The Reset Mechanism Everyone can imagine that a chronograph
imitation IWC watches
The Reset Mechanism Everyone can imagine that a chronograph is only useful if it can be reset to zero. This was not possible with the first pocket watch chronographs. Finally, when the watch-maker Adolphe Nicolet invented the heart cam in 1884, a chronograph could be reset to zero after timing an interval without waiting for the chronograph counters to arrive back on zero.
This is achieved with the use of a reset lever with flat, hammer surfaces pressing against the heart-shaped discs that are fixed on the chronograph counters’ arbors (each arbor of the chronograph—seconds, minutes and hours—needs a heart cam to reset to zero). The reset hammers press against the edge of the heart cams (in whatever orientation they have stopped), causing them to rotate until the hammer is resting against the flat portion of he cam and the counters are reset. A simple principle, but there is again our old challenge: no space. As you have probably already guessed, Paul Gerber found a way.
The Split-Seconds Mechanism Never satisfied with “good enough,” Lord Arran (the owner of the watch) wanted to have a rattrapante or split-seconds chronograph mechanism installed. Gerber embraced the challenge as an impassioned watchmaker and as a perfectionist. The result, like the other complications, is a beauty in its own right. As a matter of course, this mechanism also looks like it belonged there from the beginning.
Operated by a pusher mounted coaxially in the crown and controlled by an octogonal rim wheel, the delicate, pincer-like, split-seconds brake levers gently clamp the split-seconds wheel and stop it. A second push of the split-seconds button moves the rim wheel another step, the brake levers release the split-seconds wheel, and it “catches up” with the chronograph wheel. The catching up action occurs because of the tiny split-seconds lever, mounted on the split-seconds wheel, which presses against an auxiliary heart cam mounted on the chronograph wheel arbor. The tension of this lever must be very precisely adjusted so that the split-seconds wheel catches up properly without placing an undue strain on the mechanism while the chronograph is running and the split-seconds wheel is stopped.
One of the main challenges in the construction of the split-seconds mechanism (in addition to the slender column/rim wheel) was to get the operating lever to connect the pusher in the crown to the rim wheel (around the gongs). Gerber also mastered this problem. “Of course,” one is tempted to say.
Square Peg in Round Hole, How could Paul Gerber get all these magical works into the movement? The implementation of the chronograph mechanism caused some changes to the existing movement. Two changes should be highlighted here. One is a problem of thickness. The additional arbors for the chronograph wheel and split-seconds wheel had to find their way through the central axis of the movement, and the jumping minute counter arbor likewise had to find its way through the seconds wheel pinion. Because of this, new larger pinions were necessary and consequently, new jewels with larger holes.
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