SIHH 2019: Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar

On the watch fair SIHH 2019 the brand Vacheron Constantin launched the new innovative model Traditionnelle Twin Beat Perpetual Calendar (Ref. 3200T/000P-B578), which especially focuses on the needs of its owner. It is particularly special due to its active and standby modi: When the model is worn it beats at a high frequency, when the owner takes the piece off, he can slow the calibre down by activating a second balance, extending the power reserve can to 65 days.

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar Ref. 3200T/000P-B578

This model again combines the brand’s tradition with the spirit of modern time. The Traditionelle Twin Beat Perpetual Calendar has two balances, each operating with a different frequency. The wearer of the model is able to switch between active-mode and atandby-mode with the pusher at the eight o‘clock position. The active-mode with a 5 Hz (36.000 vph) balance and a power reserve of 4 days should be used when the watch is worn on the wrist. The standby-mode should be activated when the watch is taken off for sleeping, as well as for longer wearing breaks. Therefore the model is powered by its second balance with a drastically reduced frequency of 1,2 Hz (8.640 vph). This function makes it possible to extend the watch’s power reserve to 65 days. During standby-mode all indications stay up-to-date, so that the dates are still correct when the owner switches back to active-mode.

The Perpetual Calendar

The perpetual Calendar is called perpetual, because it is able to display the date information despite variable months and leap years. Though until now the use of the perpetual calendar was restricted by the limits of conventional mainspring technology, making it necessary in most cases to set a perpetual calendar watch each time before it is worn. The new Vacheron Constantin model however shows the correct date and month even after not wearing the model for 2 months. The word ‘perpetual’ gets true significance with the Traditionelle Twin Beat Perpetual Calendar.

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar Ref. 3200T/000P-B578

The Twin Beat-System

To change between the modi of the watch, without interfering with the balance, the model is equipped with a patent-pending mechanical system: the Twin Beat-System.

This system is mainly inspired by the seasonal time system of the Japanese Edo-Periode (1603-1868), which divided day and night into 6 different segments, whose length would vary depending on the time of the day and the season. Clocks from this period were equipped with a single or double foliot balance enabling automatic changes in their operating speed.

To make the operation of the Twin Beat system possible, the mode selector runs on an all-or-nothing principle, allowing only one balance to oscillate at a time. This all-or-nothing construction ensures that the switch is instantaneous, with no lag when transitioning from one mode to the other. This guarantees that the timekeeping operations of the calibre 3610 QP are never interrupted. In the course of this both the active and standby balances are driven by the same mainspring barrel. 

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar Ref. 3200T/000P-B578

In order to fully maximize the potential power reserve with the help of the Twin Beat-System, the perpetual calendar mechanism was reworked to use as little energy as possible. 

Jumping indications often have drastic influence on the balance of a movement and its energy reserve. The balance loses amplitude and the chronometry of the entire movement is compromised. This effect can be exaggerated in a watch with a perpetual calendar timepiece. 

The Traditionnelle Twin Beat Perpetual Calendar has jumping indications for the date, month and leap year. Therefore the jumping mechanism has been completely redesigned, utilising a sprung dual-gear compound system that requires four times less torque than a conventional jumping display. With this improvement the effect on the amplitude of the active balance is relatively small.

Technical challenges

In order to support the main features of the Traditionnelle Twin Beat Perpetual Calendar — the perpetual calendar and the innovative Twin Beatsystem — a new hairspring was created specifically for the needs of the highly sensitive standby balance. The hairspring of the standby balance is, with measurements of 0.0774 mm by 0.0159 mm, nearly four times smaller and far more delicate than the hairspring of the active balance. 

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar Ref. 3200T/000P-B578

Because the calibre 3610 QP has two balance wheels, only one of which is allowed to oscillate at one time, the hour and minute hands have to draw variable information from two gear trains for one reading of the time. This is accomplished by a gear differential that allows the hands to read more than one input source of timekeeping data.

A second differential is mounted on the barrel for the dual purpose of winding the mainspring and also reducing the mainspring torque as it is directed towards the standby mode balance. Two final differentials translate the power reserve into the subdial that indicates remaining mainspring wind.

The calibre 3610 was made of 480 pieces in total. It is only 6 mm in height and has a diameter of 32 mm.

Modern Design

Movement plates and bridges are decorated with Côtes de Genève and then treated with NAC, a dark and resistant coating.

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar Ref. 3200T/000P-B578

On the sun-blasted dial clean radial guillochage are applied, which remind of the 18th-century art of engine turning and frosted finish. Therefore the dial is divided into two main segments in a multi-stage process. A gold dial segment is decorated with hand-guillochage, and then fitted within an outer segment of sapphire crystal. Gold hour indices are then set into the sapphire-crystal dial segment, which is further laser-engraved and ink-filled.

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