El Primero 4805 SK, Manual Calibre 16½; Frequency: 36,000 VpH (5 Hz); Power-reserve approx.: 50 hours
Hours and minutes in the centre, Tourbillon: - The carriage is positioned at 6 o'clock; The carriage makes one turn per minute; Power-reserve indication between 4 and 5 o'clock; Fusée-chain transmission connected to the barrel
As a mechanical movement’s mainspring unwinds, the torque it delivers to the regulating organ drops, resulting in less efficient chronometric performance of the movement. A centuries-old solution to counter this and achieve constant force lies within the power source and its transmission. Known as the “fusee and chain” system, it features miniature chain is coiled around a conical “fusee” and attached to the mainspring barrel. As the mainspring unwinds, more of the chain wraps around the barrel, detaching itself from the wide conical base of the fusee. The greater turning movement provided by the fusee compensates the weakening mainspring pull, thus maintaining the torque and, consequently, the amplitude of the regulating organ constant throughout the duration of the mainspring’s autonomy.
By combining the fusee and chain mechanism with a tourbillon regulating organ, Zenith places precision at the forefront of its unique take on haute horlogerie. Highlighting the unique technical and aesthetic prowess of the piece, the Defy Fusee Tourbillon is produced in two different editions.
The first version features a light yet robust carbon case, crown and buckle head. The carbon fibre treatment even extends to the open dial, with the central skeletal element and surrounding flange ring giving off the unique shimmer of this material. To complete the high-tech look, the Defy Fusee Tourbillon in carbon is fitted on a black rubber strap with a “Cordura” fabric effect and blue stitching. A second strap is also supplied, in black rubber with a woven carbon effect. The Defy Fusee Tourbillon in carbon is limited to 50 pieces.