flywheel, heavy metal wheel attached to a drive shaft, having most of its weight concentrated at the circumference. Such a wheel resists changes in speed and helps steady the rotation of the shaft where a power source such as a piston engine exerts an uneven torque on the shaft or where the load is intermittent, as in piston pumps or punches. By slowly increasing the speed of a flywheel a small motor can store up energy that, if released in a short time, enables the motor to perform a function for which it is ordinarily too small. The flywheel was developed by James Watt in his work on the steam engine.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.