The Greubel Forsey QP à Équation timepiece, which was created after seven years of research, the assembly of no fewer than 624 parts, three patents, and the combination of two inventions, revolutionises one of the oldest watchmaking complications, the perpetual calendar, by incorporating an equation of time.
To create this watchmaking complication, Greubel Forsey has developed a Mechanical Computer: this enabled ergonomics and readability of the various functions to be simplified, and for all corrections – including days – to be made rapidly by turning the bi-directional crown.
The QP à Équation houses Greubel Forsey’s seventh invention, the Mechanical Computer, an entirely integrated 25-part component that brings a totally new interpretation to some of the calendar functions incorporated in age-old astronomical clocks. It is composed of a set of coding wheels superimposed in a coaxial manner, along with removable fingers programmed by this ingenious system.
Depending on their rotation speeds and number of teeth, these wheels provide a variety of information. The Mechanical Computer also directly drives a system of sapphire disks that displays the equation of time, i.e. the difference between the “real” solar time and civil time.
Paramount to this was simplifying the way all the indications can be corrected by turning the bi-directional crown. Despite its multiple functions and displays, added to its combination of three patents and two inventions, Greubel Forsey’s QP à Équation Millésimé remains as easy to set as a simple calendar.
The dial of the QP à Équation indicates leap years, the 24 hours of the day and night, the day of the week, the large date, the month, the hours, the minutes and the seconds, as well as the chronometric 72-hour power reserve. On the movement side, this timepiece displays the equation of time with the months, seasons, solstices and equinoxes, as well as the calendar year.
This new interpretation of the perpetual calendar features the Equation of Time incorporated within it, along with the addition of new functions and displays that aim to optimise readability and pleasure of use.
Three apertures lined up in the sub-dial at 3 o’clock give an unequivocal indication of the day, date and month for enhanced visual comfort. The large date boosts readability, making it especially easy to make out the elements of the calendar.
The timekeeping of this timepiece relies on Greubel Forsey’s third invention: the Tourbillon 24 Secondes, which uses a fast rotation speed and inclined angle to solve the problem of critical positions of the oscillator in relation to gravity. A 25° angle and the rapid revolution of the tourbillon cage significantly improve the chronometric performance of a system containing only one tourbillon, especially in stable positions.
The QP à Équation is available in a Millesimé Edition with a rhodium-coloured gold dial. This new Millésime’s white gold case measures 43.5mm by 16 mm thick and provides a simplified linear display.
Technical details
Model: Greubel Forsey QP à Équation Millesimé Edition in White Gold with Rhodium-coloured Dial
Movement
Hand-wound movement with 4 patents
Bidirectional perpetual calendar • day, date, month, calendar year, leap year, day/night • equation of time with month, season, solstice and equinox • function selector • Tourbillon 24 Secondes • hours and minutes • small seconds • power-reserve
Movement dimensions
Diameter: 36.40 mm
Thickness: 9.60 mm
Number of parts
Movement: 624 parts
Tourbillon cage: 86 parts
Weight of the cage: 0.37 g
Number of jewels
• 75
• 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, 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
• 4 engraved gold plates, one with the individual number
• Flat black polished steel tourbillon bridges
• Synthetic sapphire mechanical computer bridge
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 profiled teeth on escape wheel pinion
Dial displays
• Hours and minutes
• Small seconds
• 72-hours power reserve on a sector
• Day of the week, large date and month
• Leap year
• Day-and-night with red safety zone
• Function selection (perpetual calendar or H/M time adjustment)
Back displays
• Equation of time with month, season, solstice and equinox
• Calendar year
Exterior
Case
In white gold with asymmetrical convex synthetic sapphire crystal
Diameter: 43.50 mm
Height: 16.00 mm
Transparent back with asymmetrical synthetic sapphire crystal
Three-dimensional, variable geometry-shaped lugs
Raised polished engraving “QP à Équation” and “Greubel Forsey” on a hand-punched background
Gold security screws
Polished bezel, caseband with hand-finished straight graining
Hand-engraved individual number
Water resistance of the case: 3 atm – 30 m – 100 ft
Crown: In white gold with engraved GF logo
Dial
Multi-level gold dial, anthracite or rhodium-coloured
Gold hour markers
Small second, power-reserve and leap year in gold
Gold perpetual calendar aperture with polished raised engraving
Gold GF logo
Hands
Hours and minutes in polished gold or black treatment, with Super-LumiNova
Small seconds, power-reserve and leap year indicator hand in polished blued steel or black treatment
Strap and clasp
Hand-sewn alligator
White gold folding clasp, hand-engraved with the GF logo
