Greubel Forsey Nano Foudroyante EWT – Flying Tourbillon, Foudroyante and Chronograph

While we know Greubel Forsey for oversized and rather outgoing wristwatches with at least one, but often two or even four tourbillons, their latest timepiece seems moderate, both in size and in looks. Yes… let that sink in… The press release is mostly trumpeting about saving nano joules of energy with their 10th fundamental invention, a special energy-saving foudroyante. On a very personal note, I have to say, that I find fast-rotating foudroyante hands visually annoying and distracting. So, truth be told, the 10th Fundamental Invention from Greubel Forsey started – in my inbox – with a setback. However, the case size mentioned, 37.9mm (and that coming from Greubel Forsey), made me especially curious to take a closer look and see what it’s all about.

So… a much smaller Greubel Forsey. That in itself is already big (pun intended) news. And to my surprise, it’s their very first chronograph, something that is almost not underlined in the press release! Plus, it’s their first flying tourbillon. However, after seeing so many watches with multiple tourbillons from GF, you would almost not be swept off your feet by a ‘simple’ flying tourbillon. And there is more here as we’ll see later. But again, a pleasantly sized, 37.9 mm in diameter and 10.5 mm thick, wrist chronograph from Greubel Forsey is already a serious novelty. And since the brand is not only known for adding a lot of tourbillons to their watches, they are also known for spectacular, best in class, finishing of the movements. So, altogether something that should be of interest to serious collectors – with a very serious budget.

What popped into my inbox:

Press release: 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.

… This new Fundamental Invention is the most technologically disruptive—not only for Greubel Forsey but also for the universe of mechanical watchmaking. 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.

…and the press release goes on about saving nano joules.

But let’s get back to what is behind the rather pompously named “10th Fundamental Invention”. A foudroyante is a hand that completes a full rotation in one second to display fractions of a second. The complication is usually incorporated into a chronograph to measure time intervals with greater precision and/or legibility than a sole second hand would do. But that is not the case here, as the foudroyante hand is not connected to the chronograph and cannot be stopped. So in terms of precise reading of the elapsed time very accurately, it’s useless.

Here the foudroyante hand is connected to the escapement (more details further down the article) and with its small foudroyante dial, it rotates happily in circular movements atop the flying tourbillon while constantly in a vertical orientation.

And if you allow me a small digression, interestingly early examples of a foudroyante were made by Tixier (the great-grandfather of the independent watchmaker now working together with Dominique Renaud!) circa 1850 in the Val de Travers. These were not connected to a chronograph function either, however here they served as a simple second hand. Its mechanism consisted of “simply” mounting a hand on its 4-toothed escapement wheel that was rotating once per second with its 14.400vph frequency (visualised in the drawing below).

Back to modern days and Greubel Forsey, what they have done to drive the foudroyante deserves a closer look, although not much is mentioned in the press release. The system seems to be derived from their 2017 Nano release (patent EP 3220207 A1) relating to the creation of a display mechanism for a system driving through a first toothing and comprising a second toothing; a super small gear module, to drive a display directly or indirectly. The aim of it is to allow a size reduction and therefore a reduction of inertia and energy consumption. EWT stands for Exceptional Wheel Technology, to clarify.

For the foudroyante, the idea is to apply these “nano-mechanics” directly to the escapement wheel (axis) to drive 6 jumps per second. In the instance of this new 2024 Foudroyante, the display is no longer lateral, thus visible via an opening of the case flank, through a loupe.

Instead, it uses a dedicated set of gears, a differential, to display it “dial side” – which is way more practical. An additional challenge for GF was to embed this into a flying tourbillon, creating an assembly that would be small and light enough. One may wonder if it makes sense to incorporate such an assembly in a tourbillon whose purpose is to improve precision – something that has always been a really serious topic at Greubel Forsey.

What can be the influence on the watch’s precision of this extra ‘burden’ on such a critical element of the escapement? The Tourbillon cage ends up at 142 parts! The brand reassured us that it was light enough to ensure that chronometry was not disturbed. And that they would have never moved forward if it did. After all, the whole idea of this “nano” concept is to demonstrate the capacity to miniaturize mechanisms. So, if I am not fully convinced by the Foudroyante functionality here, the complexity of this flying tourbillon and the technical feat in itself is pretty impressive.

Another feat on one of the main points of this 10th fundamental invention, as explained by the press release, is a “revolution in energy management”. The foudroyante is traditionally an energy greedy mechanism and the miniaturization performed by GF is, once again, quite impressive.

However, this same press release mentions a power reserve of only 24 hours when the chronograph is running which sounds a bit disappointing. We had to check this with the brand… And they informed us that the power reserve was actually approx. 40 hours, but mentioned in the press release is a “chronometric power reserve” – 24-hour to ensure perfect chronometric performance and they encourage users to keep their watch properly wound.

Now that we have talked about the foudroyante, I would like to say a few words about the superb chronograph itself; Greubel Forsey’s first chronograph! And again the press release has almost no information except that it’s a “manual wind flyback”. As if GF’s first chronograph is a side issue…

Greubel Forsey’s first chronograph should be big news, although the thing that triggered me was the concise size as the word “chronograph” is absent in the entire press release. The movement measures only 31mm in diameter and is therefore small enough to fit in a beautiful, moderately sized watch. The compact calibre, with 428 components, is a hand-wound column-wheel actuated flyback chronograph with a vertical clutch. The movement offers a breathtaking view of the typical top-notch Greubel-Forsey finishes; gorgeous chamfers, the finishing of the surfaces and the chatons. There are a few difficult inner angles, but nothing too complex at first sight. Maybe the chamfers on the long curves are more difficult to obtain by hand.

The case is crafted in white gold, while the bezel and caseback are crafted from tantalum. It comes on a hand-sewn non-animal material strap with a white gold folding clasp that’s engraved with the brand’s GF monogram. Limited to 11 pieces only, it is priced at CHF 465,000.

For more information, please visit Greubel-Forsey.com.