotor, french moteur en Ã©toile) in some languages. the radial configuration was very commonly used for aircraft engines before turbine engines became predominant. ==engine operation== since the axes of the cylinders are coplanar, the connecting rods cannot all be directly attached to the crankshaft unless mechanically complex forked connecting rods are used, none of which have been successful. instead, the pistons are connected to the crankshaft with a master-and-articulating-rod assembly. one piston, the uppermost one in the animation, has a master rod with a direct attachment to the crankshaft. the remaining pistons pin their connecting rods' attachments to rings around the edge of the master rod. extra "rows" of radial cylinders can be added in order to increase the capacity of the engine without adding to its diameter. four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation. for example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4 and back to cylinder 1. moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression. the active stroke directly helps compress the next cylinder to fire, making the motion more uniform. if an even number of cylinders were used, an equally timed firing cycle would not be feasible. the prototype radial zoche aero-diesels (below) have an even number of cylinde
Piston_engine_configurations Radial_engines