The Carrousel GRAND COMPLICATION

(hence the term “overcoil”), both centering and concentricity would be improved and along with that rate keeping of the watch. As it has done with several of its newest movements, Blancpain has constructed its balance spiral with a Breguet overcoil. The fabrication is painstaking as the upward and inward bend of each balance spiral is delicately fashioned by hand.

In adding a chronograph to the carrousel Blancpain achieved a world first as that combination has never been done before in a wristwatch. Indeed, because the chronograph incorporates a flyback function, meaning that instead of three pushes to command a stop, return to zero and restart for the chronograph, a single push of the lower button will suffice, the combination is a “double world first” in that a flyback has never before been combined with a carrousel in a wristwatch.

In the same way that the carrousel is heart of the grand complication’s timekeeping, the vertical clutch mechanism is the nerve center of the chronograph. Although Blancpain drew upon its nearly thirty years’ of experience in the construction of vertical clutch chronographs for this new grand complication, the design for the Le Brassus Carrousel Répétition Minutes Chronographe Flyback was evolved considerably. Throughout its collections, Blancpain’s chronographs have placed the minute counter for the chronograph in a subdial at the 3 o’clock position. A completely different architecture was sought for this first pairing of a chronograph and carrousel, one with a central large minute counter hand which would read upon the outer chapter ring of the watch dial. Much more was

involved than changing the gearing to move the indication from 3 o’clock to the center. Because the hand would be considerably longer than with a small subdial, the minute counter gear train was entirely redesigned. The minute counter hand is expected to move smartly to the next minute as the chronograph seconds hand passes 60. In order to ensure perfect motion without flutter or oscillation, Blancpain’s movement designers determined that a form of gear construction was required which differs from that which it has previously used in its chronographs. Instead of a classic solid tooth profile, the ideal answer was found with teeth that incorporate a “split.” The purpose of the “split” was to build into each tooth a form of shock absorber. These miniature shock absorbers not only produce a perfectly smooth advancement of the minute hand, they prevent unwanted wiggles if the watch is subjected to an external blow.

Ideally two gears should mate with the teeth of one falling into the troughs of the other. But as starting is a random event, the mating of the gears may not necessarily occur with teeth oriented toward troughs; sometimes a tooth will first contact another tooth. This causes an undesirable jump in the movement of the seconds hand. Further, to compensate for play in the engagement of teeth and troughs which would produce unwanted fluttering of the chronographs seconds hand as it circles the dial, a tension spring is employed with these designs. Although the tension spring helps smooth the movement of the hand, it adds drag to the running of the watch, changing the running rate when the chronograph is operating in comparison with its rate when it is not operating. Finally as the teeth of the wheels for these high grade chronographs are extremely fragile owing to their fine sharply triangular shape, to minimize wear, it is always advised to avoid running the chronograph constantly.

All of these drawbacks are cured with Blancpain’s vertical clutch design. Instead of relying upon the mating of two gears when the chronograph is started, two disks are pushed together. Starting takes place perfectly every single time with no jumping. Nor is there a need for a tension spring. The two plates rotate together with no risk of flutter. And with no need for a tension spring, there is essentially no change in the running rate of the watch when the chronograph is engaged. Finally by dispensing with fine triangular shaped gears that wear upon each other when engaged, the chronograph can be run constantly if the owner so desires. In short, Blancpain’s construction delivers the type of chronograph performance and operation that befits a true grand complication.

There was one more challenge associated with incorporating the chronograph within this new grand complication. As one of the complications is a minute repeater, its gongs (which are in the form of steel rings) encircle the movement. The standard placement of the chronograph pushers for start/stop and return to zero would cause their shafts to collide with the repeater’s gongs.

_{Figure A. The vertical clutch mechanism with the chronograph stopped; the two arms are holding the seconds hand disk away from contact with the bottom plate.}

_{Figure B. The vertical clutch mechanism with the chronograph running; the two arms have been pulled away by the column wheel allowing the two plates of the clutch to come into contact with each other.}