Hartnell governor is a spring controlled centrifugal governor, in which a spring controls the movement of the ball and hence the sleeve. Above fig shows a Hartnell governor. It consists of a frame /casing, in which a pre compressed helical spring is housed. The casing and spring can rotate about the spindle axis. The spring applies a downward force on the sleeve through an adjustable collar. The spring force can be adjusted by a nut provided. Two bell crank levers are pivoted at O,O’ to the frame, each carrying a ball at one end a roller at another end. The roller fits into the grooves of the sleeve.

The sleeve moves up and down depending on the governor’s speed. When the speed of the governor/ engine increases, the ball tends to fly outward from the axis of the governor, but the ball’s movement is constrained. The bell crank lever moves on a pivot, roller end of lever lifts the sleeve upward against the spring force. This movement transferred to the throttle valve through a suitable mechanism, the result is low fuel supply and decreasing speed.

When speed decreases the sleeve moves downward, and throttle open to more fuel supply; which results in increasing speed.