Friday 09 November 2018: The Grande Sonnerie, the most complex Greubel Forsey creation to date, has been awarded the “Mechanical Exception” prize at the Grand Prix d’Horlogerie de Genève.
Conducting 11 years of research, assembling no less than 935 parts, filing two patents, incorporating Greubel Forsey’s third Fundamental Invention (Tourbillon 24 Secondes), developing an acoustic resonance cage generating an extreme purity of sound, installing eleven functional safety features ensuring unparalleled intuitive ease of use, performing a three-year wearing test… As highlighted by this only partial list of the stages involved, the creation of the Grande Sonnerie was indeed a monumental undertaking by Robert Greubel, Stephen Forsey and their team. This timepiece embodies the quintessence of their expertise and their ideal of horological excellence.
The most complex Greubel Forsey creation to date
The Grande Sonnerie is undoubtedly one of the greatest horological complications. Right from the beginning of their partnership, Robert Greubel and Stephen Forsey began reflecting on what their own resolutely contemporary vision of this regal complication might be. For eleven years, the Grande Sonnerie set the cadence of their day-to-day lives, as they worked in the utmost secrecy to assemble the 935 components of this timepiece, and above all to ensure absolute harmony between the movement, the exterior and the acoustics.
Its ergonomics guarantee unparalleled intuitive ease of use. To ensure optimal architectural balance, obsessive attention to detail was devoted to the intelligent integration of the most important mechanisms and indications (tourbillon, cathedral gongs, striking hammers, power-reserve display…).
The creators thus succeeded in completing the Grande Sonnerie within a titanium case measuring 43.5 mm in diameter and a height of just 16.13 mm – an entirely reasonable size given the complexity of the timepiece.
Acoustics
The acoustics of this Grande Sonnerie is all the more impressive given that the timepiece is water-resistant to 3 Atm (approx. 30 metres), an outstanding accomplishment serving to ensure that the sound emits a clear, strong strike. Much like a stringed instrument, the titanium acoustic resonance cage was developed inside the caseband itself, so as to provide the loudest possible volume. The extremely pure crystalline strike is transmitted thanks to one-piece double cathedral gongs – on three levels and respectively sounding high and low notes – that are visible through the tourbillon’s lateral window.
The two striking hammers are notably visible on the dial side, featuring flat black-polishing, hand bevelling and polished countersinks. The gold bridge supporting them is relief-engraved and has the same exceptional finishes, as well as straight-grained flanks. While the movement is manual-winding, the striking mechanism also features an automatic winding system by means of a platinum oscillating weight engraved with the Greubel Forsey guiding spirit – and delivering some 20 hours’ strike reserve in Grande Sonnerie mode. The Grande Sonnerie strikes the hours and quarters in passing, while the Petite Sonnerie sounds only the full hours in passing. A Silence mode can be activated via a pusher. On demand, a minute repeater and its additional mechanism strike the time to the exact quarter and minute. This timepiece also includes another feat thanks to a silent speed regulating governor, using an inertia flywheel specially designed to muffle the whirring sound habitually made by traditional strike speed regulation mechanisms.
The Tourbillon 24 Secondes, the third Fundamental Invention
The timekeeping precision of the timepiece is ensured by the third Fundamental Invention: the Tourbillon 24 Secondes, which uses fast rotational speed and an inclined angle to solve the problem of the oscillator’s critical positions in relation to gravity. The 25° angle and the rapid revolution of the tourbillon cage significantly improve the precision timekeeping performance of a system comprising just one tourbillon, especially in static positions. Among the other salient characteristics of this timepiece are a frequency of 21,600 vibrations/hour and a chronometer-worthy power reserve of 82 hours.
The Grande Sonnerie is an exclusive achievement attained by very few watchmakers. Despite its complexity, Greubel Forsey will aim to complete five to eight of these timepieces each year.
Robert Greubel and Stephen Forsey would like to express their warmest thanks to the entire Greubel Forsey team, without whom this great feat would not have been possible.
Greubel Forsey Grande Sonnerie
In titanium – Millésimé
Patented hand-wound movement and striking-mechanism & Full striking-mechanism with automatic winding
Petite and Grande Sonnerie timepiece • minute repeater on demand by crown mounted pusher • striking modes selection by pusher • grande and petite sonnerie, silence • striking power reserve • Tourbillon 24 Secondes • hours and minutes • small seconds • movement power reserve
Movement
Movement dimensions
- Diameter: 36.40 mm
- Thickness: 11.13 mm
Number of parts
- Timepiece: 935 parts
- Movement: 855 parts
- Cage tourbillon: 86 parts
- Weight of the cage: 0.37 g
Number of jewels
- 85
- 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
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
- Flat black polished steel tourbillon bridge, with 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 a fixed wheel and profiled teeth on escape wheel pinion
Movement and striking-mechanism displays
- Hours and minutes
- Small seconds on a sector
- 72-hours power reserve on a sector
- Three striking modes: GS (Grande Sonnerie) strikes the hours and quarters in passing PS (Petite Sonnerie) strikes the full hours in passing SL (Silence) does not strike in passing
- Striking power reserve on a sector
Striking-mechanism
Acoustic
- One-piece cathedral gongs on three levels, two notes, visible through the tourbillon’s lateral window, flat black polished steel gongs block, with polished bevelling and countersinks
- Two flat black polished steel visible hammers, with polished bevelling and countersinks
- Flat black polished hammers bridge, with a raised polished engraving, with polished bevelling and countersinks, straight-grained flanks
- Silent speed regulating governor
- Dedicated striking barrel maximising hammer force and striking power reserve (about 20 hours in Grande Sonnerie mode)
- Striking rhythm optimised without pause
Mechanism
- Visible on movement side, straight-grained or circular-grained steel, with polished bevelling and countersinks, straight-grained flanks
- Protected with eleven securities, for example when striking is in progress, when time setting when the dedicated striking barrel is wound down…
- Minute repeater striking hours – quarters – minutes, down to the minute
Automatic winding (only for striking-mechanism)
- Oscillating weight in platinum with relief-engraved texts, flat black polished, with polished bevelling, straight-grained flanks
- Flat black polished gold central plate with relief-engraved “GF” logo, polished bevelling and countersinks, straight-grained flanks
- Gold peripheral plate, circular-grained, engraved and lacquered “Grande Sonnerie” with polished bevelling and countersinks
- Flat black polished gold decorative plate with relief-engraved text, with polished bevelling and countersinks, straight-grained flanks, with a screwed gold chaton
Exterior
Case
- In titanium 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 “Grande Sonnerie” and “Greubel Forsey” on a hand-punched background
- Gold security screws
- Hand-polished bezel, caseband and caseback
- White gold modes selection pusher, with a raised engraving on a hand-punched background
- Hand-engraved individual number
Case dimensions
- Diameter: 43.50 mm
- Height: 16.13 mm
Water resistance of the case
- Water-resistant 3 atm – 30 m – 100 ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown with pusher
- In white gold with engraved GF logo
Dial
- Multi-level in gold, black colour
- A window showing the hammers and the gongs
- Gold hour markers
- Gold display sectors
- Gold GF logo
Hands
- Hours and minutes in gold with Super-LumiNova, small seconds and power reserve in polished gold
- Striking modes and striking power reserve in polished gold
Strap and clasp
- Hand-sewn alligator
- Titanium folding clasp, engraved with the GF logo
For more information please visit the Greubel Forsey Website