Consider a chronograph mechanism as a separate subsystem, which, through a “clutch”, is coupled to the movement to power the chronograph’s indicators once activated. The most widely used is a “lateral clutch”, as was found on all prior movements used in Rolex’s chronograph watches. Lateral clutch-based chronographs work well in general, and are visually very appealing; however they have a couple significant disadvantages: 1. Loss of amplitude in the balance wheel’s oscillation when the chronograph is engaged, affecting timekeeping accuracy, and 2. Backlash. When the chronograph is either started or stopped, the chronograph seconds hand typically hops, or jumps, due to the imperfect, mis-aligned mating of the lateral clutch’s gear with the teeth of the movement’s driving gear.
By design, the 4130’s vertically coupled approach enables absolutely precise starts and stops of the chronograph seconds hand. When started, stopped, or reset, no unwanted jitters are seen on any of the watch’s hands. The vertical clutch also allows the chronograph to run continuously for extended periods, with no impact on timekeeping accuracy.