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Four tourbillons orbiting the Earth
Robert Greubel and Stephen Forsey have shown creative daring and boldness in uniting their second Fundamental Invention, the Quadruple Tourbillon, with their ground breaking interpretation of the GMT with its outsized rotating globe.
Click , to see the large size. ▶ BIG FOTO
Click , to see the large size. ▶ BIG FOTO
Click , to see the large size. ▶ BIG FOTO
A highly complex mechanism
Working on the principle that the more different positions the regulating organ moves through, the more precise the timekeeping will be, Robert Greubel and Stephen Forsey invented the Quadruple Tourbillon with a spherical differential. Right from the original idea the concept was clear. While coupling four separate tourbillons would have been challenging, they sought a more compact solution. To save space in all three dimensions, they chose to construct the tourbillons in pairs within a unique system of compact cages, an extremely challenging feat.
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Bringing the planet to the wrist
Having mastered the tourbillon, Robert Greubel and Stephen Forsey have continued to investigate and reinterpret other horological mechanisms, notably a practical and much appreciated complication: simultaneous multiple time zones display.
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In 2011, the two Inventor Watchmakers expressed their own vision of this modern day function in the ground breaking timepiece aptly named the GMT, more recently joined by the GMT Earth. In this patented system, the second time zone indication on a separate subdial is paired with a universal time display providing an intuitive reading of the time around the world thanks to a world first: an outsized globe completing one full rotation every 24 hours, following planet Earth itself.
An impressive three-dimensional sight
In bringing the Quadruple Tourbillon and the GMT mechanisms together, Greubel Forsey not only accomplished a major technical feat that led to the creation of a new hand-wound calibre comprising 705 parts, including three fast-rotating barrels. The Inventor Watchmakers also tackled this challenge from an architectural angle to create a timepiece in which the three-dimensional approach is expressed on many levels. The main hours/minutes dial between 1 and 2 o’clock forms the highest point of the dial, where it is underlined by the subtle asymmetry of the case and complemented by a 72-hour chronometric power-reserve display. The next level is it at 4 o’clock, with the coaxial small seconds and second time zone display which is adjustable in one-hour increments by means of a pusher.
Click , to see the large size. ▶ BIG FOTO
Click , to see the large size. ▶ BIG FOTO
A practical but refined case back
Universal time is visible through the case back, with a fixed 24-hour scale bearing day/night zones and a disk with three-letter abbreviations of 24 cities representing the various time zones. This disk also distinguishes between the time zones that implement Summer Time (Daylight Saving Time) appearing in a light colour; and those that do not (shown on a dark backdrop). The case back also provides a chance to admire the Quadruple Tourbillon as well as frosted bridges with jewels set in gold chatons. The two complex asymmetrical convex sapphire crystals protecting the dial and case back also called for the utmost expertise.
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TECHNICAL SPECIFICATIONS
Collection: GMT Quadruple Tourbillon
- GMT Quadruple Tourbillon - Unique edition of 66 pieces
11 pieces in white gold
Hand-wound movement with 3 patents
• universal time on 24 time zones • cities observing summer time
• lateral window showing the equator and southern hemisphere
• GMT pusher • Quadruple Tourbillon • hours and minutes
• small seconds • power-reserve
Movement
Dimensions
• Diameter : 39.50 mm
• Thickness : 13.00 mm
Number of parts
• Movement: 705 parts
• Four tourbillon cages: 260 parts
• Total weight of the cages: 2.25 g
• Spherical differential: 28 parts
Number of jewels • 84
• Olived-domed jewels in gold chatons
Chronometric power reserve • 72 hours
Barrels
• Three series-coupled fast-rotating barrels (1 turn in 3.2 hours),
one of which is equipped with a slipping spring to avoid excess tension
Balance wheel
• Variable-inertia with white gold mean-time screws (10.70 mm diameter)
Frequency • 21’600 vibrations/hour
Balance spring
• Phillips terminal curve
• Geneva-style stud
Main plate
• Nickel silver, frosted and spotted with polished bevelling and countersinks,
straight-grained flanks, nickel-palladium treatment
Bridges
• Nickel silver, frosted and spotted, polished bevelling and countersinks,
straight-grained flanks, nickel-palladium treatment
• Gold plate engraved with the individual number
• Flat black polished gold plates with relief-engraved text,
polished bevelling and countersinks, straight-grained flanks
• Four flat black polished steel tourbillon bridges,
hand-polished bevelling and countersinks, straight-grained flanks 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 counterweight per double cage bearing the individual number
Gearing
• Involute circle profile
• Conical gearing with profiled teeth
Displays
- • Hours and minutes
- • Small seconds (mean performance)
- • 72-hours power reserve on a sector
- • 2nd time zone GMT
- • 24 time zones universal time
- • Rotating titanium globe with universal time
- • Cities observing summer time
- • Day-and-night
Case
• In white gold with asymmetrical convex synthetic sapphire crystal
• Transparent back with asymmetrical convex synthetic sapphire crystal
• Lateral window with shaped synthetic sapphire crystal
• Three-dimensional, variable geometry-shaped lugs
• Raised polished engraving “GMT Quadruple” and “Greubel Forsey” on a hand-punched background
• Gold security screws
• Polished bezel, caseband with hand-finished straight graining
• White gold GMT pusher with raised engraving on a handpunched background
• Hand-engraved individual number
Case dimensions
• Diameter : 46.50 mm
• Height : 17.45 mm
Water resistance of the case • Water-resistant 3 atm - 30 m - 100 ft
(standard NIHS 92-20/SN ISO 22810:2010)
Crown
• In white gold with engraved and black lacquered GF logo
Dial
• Multi-level in gold, anthracite colour
• Gold hour-ring, circular-grained with polished bevelling, black treatment
• Gold hour markers
• Power-reserve and GMT in gold, hand matt lapped
• Small second, circular-grained
Hands
• Hours and minutes in polished gold, with Super-LumiNova
• Small seconds in polished steel, black treatment
• Power-reserve in polished steel, hand-polished countersink
• 2nd time zone GMT indicator, red
Strap and clasp
• Hand-sewn alligator
• White gold folding clasp, hand-engraved with the GF logo
Unique edition
Limited Edition of 66 pieces.
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Press Release - 2019
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GREUBEL FORSEY SA
For further information:
Communication Department
press@greubelforsey.com – +41 79 194 2884
Eplatures-Grise -16 P.O. Box 670
2301 La Chaux-de-Fonds - Switzerland
+41 32 925-4545
+41 32 925-4502
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