The watchmaker-inventors Robert Greubel and Stephen Forsey, based in their atelier in La Chaux-de-Fonds, wished to surpass the accomplishments of existing movements by plunging deeper into the subject and inventing a Tourbillon which significantly improves the functioning of a wristwatch.
After four years of effort, they created a Tourbillon within a tourbillon, in such a way that this new complication permanently compensates the gravity-related errors of rate in all wristwatch positions. Named the Double Tourbillon 30°, due to the angle that links the two mobile cages, the patented double Tourbillon system is a decisive technical advance and a milestone in watchmaking history.
Inside an exterior Tourbillon with a diameter of around 15mm which turns in a four-minute period, an interior Tourbillon, smaller in size and inclined at 30 degrees in relation to the first cage, revolves in 60 seconds. It contains the escapement, free sprung balance system with flat hairspring and Phillips terminal curve.
A mark of its sophistication is the two cages which comprise 128 elements and altogether weigh a mere 1.17 grams. The main characteristic of the invention, that is the 30-degree inclination of the interior cage rotation axis in relation to the rotational speed of the two Tourbillon cages, create the optimal conditions for the balance wheel to oscillate permanently in all positions: the compensation of the differences in rate due to the earth’s gravity pull is no longer limited to the vertical position.
The choice of 30 degrees for the angle between the two turning carriages ensures a better chronometric performance whilst maintaining a perfectly acceptable depth to the watch. Furthermore, the exterior Tourbillon’s rapid rotational speed of four minutes gives ideal mobility to the balance wheel by avoiding prolonged exposure to the earth’s gravitational pull in less favourable positions of the watch.
The Double Tourbillon 30° is driven by twin barrels geared in line, one of which is equipped with a slipping spring so as to avoid any defect caused by excess tension on the mechanisms during winding. It has a power reserve of at least three days, i.e 72 hours.
A conical gearing, composed of a wheel and a pinion, with profiled teeth specifically made for the Double Tourbillon 30°, was chosen so as to enable an improved power transmission, superior to that of classical solutions. The architecture of this movement within a diameter of 36.4mm is entirely dedicated to the presentation of the Double Tourbillon 30°.
Its unconventional construction uses two plates so as to organise the gear-trains and bridges in discrete fashion, leaving space for the rotation of the imposing cages. The plates and bridges are made of solid nickel silver, a traditional watchmaking alloy (copper, zinc and nickel), used in production of small, very high quality series, with a “jade gold” finish exclusively reserved for Greubel Forsey.
The bridges are decorated with a subtle graining and the plates are finely circled so as to enhance the movement. The domed and olived jewels are fitted into gold chatons.
Model: Greubel Forsey Double Tourbillon 30° Vision
• Hand-winding Movement, Calibre GF 02
• Double Tourbillon 30°, Exterior Tourbillon rotating cycle of 4 minutes, Interior Tourbillon rotating cycle of 1 minute, Power Reserve indicator,Patented Movement.
Diameter, 36.4mm; Height, 9.65mm
Number of components
• Complete Movement: 301 components
• 2 Tourbillon carriages: 128 components
• Weight of 2 carriages: 1.17g
Number of jewels: 39, Domed and olived 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)
Vibrations: 21600 vibrations p/hour
• Flat balance spring with overcoil and Phillips curves
• Geneva-style stud
2 nickel silver plates with fine circular graining centred around the Tourbillon, finished in «jade gold»
Bridges :Frosted nickel silver, finished in «jade gold»
• Involute circle profile
• Conical gearing with corrected profile
• Inclined at 30°, 1 rotation per minute indication at 9 o’clock
• 1 rotation every 4 minutes shown at 6 o’clock
• Carriage pillars, hand-finished bevelling and piercing
• Solid gold counterweight plate engraved with individual watch number
• Hours and minutes
• Small seconds and rotating cycle of 1 minute on subsidiary dial at 9 o’clock
• Indicator of exterior Tourbillon rotation cycle of 4 minutes at 6 o’clock
• Sectorial power reserve indicator decentred at 3 o’clock
• In red, white gold or platinum with convex sapphire glass on the dial side
• Convex transparent sapphire glass case back
• Security screws in white gold
• Infinite Spiral hand engraved around the periphery of the case
• Name of model and individual number hand-engraved
• Case dimensions :Diameter, 43.5mm;Thickness, 15.76mm
• Water resistance: 30m
• Lugs :Technical, 3 dimensional, variable geometry-shaped
• Crown :GF logo engraved and hard lacquered in black
• 18 carats gold
• Silvered or black gold finish
• Gold applied indexes
• 4 visible security screws in blued steel or polished steel
• Mother-of-pearl and 18 carats gold
• Gold applied indexes
• 4 visible security screws in blued steel or polished steel.
Hands: Hours, minutes in gold or polished blued steel, Small seconds, power reserve, 4 minutes in polished blued steel
Logo and name: In gold and printed
Hand sewn black or brown alligator, gold folding clasp, with hand engraved GF logo