With their brand new GMT SPORT timepiece, Robert Greubel and Stephen Forsey have pushed back the limits of ergonomics and wrist comfort. They have invented a totally new case form, perfectly round from above, while revealing the accentuated arched and ovoid shape from other angles.
The aerodynamics of this timepiece 4 patents are reinforced by its integrated lugs and strap resulting in distinct functional forms that perfectly ft any wrist. The sweeping satin finished bezel with Greubel Forsey’s values relief engraved on its outer bevel, follows this unique case shape. The curved profile of the 45 mm diameter case and ovoid sapphire crystal provide the perfect showcase for an entirely new movement architecture with an arched bridge and inclined gear train.
Already in 2015, the GMT Black paved the way for the GMT Sport. Building on this foundation, Robert Greubel and Stephen Forsey have invented and now present the result, a lightweight and ultra-strong, profiled titanium case with ovoid bezel and integrated lugs to showcase the new movement. Water resistant to 100 meters, the new GMT Sport stands out as their most sport oriented timepiece to date.
The movement was constructed from scratch – from the suspended arched bridge for the hours and minutes display, to the unique showcase of the Tourbillon 24 Secondes and the universal time display with three-dimensional globe.
The display side of the GMT Sport presents classic Greubel Forsey architecture, an open, orchestrated theatre between suspended bridges, semi-apparent wheels and floating dials in three dimensions. In keeping with the sporting vocation of this timepiece, the focus is on legibility and efficiency. The hours and minutes are displayed by concentric open-worked hands whose curved profile follows the curvature of the case and movement.
Mounted on the suspended arch centre bridge with black treated openings, the gear train literally follows the curve of the bridge, overlooking the globe to drive the hour and minute hands. Ensuring excellent visibility in the dark, the triangular tips of the arrow-shaped hands and the markers on the minute-hour-ring are enhanced with luminescent coating.
Suspended three-dimensional displays and 11 o’clock combines the small seconds on a large rotating disc, and the second time zone display with a hand. These two coaxial displays with red triangular indexes underline this timepiece’s technicity. The 72-hour chronometric power reserve (ensured by two coaxial barrels in series) is indicated on a sector at 3 o’clock with its open-worked hand and highlighted red triangle. Housed underneath the arched bridge, the power reserve differential is subtly engraved with Greubel Forsey’s values. Whether they are visible on the dial side or concealed in the caseback side, each of the 435 components of this hand-wound movement, including titanium plates and bridges, respect the most demanding criteria of the Greubel Forsey Atelier and the teams utmost concern for the finest workmanship.
The 24 Seconds Tourbillon is showcased at 1 o’clock secured by its distinctive and highly polished tourbillon bridge with black finished openings. This third Fundamental Invention by Greubel Forsey in the field of the tourbillon (after the Double Tourbillon 30 ° and the Quadruple Tourbillon) stands out with its cage inclined at 25 ° completing one full rotation in 24 seconds.
The faster speed combined with the inventive cage inclination, significantly improves chronometric performance in a single-tourbillon system, with minimal movement height. This exclusive and patented configuration counters the disturbances induced on the movement by earth’s gravity, especially in stable positions. The rotating tourbillon cage housing the regulating organ has 88 components, for a weight of 0.38 grams – a feat made possible in particular by light alloy pillars and titanium bridges.
Precision and reliability summarise Greubel Forsey’s ground-breaking GMT mechanism, presented for the first time in 2011, with the GMT Black presented in 2015.
In this double-patented mechanism, the second time zone indication on the auxiliary dial between 10 and 11 o’clock is combined with a universal time display to intuitively read the current time anywhere in the world.
The remarkable innovation and striking spectacle of the terrestrial rotating globe – seen from above the North Pole – performs each complete anticlockwise turn on its axis in 24 hours. It’s surrounded by a sapphire crystal ring with 24-hour divisions; where the wearer can read local time for all longitudes, including the day / night indicator (light zone / dark zone).
On the caseback side of the GMT Sport, outer and central rings complete the sapphire cities disc to give UTC Universal and Summer Time for 24 cities in major time zones. This disc distinguishes those time zones applying summer time (on a light background) from those that do not (on a dark background).
Reviewing the ergonomics, the GMT’s functions use two pushers located on the left side of the case; one to select the second time zone and the other for synchronising the local time with the globe. The titanium and rubber crown also ensures optimum setting.
Created in a limited edition of 11 pieces, the GMT Sport with the key Greubel Forsey values in relief on the bezel has a black or blue rubber strap. A titanium folding clasp reinforces the comfort and ergonomics of this Greubel Forsey timepiece.
Technical details
Model: Greubel Forsey GMT Sport Titanium Limited Edition
Special features
Hand-wound movement with 3 patents • Patents pending
GMT • 2nd time zone • rotating globe with universal time and day-and-night • universal time on 24 time zones • summer and winter time • cities observing summer time • GMT and Earth pushers • Tourbillon 24 Secondes • hours and minutes • small seconds • power-reserve
Movement
Movement dimensions
• Diameter: 36.90 mm
• Thickness: 13.18 mm
Number of parts
• Movement: 435 parts
• Tourbillon cage: 88 parts
• Weight of the cage: 0.38 g
Number of jewels
• 63
• Olived-domed jewels in gold chatons
Chronometric power reserve
• 72 hours
Barrels
• Two coaxial 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 gold mean-time screws (10 mm diameter)
Frequency
• 21’600 vibrations/hour
Balance spring
• Phillips terminal curve
• Geneva-style stud
Bridges and main plate
• Titanium
• Frosted and spotted, polished bevelling and countersinks, straight-grained flanks, black treatment
• Multi-level, suspended-arch bridge, polished with black treatment in relief, polished beveling and countersinks, straight-grained flanks
• Flat black polished tourbillon bridge with black treatment in relief, spotted, polished bevelling and countersinks, straight-grained flanks
Tourbillon
• Inclined at a 25° angle, 24-seconds rotation
• Light alloy cage pillars
• Titanium cage bridges
• Gold counterweight
Gearing
• Involute circle profile
• Tangential inclined gear on fixed wheel and on escape wheel pinion
• Inclined gear and profiled teeth on intermediate wheels of the set-hands mechanism.
Displays
• Hours and minutes, on suspended-arch bridge
• Small seconds on disc
• 72-hours power reserve on a sector
• 24-seconds tourbillon rotation
• Rotating titanium globe with universal time
• Day-and-night
• 2nd time zone GMT
Movement side
• 24 time zones universal time
• Summer time
Exterior
Case
Titanium with curved synthetic sapphire crystal
Three-dimensional, variable geometry-shaped bezel with raised engraved text
Case-band diameter: 42.00 mm
Bezel diameter: 45.00 mm
Case height: 15.70 mm
Profiled lugs, screwed fixing
Engraved pushers
Transparent back with high domed synthetic sapphire crystal
Titanium security screws
Raised engraving “GMT Sport” and “Greubel Forsey”
Height on synthetic sapphire crystals: 17.80 mm
Water-resistant 10 atm – 100 m – 328 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown
Titanium and rubber with GF logo
Colour-coded rubber capping, interchangeable
Dial side
Three-dimensional, variable geometry hour-ring, with luminescent hours and minutes indexes
GMT indicator with raised engraving
Power-reserve indicator, engraved and lacquered
Tourbillon rotation indicator in gold
Rotating globe with fixed day-and-night UTC indicator in synthetic sapphire, engraved and lacquered
Movement side
Synthetic sapphire disc displaying city names surrounded by 2 rings (UTC engraved on the case / Summer time engraved on a gold movement plate, lacquered and hand matt-lapped)
“Summer time” plate with limitation number, raised engraving, hand matt lapped
Hands
Polished steel curved shape hours and minutes, with Super-LumiNova
2nd time zone GMT indicator, red triangle
Small seconds, fixed red triangle
Power-reserve indicator, in polished steel
Aluminium 24-seconds double-tipped hand, black treatment
Strap
Rubber with relief text
Titanium folding clasp, engraved GF logo
