For the moment we can’t take new orders until further notice. We are now processing the overwhelming amount of reservations we’ve received after the launch of our 1941 Grönograaf on July 6 2022. Thank you for your patience and understanding.
The Grönefeld One Hertz is the world's first and only series wristwatch with independent dead seconds. It features a beautiful solid silver dial and an entirely in-house developed movement with stainless steel bridges and exceptional fine finishing. 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 – in wristwatches was usually derived from constant force devices. The Grönefeld One Hertz is unique among wristwatches in that to maximize precision, its dead seconds are powered by a secondary gear train, independent of the gear train for the hour and minute indications.
The Grönefeld One Hertz was awarded the prestigious special Jury Prize by the watch magazine 0024 and was voted the Watch of the Year by the readers of Timezone.com.
Sorry, sold out. € 73,550.00
The One Hertz’s calibre G-02 is a totally original, in-house developed movement featuring stainless steel bridges and exceptional fine finishing. In a dead seconds complication, friction of the mechanism has to be absolutely minimal so it does not interfere with the escapement and timing. For the One Hertz, Bart and Tim Grönefeld developed an independent dead seconds mechanism that is driven from its own secondary gear train with its own independent power supply. The dead seconds are driven from one mainspring barrel and the hours and minutes from another.
The One Hertz’s innovative dual drive train results in less friction compared to other jumping seconds mechanisms. A more constant amplitude is obtained and thus assuring superior accuracy.
|Calibre G-02||Mechanical hand-wound movement; independent dead seconds|
|Movement||Diameter 15 1/4 ’’’ 34 mm; thickness: 9.5 mm|
|Number of components||285 in the whole movement|
|Number of jewels||39 jewels in gold chatons|
|Power reserve||72 hours|
|Barrels||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|
|Balance wheel||Free sprung variable inertia balance wheel (9.12 mm diameter)|
|Balance spring||Phillips terminal overcoil curve; triangle-style stud|
|Escapement||Swiss lever escapement|
|Mainplate||Spotted and snailed rhodium plated nickel silver|
|Bridges||Hand bevelled; stainless steel X46 Cr13 Micro-blasted centre; circular grain on the top; relief engraved in the micro blasted surface|
|Gearing||Two gear trains with their own energy sources (2 barrels)|
|Dead seconds||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|
|Winding-setting||Crown with push function to choose between winding or setting; hacking seconds|
|Power reserve||Classic Breguet mechanism by means of a cone moving up and down on the threaded barrel arbor|
|Indications||Hours and minutes; large seconds; power reserve indicator; winding-setting indicator|
|Case||5N red gold case; 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; 8 security screw|
|Number of case components||68|
|Case dimensions||43 mm x 12.5 mm|
|Water resistance||3atm/30 meters/100 feet|
|Crown||Engraved with “G” logo and push to set/wind function|
|Dial||in solid silver|
|Seconds chapter ring||Rhodium plated with circular graining and beveled edges
|Hands||Hours and minutes, large seconds counter poised, power-reserve and winding-setting|
|Strap||Hand-sewn mat brown, alligator leather. 22mm-18mm|
|Buckle||Red Gold Au750 5N buckle, engraved with Grönefeld logo. 18mm|
|Weight||Approximately 141 grams. Including strap and buckle.|