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Grande sonnerie

Strikes the time automatically as it passes; the most demanding audible

What it is

The grande sonnerie (great strike) automatically strikes the hours and quarter-hours as they pass without any input from the wearer; the opposite of the on-demand repeater. At each quarter-hour, the strike train fires automatically: the full hour count on the low gong, then the quarter count on the combined gong. At 3:45 it would sound three low tones plus three combined tones. It is the most demanding audible complication in watchmaking and one of the rarest in production.

History

Grande sonnerie pocket watches were made from the 17th century onward as miniaturisations of public tower-clock striking traditions. In wristwatches the complication is extraordinarily rare: the Audemars Piguet Grande Sonnerie ref. 25643, the Patek Philippe Grand Complications, and the A. Lange & Söhne Grand Complication are the primary references. Almost no independent maker builds a grande sonnerie; even the major manufactures produce only a handful per year. The reason is volume: the striking mechanism must power the strike train for a full 24 hours of automatic chiming between windings, requiring a substantially larger striking barrel than a minute repeater.

How it works

A dedicated striking mainspring, wound separately from the going-train mainspring, powers the strike mechanism. A release mechanism triggered by the hour and quarter snails fires the hammer-and-gong system automatically as each quarter passes. The grande sonnerie fires at 3:45 like this: at the moment the going train reaches 3:45, the strike release trips, striking three low tones for the hour and three combined tones for the three quarters. A silence lever allows the owner to disable automatic striking without disabling the on-demand minute-repeating function that is almost always paired with a grande sonnerie.

Parts required

Second (striking) mainspring and barrel, self-contained striking train with fly governor, strike release mechanism triggered by hour and quarter snails, silence mechanism (grande sonnerie / petite sonnerie / silent switch), two gongs and hammers; all additional to the full going-train components

What makes it difficult

The striking mainspring must power the full strike train for 24 hours of automatic chiming; every quarter, every hour; before being wound again, requiring a substantially larger barrel than a minute repeater and careful power budgeting. The silence mechanism (switching between grande sonnerie, petite sonnerie, and silent modes without disrupting either mainspring) is a mechanism within a mechanism. Ensuring the automatic strike fires at the precise correct instant requires the release mechanism to be exactly timed against the going train's motion-works. All of this must be made to fit inside a wristwatch case.

In the catalog

Related

See it in the catalog

Grande sonnerie | Grail Atlas