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<< Back to Robb Report, December 2012

Inside Moves

James D. Malcolmson

When quartz technology proved its superior accu­racy in the late 1960s, the Swiss were forced to turn their attention to the more luxurious aspects of mechanical timepieces, like design, decoration, and complication. But far from being a dead issue, mechanical movements that are designed and prepared for high levels of precision are now one of the most desirable categories for many watch collectors. Rather than building arcane devices, watchmaking’s best minds are here engaged in timekeeping’s essential problem. Their work is understandable, and in many ways more compelling than the other, more pyrotechnic constructions that have come to define high-end watchmaking.

Technical director Jean-Pierre Musy is a key figure in the brain trust behind Patek Philippe’s movements. Graying and genial, Musy appears professorial in his well-lit office filled with books and technical papers. Despite the complex and quantitative nature of his day-to-day work, Musy is able to explain simply the features that make a more precise watch. "The whole balance wheel and escapement assembly is the area that most affects accuracy," he says. "Optimally, a balance wheel should be as large as possible, and the hairspring should not be restricted in its movement."

In fact, the so-called free-sprung balance system is a common feature in many of the newest, high-accuracy timepieces. Unlike the common index regulation system that allows a watchmaker to adjust the rate of the watch by slightly altering the length of the hairspring—the metal spiral controlling the oscillating balance wheel—the free-sprung balance allows the whole assembly to move with an unimpeded and more accurate motion regardless of the position of the watch. This system is most associated with Patek Philippe, from the introduction of the Gyromax balance wheel in 1948 and following patent in 1949. The rate is adjusted by a system of eccentric weights on the rim of the balance wheel itself. By moving the position of these weights, the watchmaker can change the inertia and therefore the rate of the balance.

Greubel Forsey, a specialist in precision-oriented multiaxis tourbillons, is a proponent of the large, free-sprung balance wheel. "Large balance wheels can give good performance at medium frequencies, like smaller balances at higher frequencies," offers Greubel Forsey cofounder Stephen Forsey. (Greubel Forsey timepieces beat at 3 Hz or 21,600 vibrations per hour.) "Some carmakers achieve good results with six cylinders, while others do it with twelve."

François-Paul Journe is another watchmaker known as a zealot in matters of precision. "A chronograph or a watch with a calendar also cannot be a true chronometer, because these functions consume a lot of energy, so the accuracy will be diminished," he opines. "A real chronometer is three or four wheels and a couple of barrels. It can be built with or without a fusee. The movement has to have linear strength, good oils, and an escapement without too much friction. The balance must have high inertia as well as an aerodynamic profile so it does not suffer from atmospheric pressure."

Journe recently had the opportunity to put some of these theories into practice. His latest Chronomètre Optimum is built like a complicated watch, with all the mechanisms, including a new escapement design devoted to making the watch precise. Even if you do not obsessively track the accuracy of your watches, you cannot help but enjoy the thoroughbred quality of these timepieces.

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Studio Dino Eisele