DRIVING:

In horology, the Gear — wheel, pinion or Intermediate wheel — that drives the next gear in a kinematic chain is said to be driving, as opposed to the driven one, which receives the motion. The driving component transmits to the driven component the torque and energy needed for its rotation, according to a gear ratio determined by the number of teeth in mesh. The qualification depends on the direction of energy flow and not on the size of the component: in the Train (wheel train) of the going train, which runs from the Barrel toward the Escapement and whose rotational speed increases at each stage (multiplying Train (wheel train)), it is the wheel — bearing the greatest number of teeth — that is Driving, and the pinion of the next wheel that is driven. In the motion work, a reducing Train (wheel train) where the speed decreases, the hierarchy is reversed: the pinion, center or sliding, is Driving, the wheel, of minutes then hours, is driven. The term, borrowed from the general vocabulary of mechanics — one also speaks of a driving strand for a belt or a chain —, makes it possible to describe unambiguously the direction of transmission through a train of Gears, the primary condition for analyzing the efficiency of a Movement.