Grönefeld “One Hertz Techniek” Limited Edition

After the successful launch of award winning timepiece “One Hertz”the world’s first independent dead seconds series wristwatch ; the Netherlands based watchmakers Bart and Tim Grönefeld unveil their new model in the same One Hertz line  with a revealing open dial to showcase the complex mechanics within.

The brand new One Hertz Techniek is the world’s only series wristwatch with independent dead seconds, featuring a stunning, open-work dial that showcases the intricate upper mechanics of Grönefeld’s own proprietary movement, the calibre G-02.

Grönefeld “One Hertz Techniek” Limited Edition watch

While the dial is dominated by a large dead seconds chapter ring in sapphire, the other indications, bridges and Grönefeld logo are crafted in stainless steel, which is relief engraved, bevelled and finished completely by hand.

The open dial is framed by a gleaming high-tech Grade 5 titanium case available in two versions: natural polished and brushed titanium or black DLC – when the timepiece becomes the “One Hertz Techniek Nocturne”.

Grönefeld “One Hertz Techniek” Limited Edition watch

Both versions feature the Grönefeld’s own ergonomic winding and setting mechanism, selected by simply pushing the crown in, rather than pulling it out.

Gronefeld “One Hertz Techniek” Limited Edition watch

The open dial is such that the mechanics behind each one of the One Hertz’s indications and signature features are subtly – and beautifully – revealed.  At the heart of the hour and minutes subdial at 2 o’clock, we see the hour wheel – logically rotating in 60 minutes – offering a splash of colour and contrast to the largely monochrome movement.

The independent dead seconds – where the second hand advances in full steps of one second instead of the more usually smooth sweeping action of mechanical seconds – features prominently in a large subdial at 7 o’clock. The open dial affords rich views of the large, stainless steel gear train bridge for the dead seconds mechanism, the dead seconds escape wheel and the centre wheel. At the top of seconds dial at 11 o’clock, the lever and spring of the power reserve indicator can also be seen.

The whole ensemble of indications and exposed mechanisms are set off against the dark texture of the hand-frosted mainplate and bridges.

Gronefeld “One Hertz Techniek” watch movement

Turning over the One Hertz Techniek completes the mechanical feast for the eyes with the sumptuous display back featuring no fewer than nine finely-crafted stainless steel finger bridges. The One Hertz is the world’s first series movement with all the bridges in stainless steel.

Grönefeld “One Hertz Techniek” Limited Edition watch

The “One Hertz Techniek” is a limited edition of 30 pieces in Grade 5 titanium, with either a natural finish (“One Hertz Techniek”) or black DLC coated (“One Hertz Techniek Nocturne”).

Grönefeld “One Hertz Techniek” Limited Edition watch

Winding-Setting mechanism and hacked seconds

With the One Hertz, winding and setting are selected by pushing the crown in, instead of pulling it out – a very ergonomic system. The winding-setting (W S) indicator at 3 o’clock provides a neat visual signal as to the mode selected, and the winding-setting lever and its spring are visible around the indicator thanks to the open dial. What’s more, the counter-poised seconds hand can be ‘hacked’ – i.e. stopped – when ‘setting’ is selected, to ensure maximum precision when adjusting the time.

The “One Hertz Techniek” and the “One Hertz Techniek Nocturne”

While the One Hertz Techniek is available in polished and brushed natural Grade 5 titanium, Bart and Tim Grönefeld have harnessed the talents of Finnish company DIARC, world-renowned for their coating techniques, to offer a striking black DLC coated version as well. Bart and Tim have dubbed this black version the “One Hertz Techniek Nocturne” after ‘nocturne’, the style of painting that depicts scenes evoking night.

Dead seconds

The dead seconds complication was a very respected mechanical complication until the 1980s because it denoted superlative accuracy. It was traditionally derived from other mechanisms such as a constant force device or remontoir d’égalité. However, the popularity of dead seconds faded with the dominance of quartz movements, which also stepped in full seconds. A smooth sweeping second hand came to differentiate mechanical from quartz.

But with the One Hertz and its unique secondary gear train, Bart and Tim Grönefeld have resurrected this long-neglected complication and re-positioned it where the complication originated – on the pedestal of high precision.

The stepping movement of the large second hand of the One Hertz subtly signals its unique mechanism, imperceptible to most, but obvious to haute horlogerie connoisseurs, who will appreciate the sublime, flawless fine-finishing of all 285 components of the calibre G-02 movement.

History of Dead Seconds 

With the introduction of the pendulum in the 17th century, clocks finally became accurate enough to measure seconds. It was 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 miniaturisation. As portable pocket watches became more accurate, watchmakers naturally thought to copy the one-second steps of the seconds hand which signified a precision timepiece. However, the rapidly oscillating balance meant that it could not be directly driven as with the pendulum, so it required either a new mechanism if independent, or be driven from another complication e.g. constant force device. While pocket watches have featured independent dead seconds in the past, the Grönefeld One Hertz was the first series wristwatch to feature independent dead seconds.

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.

One Hertz 

The hertz (symbol: Hz) is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. This SI unit is named after Heinrich Hertz. One Hertz simply means “one cycle per second”.

The second (SI symbol: s), sometimes abbreviated sec., is the name of a unit of time, and is the international base unit of time. To highlight the SI seconds, the One Hertz displays dead seconds with a large seconds hand in its own dial. Hours and minutes are non-SI units of time because they do not use the decimal system so are displayed separately.

Mechanical wristwatch movements often have balance frequencies of 2.5 to 5 hertz, which results in the seconds hand making tiny steps of 5 to 10 steps each second and looking like a smooth movement. The seconds hand of the One Hertz is either stationary (dead) or jumping in a full one-second increment each second.

The “One Hertz” independent dead seconds complication

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 at 3 o’clock. A power reserve indicator at the top of the dead seconds dial keeps track of the 72 hours of autonomy.

The “One Hertz Techniek” watch is a limited edition of 30 pieces.

Technical details

Model: One Hertz Techniek

Features and indications
Independent dead seconds – large dial at 7 o’clock
Hour and minutes – subdial at 2 o’clock
Power reserve indicator at 11 o’clock
Innovative Winding-Setting mechanism
Winding-Setting indicator at 3 o’clock
In-house calibre G-02

Case and dial
Case material: Grade 5 polished and brushed titanium and black DLC (Diamond Like Carbon) coating
Engraving: “Titanium”, “Limited 30 pieces” and the serial number
Screws: Stainless steel security screws
Case dimensions: 43 mm x 12.5 mm
Sapphire crystals: Top domed with antireflective treatment both sides; flat display back with antireflective treatment on both sides
Water resistance: 3atm/30m/100 feet
Crown: Titanium, black DLC coated with engraved “G” logo and push to set/wind function
Dial: Stainless steel open dial. Relief engraved, bevelled and finished by hand
Hands: Hours and minutes, large counter-poised seconds, power-reserve and setting-winding

Strap and buckle
Hand-sewn matte black, alligator leather with steel tang buckle black DLC coated (Nocturne), Grönefeld logo

Calibre G-02: Mechanical hand winding, independent dead seconds, power reserve indicator and setting mechanism indicator.
Dimensions: 34mm x 9.5 mm
No. of parts: 285
No. of jewels: 39 jewels set in gold chatons
Power reserve: 72 hours
Barrels: 2 barrels, one for the going gear train and one for the independent dead seconds mechanism. Both barrels are wound at the same speed and in the same direction
Balance wheel: 9.12 mm free sprung variable inertia balance wheel Balance frequency: 21’600 bph / 3Hz
Balance spring: Phillips terminal overcoil curve, triangle-style stud
Escapements: Swiss lever escapement and unique dead seconds escapement
Main Plate: Hand frosted and spotted black rhodium plated nickel silver
Bridges: Stainless steel hand bevelled, micro-blasted, circular grain on the top, relief engraved on micro blasted surface
Gearing: 2 independent gear trains each with their own energy sources (2 barrels)

Dead seconds mechanism: Independent mechanism, cam with 30 teeth on the going gear train on the fourth wheel, escape wheel on the fourth wheel of the independent gear train, unique double lever with 4 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

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.