The world's first and only series wristwatch with independent dead seconds
One Hertz / DuneA limited edition of 20 pieces in red gold
The One Hertz Dune sees the One Hertz – the world’s first and only production wristwatch with independent dead seconds – receive an sophisticated red gold case and stylish brown dial.
Dead seconds is where the second hand advances in full steps of one second instead of the usual smooth sweeping action of mechanical seconds.
With the One Hertz, Bart and Tim Grönefeld have resurrected this long-neglected horological complication and re-positioned it on the pedestal of high precision.
Until the arrival of the One Hertz, dead seconds – secondes mortes in French – was derived from other mechanisms, usually a constant force device or remontoir d'égalité.
But the Grönefeld One Hertz is unique among wristwatches in that its dead seconds are powered by a secondary gear train, independent of the gear train for the hour and minute indications.
The quartz-like movement of the large second hand of the One Hertz subtly signals its unique mechanism, imperceptible to most, but obvious to haute horlogerie aficionados who will appreciate the flawless fine-finishing of Grönefeld’s own proprietary movement, the calibre G-02.
The One Hertz indicates hours and minutes on a sub-dial at 2 o'clock, a large sub-dial for the dead seconds filling the majority of the dial with a power reserve indicator at 12 o'clock, and a winding-setting (W-S) indicator at 3 o'clock.
Setting-winding is ergonomically selected by pushing the crown instead of pulling it out.
The One Hertz is a prize-winning timepiece. It was awarded the Innovation prize in the 0024 WatchWorld Watch of the Year contest and was voted Watch of the Year by members of the influential watch forum Timezone.
The calibre G-02 is a totally original, in-house developed movement.
Displaying dead 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.
Bart and Tim Grönefeld used an independent dead 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 is with this system guaranteed to an absolute minimum and the complication has no adverse influence on the escapement and free sprung 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 dead seconds dial keeps track of the 72 hours of autonomy.
Mechanical hand-wound movement; independent dead seconds
Diameter 15 1/4 ’’’ 9.5 mm; thickness: 34 mm
Number of components
285 in the whole movement
Number of jewels
39 jewels in gold chatons
2 barrels, one for the going geartrain and one for the independent dead seconds mechanism; both barrels are wound at the same speed and in the same direction
Free sprung variable inertia balance wheel (9.12 mm diameter)
Phillips terminal overcoil curve; triangle-style stud
Swiss lever escapement
Spotted and snailed rhodium plated nickel silver
Hand bevelled; stainless steel X46 Cr13 Micro-blasted centre; circular grain on the top; relief engraved in the micro blasted surface
Two gear trains with their own energy sources (2 barrels)
Independent mechanism; cam with 30 teeth on the fourth wheel of the going geartrain; special escape wheel on the fourth wheel of the independent geartrain; double lever with four jeweled pallets
Crown with push function to choose between winding or setting
Classic Breguet mechanism by means of a cone moving up and down on the threaded barrel arbor
Case and dial
Hours and minutes; large seconds; power reserve indicator; winding-setting indicator
18k red gold; polished bezel and centre band with hand-finished straight graining; sapphire crystal on the front is slightly domed with anti-reflectiove treatment on both sides; sapphire crystal on the back is flat with anti-reflection treatement on the inside; engraving of serial number and model; gold security screws
Number of case components
diameter: 43 mm; thickness: 12.5 mm
3atm/30 meters/100 feet
Engraved with “G” logo and push to set/wind function
Made of sapphire
Hours and minutes, large seconds counter poised, power-reserve and winding-setting
Hand-sewn, alligator leather with ardillon buckle engraved with the Grönefeld logo