Rotonde de Cartier Astrorégulateur watch
Mastering gravity: a watchmaker's dream
The Watch Quote™ - December 19th, 2010
The Calibre 9800 MC is a highly original movement that compensates for the effects of gravity on the timing mechanism in vertical positions. The subject of four patent applications, this movement is the fruit of five years of development within the Cartier Manufacture, where it was designed, developed, produced and assembled. This new Grande Complication timepiece testifies to Cartier's deep-felt commitment to fine watchmaking.
Mastering gravity: a watchmaker's dream
Compensating for the effects of gravity has always been one of watchmaking's greatest challenges. Gravity disturbs the isochronism of a watch by displacing the centre of gravity of its balance spring. Until now, the tourbillon has been the oldest and most common solution to this problem. The tourbillon carriage revolves on its own axis in one minute, passing through all possible centres of gravity. The tourbillon’s escapement averages out the errors, thus cancelling out any variations in rate that occur in the vertical positions.
An alternative solution to the problem of gravity
The designers and master watchmakers at the Cartier Manufacture in La Chaux-de-Fonds have developed a movement that offers an alternative solution to the tourbillon. Isochronism depends on the regularity of the oscillating frequency and as this is disturbed by the effects of gravity, the oscillator should ideally have a single centre of gravity that remains constant in every vertical position.
Cartier has therefore designed an innovative anti-gravity system using the only element that always returns to the same position in the vertical plane: the rotor. In the 9800 MC Astrorégulateur movement, the escapement, the oscillator and the pendular seconds have been positioned on the rotor to maintain the centre of gravity in a single position. By adjusting the oscillator in this one position, the master watchmaker ensures that the platform of the Astrorégulateur movement avoids the disturbing effect of gravity on timekeeping in all vertical positions. A genuine masterpiece of watchmaking design, the rotor carries and supports five times the number of components of a traditional tourbillon carriage.
An ingenious system of differentials to ensure consistent timing
The unpredictable movements of the wearer’s wrist apply forces of various strengths on the entry lip of the escapement. These forces must be corrected in order to maintain the escapement at a constant speed, as this is a necessary condition for good timekeeping. The watchmaker-designers therefore invented a system composed of two differentials that change the speed transmitted by the wrist to the micro-rotor into a constant speed, thus ensuring the regular advance of the seconds indicator that moves with the rotor and, therefore, the good timing performance of the watch.
A platinum inertia block for a self-winding movement
A platinum inertia block has been integrated into the micro-rotor to make it sufficiently heavy to return to the same position and thus ensure the winding of the mechanism. This winding is unusual in that it is bi-directional: the movement is wound as the weight oscillates in either direction.
A niobium-titanium case
Cartier has chosen a case with a diameter of 50 mm to showcase this exclusive movement. Its niobium-titanium alloy reduces its weight to just 55 g, which ensures exceptional comfort on the wrist. Niobium-titanium also has optimal shock-absorbing properties, which convert any violent impacts into a softer shock charged with the same energy but released over a longer period of time. Until now, this alloy has only ever been used in a concept watch, the IDone
Cartier’s artisan watchmakers devote almost 60 hours to hand-finishing the Calibre 9800 MC. The main plate is circular-grained, while the bridges are bevelled, drawn and decorated with Côtes de Genève. Limited-edition series of 50 individually numbered timepieces worldwide.