The ball head is the component that responds to speed changes of the unit. There are various designs of ball heads, but generally, they consist of two flyweights attached to arms that pivot near the axis of rotation. The arms are attached to a collar on a shaft. As the ball head rotational speed increases, the flyballs move out because of centrifugal force pushing a rod down. The rod, usually termed the speeder rod, acts on the pilot valve to route oil to the main valve and the servomotors. On a Pelton governor, the flyweights are.
