Twenty-twenty-four marks Greubel Forsey’s 20th anniversary, an occasion that the watchmaker is celebrating with its very first chronograph, the Nano Foudroyante EWT. The brand’s tenth “Fundamental Innovation” since its founding in 2004, the Nano Foudroyante EWT is a flyback chronograph with a flying tourbillon and an independent micro-scale lightning seconds, or foudroyante.

The watch marks many firsts for the brand. Aside from being Greubel Forsey’s first chronograph, it is also the brand’s first flying tourbillon – noteworthy given its longtime focus on the tourbillon. Despite its extensive history with innovative tourbillon constructions, Greubel Forsey (GF) has never created one with a flying architecture until now. 

Initial thoughts

For a watch enthusiast, GF is often regarded as the apex of mechanical watchmaking and chronometry. Although the brand’s styling can be too much, its core signature of high-end horology is unmistakable, and defined by exemplary finishing and exceptional engineering in equal measure. 

The Nano Foudroyante EWT is interesting in many respects. The combination of complications is unusual, even for GF, and feels like more of a platform to present the “nano” sized lightning seconds (that runs independently of the chronograph). The execution is typical of GF in being high quality. It is a perfect example of the brand’s trademark approach to watchmaking, both decoration and engineering-wise.

That said, it doesn’t feel like a conventional GF, being the smallest watch ever made by the brand, which is historically known for its oversized watches. In fact, the just-under-38 mm case feels almost like a vintage-inspired watch, especially with its domed “box” crystal, which can’t be said for any other GF creation. The Nano Foudroyante EWT does feel like a GF watch though, because it is still hefty and dense, despite the smaller size.

The aesthetics of the dial and case are recognisable as GF, since they employ elements found in other models. While the execution of the dial and hands are top quality as expected, the design feels a little too plain, with the dial feeling a little like a prototype design.

More broadly, the watch illustrates the deliciously novel mechanical philosophy of the brand, which can only come from the minds of  great watchmakers. A watch like this indicates a pivot for the brand, which seems to be moving away from its focus on sports watches and back to high-end horology, indicating that GF has finally got back its bearings.

The Nano Foudroyante EWT is also typical GF in another respective – it is expensive. With a retail price of almost half a million Swiss francs, it is amongst the most expensive watches of this type on the market, even taking into account the complications and quality.

Why make something so over-engineered and expensive that is not all that useful in itself? The answer likely lies in the fact that the Nano Foudroyante EWT is less a product for the catalogue but a proof of concept for the micro-gear mechanism, which may be extended to the going train or regulator, making way for exceptionally energy efficient movements with ultra-long power reserves.

Micro- to nano-mechanical

EWT is short for Experimental Watch Technology, a research and development programme inside GF seeking to reinvent familiar watchmaking concepts and mechanisms. 

One of its earlier endeavours was miniaturising components to an almost nano scale, with the goal of reducing energy consumption. The first prototype with a “nano” foudroyante hand was presented in 2017. Traditionally a foudroyante hand — which travels at a rapid one revolution per second — is geared to the escape wheel and ends up consuming a large quantity of the mainspring’s energy, resulting in an impractically short power reserve.

EWT scaled down the components of the foudroyante, reducing its energy consumption. That said, the components are still large enough to be handled by tweezers. “Nano” refers rather to the energy consumption, rather than actual nanotechnology, which sits at another scale entirely, with measurements in billionths of a metre.

Composed of parts made via LIGA lithography, the micro-mechanical system that debuted in 2017 has now been implemented in the Nano Foudroyante EWT. Since the balance runs at 3 Hz, the escapement unlocks the escape wheel twice per oscillation, which means the escape wheel travels forwards by six steps a seconds. This means the lightning seconds hand races forward six times a second, completing a full revolution.

But the micro-scale of EWT means a reduction in energy consumption by a factor of 1,800. The nano-foudroyante system only consumes 1.6 nanojoules per tick. And though it is not actual nanotechnology, the foudroyante is tiny, occupying 90% less volume than a conventional lightning seconds mechanism.

Though the foudroyante in the Nano Foudroyante EWT runs constantly, it consumes negligible amounts of energy, meaning it has no impact on chronometry. With the chronograph running and the foudroyante hand speeding around the dial, the watch has a short 24 hours of “chronometric” power reserve, meaning it stays stable and within chronometer specifications. Considering the experimental nature of the Nano Foudroyante EWT, the single-day power reserve is acceptable, but it will presumably be lengthened with further development of the concept.

A bundle of complications

Nano Foudroyante EWT might be misleading: the watch is much more than just the tiny lightning seconds. Packaged in the small, 37.9 mm case – almost tiny by GF standards – is an integrated chronograph movement with a flying tourbillon regulator that also carries the foudroyante on its cage.

The presentation is certainly restrained. The case is simple in shape, but finished well. The case middle is white gold while the bezel and back are tantalum.

Aside from the compact case, the dial is a sombre silver with simple markings. The typical GF typeface and hands are present, along with the asymmetric layout characteristic of the brand. 

Given the small diameter of the dial, the flying tourbillon dominates with its large cutout located in between five and six o’clock. The tourbillon doesn’t resemble a conventional tourbillon, since neither the free-sprung balance nor the cage are prominent.

Instead, taking centerstage is the sub-dial for the foudroyante, which is actually mounted on the tourbillon cage, above the balance. The lightning seconds hand completes one revolution a second, while the lightning seconds sub-dial is making one revolution a minute along with the tourbillon cage. While this double-axis rotation is happening, the seconds sub-dial maintains its vertical orientation relative to the rest of the dial, creating the optical effect of a floating register.

The vertical orientation of the sub-dial is accomplished by a differential gearing that keeps it in the same relative position. The level of mechanical mastery required to implement this on a flying tourbillon cage can’t be overstated. Unsurprisingly, the tourbillon assembly comprises of a staggering 142 pieces, equivalent to an entire simple time-only movement.

While the tourbillon-foudroyante is the most novel element of the movement, it also incorporates a flyback chronograph. In its 20 years, GF has launched double and quadruple tourbillons, a perpetual calendar, and even a grande sonnerie, but never a chronograph. Given GF’s repertoire, it is perhaps no surprise that the brand’s first chronograph is unorthodox.

Examining the movement from the back side results in momentary confusion.

A large, open-worked bridge finished with frosting seems like a horizontal clutch arm at first glance. Some levers and a column wheel are visible, but the architecture doesn’t adhere to the classic chronograph architecture in any discernible way. The column wheel appears to sit isolated, while the visible steel levers seem to have familiar shapes and undefined functions. 

Many traditional chronograph components, including the reset hammers and clutch, are not apparent. Much of the chronograph works seem concealed, enhancing the mystery.

According to GF, the movement employs a special type of vertical clutch incorporating a patented device to eliminate gear play. Not much else was disclosed, so the exact nature of the vertical clutch remains unknown for now.

Even the arrangement of the pushers is unconventional. The button at two o’clock starts and stops the chronograph, while the pusher co-axial with the crown is for reset and flyback – the inverse of the traditional configuration of chronographs.

Construction aside, the movement is classic GF style in terms of finishing.

All of the brand’s favourite decorative techniques are employed, including black polishing for the steel levers and bridges, and a granular frosting on the open-worked bridge that’s also finished with wide, rounded bevelling. Every jewel on the open-worked bridge sits in its own gold setting.

A subtle reference to GF’s past work is the micro relief engraving on the chronograph seconds wheel, one of the handful of instances that GF has put this on a moving part instead of the case or bridge.

Although atypical and ambiguous, the movement architecture is deeply layered. Combined with the lustrous finishing, the result is a deeply appealing, intricate mechanical landscape.

Key facts and price 

Greubel Forsey Nano Foudroyante EWT

Diameter: 37.9 mm
Height: 10.49 mm
Material: White gold and tantalum
Crystal: Sapphire
Water resistance: 30 m

Movement: In-house flyback chronograph movement with one minute flying tourbillon
Functions: Hour, minutes,  small seconds, flyback chronograph, foudroyante, and flying tourbillon
Winding: Manual winding
Frequency: 21,600 beats per hours (3 Hz)
Power reserve: 24 hours with the chronograph running

Strap: Textile strap with white gold GF buckle

Limited edition: 11 pieces
Availability: Fom the Greubel Forsey and retailers
Price: CHF465,000 before tax

For more information, visit greubelforsey.com.

Addition November 2, 2024: Amended the text to make clear the lightning seconds is independent of the chronograph and constantly running.