A flywheel's a mechanical device with a significant moment of inertia used as a storage device for rotational energy. Flywheels resist changes in their rotational speed, which helps steady the rotation of the shaft when a fluctuating torque's exerted on it by its power source such as a piston-based (reciprocating) engine, or when the load placed on it's intermittent (such as a piston pump). Flywheels can be used to produce very high power pulses as needed for some experiments, where drawing the… (More on Flywheel)