Cartier: Rotonde Minute Repeater Mysterious Double Tourbillon25 January 2017
Cartier brings the aesthetic of its mysterious movement to one of the most demanding complications in the watchmaker’s repertoire: the minute repeater.
The Rotonde de Cartier watch combines the mysterious movement and this particular complication for the first time. In addition to the technical feat of assembling 448 parts in a case measuring a mere 11.15 mm, the timepiece is aesthetically stunning. The open-work mechanism and contrasting black rhodium plating expose the transparency of the mysterious double tourbillon, and reveal the minute repeater.
The mysterious double tourbillon
Its flying tourbillon, which effects a complete rotation in 60 seconds, appears to float in mid-air, seemingly unconnected to the movement. Adding to the illusion is the sapphire disc bearing the tourbillon that in turn completes one rotation every five minutes.
The spectacle of the mysterious double tourbillon, off-centred between 9 o’clock and 10 o’clock, is all the more impressive for the action of the minute repeater hammers visible at 6 o’clock, an unmistakeable stylistic signature of Cartier Fine Watchmaking.
The minute repeater
From the case “45mm” to the mechanism, Cartier watchmakers have designed this watch to chime the time. All of the four qualities of sound have been considered to optimise the acoustics of the Rotonde de Cartier watch with calibre 9407 MC.
Loudness refers to the volume of the sound and is measured in decibels. To achieve improved loudness for the minute repeater, the weight of the Rotonde de Cartier watch has been reduced to a minimum. The titanium case is hollowed out; the push-piece is fitted with a trigger and, thanks to the absence of a dial, the head of the watch is reduced to weigh less than 50 grams. The movement is attached to the case at four points, with the gongs attached at an additional two points, which serves to maximise the transmission of sound vibrations between the minute repeater mechanism and the watch. Measuring 45 mm in diameter, the watch presents an ideal surface for resonance.
Timbre is primarily determined by the choice of note and the clarity of the sound. To ensure a harmonious sound, the gongs of the calibre 9407 MC are tuned to B (5th octave) for the hours and D (6th octave) for the minutes. When the minute repeater is activated, an inertia y-wheel visible at 7 o’clock turns silently, ensuring a clear sound free of unwanted noise.
Richness gives personality to the sound produced by a minute repeater, and is determined by the geometry and material of the gongs used for the movement. The calibre 9407 MC features square gongs made from hardened steel, which deliver a rich sound with eight harmonics.
Duration is determined by the regularity of the hammer strikes on the gongs. Because the gongs have a square profile, the hammers can be directed to strike a precise surface. This construction ensures the same sound is produced from one strike to the next. The inertia y-wheel regulates the striking speed of the hammers to ensure the strikes are consistent.
The Rotonde de Cartier watch with 9407 MC movement is certified “Poinçon de Genève”, which attests to the expertise of the Cartier workshops in designing and assembling the watch, as well as meticulously hand-finishing each of the parts.
The Rotonde de Cartier Minute Repeater Mysterious Double Tourbillon is a numbered limited series of 50 pieces also available in versions set with baguette-cut diamonds. (Price €.515.000)