GREUBEL FORSEY – Nano Foudroyante Tourbillon Chronograph White Gold Edition

GREUBEL FORSEY – Nano Foudroyante Tourbillon Chronograph White Gold 37,9 mm Limited Edition 2025

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WE ARE BACK WITH A PARADIGM-SHIFTING CREATION.

Greubel Forsey unveils the first official limited edition of its Nano Foudroyante: a breakthrough timepiece born from years of research, now matured beyond its Experimental Watch Technology (EWT) origins.

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Limited to just 22 timepieces, this creation marks a significant new chapter in Greubel Forsey's 10th Fundamental Invention.

FROM PROTOTYPE TO TIMEPIECE

Originally presented in 2024 as a commemorative EWT edition, the Nano Foudroyante was Greubel Forsey’s most technically radical concept to date. Today, it has evolved into a fully realized and independent creation – no longer tethered to an anniversary or prototype designation.

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The new Nano Foudroyante is crafted entirely in white gold, replacing the original combination of white gold and tantalum. It presents a different architectural identity: the gold dial is now finished in rhodium with a blue minute track, while the hands are rendered in blued steel with matching cannon pinions. 

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The foudroyante dial itself is now white with transferred numerals, enhancing legibility and echoing the crisp visual language of the tourbillon aperture. A blue textured rubber strap completes the aesthetic – a clear evolution from the original edition, and a declaration of this timepiece’s own distinct personality.

NANOMECHANICS: REINVENTING THE POSSIBLE

At the heart of this timepiece lies a disruptive idea: nanomechanics – the control of energy at the nanojoule scale inside a mechanical movement. This paradigm shift enables the Nano Foudroyante to operate its eponymous complication using just 16 nanojoules per jump, compared to 30 microjoules in traditional designs – a staggering reduction by a factor of 1,800.

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The complication divides each second into six segments using a lightweight, red-treated hand that rotates once per second, driven directly by the oscillations of the 3Hz balance wheel. There is no traditional gear train; instead, a minimalist series of low-inertia wheels efficiently distributes energy through the movement.

A COMPACT AND REFINED ARCHITECTURE

The Nano Foudroyante mechanism is embedded within Greubel Forsey’s first flying tourbillon, creating a visual and technical centerpiece. The foudroyante’s dial remains permanently oriented to twelve o’clock, even as the tourbillon rotates – ensuring optimal readability.

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The timepiece features a hand-wound flyback with 2 patents, totaling 428 components (including 142 for the tourbillon cage). Despite this complexity, the movement measures just 31.60mm in diameter and fits within a 37.90mm white gold case – Greubel Forsey’s most compact ever.

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The case is fitted with a high-domed sapphire crystal, straight-grained finishing on the caseband, and a transparent caseback. Subtle engravings – “Nano Foudroyante” and “Greubel Forsey” – stand out in polished relief over a hand-hammered background.

A NEW CHAPTER, FULLY REALISED

This timepiece embodies maturity and intent, created for 22 collectors who will experience Greubel Forsey’s most energy-efficient, compact, and conceptually advanced timepiece to date.

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 TECHNICAL DETAILS  

 Model:  Nano Foudroyante Tourbillon Chronograph White Gold

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Nano Foudroyante
In white gold
Limited Edition
Hand-wound chronograph movement with 2 patents

• Flying tourbillon with Nano Foudroyante • hours and minutes • small seconds
• 60-second tourbillon rotation • chronograph seconds (trotteuse)
• 60-minute counter • flyback function  

MOVEMENT

MOVEMENT DIMENSIONS
• Diameter: 31.60mm
• Thickness: 9.40mm
NUMBER OF PARTS
• Movement: 428 parts
• Tourbillon cage: 142 parts
• Weight of the cage: 0.835g
NUMBER OF JEWELS • 53
• Olived-domed jewels in gold chatons
CHRONOMETRIC POWER RESERVE
• One full day, with chronograph engaged
BARRELS
• Fast rotating barrel (1 turn in 3.7 hours) with a fixed main spring bridle
BALANCE WHEEL
• Variable-inertia with gold mean-time screws (10mm diameter)
FREQUENCY • 21’600 vibrations/hour
BALANCE SPRING
• Phillips terminal curve
• Geneva-style stud
BRIDGES AND MAIN PLATES
• Nickel silver, frosted and spotted with polished bevelling and countersinks, straight-grained flanks, nickel-palladium treatment
• Straight-grained and flat black polished steel chronograph mechanism, polished bevelling, straight-grained flanks
• Three-dimensional column wheel, frosted and circular-grained, polished columns
• Central seconds wheel, circular-grained, polished bevelling with relief-engraved texts
• Gold plate, circular-grained, with engraved limitation number
TOURBILLON
• Flying Tourbillon with embedded Nano Foudroyante mechanism
• Foudroyante dial, constant vertical indication
• Titanium cage bridges, polished bevelling, straight-grained flanks, with engraved GF logo
• Platinum counterweight
GEARING
• Involute circle profile
• Micro-module with reduced play
DISPLAYS
• Hours and minutes
• Small seconds
• 60-second tourbillon rotation
• Foudroyante, sixth of a second
CHRONOGRAPH
• 60-second flange
• 60-minute counter, semi-instantaneous

EXTERIOR 

CASE

• In white gold with high domed synthetic sapphire crystal
• Hand-polished bezel, caseband with hand-finished straight-graining
• Transparent back with high domed synthetic sapphire crystal
• Raised polished engraving “Nano Foudroyante” and “Greubel Forsey” on a hand-punched background
• Gold security screws
DIMENSIONS
• Caseband diameter: 37.90mm
• Bezel diameter: 38.30mm
• Case height: 10.49mm
• Height on synthetic sapphire crystals: 14.34mm
WATER RESISTANCE OF THE CASE • Water-resistant 3atm - 30m - 100ft
(standard NIHS 92-20/SN ISO 22810:2010)
CROWN AND PUSHERS
• Crown with pusher, in white gold, engraved GF logo
• Pusher in white gold, hand-polished

DIAL

• Multi-level in gold, rhodium-coloured, minute-circle with blue finish,
small seconds and chronograph minutes counter with polished bevel,
engraved and lacquered indications, with a visual opening for the tourbillon
• Foudroyante in light alloy, polished bevel with flat black polished central plate.
HANDS
• Hours and minutes in polished blued steel with Super-LumiNova, hand-polished countersink, flat black polished head
• Small seconds and chronograph hands in polished blued steel, hand-polished countersink, flat black polished head
• Tourbillon and Foudroyante in light alloy, red treatment

STRAP AND CLASP

• Hand-sewn textured rubber
• White gold pin buckle, hand-engraved GF logo

🔰 Limitation 
Limited Edition ✅ Only ❱❱❱ 22 pieces.

🔴 Price  CHF 465'000 (excl. taxes)💰

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Press Release - 2025
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GREUBEL FORSEY SA
For further information: 
Communication Department 
press@greubelforsey.com – +41 79 194 2884
Eplatures-Grise -16 P.O. Box 670 
2301 La Chaux-de-Fonds - Switzerland
+41 32 925-4545
+41 32 925-4502
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GREUBEL FORSEY – Nano Foudroyante EWT Edition

GREUBEL FORSEY – Nano Foudroyante EWT Tourbillon Tantalum / White Gold 37,9 mm 20th Anniversary Limited Edition 2024

 GREUBEL FORSEY UNVEILS ITS 10TH FUNDAMENTAL INVENTION

To celebrate the 20th anniversary (2004-2024), Greubel Forsey presents its 10th Fundamental Invention: the Nano Foudroyante EWT. The mechanism’s energy is managed at the nanojoule scale, significantly reducing the number of components and the overall dimensions. 

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The result is a 37.9 mm timepiece that combines the world’s first perpetual Nano Foudroyante with Greubel Forsey’s first flying tourbillon and manual wind flyback. This timepiece, set in a white gold and tantalum case, will be limited to just 11 pieces.

LEGACY OF INNOVATION

The first Fundamental Invention by Robert Greubel and Stephen Forsey was launched in 2004, marking the Atelier’s commitment to research and invention. For over 20 years, this focus has been at the heart of all Greubel Forsey’s Fundamental Inventions and timepieces. Today, Greubel Forsey’s research is even more fundamental, aiming to completely rethink the approach to the conception of a timepiece. This endeavor demonstrates a major technological leap, comparable to the transition from tower clocks to wristwatches.

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Originally, horological instruments were large and public. Over time, they became transportable (table clocks, marine chronometers), then portable with pocket watches, and finally wearable with wristwatches. This evolution reaches its peak today with nanomechanics — a revolution Greubel Forsey is pioneering. 

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Thus, Greubel Forsey introduces its 10th invention: the Nano Foudroyante. This new Fundamental Invention is the most technologically disruptive — not only for Greubel Forsey but also for the universe of mechanical watchmaking.

NANOMECHANICS: A NEW HORIZON

What is nanomechanics? It is a realm beyond the miniaturization of components to the nanometric scale. When we talk about nanomechanics, we’re talking about controlling energy on a nanojoule scale within a mechanical movement. 

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This revolution in energy management within a caliber allows for a drastic reduction in both energy consumption and the number of components.

A REVOLUTIONIZED MECHANISM

To demonstrate the feasibility of nanomechanics, Greubel Forsey has reinvented the foudroyante second. Its hand completes one revolution per second, dividing it into segments according to the movement’s frequency. In this Nano Foudroyante, each oscillation of the 3 Hz balance wheel produces two beats, totaling six beats per second, allowing the hand to divide the second into six distinct segments. This is an energy-intensive complication by nature. 

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However, by managing energy on a nanojoule scale, Greubel Forsey has radically rethought its design and construction. Compared to a traditional foudroyante that consumes 30 μJ (microjoules) per jump, the Nano Foudroyante operates with only 16 nJ (nanojoules) per jump, reducing energy consumption by a factor of 1,800. 

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The mechanism’s volume is therefore reduced by 90%. Here, the focus is not just on measuring fractions of a second but as a proof of concept for a completely new approach to watchmaking, which is why this Nano Foudroyante was chosen to be a perpetual display.

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It eliminates the entire gear train required in a traditional foudroyante to divide the second, as the information is sourced directly, distributing and managing the energy from the movement through a minimal number of low-inertia wheels. 

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Fewer components mean less volume: this Nano Foudroyante EWT is very compact, with 428 components, and the movement measures no more than 31 mm in diameter within a 37.9 mm case (the smallest ever built by Greubel Forsey).

HOROLOGY AT ITS PEAK

There’s more: true to Greubel Forsey’s passion for the tourbillon, this Nano Foudroyante is integrated within a flying tourbillon — the first ever made by Greubel Forsey. Finally, an additional innovation: although this flying tourbillon rotates constantly, the Nano Foudroyante’s dial remains permanently aligned towards twelve o’clock for optimal readability.

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Together with the flyback, these three features complete Greubel Forsey's 10th Fundamental Invention: a Nano Foudroyante, set within a flying tourbillon, with an oriented reading axis.

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This is just the foundation and not the end result: this 10th Invention is powered by a manual-winding flyback movement. This complication presented by Greubel Forsey, includes column-wheel control within the strong architectural design and exceptional finishing, a signature of Greubel Forsey.

A LIMITED EDITION MASTERPIECE

The timepiece will be made in a limited edition of just 11 pieces in this inaugural, refined version, emphasizing its disruptive technical character and highlighting the personality of a timepiece brilliantly conceived in the EWT (Experimental Watch Technology) laboratory.

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The white gold case offers an additional surprise, with a bezel and back crafted from tantalum — a first for Greubel Forsey, who have never used this material before. Known for its gray-blue sheen and complexity in machining and finishing (with a melting point above 3000°C), tantalum requires rare expertise. 

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The Atelier also preserves its essential aesthetic signatures, including polished relief engravings of “Nano Foudroyante” and “Greubel Forsey” on a hand-hammered background, hand-satin-finished white gold, and a highly architectural movement. This masterpiece displays the movement around its column wheel with rare 3D monobloc geometry, visible through the back. 

The timepiece is engraved with “2004 – 2024” and “20th Anniversary” to mark this milestone.

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 TECHNICAL DETAILS 

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Nano Foudroyante EWT
In white gold and tantalum
Hand-wound movement with 2 patents

MOVEMENT

NUMBER OF PARTS
• Movement: 428 parts
• Tourbillon cage: 142 parts
NUMBER OF JEWELS
• 42
• Olived-domed jewels in gold chatons
CHRONOMETRIC POWER RESERVE
• One full day, with chronograph engaged
FREQUENCY • 21’600 vibrations/hour
TOURBILLON
• Flying Tourbillon with embedded Nano Foudroyante mechanism
• Foudroyante dial, constant vertical indication
• Titanium cage bridges, circlar-grained, polished bevelling, straight-grained flands with engraved GF logo
• Platinum counterweight

EXTERIOR 

CASE
• Tantalum and white gold with high domed synthetic sapphire crystal
• Tantalum hand-polished bezel, transparent tantalum back
• White gold caseband with hand-finished straight-graining
CASE DIMENSIONS
• Diameter: 37,90mm
• Height: 10,49mm
WATER RESISTANCE OF THE CASE
• Water-resistant 3atm - 30m - 100ft (standard NIHS 92-20/SN ISO 22810:2010)
DIAL SIDE
• Multi-level in gold, rhodium-coloured, engraved and black lacquered hour-ring and minute-circle with a visual opening for the tourbillon
• Small seconds and chronograph minutes counter in gold, polished bevel
• Foudroyante, frosted, fractions of seconds engraved and black lacquered
STRAP AND CLASP
• Non-animal material, hand-sewn
• White gold pin buckle, hand-engraved GF logo

🔰 Limitation 
Limited Edition ✅ Only ❱❱❱ 11 pieces.

🔴 Price on Request 💰

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Press Release - 2024
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GREUBEL FORSEY SA
For further information: 
Communication Department 
press@greubelforsey.com – +41 79 194 2884
Eplatures-Grise -16 P.O. Box 670 
2301 La Chaux-de-Fonds - Switzerland
+41 32 925-4545
+41 32 925-4502
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GREUBEL FORSEY – Mechanical Nano Foudroyante EWT

GREUBEL FORSEY – Major Projects Mechanical Nano Foudroyante EWT – Unique Piece

The First Nano Foudroyante EWT

Mechanical Nano – Episode 2: Following intense research on the mastery of nano-energy within the context of our Mechanical Nano project, Greubel Forsey announces a new breakthrough in mechanical watchmaking and presents the first Nano Foudroyante EWT.

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Mechanical Nano applied to the foudroyant jumping seconds.

• LESS ENERGY USED – a reduction in the amount of energy consumed by a factor of 1,800
• LESS SPACE USED – 96% less compared to a conventional mechanism
• RENEWED INVENTIVENESS – example: patent filing No.: EP 3220207 A1

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From tower clocks to wristwatches, the history of clock and watch-making over the past four centuries chronicles the ever-increasing miniaturisation of mechanisms. Up until now, the power needed to drive a wristwatch mechanism has been a limiting factor in terms of design and innovation.

Greubel Forsey’s fundamental work on Mechanical Nano, based on the mastery of energy and available space, is once again confirmed and now applied in a watch mechanism. In the process of developing the 180-day power reserve movement, the decision was taken to apply Mechanical Nano to the foudroyant jumping seconds mechanism. This watchmaking complication consists of a hand that makes one rotation every second to indicate the fractions of a second.

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For over ten years, Greubel Forsey’s EWT (Experimental Watch Technology) Laboratory has been working to push the boundaries of mechanical watchmaking and has had particular success in the domain of the Mechanical Nano project. Thanks to this totally new concept and following the recent application of patent No. EP 3220207 A1, Greubel Forsey is unveiling the first Nano Foudroyante EWT.

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The innovative mechanism of the Nano Foudroyante EWT

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Mechanical Nano has led Robert Greubel and Stephen Forsey, as well as the engineers and designers at Greubel Forsey, to completely rethink the mechanism of the traditional foudroyant jumping seconds. This new construction consists, first of all, of a mobile (a) with a very low moment of inertia, which takes its information directly from the escape wheel (b). This principle means that a full gear train is no longer needed to ensure the sub-division of seconds (c), since the information is obtained from the wheel, which distributes and gives the rhythm to the energy of the movement. Energy consumption can now be expressed in nanojoules (nJ).

The first Mechanical Nano watchmaking application

This first application focuses on the reduction of inertia and on the energy savings it made possible. The display of the Nano Foudroyante EWT is by a miniature hand. This is made clearer to read by an optical system with 23x magnification.

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Practical EWT Laboratory tests confirm the theory and calculations, corroborating the studies on the savings of energy and space. On the basis of this first demonstrator there are a number of different innovative possibilities that will enable further optimisation of energy.

The results

Compared to a traditional foudroyant jumping seconds mechanism, the Greubel Forsey Nano Foudroyante EWT consumes 1,800 times less energy and occupies 96% less space. All of this research has made it possible to create a truly original and innovative foudroyant jumping seconds mechanism that makes best use of energy and available space in the movement of a mechanical timepiece.

Backed by their EWT (Experimental Watch Technology) lab, they became involved with these questions early on by developing new concepts. They already have the beginnings of a solution to one of the main constraints of mechanical watchmaking: available space and the consumption of energy.

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“Mechanical Nano” has ushered in a new era of watch-making engineering, rich in extraordinary perspectives. This new approach is based on the consumption of energy on the scale of the nanojoule (nJ), with the aim of creating new watch mechanisms. It will allow for:

• ƒ a considerable reduction in the energy consumed
• ƒ an increase in the number of complications in the same space

Mastering nano energy (Problem)

In order to master and reduce energy on a nanometric level, two possibilities were explored:

•  reducing the inertia of the components
•  reducing friction

Practical application

After intensive research on inertia and friction, Greubel Forsey filed landmark patents and decided to apply this approach to a practical case study: the watchmaking mech-anism of jumping foudroyant seconds.

Fig. 1 : Système de foudroyante classique.

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Presentation of the classic jumping foudroyant seconds system

In order to display the instants that divide seconds into fractions of seconds depending on the frequency of the balance wheel, it is essential to incorporate, along with the going train, a second gear train dedicated to the jumping seconds system. This second gear train starts from a second main-
spring barrel and synchronises at the level of the escape wheel intermittently, in order to divide seconds into equal parts, thereby offering a clearer reading of the passing seconds.

Presentation of the innovative jumping foudroyant seconds system

The goal is to reduce energy needs by creating a new jumping foudroyant seconds system with low energy consumption, within the scale of nanojoules. Research on reducing energy consumption focused on two possibilities: the reduction of both inertia and of friction. This research completely revolutionises the approach to making watches and has led to a complete rethinking of watchmaking mechanics.

Fig. 4 : Démonstrateur P1 – Nano-foudroyante.

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As this system consumes energy at a nanometric scale, it is possible to imagine creating a timepiece where the jumping foudroyant seconds is connected directly to the escape wheel.
First, it was decided to minimise the influence of the dis-play on this demonstrator, named P1. Indeed, this demon-strator focuses on the energy aspect and on the energy sav-ings that follow from it.

First experiment with the nano-foudroyant jumping seconds: demonstrator P1

The nanoenergy approach led to completely rethinking the jumping seconds mechanism.

Fig. 9 : Démonstrateur P2.

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This new creation consists, first of all, of a mobile with a very low moment of inertia, which takes its information from the escape wheel. This principle means that a full gear train is no longer needed to ensure the division of seconds, since the information is obtained directly from the escape wheel, which distributes and gives the rhythm to the energy distri-bution of the movement.

Second experiment with the nano-foudroyant jumping seconds: demonstrator P2

After validating the work on the reduction of inertia in the making of the first demonstrator, P1, it was neces-sary to work on the reduction of friction by making a sec-ond demonstrator, P2, one that was both functional and equipped with a nano-foudroyant jumping seconds system with a normal-sized display.

In the second demonstrator, P2, all the parameters were optimised in order to compensate for the greater inertia of the hand and of the escape wheel. This concerns, in particu-lar, the application of the patented GF Diamond Pivot system (US 2011/0044141 A1), (demonstrator P1 made use of traditional pivot system).

Fig. 8 : Démonstrateur P1

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Diamond pivot systems can have a friction coefficient of 0.03, as opposed to 0.1 for steel and ruby pivot organs. They make it possible to avoid the use of lubrication and thereby eliminate viscous frictional torque.

Calculating the reduction of inertia: demonstrator P2

The escape wheel has a moment of inertia of  J r 3 = 5.53 mg mm 2 .
The moment of inertia of the hand with its pinion is J a = 292 µg mm 2 . With a gear ratio of  r = 60 / 9, the moment of inertia experienced by the escape wheel is

The initial torque of the mainspring barrel is 460 g mm. In order to keep the same amplitude with the nano-foudroyant jumping seconds system, the empirical relationship gives the relative variation of torque:

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Fig. 6 : Démonstrateur P1 – Loupe.

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The torque of the mainspring barrel should thus rise to 464 g mm. By remaining with a torque of 460 g mm, the amplitude will diminish by just 1.2° (which does not influence the timekeeping of the movement). This loss of amplitude corresponds to a consumption of 5 nJ per vibration. This confirms the optimisation of the mechanism, which largely compensates for the inertia of the display.

For demonstrator P2, the gear between the pinion and the wheel no longer has a spring, initially planned for avoid-ing floating of the hand. By eliminating tension between the pinion and the wheel, demonstrator P2 will consume less energy. The difference in energy reduction between the two demonstrators is 3.5x.

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Fig. 7 : Démonstrateur P1.

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5 nJ per jump, 6,000 times less. This nano mechanism occupies 25 times less space than a traditional mechanism.
All of this research makes it possible to create a new foudroyant jumping seconds mechanism that makes best use of energy consumption and available space in the move-ment of a mechanical timepiece. This new design of the functions does not in any way compromise the timekeeping.

This first practical application confirms the concept and demonstrates that the potential for development is enor-mous. We stand on the threshold of a new era, that of the “Mechanical Nano”.

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The Future

Having initiated the project over a decade ago, research and development on a movement with a 180-day power reserve is still going strong.

The Nano Foudroyante à Affichage, a new project Following validation of the reduction of inertia with this demonstrator, Greubel Forsey’s EWT Laboratory is currently working on validating a Nano Foudroyante based on the same fundamental principles, where the foudroyant jumping seconds is displayed on a standard size subdial: the Nano Foudroyante à Affichage. The practical results obtained from this research will be featured in an upcoming publication. Sharing is a value that is dear to both Robert Greubel and Stephen Forsey. To that end, progress on Mechanical Nano research will be made public at regular intervals.

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GREUBEL FORSEY SA
For further information: 
Communication Department 
press@greubelforsey.com – +41 79 194 2884
Eplatures-Grise -16 P.O. Box 670 
2301 La Chaux-de-Fonds - Switzerland
+41 32 925-4545
+41 32 925-4502
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