DRIVEN

In horology, the Gear — wheel, pinion or Intermediate wheel — is said to be driven when it is turned by the one preceding it in the kinematic chain. The driven part receives the Movement and energy from the driving part, which makes it turn. The qualification depends on the direction of transmission: in a Train (wheel train) multiplying train, where speed increases (from the Barrel to the Escapement), the wheel is driving and the pinion of the following mobile is driven. In a step-down train (wheel train), where speed decreases (as in the motion work going from minutes to hours), it is the pinion that is driving and the wheel that is driven. The driving-driven pair thus describes, at each stage, the transfer of energy between two mobiles. The shape of the teeth, the ratio of the number of teeth and the quality of the meshing determine the efficiency of each pair and, cumulatively, that of the entire train (wheel train) — and therefore the efficiency and precision of the movement.