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
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
---------------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.
--------------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.
---------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
--------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.
-------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.
-------------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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