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  • Technical
  • Non-classified

Différentiel d’Égalité

Greubel Forsey 2018

Men's

Robert Greubel and Stephen Forsey first presented their Différentiel d’Égalité in 2008, as part of their Experimental Watch Technology programme, followed by a more advanced technical demonstrator two years later. Their invention enables a steady flow of energy from the mainspring barrel to the regulating organ, which maintains a constant balance amplitude throughout the entire power reserve. The principle, though simple, is difficult to implement: energy is no longer transferred directly through the gear train to the sprung balance, but "intercepted" by an intermediate spring that releases energy and rewinds once per second – hence why the seconds hand advances in a single jump per second (deadbeat seconds) rather than a succession of small steps. In addition, the 30° inclination of the balance counters the effects of the Earth's gravity.

Function

  • Function
    Hours, Minutes, Small seconds

Complications

  • Display
    Stop function via the crown
    Power-reserve indicator
    Deadbeat seconds or independent seconds
  • Regulating mechanism
    Constant-force escapement
  • Other complication
    See presentation text

Movement

  • Energy supply
    Manual-winding
  • N° of components
    359
  • N° of jewels
    47
  • Power reserve
    60 hours
  • Vibrations
    21600
  • Form
    Round
  • Height/thickness
    9.99 mm
  • Diameter
    36.40 mm

Case

  • Form
    Round
  • Material
    White gold
  • Height/thickness
    15.30 mm
  • Diameter
    44.00 mm
  • Back
    Sapphire
  • Water-resistance
    30 m

Dial

  • Material
    Openworked / sapphire
  • Colour
    Black / grey

Strap

  • Material
    Alligator
  • Colour
    Black
  • Fastening
    Folding clasp

Characteristics

  • Limited/numbered edition
    33