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THE GRANDE SONNERIE

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1. Definition and principle

The grande sonnerie is the most complete striking complication in the family of passing strikes. Its fundamental principle consists in stamping the hours and quarters at every quarter hour. Thus, at each quarter, the listener first hears the value of the hours, then that of the elapsed quarters. This systematic double strike clearly distinguishes it from the petite sonnerie, which only indicates the hours on the full hour. On the other hand, like the latter, the grande sonnerie is triggered Automatically, without any intervention from the user. It thus represents the highest level of sound information among passing strikes. However, this exhaustiveness comes at a direct cost: the energy consumption of the striking Barrel is considerable.

2. Position within the family of strikes

Passing strikes bring together all complications that strike the hour Automatically. Within this family, two main levels coexist. On one hand, the petite sonnerie strikes the hours only on the full hour. On the other hand, the Grande sonnerie repeats the value of the hours at every quarter. In contrast, the Minute repeater does not belong to the passing strikes, since it only strikes on demand. The Grande sonnerie thus represents the logical culmination of the concept of automatic and continuous sound information.

3. The striking sequence

The Grande sonnerie strikes its sequence in two successive phases at every quarter hour. First, it strikes the value of the hours on the low-pitched gong. Then, it strikes the number of elapsed quarters on the high-pitched gong. For example, at 10:15, the watch strikes ten low strokes followed by one high stroke. At 10:30, it strikes ten low strokes followed by two high strokes. At 10:45, finally, it strikes ten low strokes and three high strokes. Then, at 11:00, it starts again with eleven low strokes and no high stroke. Thus, the listener can identify the full time at every quarter, without prior memorization. This reading Autonomy constitutes the decisive advantage of the Grande sonnerie over the Petite sonnerie.

4. Release and energy source

Like any passing strike, the Grande sonnerie requires a striking barrel independent of the mainspring. This second barrel must be wound regularly to power the striking train. The crown generally winds the two springs in two different directions of rotation. However, the Grande sonnerie strikes the hours four times per hour, compared to only once for the Petite sonnerie. Consequently, the consumption of the striking barrel is considerably higher in Grande sonnerie mode. This is why most Grande sonnerie movements incorporate a striking barrel with greater capacity. This energy constraint requires particular rigor in the design of the striking train and its gears.

5. Time reading: snails and racks

To determine the number of strikes to sound, the mechanism relies on stepped cams called snail cams. Each snail cam has as many steps as there are values to encode. Facing each snail cam, a rack positions its feeler on the corresponding step. For the Grande sonnerie, two snail cams are necessary: the hour snail cam and the quarter snail cam. Every quarter of an hour, the mechanism successively queries these two snail cams. First, it reads the hour snail cam, then the quarter snail cam. Each reading determines how many teeth of the rack engage, and therefore how many strikes will be struck. This system is identical to that of the Minute repeater, except that it activates automatically as the hours and quarters pass.

6. Gongs, hammers and sound

The sound of the Grande sonnerie relies on two gongs tuned to different pitches. The low-pitched gong is used exclusively to announce the hours; the high-pitched gong, to announce the quarters. These gongs are struck alternately by hammers activated by the striking train. In modern watches, the gongs often take the form of metal wire springs coiled around the Movement. This arrangement increases the vibrating Length and thus improves the acoustic quality. Furthermore, the material and thickness of the Case directly influence the final sound. Thus, tuning the gongs and adjusting the hammers require a level of care comparable to that of a Minute repeater.

7. Speed regulation: flywheel and Pallets (lever)-Regulator

Without a Regulating organ, the energy stored in the striking Barrel would be consumed in a fraction of a second, making the striking incomprehensible and irregular. Two types of Regulators are used for the Grande sonnerie, as for the Petite sonnerie or the Minute repeater.

The flywheel (or regulating flywheel) is a rotating component whose blades, subjected to air resistance, slow down the rotation of the striking Train (wheel train) and impose a regular cadence. The flywheel’s blades move according to the energy received from the striking Barrel under the effect of centrifugal force. At the start of the striking sequence, when the Barrel’s energy is highest, the flywheel’s blades move away from the flywheel’s Axis, further slowing the striking Train (wheel train). Conversely, when the Barrel’s energy weakens, the flywheel’s blades move closer to the center and accelerate the rotation of the striking Train (wheel train). Proper Regulation / Adjustment of the flywheel ensures a constant rhythm of the Stamping strokes throughout the striking process.

The Pallets (lever) Regulator, composed of a Pallets (lever) with two pallets alternately engaging with a wheel, constitutes the second system. An Eccentric — a small off-center Cam controlling the position of the pallets — allows fine adjustment of the striking speed after Assembly, facilitating fine-tuning and allowing adaptation to the acoustic requirements of the Case. In return, this system is slightly less silent than the flywheel and more sensitive to wearing positions.

8. The mode selector

The Grande sonnerie is commonly combined with a Petite sonnerie and, in this case, it is systematically paired with a three-position selector. First position: Grande sonnerie active. Second position: Petite sonnerie active. Third position: complete silence. In Grande sonnerie mode, the watch strikes the hours and quarters at every quarter hour. In Petite sonnerie mode, it strikes the hours only on the full hour. Finally, in silent mode, all Passing strike is suspended. This selector is essential to adapt the watch to the context of use. Indeed, silent mode is necessary during a meeting or at night. Moreover, the Petite sonnerie position helps to preserve the Power reserve of the striking Barrel.

9. Association with the Minute repeater

The vast majority of Grande sonnerie watches also incorporate the Minute repeater. This combination allows the user to obtain the exact time to the nearest minute, with a simple press on a pusher. Indeed, the passing strike automatically informs at each quarter; the minute repeater fills in the interval. Technically, the two complications generally share the same gongs and hammers, thus simplifying construction. Nevertheless, their coexistence on the same movement requires precise coordination of the release mechanisms. In particular, a locking device prevents the repeater from striking if the passing strike is in progress. These watches combining grande sonnerie and Minute repeater are among the most ambitious achievements in mechanical high horology.