Monochrome Watches
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Grönefeld One Hertz – independent deadbeat seconds

| By Frank Geelen | 4 min read |

Introducing “One Hertz”…  The world’s first wristwatch with independent deadbeat seconds! After the Grönefeld GTM-06 tourbillon minute repeater, Tim and Bart Grönefeld created an absolute high-light in the world of horlogerie.

Dutch watchmakers Tim and Bart Grönefeld present “One Hertz”, the world’s first and only ‘production’ wristwatch withindependent deadbeat seconds (secondes morte in French). But what is so special about an independent deadbeat seconds complication? There are other watches with a deadbeat seconds complication, although very rare.

The Grönefeld One Hertz is unique among wristwatches in that its deadbeat seconds are powered by a secondary gear train that is independent of the gear train for the hour and minute indications. The deadbeat seconds are driven from one mainspring barrel and the hours and minutes from another. Friction with this system is guaranteed to an absolute minimum and the complication has no adverse influence on the escapement and freesprung balance.

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The Grönefeld One Hertz features a brand new in-house developed movement. Calibre G-02 is a hand-wound movement with two barrels providing 60 hours of power reserve. One barrel is for the hours and minutes, the other barrel provides the power, through the secondary gear train, for the deadbeat seconds.

A wristwatch with deadbeat seconds shows a second hand that advances in full steps of one second instead of an apparently smooth sweeping action. This complication was a very respected complication until the 1980s when it’s popularity died with the dominance of quartz movements, which also has a second hand that advances in full steps of one second. With their new One Hertz, with its unique secondary gear train, Tim and Bart Grönefeld have resurrected this long neglected complication and re-positioned it where the complication originated, on the pedestal of high precision.

Calibre G-02 indicates hours and minutes on a sub-dial at 2 o’clock, a large sub-dial for the dead beat seconds, filling the majority of the dial with a power reserve indicator at 12 o’clock, and a setting-winding indicator at 3 o’clock. This indicator shows selected mode of the innovative “push to set, push to wind” function.

The movement’s two mainspring barrels are wound simultaneously from the crown and give the Grönefeld One Hertz 60 hours of autonomy.

The specifications of the in-house developed movement used in the One Hertz, calibre G-02, are phenomenal:

  • 254 parts, 39 jewels set in gold chatons it makes a rather large movement: 35mm x 9.4mm
  • Two barrels, one for the going gear train and one for the independent deadbeat seconds mechanism; both barrels are wound at the same speed and in the same direction, providing 60 hours of power reserve
  • The free-sprung Gyromax balance wheel has a diameter of 9.12mm and vibrates with a frequency of 21’600 bph or 2.5Hz
  • Balance spring: Phillips terminal overcoil curve, triangle-style stud
  • Main Plate and bridges are finished to the highest degree, also the parts nobody else than the watchmaker will see
  • Two independent gear trains each with their own energy source
  • Deadbeat seconds mechanism: Independent mechanism, cam with 30 teeth on the going gear train on the seconds wheel, escape wheel on the seconds wheel of the independent gear train, double lever with jewelled pallets
  • Winding-setting mechanism: Push function crown for winding or setting
  • Power reserve mechanism: Classic Breguet style by means of a cone moving up and down on the threaded barrel arbour

Now enough talk… here is the new beauty! (click to enlarge)

The stainless steel case measures 43mm x 12.5mm and is water resistance to a pressure of 3 atm or 30m/100feet. The sapphire crystal is domed and with anti-reflective treatment on both sides; the display back’s sapphire crystal has anti-reflective treatment on the inside.

  • In 2008, after working anonymously behind the scenes for the most prestigious Swiss brands, Tim and Bart Grönefeld presented the first watch bearing their own name, the GTM-06 Tourbillon Minute Repeater.
  • In June 2010 Tim and Bart presented their second watch, the One Hertz, the world’s first wristwatch with independent deadbeat seconds and featuring a completely new in-house movement.

The One Hertz launches as a limited edition with the name “One Hertz 1912”. This was the year Tim and Bart’s grandfather started his career as a watchmaker. The name Grönefeld and the art of watchmaking have a family history spanning nearly one hundred years, representing a continuous, unbroken watchmaking family history that is exceptionally rare to find anywhere in the world today.

The name of this limited edition, One Hertz 1912, already gives it away. It’s limited to (only) 12 pieces… be fast if you’re interested in this phenomenal landmark in watchmaking history!

Check the Grönefeld website and Facebook page for more information.

2 responses

  1. @Kyle… indeed, especially the new developed in-house movement with independent deadbeat seconds. Now i’m curious how fast the 12 pieces will be gone.

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