Cartier’s in-house genius Carole Forestier takes a highly original approach to combating the effects of gravity on timekeeping. In a nutshell – quoting Cartier – “the escapement, the oscillator and the pendular seconds have been positioned on the rotor…”. Warning: trying to visualize an escapement mounted on a rotor may cause pain in the visual cortex. Let’s see how it was done…
The Astrorégulateur movement – Caliber 9800 MC – has been five years in the making and it is the object of four patent applications. The movement has been designed, developed, produced and assembled entirely within the Cartier Manufacture in La Chaux-de-Fonds.
Watchmakers have long studied means to compensate for the effects of gravity on the balance spring; the tourbillon is perhaps the best-known mechanical countermeasure. The tourbillon carriage revolves on its own axis, typically in one minute, averaging out the errors and so canceling variations in rate that occur in the vertical positions. Cartier offers an alternate solution. Again quoting Cartier:
“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 center 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 center 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.”
As can be seen in the image below, the balance wheel and hairspring are mounted opposite (in this image, above) the micro-rotor’s oscillating weight. SJX has posted a 12 second YouTube video showing the spinning rotor/escapement combination in action.
During the course of an average day, your wrist moves in many directions and at differing speeds, subjecting the escapement to a variety of accelerations as the rotor spins. In this regard Cartier says “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.”
Cartier also offsets the escapement’s weight, which might inhibit the rotor’s motion, by integrating a platinum “inertia block” into the micro-rotor to guarantee that it is heavy enough to achieve winding and to always return to the same position when at rest.
Each movement receives 60 hours of hand finishing. The main plate is circular-grained, while the bridges are beveled, drawn and decorated with Côtes de Genève. The 32.5mm movement is housed in an oversized 50mm case that weighs a mere 55 grams. This is achieved by fashioning the case from niobium-titanium alloy, previously used only in the ID One concept watch.
The Astrorégulateur will be produced in a limited series of 50 numbered pieces worldwide, each powered by an individually numbered movement. I think it is safe to say that this piece will generate quite a buzz at SIHH 2011.
Rotonde de Cartier Astrorégulateur watch
Case: niobium-titanium on leather
Diameter: 50 mm
Crown: circular-grained in titanium or 18 carat white gold, set with a sapphire cabochon.
Crystal : sapphire
Case back: sapphire crystal
Water-resistance: 30 meters / 100 ft / 3 bars
Dial: galvanic guilloché, slate-gray color, silvered openwork grill with sunburst effect, black transferred Roman numerals
Hands: sword-shaped in blued steel
Strap: black alligator skin
Clasp: double adjustable folding in 18 carat gold
Limited series of 50 individually numbered timepieces
Calibre 9800 MC Astrorégulateur
Movement: Manufacture self-winding mechanical , Calibre 9800 MC, hours, minutes, with escapement fitted on the oscillating weight to counteract the effects of gravity in vertical positions.
Casing-up diameter : 15 ½ lines (35.2 mm)
Total diameter: 15 ¾ lines (35.8 mm)
Thickness: 10.1 mm
Number of jewels: 43
Number of parts: 281
Balance: 21,600 vibrations/hour
Power reserve: approx. 80 hours
Individually numbered movement