A foudroyante is an indication displaying fractions of a second. A foudroyante is also known as ‘flying seconds’ and is usually displayed as a one-second (chronograph) counter rotating 360° in one second and stopping at the fraction of a second when the chronograph is stopped.

The foudroyante hand is visually spectacular as it is running faster than the eye can follow – foudroyante is French for lightning fast!

The foudroyante indication of the Nano Foudroyante EWT runs constantly from the tourbillon and is independent of the chronograph.

While following fractions of a second might be useful for some, the downside of a foudroyante is that it uses a lot of a mechanical watches’ precious energy to rotate a hand every second.

Greubel Forsey has solved the energy problem with the Nano Foudroyante EWT.

Greubel Forsey Nano Foudroyante EWT on the wrist

Note that in naming this model, Greubel Forsey uses the term ‘Nano’ as referring to the mechanism’s tiny energy consumption rather than nanotechnology, which is measured to one 100 millionth of a millimeter.

The foudroyante nano indication rotates 360° every second in 6 steps (3 Hz balance frequency). But it reduces energy consumption compared to a standard foudroyante mechanism by 1,800 times – moving the hand requires just 1.6 nanojoules per tick. One watt is one joule per second, so a nanojoule is just one billionth of a watt per second.

Greubel Forsey Nano Foudroyante EWT: monopusher chronograph with flying tourbillon and foudroyante seconds

From the press release:

Greubel Forsey’s 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.

The result is a 37.9mm 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.

Greubel Forsey Nano Foudroyante EWT: monopusher chronograph with flying tourbillon and foudroyante seconds

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.

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.

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.

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

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 3Hz 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. However, by managing energy on a nanojoule scale, Greubel Forsey has radically rethought its design and construction. Compared to a traditional foudroyante that consumes 30μJ (microjoules) per jump, the Nano Foudroyante operates with only 16nJ (nanojoules) per jump, reducing energy consumption by a factor of 1,800.

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.

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.

Fewer components mean less volume: this Nano Foudroyante EWT is very compact, with 428 com­ponents, and the movement measures no more than 31mm in diameter within a 37.9mm 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.

Greubel Forsey Nano Foudroyante EWT: monopusher chronograph with flying tourbillon and foudroyante seconds

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.

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.

Greubel Forsey Nano Foudroyante EWT on the wrist

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.

Greubel Forsey Nano Foudroyante EWT: monopusher chronograph with flying tourbillon and foudroyante seconds

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.

Movement of the Greubel Forsey Nano Foudroyante EWT

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.

Movement of the Greubel Forsey Nano Foudroyante EWT

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.

Greubel Forsey Nano Foudroyante EWT on the wrist

For more information, please visit https://greubelforsey.com/en/watches/nano-foudroyante

Quick facts: Nano Foudroyante EWT
Patents: 2
Movement:
Number of components: movement 428 components, tourbillon cage 142 components
Number of jewels: 42, olive-domed jewels in gold chatons
Power reserve (chronometric): one full day with chronograph engaged
Frequency: 3 Hz, 21’600 vibrations/hour
Tourbillon: Flying tourbillon with embedded Nano Foudroyante mechanism, titanium cage bridges
Foudroyante dial: constant vertical indication
Finishing: circular-grained, polished beveling, straight-grained flanks with engraved GF logo
Counter weight: platinum counterweight
Case:
Material: tantalum and white gold with high domed synthetic sapphire crystal, white gold caseband with hand-finished straight-graining
Bezel: tantalum hand-polished bezel, transparent tantalum back
Dimensions:  37.9 mm diameter x 10.49 mm high
Water resistance: 30m – 100ft  (standard NIHS 92-20/SN ISO 22810:2010)
Dial side: multi-level in gold, rhodium-colored, engraved and black lacquered hour-ring and minute-circle with a visual opening for the tourbillon
Indications: central hours, minutes and seconds, chronograph seconds and minutes counters in gold with polished bevels
Foudroyante: frosted, fractions of seconds engraved and black lacquered
Strap/clasp:  Non-animal material, hand-sewn, white gold pin buckle, hand-engraved GF logo
Limitation: 11 pieces
Price: 465,000- Swiss francs

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