Tourbillon 24 Secondes © Greubel Forsey
The race against gravity
Following up on the research and development work that led to the Invention of the Double Tourbillon 30° and the Quadruple Tourbillon à Différentiel Sphérique, inventor-watchmakers Robert Greubel and Stephen Forsey decided to draw upon the exclusive resources of the EWT® platform to take the exploration of the Tourbillon regulator in a different direction.
For their third fundamental Invention, they chose to use the unexplored possibilities of the rotating cage, opting for the high rotation speed of a uniquely inclined cage capable of performing a complete rotation in 24 seconds.
This high velocity combined with a 25-degree inclination of the cage enables the Tourbillon 24 Secondes Incliné to offer an innovative solution to the flaw in equilibrium by keeping the regulating mechanism's exposure to the critical position to an absolute minimum – meaning that the balance and its spring are placed parallel to the earth's surface.
While apparently simpler than Greubel Forsey's first multi-axis constructions, this new solution in fact raised some tough new problems and required the inventor-watchmakers to draw upon all the mathematical and micro-mechanical engineering resources at their disposal in order to solve some very specific issues.
Apparent simplicity
One of the major problems caused by the cage's high rotation velocity is the sheer inertia of the system, a high quantity of mechanical energy is required to start the cage, which advances in steps that are two and a half times greater than in conventional Tourbillon systems. Complex research was undertaken in order to reduce the weight of the mobile components to a minimum, and extremely low-density alloys already widely deployed in the aeronautical and aerospace industries were used. Materials such as Avional and titanium, which have specific weights two to three times lower than that of steel, are perfectly suited to extreme use and made it possible to create a complete 88-part Tourbillon system weighing only 0.39 grams.
Another cutting-edge innovation incorporated within the Tourbillon 24 Secondes Incliné is a specially constructed inclined gear profile, optimising efficiency within the relatively small space of the mechanism. It ensures ideal meshing of the moving parts while eliminating any risk of binding. This array of improvisations has led to a significant increase in the performance of a single Tourbillon
Useful asymmetry
The off-centred mechanism principle underlying the architecture of the Tourbillon 24 Secondes Incliné have made it possible to enhance the visibility of the fast-rotating cage – another cherished Greubel Forsey quality. Both the lateral view afforded by the window in the central case band and the dial opening enable the viewer to admire the extreme angular velocity of the cage.
The mechanism
A new approach for a 3rd Invention
When angles enhance velocity
Over two centuries after the brilliant idea of the Tourbillon was first conceived by Abraham-Louis Breguet, Greubel Forsey are tackling the flaw in equilibrium and the effects of gravity on balance for a third time. The Tourbillon 24 Secondes Incliné (Calibre GF01) is the result of an innovative approach respectful of aesthetic harmony and technical perfection.
After inventing a first Tourbillon system specifically designed for wristwatches in the shape of its Double Tourbillon 30°, Robert Greubel and Stephen Forsey took their research a step further with the help of their EWT® technological platform to develop: the Quadruple Tourbillon à Différentiel Sphérique.
While their first two Inventions pursued the same aim in the same way – namely multi-axis Tourbillon systems aimed at minimising the regulating mechanism's exposure to the dreaded critical position through a combination of velocity and carefully determined angles – the Tourbillon 24 Secondes Incliné makes use of the speed of rotation and the angle of inclination of the regulator in order to resolve this problem.
The invention set free
Entirely in tune with the Greubel Forsey philosophy, this third invention is intended to be timeless, spectacular and magical: totally detached from its gear trains, the system appears to be moving in complete freedom and may be observed in full from both front and side. The shape of the rounded-off steel Tourbillon bridge further broadens the visual access to the mechanism and provides a view of the carriage in titanium and the pillars in Avional. The use of these low-density, high-resistance materials borrowed from the aviation industry was the only means of coping with the huge stresses imposed by the cage's high rotation speed.
The Tourbillon 24 Secondes Incliné is guaranteed to create a strong impression considering that the rotating cage is composed of 88 parts weighing 0.39 grams in all. A graduated 24-seconds circle placed beneath the system serves to quantify the impressive progress of this record-breaking timepiece.
Harmonious asymmetry
To clothe the high-speed technical performance and incredible complexity of its third Invention, Greubel Forsey has once again opted for an artistic dimension and for beauty. The asymmetrical case construction offers the wearer of the Tourbillon 24 Secondes Incliné a unique and personal view of the fast-moving operation of his timepiece, since the openings in the dial and along the central band of the case are optimally placed for his line of vision.
The various items of information regarding the modus operandi of the model appear on an exquisitely velvet-finished gold dial. A small seconds sector complements the Tourbillon rotation indication placed beneath the inclined cage, while a power-reserve sector provides a constant update on barrels' winding level.
A convex asymmetrical crystal sets the finishing touch to this exceptional watchmaking accomplishment, while the case-back enables one to admire the superlative finish of the frosted nickel silver bridges and plates, as well as the olive-domed jewels placed in gold settings.
TECHNICAL DATAS
Mechanical hand-wound movement, Calibre GF 01
Tourbillon 24 Secondes, 24-second Tourbillon rotation indicator,
seconds indicator and power-reserve indicator.
Patented 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 black mirror-polished and beveled Tourbillon bridge
• Black PVD-coated titanium platform under the Tourbillon and 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
Habillage
Case
• Platinum 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 : 16.11 mm
Water resistance of the case
3atm – 30m – 100ft
Crown
Platinum with engraved and black lacquered GF logo
Dial
• Gold dials
• Gold appliques
• Gold display sectors
• Applied gold logo
Hands
• Hours and minutes with Superluminova, small seconds and power-reserve in gold
• 24-second double-tipped hand, black anodised aluminium
Strap
Hand-sewn black, brown and dark blue, alligator leather with gold folding clasp, hand-embossed with the Greubel Forsey initials
