> consists of two balls attached to pendulum rods and swinging on opposite sides of a rotating shaft Random aside: This is the origin of the phrase "balls out"

> consists of two balls attached to pendulum rods and swinging on opposite sides of a rotating shaft Random aside: This is the origin of the phrase "balls out" to mean going full-blast. When the locomotive was putting out maximum power the spinning balls on the governor would be furthest out, inscribing their largest circle.