The large wheel connected to the crankshaft provides the momentum to keep the crankshaft turning without the application of power, through the energy generated during the power stroke. This energy is also used to drive the crankshaft, connecting rods and pistons during the three idle strokes of the 4-stroke cycle. 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.