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The Foudroyante

 

As one of the rarest complications at all, the Foudroyante à la Habring2 is additionally unique in that it is an addition to a Chronograph mechanism (e.g. Girard-Perregaux), but it is added as a stand-alone complication (well, together with the jumping seconds, of course!). Thus, with a Habring2 Foudroyante one acquires a timepiece with two fast jumping time indications (Foudroyante & Jumping Seconds):



What is so mesmerising with a Foudroyante is not only the optical appeal of this complication, based upon the speed and precision (of the jumping hands, if implemented well ;-)), but also the care and precision needed to actually realise such a watch.


As one can anticipate, Habring2's implementation is simple and straightforward. One the escapement wheel's pinion a large Foudroyante wheel is mounted that interacts with a second, small Foudroyante wheel. On top of the latter's pinion we find the Foudroyante hand. One main difference compared to other Foudroyante constructions is the lack of a separate spring barrel to drive the hand!



The primary challenge of the Foudroyante is thus that it is driven from the same mainspring barrel than the going train. This implies that the necessary energy needs to be considered for the overall energy balance of the movement.

What Habring2 managed to accomplish is nothing short of amazing: Surely, the energy drain from the mainspring barrel is higher and the torque as well (due to the fact that the Foudroyante mechanisms interacts with the escapement wheel). Thus, also the balance's amplitude is lower but still within the specifications of the ETA Valgranges base movement!

How is that possible? Well, the reason is that the functional components of the mechanisms are nearly weightless!

I'd like to highlight three separate issues to illustrate how it is achieved. First, we look at the Foudroyante hand: Note how tiny it is compared to the balance wheel:



It is quite obvious that specific production techniques are needed to produce such a watch. In this case, the hands are stamped into extremely thin aluminum sheets and subsequently cut out with scissors:





Second, the large Foudroyante hand merits a closer view:



With patience and care Richard puts together wheel and bearing:



To illustrate how tiny and lightweight the wheel is I asked Richard to tell me the weight of the wheel. His answer: "Sorry, we don't have a balance that would be sensitive enough... but its so light it swims on water!" - which he gladly proved to me:



Mounting the bearing on the wheel requires patience, a steady hand and good eyes:







Fixing it:



(Almost) Finished:



Only the axis needs some polishing:



The third part is the small Foudroyante wheel. Its also of minuscule dimensions:



Like the Foudroyante hand, it comes as a sheet of galvanised aluminum:





Polishing of the hole:



Now the components of the mechanism are finished and can be assembled:



The results is a watch that certainly demonstrates watchmaking aptitude in an unusual implementation. Like my neighbour said: "Its a watch that really mirrors my very hectic life!"









This message has been edited by Magnus Bosse on 2012-04-28 09:40:13

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