Defy El Primero Fusee Tourbillon

• Limited Edition: 50 pieces
• Case: black carbon
• Size: 44mm
• Movement: hand-wound manufacture El Primero 4805 SK
• Function: tourbillon, power reserve, fusée-chain escapement
• Power Reserve: approximately 50 hours
• Water Resistance: 100m
• Dial: skeleton
• Caseback: sapphire crystal
• Hands: luminous hands
• Strap/Bracelet: rubber with "cordura" effect
• Factory Warranty: two years

Since the dawn of precision timekeeping, watchmakers have sought to produce timepieces that offer unfaltering performance through the use of “constant force.” Zenith reinterprets the fusee & chain constant force mechanism in a modernistic style in the new Defy Fusee Tourbillon. Housing the new El Primero 4805 SK caliber, a manual-winding movement that follows the Defy code of avant-garde movement architecture with an open three-dimensional impact, the Defy Fusee Tourbillon is available in Carbon.

Upon a first glance, it’s immediately clear that the Defy Fusee Tourbillon’s caliber is out of the ordinary. The spoke design of the bridges is amplified by their bicolor finish, where the top satin-finished surface is given a black treatment, while its polished sides are a lighter grey rhodium tone. The layout of the bridges offers a balanced layout of the various functions and complications. On the top half of the movement, one can admire the uniquely conceived fusee and chain constant force mechanism. The chain, which consists of 575 individually hand-assembled components, features a bold blued treatment: a first for a wristwatch fusee and chain system. On the opposite end at 6 o’clock, a tourbillon cage with an entirely new construction featuring an off-centered balance wheel makes a full rotation every 60 seconds. Like the chain, the tourbillon cage is embellished with a striking blue color, reinforcing the visual effect of the Defy Fusee Tourbillon’s unique moving parts. Positioned at the edge of the dial between 4 and 5 o’clock, a red-tipped hand indicates the power reserve, a handy feature when manually winding the Defy Fusee Tourbillon with its 50-hour power reserve.

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.

The Defy El Primero Fusee Tourbillon features a light yet robust carbon case, crown and buckle head. The carbon fiber 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.

One thing is certain: the Defy Fusee Tourbillon solidifies Zenith’s position as a leader in building the future of watchmaking.