Monday, September 28

In-depth Review: Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar

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Certainly the top candidate for the best complicated technical piece in this year’s SIHH 2019: the VC Twin Beat Perpetual Calendar is a shining example of the grand maison at her best. This watch ticks all the boxes: novel technical concept, clever design, excellent execution. We covered it in a special session one day before the show (link here), and here is our detailed, hands-on analytical review.

Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar

The idea was novel in the first place. And began when VC was trying to find a solution to the sometimes pesky task of setting the perpetual calendar on a hand wound watch after it has not been worn for a while, perhaps weeks. One solution was to use the crown to move all indicators one day a time, like the one first used in the Ulysse Nardin Perpetual Ludwig, and subsequently in the Moser Perpetual 1, and other of the same ilk. Another was to use a pusher which advances all indications by one day, like that used in the A. Lange & Söhne Langematic Perpetual Calendar (introduced in 2000 and updated this year with a honey gold case). So going that route is not exciting nor novel.

So VC sought to see if they can keep the handwound movement going for long enough, that the calendar indicators will all be up to date. The obvious solution is to extend the power reserve. Make it very long. Say in excess of 2 months. This can be achieved by using a huge mainspring with an energy efficient train, but will result a movement which is huge. Not an acceptable compromise, given the VC aesthetic. So the solution they came up with is a two train system, one running at a fast beat (36,000 bph was chosen) for good accuracy under all positions with a power reserve of 4 days. And the other a slow beat (8,640 bph was selected) for a good accuracy in one position (dial up) but with an exceptionally long power reserve. After initial tests, they discovered that the watch was running well over 72 days, and decided to guarantee a power reserve of 65 days.

While running under this slow beat train, an accuracy of about 9-10 seconds a day is still achieved, though this is only for one position. If left for the entire 65 days in this mode, the watch will gain or loose about 10 minutes, with all the calendar indicators still showing correctly. Note that this running rate for the slow beat movement is only available in one position – that of dial up, where it is adjusted and regulated for. This is the position required for the watch to be stored when the slow beat movement is activated.

As we understand it, due to the complexity of the movement, VC is only planning 10 movements a year as a production starting point. Perhaps volumes may increase with familiarity.

The case, dial and hands

The case is the VC Traditionnelle, which almost by definition means that it is a very refined aesthetic with classical and elegant lines. The case is in platinum and measures 42mm diameter, 12.3mm thick. Very svelte for a watch which houses a movement capable of running for a guaranteed 65 days.

The dial is divided into two parts. An upper part is a kind of half dial in gold which features engine turning and a frosted finish. This gold half dial is hand-guillochéd with a radial pattern and features sand blasting on some surfaces.

This guilloché is quite interesting. The sections are engraved with a radial pattern, and this only extends to a semi-circle, as the dial is only half. The traditional Rose Engine used for guilloché is usually set up to make the engravings in a circle, and having only half a circle to execute presents the operator with additional challenges as the blade needs to be lifted from one side of the half dial to the other. And the dial or adjustments may have moved while the blade is being moved.

The dial design and layout is logical, and clear. Especially when considering the amount of information the watch displays.

And over this slate coloured gold half dial, is a sapphire glass dial covering which extends to a minute chapter ring covering the entire dial. An aperture is made in the center of this half-dial and filled in white to show the twin power reserve indicators, one in black for the fast beat movement, and in red for the slow beat movement. The minute track and power reserve indicators are laser engraved and infilled with ink. As the gold dial only covers the upper part, the lower part allows the sapphire glass to provide a peek into the escapement and to display the calendar indicators.

The twin power reserve indicators are engraved and ink filled on the sapphire glass dial over the gold half-dial in which an aperture is opened to display this clearly.

Indices for the hours are in gold and applied into the sapphire glass outer segment with a special technique. The hands are sleek Dauphine style gold hands for the hours and minutes, and stick pointers with small counter weight tails for the other indicators.

Overall the dial looks very classical and given the amount of information it presents, is clear, and very legible. As this is a classical dress watch, no provision is provided for luminous indicators, and the legibility suffers in low light.

The movement Calibre 3610 QP

The movement is an original development which took the VC team 4 years, and is conceived, designed, developed and manufactured in-house. The movement design is protected by two patent applications (Patents pending). One for the differential system to allow two trains to drive a set of indicators, and the second for the instantaneously jumping perpetual calendar for all indicators.

The mainspring barrel is large, but not overly so. The barrel power/volume ratio is 4 times less than than the one used in the Traditionnelle 14 Day Tourbillon.

The movement features a twin wheel train system with two independent trains in which only one is operating at any one time. To achieve this, a switch is used to stop one and start the other, allowing the user to select which of the two trains are used. Also, a complex differential system needed to be developed to allow the canon pinion, which supplies the watch with all the indicator information, to rotate at the correct (always constant) speed, while the trains are switched from fast to slow and vice versa. The energy used in the slow beat system is 20 times less than the consumption of the high beat.

The twin wheel train system: code name Genenergy

The working codename for the movement was Genenergy – GENeva ENERGY. The original concept was to save energy in every part of the movement and to produce the most efficient system possible.

The movement comprise of a mainspring system powering two movement trains. Only one train is driven at any one time, and a specially designed switching system is designed to allow the user to select which of the two trains is desired to run.

The pusher at 8 o’clock on the case band selects which of the two balances are running. An all or nothing mechanism is installed to ensure that only one train is operating at any one time. But the system allows for a small “cheat”: as the slow beat system takes a longer time to stabilize than the fast beat one immediately after starting up, it is allowed a short headstart.

The switching system controlled by the user switch on the case. At the push of the button, the system selectively hacks one of the balance wheels, stopping one and freeing the other. The slow beat balance is in silicon to safe weight and be more energy efficient, but the high beat movement is traditional.
Photograph of a print presented by VC.

The canon pinion is specially constructed and not part of the power flow of either train, and hangs off the mainspring barrel. This pinon/wheel (seen in in the middle, between the two trains) makes 1 revolution every hour and is the source of information for the entire watch, from which is derived the minutes and perpetual calendar data. This rotation must be the same regardless of which train is operating. As the fast beat train runs the barrel at the different speed than the slow beat, the pinion requires a differential to ensure that it rotates at the same (1 revolution per hour) speed regardless of which train is selected. This differential can be seen in the diagram below, and is a complex and tricky bit of engineering.

Technical drawing as presented by VC showing the two train system. Note the special canon pinion in the lower center hanging off the mainspring barrel. Here, the left train is the high beat train and the right is the slow beat train. The speed of rotation of the wheels in the left train is significantly faster than that of the right train, and as a result the mainspring barrels rotate at a different rate depending on which train is selected. A differential on the canon pinion is thus required to ensure that both these rates result in a constant rotation of the said pinion, where all indicator information is derived from.
Photograph of a print.

Another special construction developed for this movement is the new hairspring required for the slow beat movement. As it beats very slowly at only 1.2 Hz, the hairspring is only 15 microns thick.

The perpetual calendar

The perpetual calendar system used in the Twin Beat is a development over the VC Caliber 2755. The 2755 is used in many of VC’s earlier perpetual calendar. One example is the VC Atelier Maître Cabinotiers.The system uses a dragging system, where all indicators move slowly to the new date over a period of time. In the new movement, the system uses a low energy system of small springs (remontoire like, but as it is not within the power flow of the movement train, we refrain from using the term) and a snail mechanism to affect the instant jumps.

Model of the perpetual calendar system showing the low energy, instantaneous jumping mechanics.
Presented by VC.

This system is filed for a patent which is pending.

Competitive landscape

The landscape for a twin train, user switched system for a perpetual calendar is solely inhabited by this VC. No competition exists. But alternatives to this system do exist, as we mentioned in the opening paragraphs.

Ulysse Nardin Perpetual Ludwig. This was the forerunner of the convenient perpetual calendar, and the first to feature easy adjustment via the crown in both directions. First introduced in 1996, it remains a strong competitor in the perpetual calendar field. It offers the alternative of fast, and fool proof adjustment of all indicators via the crown. UN still offers this movement in their current collection.

Moser Perpetual is perhaps the same concept, first used in the UN, but taken to the limit. It not only features the convenience of the crown fast adjustment in both directions, it also features the Flash Calendar system. This system causes all the indicators to jump instantaneously, but also to avoid showing the non-existant dates on short months.

Langematic Perpetual, and other Lange perpetual calendars like the one used in the Lange 1 Tourbillon Perpetual Calendar. All the Lange perpetual calendars offer the ability to move all indicators one day at a time in quick set mode by a push of a button on the case band. And the later ones also feature instantaneously jumping indicators.

Concluding thoughts

We are extremely impressed with this new VC Traditionelle Twin Beat Perpetual Calendar. The idea of a two train system which is user selected, and where one allows a “sleeper” mode to vastly extend power reserve is novel. The technical challenges brought about by this concept is tremendous, and in our view VC has met and exceeded expectations in the solutions. And aesthetically, we find the package to be very pleasing.

On the wrist the VC Twin Beat is very comfortable. The 42mm case wears smaller than the dimensions suggest, perhaps due to the relatively thin case, and to the wrist hugging design of the Traditionnelle case.

A word about the finishing. It is outstanding, as is the high norms set by VC. All the haute horlogerie details are carried out very well, and the watch carries a Poinçon de Genève as testament.

We think this is a great piece for Vacheron Constantin to bring out for SIHH 2019, and for us, it is hands down the most technical watch in this show. We think, perhaps the lessons VC has learnt from the implementation of this twin beat system may extend to future applications. Bravo VC!



  1. Just another guy on the web on

    Svelte? Classical?
    It is as thick as a Casio Pro Trek PRW3100 and 42mm in diameter, with thick, squared-off lugs!
    This is an answer to a non-existent problem. It is also ugly.
    I have just commented on the Laurent Ferrier.
    I rest my case.