Flywheel

Flywheel, in mechanical engineering, a wheel of high mass that is attached to a rotating shaft, and serves to smooth out the delivery of torque, or turning power, from a motor or engine. The large inertia of the flywheel enables it to absorb and release energy with little variation in speed. An internal combustion engine, for example, produces power in a succession of bursts that are transmitted by the driveshaft to a flywheel, which absorbs the pulses of energy smoothly into its rotational motion, thereby imparting to the shaft a nearly steady torque.

A second function of the flywheel is to store energy in industrial operations such as forging, where high power is required only intermittently— or in applications where power is required on a standby basis or for emergencies. The flywheel first became important in industry with the invention of the steam engine in the 18th century, but its use is recorded as early as the 12th century.