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Tourbillon 24 Secondes Incliné
Tourbillon 24 Secondes Incliné
24 seconds to neutralise extremes
For Greubel Forsey, the Tourbillon is an inexhaustible field of research, as is powerfully confirmed by the Double Tourbillon 30° models already invented, as well as the projects still at the experimental watch stage in the EWT laboratories. Not only do the various modern Tourbillon systems invented in the La Chaux-de-Fonds workshops bear extraordinary witness to the significant progress made in terms of microtechnical research and development, but they also offer one of the finest aesthetic visions in Technical Haute Horlogerie.
With the Tourbillon 24 Secondes Incliné (Calibre GF01), Greubel Forsey capitalizes upon the speed of rotation and the inclination of the regulator to harness the influence of gravity on the regulating organ. Enabling the moving parts to cover a major distance in a short space of time and to perform a complete rotation in just 24 seconds called for the implementation of innovative solutions including a specially constructed inclined gear profile. The use of extremely low-density alloys stemming from the aeronautical
and aerospace industries facilitated the creation of a unique and ultralight Tourbillon system inclined at a 25° angle, perfectly suited to the powerful stresses imposed by the speed and in particular by the cage advancing in steps which are two and a half times greater than in conventional tourbillon systems.
In comparison to the eXperimental model presented at its development stage in EWT, the definitive version of the Tourbillon 24 Secondes Incliné has an even lighter mechanism: the complete system composed of 88 parts weighs a mere 0.39 grams, which is 17% less than the laboratory version...
The construction of the Calibre GF01 has off-centred the Tourbillon 24 Secondes Incliné system, a technical option that provided scope to define an original case and dial architecture characterised by a well-balanced asymmetry. The latter serves to ensure ideal visual access to the mechanism and to the various items of information.
The matt-finished dial displays the 72-hour power reserve, while the seconds are read off by a double-tipped gold hand moving across a dedicated sector.
A wide opening right through the dial and plate, complemented by a lateral window, facilitate visual access to the high-speed 25° inclined Tourbillon, which seems to enjoy complete liberty of movement free of any gear-trains. Only the ultra-light Tourbillon cage with its titanium bridges and Avional pillars appear in the field of vision. One may also observe the rapid rotation of the cage on a 24-second subdial placed on a titanium and black PVD-coated platform. The case-back provides ample views of the superlative finishing on the frosted nickel silver bridges and plates, as well as the olive-domed jewels placed on gold settings.
Efficiency
As the third Greubel Forsey invention, the Tourbillon 24 Secondes Incliné (T24Si) draws another advantage from the possibilities of the rotating carriage: namely its high angular velocity. To resolve an identical problem, meaning how to avoid prolonged exposure of the regulating organ to the critical positions in relation to gravity, the Inventor Watchmakers in the Ancien Manège in La Chaux-de-Fonds are once again demonstrating that the resources of mathematics and micro-mechanical engineering are extremely promising, and that their “storehouse” of inventions is far from exhausted. Watch this space...
For this new inclined Tourbillon, achieving the lowest possible variations in all positions is no longer done by averaging the variations (Double Tourbillon 30°) or by averaging the averages of the same variations (Quadruple Tourbillon à Différentiel Sphérique), but rather by a race to more rapidly change position.
Controlled speed
To take advantage of a high velocity of the single carriage in the T24Si, new issues had to be faced, including the high energy consumption involved in starting the system and new mechanical stresses such as the 2.5 times larger jump of the carriage. Complex research has enabled Greubel Forsey to resolve this extremely specific situation by innovating in several directions. Using a new inclined gear profile and an ultra-light tourbillon cage has enabled the construction of a system perfectly suited to the powerful stresses imposed by the high velocity. Taken together, the 85 parts of the Tourbillon 24 Secondes Incliné system weigh a mere 0.469 grams. But above all, this higher velocity significantly improved the performances of this single-axis tourbillon.
Third eXperimental watch®
Redesigned architecture
The brand-new construction of the T24Si reflects the spirit of the two first creations by Inventor Watchmakers Robert Greubel and Stephen Forsey; it further demonstrates the same determination to liberate the mechanism of the rapid-rotating Tourbillon, which is particularly spectacular due to the high angular velocity.
The distinctive features of the size and shape of the parts in this Tourbillon may be observed within an extremely technical environment, particularly thanks to the indicator on the platform of the cage.
Less complex?
The Tourbillon 24 Secondes Incliné might appear less complex than the two first Greubel Forsey inventions, the Double Tourbillon 30° and the Quadruple Tourbillon à Différentiel. This is absolutely not the case, since the new version is entirely on a par with its predecessors: the performances it is showing at the current stage of development in EWT® are absolutely remarkable and it looks set to boast an excellent performance/complexity ratio.
Mastering speed
Inertia
The major difficulties encountered by the Inventor Watchmakers in developing the T24Si are partly linked to the high angular velocity, and to the inertia of the masses that have to be set into motion much faster than in a standard Tourbillon. Cutting-edge research into the weight of various components and the definition of a dedicated gear system successfully overcame these problems.
Micro-aeronautics
Aluminium and its alloys feature a set of properties rendering them indispensable in many circumstances, and particularly in the fields of aeronautics and aerospace. These virtues include its low density, almost three times lower than steels; and its resistance to atmospheric corrosion ensured by the layer of Al2O3 oxide that forms on its surface.
The particularly lightweight Avional alloy chosen by the Greubel Forsey laboratory is highly resistant to mechanical stresses, since its properties are as good as those of carbon steel. Greubel Forsey determined that the A1CuMg2 (Avional) alloy, featuring a mechanical resistance ranging from 200 N/mm2 in its soft state to over 470 N/mm2 in its most resistant state, would be ideal for making the four pillars of the T24Si cage.
Titanium too
In addition to mechanical properties that are very similar to those of Avional, Titanium has even higher resistance and is ideal for making the upper and lower carriage bridges of the T24Si.
Extreme difficulty
The task was even harder when it came to solving the geometry of the inclined gearing of its satellite pinion. A number of complex simulations backed by laboratory tests drew upon the entire range of EWT® resources. Representing a technical achievement that would have been impossible prior to the developments undertaken by Greubel Forsey for the Quadruple Tourbillon à Différentiel, a unique and original conception was selected to ensure the best efficiency according to the speed and the forces. For a given angle, numerous options were explored and various profiles were studied to ensure ideal meshing of the moving parts, while eliminating the risks of butting and optimising the efficiency of the overall system.
TOURBILLON 24 SECONDES INCLINÉ
Mechanical hand-wound movement, GF Calibre 01
Tourbillon 24 Secondes Incliné, 24-second Tourbillon rotation indicator,
seconds indicator and power-reserve indicator. Mechanism T24Si, patent pending
Movement
Movement dimensions • Diameter: 36.4 mm • Thickness: 9.65 mm
Number of parts • Complete movement: 280 parts • Tourbillon cage: 88 parts • Weight of the cage: 0.39 g
Number of jewels 36 Olive-domed jewels in gold chatons
Power reserve 72 hours
Barrels Rapid rotating twin barrels (1 Turn in 3.2 hours) one of which equipped with a slipping spring so as to avoid excess tension
Balance wheel Free sprung balance with white gold mean-time screws (10 mm diameter)
Frequency 21’600 vibrations/hour
Balance spring • Phillips terminal curve • Geneva-style stud
Main Plates Spotted and snailed palladium-finished nickel silver
Bridges • Hand bevelled, frosted and spotted palladium-finished nickel silver “Greubel Forsey” gold nameplate, relief-engraved gold plate with the number of the timepiece
• Steel conical bevelled Tourbillon bridge • Positioned on a black PVD-coated titanium platform with mirror-polished backdrop
Gearing • Involute circle profile • Tangential inclined gear with profiled teeth, on fixed wheel and escape wheel pinion
Tourbillon cage • Inclined at a 25° angle, 24-second rotation • Cage pillars in Avional • Titanium cage bridges • Gold counterweight
Displays • Hours and minutes • Small second sector • 72-hour power reserve on a sector • 24-second Tourbillon rotation indicator at 8 o’clock
Exterior
Case • In gold with asymmetrical convex sapphire crystal • Transparent back with asymmetrical convex sapphire crystal • Lateral window with shaped sapphire crystal • Raised engraving of the name of the Invention on a hand-punched background • Gold security screws • Polished bezel and centre band with hand-finished straight graining • Hand-engraved individual number
Case dimensions • Diameter: 43.5 mm • Thickness: 15.76 mm
Water resistance of the case 3 ATM – 30 m – 100 ft
Crown Gold with engraved and black lacquered GF logo
Dial • Gold dials • Gold appliques • Gold display sectors • Applied gold logo
Hands • Hours and minutes, small seconds and power-reserve in gold • 24-second double-tipped hand, black anodised aluminium
Strap Hand-sewn black alligator leather with gold folding clasp, hand-embossed with the Greubel Forsey initials