Commonly made in stainless steel, the oscillating weight, or the rotor, is a key component in the winding mechanism of automatic watches. A semicircular disc, it turns freely to wind the mainspring through a pivoting movement, which in turn powers the watch. A traditional, typical rotor, it is set on the mainplate of the movement. What makes the peripheral rotor different, is that, as the name suggests, it is set on the periphery of the movement. It interacts with the gears set into the side of the movement to move the mainspring.
Even though Paul Gosteli patented the peripheral rotor in 1955, the mechanism took a long time to enter the market since manufacturers found the task of placing the stem and crown at the traditional 3 o’clock as a challenge with the peripheral rotor. Patek Philippe created and patented a similar mechanism in 1965, in which the watchmaker managed to place the crown at the caseback. It came into the market in 1970 as a limited edition Calibre 350, though most wearers found it to be unreliable and after an update in 1970 (350-I) with a single directional winding, the series was closed in 1985. It featured in watches like the Calatrava 3563 and 3569.
There are however other brands that have developed their own peripheral rotors:
Presented at the 2010 edition of BaselWorld, Swiss timepiece manufacturer DeWitt launched the Caliber DW 8014. This movement was the first of its kind to incorporate a tourbillon and an Automatic Sequential Winding (A.S.W.) device that was driven by a peripheral rotor. DeWitt has stated that this mechanism enabled the distribution of energy into the gear train through sequenced winding of the barrel, allowing for an ideal functioning range with the usage of a single, manual-type barrel.
Launched at the 2011 edition of SIHH, to commemorate the 40th anniversary of the Royal Oak, Audemars Piguet introduced the Royal Oak Offshore Self-winding Tourbillon Chronograph with the new Calibre 2897. The watch gained popularity not because of the carbon caseband or ceramic bezel but for the peripheral weight in platinum that was seated on top of ball bearings. The Swiss timepiece manufacturer managed to shift the weight of the rotor to the outer edge of the movement, in the process increasing the winding speed.
In 2012, Cartier unveiled its crown Promenade d´une Panthère. Powering this watch was Caliber 9603 MC that had a peripheral winding system that was revealed by the diamond set panther along the dial as they seemed to fight around a ring at the centre of the watch.
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