Horological Meandering

Since more than one decade, Greubel Forsey is investing in research aimed at developing a mechanical watch movement with 180 days of power reserve. For this aim, the brand set up the EWT (Experimental Watch Technology) Laboratory and implemented the Mechanical Nano project to address the two major constraints that need to be mastered: energy and space.

Today, Greubel Forsey presented Episode 2 as a major breakthrough of the Mechanical Nano project (I wrote about this before, click here ), the Nano Foudroyante EWT, a concept study that for the first time test ever, produced results obtained from a practical watch:



For introduction, a Foudroyante (or flying seconds) mechanism is a jumping seconds indicator which divides a second in several equal partitions, usually four, five, even eight times to indicate quarters, fifths or eighths of a second.

Greubel Forsey started from scratch with a complete rethink of the mechanism so that it effectively only consists of three sections.





This new construction consists, first of all, of a mobile with a double conical-toothed wheel (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):





The last aspect becomes immediately clear if one compares the construction (bottom) to a classical Foudroyante train (top):





By making use of novel state-of-the-art production techniques and a new conceptual approach to the mechanism, both complexity but also size could be tremendously reduced:





It comes as no surprise, really, that the current implementation has one drawback: it is extremely small, too small to read. The Foudroyante hand, for example is only 1.4mm long.

Greubel Forsey thus embedded a 23x loupe on the side of the case to allow appreciating it...easier:





I put together a small video showing the Foudryante hand in action:



So, what are the results of this experimental watch? Quite significant, I might say, after reading through the study* published:

As mentioned above, the currently implementation focuses on the reduction of inertia of the Foudroyante mechanism by simplifying and miniaturising the mechanism.

As the latter is directly coupled to the escape wheel, the additional inertia is easily calculated:

• (a) inertia of a classical escape wheel train
• (b) inertia after addition of the double conical-toothed wheel
• (c) inertia of the foudroyante display (arbor, pinion, hand)
• (d) inertia of the total system as experienced by the escape wheel (r=gear ratio between conical wheel and conical pinion; r=5)
• (e) relative inertia between a classical gear train and the Nano Foudroyante-added geartrain

As you can see, the differences are minimal and thus only claim a marginal cost in terms of energy usage. Just to give you an idea, the relative variation of torque on the mainspring barrel is directly dependent on the  differences in inertia:


(a=0.1025; c=1; both experimental values determined by EWT Lab)

In other words, to maintain a constant amplitude of the balance, only little additional torque is needed. If calculated further, the total loss of amplitude caused by addition of the Nano Foudroyante EWT is only 6°, while the total additonal energy consumed by the system is just 16 nanojules (nJ) per jump.

By way of comparison, a classical foudroyant seconds system consumes 30 microjoules (μJ) per jump.

In other words, the Nano Foudroyante EWT requires 1800x less energy and 96% less space!



But this does not stop here: Greubel Forsey's EWT lab is currently working on an improved version which:

(i) displays the Foudroyante seconds on the dial plane and

(ii) further reduces energy needs down to 5 nJ per vibration, resulting in only 1.2° reduction in amplitude!

For this, the patented GF Diamond Pivot system (US 2011/0044141 A1) will be implemented.

Of course, Greubel Forsey did not set out to produce a high-efficiency Foudroyante system. The overall goal is to revolutionise energy usage and space requirements of a movement, eventually enabling a wristwatch with half-a-year autonomy. The Foudroyante is just an intermediary step to prove their results in a practical application.

Impressive, impressive! Greubel Forsey is on an exciting path, and I am happy to be in-the-loop, as the progress unfolds.

Stay tuned!

Cheers,
Magnus
_____
*)

See: C Zwahlen, F Corneille, F Deschanel: Mechanical Nano. Bulletin Société Suisse de Chronométrie No. 84 (December 2017), p.23ff

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The GF EWT Lab announced their Mechanical Nano project a while ago and awaked many questions.
As we see in their Episode 2 documents the advantages are those we expected, reduction of weight and thus inertia and friction.
It would be more interesting to see how they fabricated and assembled those parts, 'though.
As we see they need a magnification of 23 times to be able to view that foudroyante hand.
Making that angled spurr gear on the escape wheel with the needed tolerances and surface quality...  I want to know how they do it.

But my needling want for more information does not make the advances that GF is making in this project any less.  Congratulations!
Don

 
Gruebel Forsey press release:

in these pictures the additional drive wheel and conical gear look like plastic, but I very much doubt they are. Guessing LIGA style build with clear silicon, or maybe even glass??
Tim

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Between the Zenith Defy Lab and the GF Nano concepts, we really enter in a new horology era.

But, beyond technology and more specifically in the case of GF, I would like to know (and see) how they will manage these reduced mouvements?

In other words, how they will embellish their watches knowing that today’s collectors have been used to see mouvements? If you have almost “nothing” to show from a caliber point of view, could it be the solid case back come back? 😊

I’m really impatient to see a final product.

Best wishes

Alkiro

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Best wishes

Alkiro

Do you think the Nano fouydroyante makes any difference here.  Surely leaving the 1/8 seconds off completely would use even less energy.  The main hands are still I assume (!) driven by gears as normal.

I am also guessing for the 180 day PR that virtually all the rest of the watch is mainspring?

A brilliant way of creating the 1/8th jumping second though.  The bearing surfaces for the drive rod for this hand must be pretty clever as well to prevent either binding or play with such a small delivered force

Regards

Tim

but it is a simple complication with which one can well prove the technology.
It is a first step.
I think the goal is to make large portions of the movement eventially, to use the reduced inertia of the parts to increase the autonomy of the movements.
My question is: how will they reduce the energy consumption of the display, the hands?
As the energy consumption of the movement falls because of reduced inertia of the parts, that of the hands, assuming they are big enough for normal use, will become the major part.
Using hands so small one needs 23x magnification to see them can't really be the answer.
I am very intrigued as to what they will come up with in the next steps as they move forward with this project.
Don

they are comparatively slow moving parts (let's consider for a movement the watch won't have a seconds hand). Thus, and I am asking you know as a watchmaker, would you think that the inertia problem there is as important as with faster moving components?
Best,
Magnus

Magnus,

Thanks for this report.

I looked on the InterWeb immediately and Google search revealed nothing at first.

I'll just read the executive summary. 

"In other words, the Nano Foudroyante EWT requires 1800x less energy and 96% less space!"

Regards,

MTF

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Would love to see the watch in person , hope they will show this concept at SIHH

are indicative of a normal sized dial and hands

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NT

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