Jaeger-LeCoultre Gyrotourbillon

Part 1

Text and photos by Ron DeCorte

March, 2005

With a host of multi-axis tourbillons on the market today it's hard to find a starting point. So when JLC offered me an opportunity for an insider view of their new Gyrotourbillon, I accepted without hesitation.

In the beginning, the tourbillon was designed to equalize balance wheel, hair-spring, and escapement errors in the vertical positions by rotating the entire escapement approximately once per minute in a singular axis. Now, with the advent of multi-axis tourbillons, the escapement is rotated through both the horizontal and vertical planes allowing yet another possibility in error correction.

The JLC Gyrotourbillon lives up to its name as a true Grande Complication, having an inclined two-axis tourbillon, perpetual calendar with instantaneous double retrograde indication, equation of time, and 8-day power reserve with up and down indication.

The Gyrotourbillon (Gyro) is the brainchild of Eric Coudray and designer Magali Métrailler. Their collaboration of engineering and design is cased in a modest sized platinum package that is easy on the eyes and the wrist. Visually, the complex mechanical attributes of the Gyro are presented in a mature and natural way without being overly dramatic or busy. Internally, the complexity is mind- boggling, having almost 600 parts and requiring a totally new engineering direction from top to bottom. The Gyro will be produced in a limited series of 75 watches, total, over the next 5 years.

In this first installment of the Gyro I will concentrate on the tourbillon, with details of other complications presented in future segments.

Note: The watches and movements featured in this article are advanced prototypes with some components more finished than others. The pictures were taken at the bench at Jaeger-LeCoultre in Le Sentier as the watchmakers are assembling, testing, and adjusting. These images are not fully representative of the final product. In other words, these watches are works-of-art, in progress.

Most of the images below can be clicked to view larger versions. You will find links to very large versions of selected images at the end of this article.

 

Eric, the genius behind the Gyrotourbillon.

 

  

Concept and execution.

 

Power is supplied via two mainspring barrels, each fitted with sapphire covers on both sides. The sapphire covers reduce mainspring drag and allow visual inspection of the mainspring operation. The first barrel, lower right, is wound directly and contains a short mainspring. The power from the first barrel is transferred directly to the second barrel, lower left, via a great wheel. This second barrel has a longer mainspring and acts as a simple remontoir. Unlike most twin barrel configurations that have both barrels supplying power directly to the center wheel in parallel, the Gyro barrel configuration uses two barrels to create a linear flow of power with each barrel spring maintaining control of the other, assuring ample but steady power to the tourbillon.

Note: Since the tourbillon is inclined, the 3rd wheel requires beveled teeth to mesh properly with the tourbillon pinion. (Enlarge the above photograph for a closer look).

 

 

From the dial side we can see the beveled 3rd wheel "A" ready to supply power to the tourbillon, and the beveled stationary wheel "B" that the inner escapement platform will revolve around.

 

   

Shown above are the outer tourbillon cage (left) and its end cap (right), with stationary 4th wheel, that allows insertion of the inner escapement platform assembly. To improve strength, threaded steel inserts are pressed into the cage where screws are used. The outer cage is machined from a solid block of aircraft quality aluminum to reduce weight, an amazing feat even with computer-controlled machines!

Note: All tourbillons must be capable of accelerating and decelerating the cage, as well as the escapement, more than 5 times each second. This requires more power, and consistent power, than a conventional stationary escapement watch.

Using modern materials, such as aluminum and titanium is a great advantage compared to some early wristwatch tourbillons since the effective mass of the cage is greatly reduced. The weight of the Gyro's outer cage would be increased by more than 300% if it were crafted from steel. Being  aluminum, it weighs a scant 0.035 grams - about the same as a grain of dried rice!

 

The inner escapement platform carries the balance wheel, hair-spring (balance-spring, pallet fork (anchor) and escape wheel. It's pivoted at each end and is made from titanium. Again steel inserts are used for screw holes to add strength.

 

    

Two views of the assembled tourbillon cage. The picture on the left is the dial facing side, and the picture on the right shows the opposite side with cage pinion that will mate with the 3rd wheel.

If you look closely at these pictures you will notice two 14K gold screws on the outer cage and one on the inner escapement platform that seem to have no purpose, but indeed they play a very useful role in poising (balancing) the cage assembly.

The balance wheel and its adjusting screws are made from 14K gold to increase the functional mass while in oscillation (like having a much larger balance wheel made from a lighter material).

Another point of importance, this tourbillon uses only jeweled suspension instead of ball bearing races that can easily be fowled by the smallest particle of dust causing stoppage.

 

Here we see the tourbillon cage assembly installed in the movement. The outer cage makes one revolution per minute and the inner escapement platform 2.5 revolutions per minute, making one complete tourbillon cycle every two minutes.

 

A detailed drawing of the Gyro tourbillon cage assembly:

Power is transmitted from the beveled 3rd wheel to pinion "A" that is fixed to the outer cage "B". Wheel "D" with 40 teeth, fixed to the inner escapement platform, will follow wheel "C" with 100 teeth making 2.5 revolutions for each revolution of cage "B" (one minute). Inner platform "E" will make 5 complete revolutions every 2 minutes.

Click here to view a video of the JLC Gyrotourbillon in action (40 mb)

Click here to view a higher resolution version (62 mb)

To view this video you will need the QuickTime player

I strongly suggest watching this video, it's quite amazing!

 

   

Hand finishing of the outer tourbillon cage.

 

Stay tuned for Part 2!

 

To view very large versions of selected images from above, please use these links:

Eric at the bench

Concept drawing

Prototype

Movement showing barrels

Movement - dial side

Movement - tourbillon installed

Detailed drawing of tourbillon

Hand finishing #1

Hand finishing #2



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© Ron DeCorte 2005, All rights reserved








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