The gravitational clock (tracking system) consists of a weight, the gears which generate rotational motion of a constant rate using gravity, and a bar to transfer motion to the telescope.

The constant rate of rotation is achieved by a balance between the gravitational force that acts to accelerate the gears inside the box, and the frictional force due to the arms which, when the rotational motion is fast enough, rub the rail (black in the figure) to decelerate the motion.