For the past 20 years of its existence, Greubel Forsey has been working from the standpoint that contemporary watchmaking is far from having exhausted all the technical possibilities of fine watchmaking. The Atelier has proven this on seven landmark occasions, developing Fundamental Inventions that rethink the basics of movement regulation and other major complications.
This focus on chronometric innovation continues with Greubel Forsey’s 8th Invention: the Tourbillon Cardan. Designed to deliver better chronometric precision, it combines three principles.
First, the tourbillon. The mechanism patented by Abraham-Louis Breguet in 1801 was designed to compensate for the differences in rate, in vertical positions. While most tourbillons have a revolution of 60 seconds, Greubel Forsey’s 8th Fundamental Invention is almost four times faster at just 16 seconds. This is the fastest yet for a Greubel Forsey tourbillon. It moves through more positions in less time, and therefore offers much a higher average performance.
What’s more, this tourbillon incorporates, for the very first time, the large balance wheel designed, developed and made in-house by Greubel Forsey. It benefits from the exemplary balance of its masses, its large size (12.6 mm) and its optimised oscillations. Its high inertia also makes it less sensitive to shocks and variations in speed.
The second principle is the tourbillon’s 30° angle. As it was conceived over two centuries ago, the tourbillon was designed for pocket watches worn vertically. For a wristwatch, its design needed to be completely rethought, and optimised for the positions adopted in everyday 21st-century life.
Thirdly, this 30° high-speed tourbillon is guided by two mobile rings, linked by two 90° axes. In 48 seconds, they tilt backwards and forwards. This construction may seem reminiscent of gimbals, but is very different from a traditional gimbal where the two rings are free to move and their job is to keep the object they contain horizontal. In the Tourbillon Cardan, the tilt of the rings is controlled (+30° to -30° range), while the degree of inclination of the tourbillon is inclined (also 30°) and never varies, offering a better ratio of angular velocity to chronometric performance.
The Tourbillon Cardan has four barrels. They are coaxially stacked, with a slipping mainspring to prevent excess tension during winding. They offer 80 hours of chronometric power reserve. Beyond that point, the timepiece still runs very well, but maybe outside the rigorous Greubel Forsey precision tolerances.
As the tourbillon cannot be held in place by a fixed upper bridge, this function is performed by the two arched cardan rings. Without adopting the traditional construction, Greubel Forsey’s 8th Fundamental Invention creates a new type of tourbillon with a flying appearance, which is both original and patented. A seemingly complex construction but with a very small number of components, it offers an open, airy aesthetic that leaves the eye free to admire its kinematics.
Some components of the Tourbillon Cardan require up to three days for hand finishing alone. A number of unique finishes have been developed specifically for this timepiece. Among them, the movement plates are in frosted nickel silver, with polished bevels and straight-grained flanks while a titanium mainplate presents a large polished flank as a backdrop to the cardan.
Even more particular: the upper bridge of the tourbillon cage is made of frosted titanium with straight-grained flanks and polished bevels, above and below. Finally, the arch is barrel-polished. It takes more than 30 hours to finish this single component. The cardan’s rings are matt finished, with polished bevels and straight-grained flanks, while the lower plate is frosted by hand, a task that requires particularly special expertise from the Atelier Manufacture.
Finally, there are two dials (hours & minutes and seconds), one circular-grained with polished flanks and a very large mirror finish angle, the other with a polished exterior flank. Greubel Forsey has also developed a high-domed sapphire crystal for this piece. It houses the full height of the tourbillon and cardan system, offering a highly architectural technical vision. The view is completely unobstructed over the balance wheel measuring 12.6 mm in diameter. One can admire the majestic swaying of the two cardan rings into which it fits.
The Tourbillon Cardan will be available in a 45.5 mm titanium case. This metal was chosen for its modernity and lightness, in keeping with the airy aesthetic of the Cardan tourbillon. Greubel Forsey plans to build just 55 pieces of the calibre over the next 5 years.