Greubel Forsey Quadruple Tourbillon Asymétrique

Realized by Robert Greubel and Stephen Forsey, the Quadruple Tourbillon à Différentiel is a blend of art and technical innovation which encapsulates the very soul of its the two creators. Transparent sapphire bridges were specifically chosen to allow unimpaired visual access to the perfectly choreographed aerial ballet of the four Tourbillons.

The founders and creative geniuses of GREUBEL FORSEY watch manufacture – Robert Greubel and Stephen Forsey – have engineered the four Tourbillons together in a contemporary design, in which elegance and harmony are the dominant features.

In the same spirit, and owing to the impressive number of parts which make up the movement, an asymmetrically-shaped case was chosen. The asymmetrical form was also an aesthetic tribute to the asynchronicity of the four Tourbillons. To complement the homogeneous ensemble, the displays of the small second and the power reserve dials are semi-circular.

With their new Quadruple Tourbillon à Différentiel, Robert Greubel and Stephen Forsey have once again demonstrated their inventive and creative prowess and continue their ascent towards the summit of horological architecture. Greubel Forsey’s second fundamental Invention is the culmination of five years of research and development.

Four separate Tourbillons are connected at the hear t of two autonomous regulating organs. Each of the two regulating organs is composed of a balance wheel oscillator placed in a cage of a first Tourbillon rotating once a minute and inclined at 30 degrees.

This mechanism rotates within the cage of a second Tourbillon rotating every four minutes. The two oscillators, independently regulated inside the four Tourbillons, are coupled by a spherical differential which transmits their combined precision to the time display. Two barrels connected in series supply power through the spherical differential to the Tourbillons.

At the heart of the Quadruple Tourbillon à Différentiel, each of the four Tourbillons make their own distinct contribution towards achieving an exceptional level of accuracy. This is due to the asynchronicity of the Tourbillons’ locations relative to each other. This ensures that it is practically impossible for the balance wheels to be in an unfavourable position, no matter which angle the watch is in.

By transmitting the averaged results of two oscillators, the spherical differential doubles the chronometric performance of the two regulating organs, and also minimizes the smallest variations in the performance of the oscillators. Ample energy is assured by two large, fast rotating barrels which guarantee a power reserve of 50 hours. The energy stored in the two barrels is transmitted equally to the two regulating organs via the spherical differential.

The technological sophistication of this movement is such that it was necessary to invent new testing instruments, and only these were able to provide the necessary information for checking and verifying the performance of the Quadruple Tourbillon.

Technical details

Model: GREUBEL FORSEY Quadruple Tourbillon Asymétrique in 5N red gold or in platinum

Movement
Mechanical hand-wound movement with patented tourbillon Calibre GF03
Diameter: 36.40 mm
Thickness: 9.70 mm
Complete movement: 534 parts
4 tourbillon cages: 261 parts
Total weight of the cages: 2.26 g
Spherical differential: 28 parts
Number of jewels: 63; Olived-domed jewels in gold chatons
Power reserve: 50 hours
Barrels: Rapid rotating twin barrels (1 turn in 3.2 hours) one of which is equipped with a slipping spring to avoid excess tension
Balance wheel: Free sprung variable-inertia balance with white gold mean-time screws (10.70 mm diameter)
Frequency: 21’600 vibrations/hour
Balance spring: Phillips terminal curve; Geneva-style stud
Main plates: Nickel silver, spotted with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment

Bridges
Nickel silver, frosted and spotted with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment
Gold plate bearing the individual number of the timepiece
2 steel tourbillon bridges (movement side): hand-bevelled, flat black polished with polished countersinks
2 synthetic sapphire crystal tourbillon bridges (dial side)

Inner tourbillons
Inclined at a 30° angle, 1 rotation per minute

Outer tourbillons
1 rotation in 4 minutes
Hand-bevelled and openworked cage pillars
1 gold numbered counterweight per double cage

Gearing
Involute circle profile
Conical gearing with corrected profiles

Functions
Quadruple Tourbillon
Hour and minute display
Small second indicator
240-second outer-tourbillons rotation indicator
Power-reserve indicator

Exterior

Case
18 k 5N red gold or platinum 950 with asymmetrical convex synthetic sapphire crystal
Diameter: 43.50 mm
Thickness: 16.11 mm
Transparent back with asymmetrical convex synthetic sapphire crystal
Lateral window with shaped synthetic sapphire crystal
Raised polished engraving “Quadruple Tourbillon” on a hand-punched background
Three-dimensional, variable geometry-shaped lugs
Gold security screws
Polished bezel and centre band with hand-finished straight graining
Hand-engraved individual number
Water resistance of the case: 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown: In 18k 5N red gold or platinum 950  with engraved and black lacquered GF logo

Dial
Black dial in gold (5N red gold version) or silvered dial in gold (platinum version)
Gold hour markers
Gold display sectors
Applied gold logo
Hands: Hour and minute, small second and power-reserve in polished gold

Strap
Hand-sewn black alligator
18 k 5N red gold or platinum 950 folding clasp, hand-engraved with the Greubel Forsey logo