Three Bridges in the Valley of Dreams

Part 5


by PeterCDE
and
Thomas Prescher
© June 2003

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The movement





The restoration work - continued

The bridges and trains as well as the escapement are now completely re-assembled. We will follow Thomas Prescher, as he completes the restoration.

The dial side

Der komplette Käfig ist montiert und eingesetzt, die dritte Brücke ist perfekt schwarzpoliert und wird montiert.
The tourbillon and third golden bridge are finished and installed.


Die Rückseite ist fertig montiert und bis auf das Stundenrad komplettiert. Dann wird das Stundenrad und das Wechselrad eingesetzt. Nun ist das Werk fertig zur Montage des Zifferblattes.
The dial side is nearly completed, with only the hour and minute wheels to be added. Now, the movement is ready for the dial.

Das Zifferblatt; die Rückseite weist Beschädigungen vom Vierkant des Federhauses auf. Die Rückseite ist beschriftet, leider ist die Beschriftung nicht lesbar. Dann wird das Zifferblatt aufgesetzt; jetzt folgen die Zeiger.
The dial; the backside is damaged by the four-sided barrel arbor. It is signed, but unfortunately the signature is unreadable. Now the dial is attached and ready to receive the hands.




Nun wird das Werk mit Zifferblatt eingeschalt. Zuletzt folgen Lünette und Gläser. Die beschädigten Stellen sind perfekt hergestellt.
The movement is cased, followed by the bezel and the crystals. The formerly damaged parts look like new.









Das Ergebnis.
The final result.

 

 

Final notes and comments

 

We see the small tourbillon no. 33338 is a very special and important timepiece. It is the result of many skills, craftsmanship and meticulous work, work of the highest difficulty both by Ernest Guinand and Constant Girard-Perregaux to build the watch and for Thomas Prescher to restore it. Before trying to state a summary, let us have a second look at Thomas Prescher.

 


four tourbillons
click on the picture to enlarge

 

After his apprenticeship he worked for IWC, Audemars Piguet and Guebelin AG where he was responsible for complicated, vintage/antique and unique pieces. Until 2002 occupations at Progress Watch AG and Blancpain followed.

Since 2002, Thomas Prescher has been independent, running his own atelier in the beautiful landscape of Twann, Switzerland. His work includes the care and restoration of complicated haute horlogerie pieces and developing his own creations. He is amazing in what he has accomplished at his young age.


the atelier
click on the pictures to enlarge

A member of the AHCI or Horological Academy of Independent Creators, his skills and creativity are reflected by pieces like the unique Falcon watch and the challenging double-axis-tourbillon:


The dual-axis tourbillon
click on the pictures to enlarge


the dual-axis tourbillon in motion

 

Finally, Thomas Prescher candidly answered some additional questions:

ThePuristS: Let´s start with the result of your impressive work: How accurate does a more than 100 years old watch run after the restoration?

Thomas Prescher: It would easily get a COSC bulletin today as it's off less than 10 seconds per day in all positions and the average error is 0 to +5 seconds.
It could do better, but the escape wheel pivots have been burnished too many times and now are very thin, which has changed the depthing of the escape wheel teeth and the detent beyond what can be adjusted. This watch was treated very badly in the past; therefore, I always had to choose between perfect function and sympathetic restoration in order to save as many original parts as possible.

A side note: In a pivoted or spring detent escapement (or chronometer escapement), the escape wheel is giving impulse to the balance in only one direction during a short section of its arc. A good picture by David Penney can can be found at antique-watch.com and a wonderful animation is featured on clock-watch.de (under "Theory"). As you may notice, a properly functioning detent escapement is dependant on the correct horizontal and vertical distance of the detent, escape wheel and balance.

 


Twann
click on the picture to enlarge

 

ThePuristS: How much time was needed for the restoration?

Thomas Prescher: Including pictures and report, about 50 hours.

ThePuristS: That is indeed very fast! Some words about the challenges; was it particularly difficult to apply such a perfect black-polish on these tiny parts of the watch?

Thomas Prescher: Well, to make a perfect black-polish always needs a tin block and diamantine abrasive. Usually smaller parts are easier to polish, as a larger part can´t be polished that easily in one attempt. You have to work section for section, which easily causes flaws in the final polishing attempt. Especially difficult was the polishing of the lower cage plate due to the fixed pillars. But a real challenge is the finishing of the golden bridges; this is a large part with relatively wide areas and it is a soft material. For this part, some additional work is needed including subsequent inspecting and cleaning with pithwood. And, of course, some methods I won´t disclose... Bevelling tiny parts is very difficult. The small size of the tourbillon cage and the movement requires you to carefully choose your methods and strategies for the finishing, which requires some experience.

ThePuristS: That is a lot of insight in the work of a master watchmaker! In the literature, such as Roland Carrera´s "Tourbillon with Three Golden Bridges" covering the 1982 re-issue, the proper "uprighting" or depthing of the gear train is regard as a particularly demanding in laying out the triple bridges movements. Can you comment on that?

Thomas Prescher: A particular difficulty of tourbillons is the correct depthing, the distance between teeth and pinions, which work together. What I noticed on this movement was wear on the center wheel, resulting from a mainspring that was too strong. A spring detent movement, which is supposed to run more or less continuously, does need a sturdy gear train. These points had to be weighed very carefully during the restoration. One aspect was an unusual friction in the winding section; finally, I decided to grease the teeth of the winding wheels. This is not a usual measure, but sorting out and removing the error would have been a massive change in the movement. As were stronger forces than usual in this section, greasing the teeth resolved the problem without need to alter the original parts of the movement.

ThePuristS: Would you like to comment on the quality of the movement?

Thomas Prescher: I don´t feel comfortable doing that. This movement has to be seen as a very unusual piece, one of only a few made and for many years the smallest tourbillon existing. The character of the watch is more a show piece or prototype, so it would not be fair to compare it with larger tourbillons or thinner/smaller movements. The originality and character of the watch is an important aspect, which was carefully obeyed during the restoration. As an example, this aspect made me keep the original mainspring although the watch will not run as long as it did once.

ThePuristS: Thank you for these informative insights!

 

 

The "Tourbillon under three golden bridges" no. 33338 is a supreme expression of horological craftmanship and science. It is an admirable achievement by every aspect: First, the production of the numerous microscopically small parts is still today an outstanding work, with the means, machines and materials some 130 years ago it was and still is a sensation. Second, the finish, assembly and regulation of the watch is still today a challenge:


construction drawing, 1981/82
click on the picture to enlarge

And third, it is an aesthetical achievement. Like almost no other watch or movement it resembles the philosophy of Girard-Perregaux: To design and manufacture own mechanisms with technical, aesthetical and qualitative characteristics of the highest standards.

A tradition which spans more than 210 years in the history of the brand and more than 130 years in the history of fine tourbillon watches, still lively and held high in the ateliers at La Chaux-De-Fonds, where the Valley of Dreams brings up Three Golden Bridges.

 

 

 

 

PeterCDE

 

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