Zenith - Defy El Primero Fusee Tourbillon

With the new Defy El Primero Fusee Tourbillon, Zenith reinterprets the fusee and chain constant force mechanism in a refreshed style. The Defy Fusee Tourbillon in carbon (ref. 10.9000.4805/78.R916) is limited to 50 pieces and has a price of Swiss Francs 85,900. The second version of the Defy Fusee Tourbillon is crafted in platinum (ref. 40.9000.4805/75.R582) and has a price of Swiss Francs 109,900.

Delivering a constant force to the regulating organ of a timepiece has always been a big challenge for watchmakers. Applied to timekeeping since the 15th century, the fusee and chain mechanism is one of the most fascinating solutions used to ensure that the driving force remains entirely stable throughout the duration of the power reserve so improving the precision of a timepiece.

More in detail, a fusee helps to maintain an even action of the spring on the gear train thanks to the changing size of the radius building the spiral. 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.

With the new Defy El Primero Fusee Tourbillon, Zenith reinterprets the fusee and chain constant force mechanism in a refreshed style.

Presented in two different editions in carbon and platinum, the new model is powered by the 5 Hz (36,000 vph) El Primero 4805 SK calibre, a manual-winding movement that follows the design codes of the Defy line with a three-dimensional architecture.

The skeletonised bridges are enhanced by a bicolour finish, where the top satin-finished surface is given a black treatment, while its polished sides are a lighter grey rhodium tone. Their arrangement creates a balanced layout of the various functions and complications.

On the top half you can recognize the fusee and chain constant force mechanism. Consisting of 575 hand-assembled components, the chain features an unconventional blued treatment that makes it stand out.

At 6 o’clock, the tourbillon cage featuring an off-centered balance wheel makes a full rotation every minute. To reinforce the visual balance with the constant force mechanism, also the tourbillon cage is enhanced by a blue colour.

The red-tipped hand positioned between 4 and 5 o’clock indicates the power reserve (50 hours when fully wound).

The first version features a light yet robust carbon case, crown and buckle head. The carbon fibre treatment extends to the open dial. Matched to a black rubber strap with a “Cordura” fabric effect and blue stitching, the Defy Fusee Tourbillon in carbon (ref. 10.9000.4805/78.R916) is limited to 50 pieces and has a price of Swiss Francs 85,900. A second strap is also supplied, in black rubber with a woven carbon effect.

The second version of the Defy Fusee Tourbillon is crafted in platinum (ref. 40.9000.4805/75.R582) and comes with a strap made of a black rubber core coated with black alligator leather. Limited to just 10 pieces, this model has a price of Swiss Francs 109,900.

Water resistant to  100 metres / 330 feet, the case has a diameter of 44 mm and a total height of 13.35 mm.

With the Defy El Primero Fusee Tourbillon, Zenith successfully combines two of the most prestigious mechanical solutions designed to improve precision to the highest possible standards. zenith-watches.com