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Updated Daily: January 2009

 
  Columns > Ron DeCorte > Double Tourbillon 30º

   Published in: Pilot Issue
 
Text Size: GR | GR | GR
 
  Gravity is the primary nemesis of accuracy in watch escapements. Other factors such as inertia and centrifugal forces also play a role in the accuracy but these are relatively constant and can be compensated for via adjustments to obtain consistent timekeeping. Gravity, however, has a strong effect on the balance wheel (A), hairspring (B), and pallet fork (C) especially given the ever changing orientation of the watch as it is worn. In other words if the watch was used in a static position all the time, such as a clock, there would be little use for the tourbillon.

So, short of sitting the watch in a stationary mode the only way to overcome the effects of gravity on the escapement is to put the escapement through as many gravitational changes as possible, over and over again, as to obtain an average. The traditional tourbillon accomplished this by rotating the escapement 360 degrees in a single plane, not a bad solution.

However GREUBEL FORSEY realized that introducing the escapement to yet another plane of rotation could be a significant improvement for the wristwatch, and they were correct. Now maybe you are asking yourself why they didn’t incline the second axis of rotation at 90 degrees, after all that would introduce an even greater number of gravitational possibilities.

But inclining the second axis to 90 degrees would significantly increase the thickness of the watch to objectionable proportions, while the 30 degree inclination actually reduces the height of the combined tourbillon cages and also ensures that the balance wheel does not find itself in an unfavourable position.

 
 
 
As way of testing their hypothesis GREUBEL FORSEY took their own escapements from their Double Tourbillon 30° and mounted it in three different conditions. In the graph on the left: The red line is a result of the escapement being mounted in a watch without tourbillon. The blue line is a result of mounting the escapement in a conventional tourbillon. And the green line is the same escapement mounted in a GREUBEL FORSEY double tourbillon with 30° inclination. The red and green lines of the graph show about 10 seconds of error over 24 hours and in six different positions and the blue line about 3 seconds. (The straighter the line the better the timing result)

In conclusion: The inner tourbillon cage carries the escapement and makes four revolutions for each revolution of the outer cage as the escapement is carried through a vast array of positions allowing for excellent equalization of errors resulting in very consistent time keeping, especially in the different wristwatch positions. But watches don’t just operate in vertical positions, they also operate with the face up and sometimes down (horizontal positions). By inclining the inner cage to 30 degrees the horizontal positions become more stable and match the vertical positions much closer than a conventional tourbillon.
 
 

The result is a watch that is constructed to the highest levels of craftsmanship and also makes some big strides in improved timekeeping.

  
 
     
 
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