Cartier the Rotonde Mysterious Hours
KEEPING THE MYSTERY ALIVE
THE MYSTERY OF SUSPENDED TIME
Breathtaking and ethereal, the Rotonde de Cartier Mysterious Hours watch hypnotises those who gaze on it with its hands that float in space. The purity of its design is such that the extraordinary watchmaking complexity of its mysterious display is forgotten. Indeed, perfecting this new Cartier Manufacture movement forced our watchmakers to rethink the traditional mechanism in its entirety. Their aim: to overcome the specific problems involved in driving large sapphire crystal discs. The paradox presented by an instrument of this kind is that the simplicity of the display conceals a watchmaking complication that demanded hundreds of hours of design calculation.
To bring a mysterious wristwatch into being, the watchmakers of the Cartier Manufacture had to overcome all the constraints inherent in perfecting a display by hands whose connection to the movement is completely invisible.
Thus, in order to limit friction between the sapphire crystal discs, it was decided that they should turn on fine pivots, like a wheel in a gear train, rather than in guide grooves, the traditional technique adopted for mysterious clocks.
This new concept, which is combined with the wheel of the hour hand, avoids friction and limits the power consumption of the movement.
With friction reduced to a minimum, the next task was to reduce the inertia of these large discs of sapphire crystal, weighing just 0.56 g and fashioned using DRIE technology (Deep Reactive Ion Etching). Thanks to this cutting-edge method, the metal parts can be made by three-dimensionally building up material, thus obtaining a gear wheel of extremely high concentric precision in one piece with the sapphire crystal disc. The geometry of the assembly is exact to the nearest micron.
PERFECTION OF DESIGN
To facilitate the final assembly of the different components under optimum conditions, Cartier opted for a modular structure. Thus the movement is made up of two separate elements: the movement proper, which occupies a crescent-shaped zone on the baseplate, and an independent display module occupying the circular space left vacant for the purpose. This sub-assembly, comprising four anti-reflective sapphire crystal discs with an antireflective finish, is assembled separately in a laminarflow hood to prevent all possible presence of dust. When the timepiece is finally assembled, the hands begin to revolve in the void, as if by magic.
By allocating 58% of the diameter of the movement to the sapphire crystal discs, Cartier has pushed back the limits of the mystery display and achieved record legibility.
KEEPING THE MYSTERY ALIVE
Timepieces with a mystery display have always been considered more fragile than other traditional complications, due to the presence of the sapphire crystal discs.
The innovative design of the calibre 9981 MC enabled it to pass all the certiﬁcation tests, including the requirement that it should resist over 500 consecutive impacts, as well as being dropped on to a hard ﬂoor from a height of one metre.
This movement with its spellbinding transparency, slimness and accuracy, with a balance oscillating at 4 Hz (28,000 beats per hour), has a power reserve of 48 hours.
The Rotonde de Cartier Mysterious Hours watch, with its fascinating balancing act, appears transparent to the last detail. But in truth, if this watch reveals the essential components of its manual-winding, individually numbered mechanical movement through the case-back, it only shows what Cartier is willing to let you see. In the past, Louis Cartier refused to give any explanation of how his mysterious clocks worked to those who sold them, so as not to divulge the secret.
Today, the mechanism that connects the movement to the hands of the Rotonde de Cartier Mysterious Hours is so designed as to disappear into the structure of the calibre and remain invisible, keeping the magic alive...
ROTONDE DE CARTIER MYSTERIOUS HOURS, CALIBRE 9981 MC
- CASE : 18-carat pink or white gold
- DIAMETER : 42 mm
- CROWN : beaded, 18-carat pink or white gold, set with a sapphire cabochon
- CRYSTAL : sapphire
- CASE BACK : sapphire
- WATE R-RESISTANCE : 30 m / 100 feet / 3 bar
- DIAL : white, galvanised, guilloché, silvered open-work grill with sunray effect, black transferred Roman numerals
- HANDS : sword-shaped in rhodium-coated steel
- STRAP : brown or black alligator skin Double adjustable folding buckle in 18-carat pink or white gold
- MOVEMENT : Manufacture mechanical with manual winding, calibre 9981 MC, mysterious display of hour and minute
- CASING-UP DIAMETER : 31.3 mm
- TOTAL DIAMETER : 31.9 mm
- THICKNESS : 4.61 mm
- NUMBER OF JEWELS : 27
- NUMBER OF PARTS : 158
- BALANCE : 28,800 vibrations / hour
- POWER RESERVE : 48 hours