is a heavy rotating disk used as a repository for angular momentum
. Flywheels resist changes in their rotation speed, which helps steady the rotation of the shaft when an uneven torque
is exerted on it by its power source (such as a piston
) or when the load placed on it is intermittent (such as a piston-based pump
). Flywheels can also be used by small motors to store up energy over a long period of time and then release it over a shorter period of time, temporarily magnifying its power output for that brief period. Recently, flywheels have become the subject of extensive research as power storage devices; see flywheel energy storage
The kinetic energy stored in a rotating flywheel is
is the moment of inertia
of the mass
about the center of rotation and ω is the angular velocity
units. A flywheel is more effective when its inertia is larger, as when its mass is located farther from the center of rotation either due to a more massive rim or due to a larger diameter.
The flywheel was developed by James Watt in his work on the steam engine.
See also gyroscope, momentum wheel