Greubel Forsey unveils its 8th Fundamental Invention: the Tourbillon Cardan, a new type of chronometric regulating mechanism based on three pillars: a rapid rotating tourbillon, a revolving 30° inclined plane and two constantly tilting rings.
The Tourbillon Cardan combines three principles. The 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, that of the 8th Fundamental Invention is almost four times faster. 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.
Second principle: the 30° angle. The tourbillon, as it was conceived over two centuries ago, was designed for pocket watches worn vertically. For a wristwatch, its design needed to be totally rethought, optimised for the positions adopted in everyday 21st century life.
Third principle: 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. Coaxially stacked, with a slipping mainspring to prevent excess tension during winding, they offer 80 hours of chronometric power reserve.
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 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.
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.
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 a 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.
The Tourbillon Cardan will be available in a 45.5 mm titanium case. Greubel Forsey plans to build just 55 pieces of the calibre over the next 5 years.
Technical details
Model: Greubel Forsey Tourbillon Cardan in Titanium
Movement
Calibre
Hand-wound calibre with patented Cardan Tourbillon
Movement dimensions
Overall diameter: 39.60 mm
Thickness: 13.53 mm
Number of parts
Movement: 389 parts
Cardan tourbillon cages: 98 parts
Weight of the cage: 0.92 g
Number of jewels
49 jewels
Olived-domed jewels in gold chatons
Chronometric power reserve
80 hours
Barrels
Four coaxial series-coupled fast-rotating barrels (1 turn in 2.7 hours), one of which is equipped with a slipping spring to avoid excess tension
Relief-engraved text, circular-grained, black treatment, polished chamfer
Balance wheel
In-house variable-inertia with 6 gold mean-time screws (12.60 mm diameter)
Frequency: 21’600 vibrations/hour
Balance spring
Phillips terminal curve
Geneva-style stud
Bridges and main plates
Titanium and nickel silver, frosted and spotted, polished bevelling and countersinks, straight-grained flanks
Hand-bevelled and openworked cage pillars
Movement side
Flat black polished steel tourbillon bridge, polished bevelling and countersinks
Gold plate engraved with the individual number, circular-grained, polished bevelling, straight-grained flanks
Cardan Tourbillon
Ultra-fast inner tourbillon cage (1 rotation in 16 seconds) in titanium, barrel-polished and hand-bevelled, inclined at a 30° angle with gold counterweight
Outer flying Cardan cages, 48-seconds cycle, double variable tilt at 30°, polished and hand-bevelled, straight-grained flanks
Gearing
Involute circle profile
Conical gearing with profiled teeth
Displays
Hours and minutes
Small seconds
Power reserve on a sector
Exterior
Case
Titanium with high domed synthetic sapphire crystal
Transparent back with high domed synthetic sapphire crystal
Hand-polished bezel, caseband with hand-finished straight graining
Titanium security screws
Raised polished engraving “Tourbillon Cardan” and “Greubel Forsey” on a hand-punched background
Water resistance: 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown: Titanium, polished, with GF logo
Dimensions
Case-band diameter: 45.50 mm
Bezel diameter: 46.00 mm
Case height: 13.81 mm
Height on synthetic sapphire crystals: 18.15 mm
Dial side
Multi-level gold dial with open-worked pillars, circular-grained with engraved and lacquered minute-circle, polished flanks
Gold hour markers
Small seconds and power-reserve indicators in gold, engraved and lacquered
Engraved and lacquered GF logo
Hands
Hours and minutes in polished steel, with Super-LumiNova
Small seconds and power-reserve in polished steel, hand-polished countersink, flat black polished head
Strap and clasp
Non-animal material, hand-sewn
Titanium folding clasp, engraved GF logo
