SIHH 2018: Greubel Forsey Différentiel d'Égalité
After years of research and development, Robert Greubel and Stephen Forsey are especially proud to present a timepiece that contains their 5th Fundamental Invention: the Différentiel d’Égalité. It ensures a regulated driving force and improves the accuracy of the timing performance. It is also the first time that Greubel Forsey has integrated a dead-beat second in one of its timepieces.
Différentiel d’Égalité,
“Regulated power for enhanced precision”
Robert Greubel and Stephen Forsey first unveiled their invention at Baselworld 2008 as part of the EWT Laboratory and then presented a more advanced version of a technical demonstrator at SIHH 2010. Since then, further exciting paths have been explored to help optimise accuracy in this new timepiece. The Différentiel d’Égalité enables steady distribution of power from the mainspring barrel to the regulating organ, which maintains a constant balance amplitude during the 60 hours of the power reserve.
Dead-beat seconds and performance
In a first for Robert Greubel and Stephen Forsey, this timepiece features dead-beat seconds. This makes it easier to read and to set the time precisely. The timepiece is equipped with a balance wheel stop and seconds reset activated by pulling the crown. The heart and the hammer of this mechanism are visible on the movement side. The 30° angle of the balance wheel and escapement minimises the e ects of gravity and ensures efficient movement performance in stable positions. This Greubel Forsey technique guarantees excellent mean/averaged balance wheel performance, which is the mark of heightened timekeeping accuracy. All of these components work together magnificently to help improve performance.
Mechanical spirit
The aesthetics of this timepiece flow from everything that’s purest in Greubel Forsey’s mechanical spirit. A large opening in its dial allows a glimpse of all the beauty and complexity of the movement. The dial side has a high-domed sapphire crystal that gives this new creation a refined silhouette. The movement side shows the “stop/reset” mechanism and the engraved inscriptions which encapsulate the key values that Robert Greubel and Stephen Forsey instil in their creations.
This white gold edition is limited to 33 pieces.
Greubel Forsey Différentiel d’Égalité
Technical specifications:
Limited edition of 33 pieces in white gold
Hand-wound movement with patented spherical Différentiel d’Égalité
Spherical Différentiel d’Égalité • inclined fixed escapement • hours and minutes • dead-beat seconds • small seconds • power-reserve • stop balance and reset on dead-beat seconds
Movement
Movement dimensions:
• Diameter: 36.40 mm • Thickness: 9.99 mm
Number of parts:
• Movement: 359 parts • Inclined fixed escapement: 71 parts
Number of jewels:
• 47 • Olived-domed jewels in gold chatons
Spherical Différentiel d’Égalité:
• 24 parts including 4 jewels and 3 satellites • Differential cage, circular-grained, polished
bevelling and countersinks, straight-grained flanks • Uniform torque, rewinding once per second with integrated spring
Chronometric power reserve:
• 60 hours ± 10% • Optimized amplitude over the entire power reserve • Stopwork mechanism
Barrels:
• Two series-coupled fast rotating barrels (1 turn in 3.2 hours), one of which is equipped with a slipping spring to avoid excess tension • Barrel with relief engraving "Greubel Forsey"
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
Main plate:
• Nickel silver, frosted and 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 • Flat black polished gold plate with raised engraved text, polished bevelling and countersinks, straight- grained flanks with gold chatons • Circular-grained gold plate with individual number, polished bevelling and countersinks, straight- grained flanks
Reset mechanism:
• Stop balance and reset activated by crown • Flat black polished steel reset mechanism, polished bevelling, straight-grained flanks
Inclined fixed escapement:
• Inclined at 30° • Flat black polished steel lower bridge, polished bevelling and countersinks, straight-grained flanks • Polished steel pillars • Flat black polished steel balance wheel bridge, barrel-polished, polished bevelling and countersinks, straight-grained flanks
Gearing:
• Involute circle profile • Spherical Différentiel d’Égalité with conical gearing • Conical profiled teeth for inclined fixed escapement
Displays:
• Hours and minutes • Dead-beat seconds • Small seconds • 60-hours power reserve on a sector
Exterior
Case:
• In white gold with high domed synthetic sapphire crystal • Transparent back with synthetic sapphire crystal • Three-dimensional, variable geometry-shaped lugs • Raised polished engraving “Différentiel d’Égalité” and “Greubel Forsey” on a hand-punched background
• Gold security screws • Hand-polished bezel, caseband with hand-finished straight graining
• Hand-engraved individual number
Case dimensions:
• Diameter: 44.00 mm • Height: 15.30 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 side:
• Multi-level synthetic sapphire hour-ring, lacquered galvanic growth hour indexes, engraved and lacquered minutes and dead-beat seconds • Small seconds and power-reserve indicators in gold, engraved and lacquered, hand matt lapped
Hands:
• Hours and minutes in gold with Super-LumiNova • Small seconds, dead-beat seconds and power-reserve in polished blued steel, hand-polished countersinks
Strap and clasp:
• Hand-sewn alligator • White gold folding clasp, hand-engraved with the GF logo
The price for the Greubel Forsey Différentiel d’Égalité is CHF 265,000.
