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Dutch watchmakers Tim and Bart Grönefeld present “One Hertz”, the world’s first and only production wristwatch with independent deadbeat seconds. While rare, the deadbeat seconds complication does exist, but to date has been derived from other mechanisms, usually a constant force device or remontoir d’égalité.
The Grönefeld One Hertz features a completely original in-house developed movement indicating hours and minutes on a sub-dial at 2 o’clock, a large sub-dial for the deadbeat 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. Setting-winding is ergonomically selected by pushing the crown instead of pulling it out.
With their 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, i.e. on the pedestal of high precision.
With the introduction of the pendulum in the 17th century, clocks finally became accurate enough to measure seconds. It was then not long before a hand indicating seconds on a long clock’s dial signified a precision timepiece. A pendulum with a period – the time to swing forward and back – of two seconds (the most common) resulted in a single tick per second.
The invention of the balance spring, which replaced the pendulum, enabled miniaturization. As portable pocket watches became more accurate, watchmakers naturally thought to copy the one-second steps of the second hand, which signified a precision timepiece; however, the rapidly oscillating balance meant that it could not be directly driven from the oscillator as with the pendulum, so it either necessitated a new mechanism if independent, or it had to be driven from another complication e.g., a constant force device. While pocket watches have featured independent deadbeat seconds in the past, the Grönefeld One Hertz is the first wristwatch featuring independent deadbeat seconds.
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.
Displaying deadbeat seconds in a wristwatch without a constant force device is no easy task. The friction of the mechanism has to be absolutely minimal so it does not interfere with the escapement.
Tim and Bart Grönefeld used an independent deadbeat seconds mechanism that is driven from its own secondary gear train with its own power supply. The 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.
The two mainspring barrels are wound simultaneously from the crown, which features an innovative “push to set, push to wind” function, with the mode selected indicated on the dial at 3 o’clock. A power reserve indicator at the top of the deadbeat seconds dial keeps track of the 60 hours of autonomy.
Technical Specifications:
- Movement dimensions: 35mm x 9.4mm
- Parts: 254
- Jewels: 39, set in gold chatons
- Power reserve: 60 hours
- Barrels: 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
- Balance wheel: 9.12mm free-sprung variable inertia balance wheel
- Balance frequency: 21’600 bph/ 3 Hz
- Balance spring: Phillips terminal overcoil curve, triangle-style stud
- Main Plate: Spotted and snailed rhodium plated nickel silver
- Bridges: Stainless steel, hand-bevelled, micro-blasted centre and the underneath spotted, circular grain on the top, relief engraved on micro-blasted surface
- Gearing: 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
