Joseph Chevalier with tourbillon. Cal. CH 1760

Andrew Babanin
Russian version: Часы Joseph Chevalier с турбийоном Калибр CH 1760

Tourbillon till now is one of the most complicated devices, made by watchmakers. Invented by king of watchmakers Abraham Louis Breguet tourbillon was made to improve accuracy of watches. That time it was quite uneasy to produce high precision parts where physical center was equal to the mathematical one. That's why the rate of watches was unstable in different positions because of influence of gravity. Breguet invented self compensating system where you could use normally produced parts (lower precision). He put parts of the escapement into the special rotating cage. A balance wheel for a minute was in all its positions, compensating gaining or slow-down appeared in certain positions. I should notice, that Breguet invented tourbillon only for pocket watches, usually placed in vertical positions. After Breguet's death only a few manufactures still produced tourbillobns. After the crisis of Swiss watch industry some manufacturers began to produce tourbillon again. I would say, that for wrist watches this complication is doubtful concerning reliability and accuracy, but till now it is most prestigious among other complications.

Fig 1. Limited edition

There are not too many tourbillon producers in the world. I would like to review Joseph Chevalier movement CH 1760, based on Progress 6361. Progress is quite famous because of the affray. The manufacture was established by ex-engineers of ETA SA. They used some ETA inventions. Besides this caliber was the first "folk" tourbillon - the price of watch was around 20000 US dollars!!! It was unpleasant to other manufacturers, so Progress was close to bankruptcy. Now it is called STT (Swiss Time Technologies). I would like to mention, that only 6 Swiss and a few German watch producers ventured to make watches with this caliber. Among them there are: Jacques Etoile, Alain Silberstein, Chronoswiss, Frederique Constant, Harry Winston and Joseph Chevalier.

Fig 2. The movement is hand engraved

The base caliber is Progress 6361 with 23 jewels, minute tourbillon and stop second feature. Diameter of the movt is 30 mm, height 5.4 mm, power reserve - 72 hours. Shock protecting device is Incabloc. It is flying tourbillon with the balance wheel placed in the center of the cage. The cage is fixed from the only side.

Fig 3. There are well finished parts under the dial. Circular Graining in the bridges, blued screws

Pay attention to the Fig.4. Minute wheel and keyless works are very common to ETA design. Moreover, you can find the 3rd wheel and intermediate wheel very common to ETA ones.

Fig 4. Keyless works in the best traditions of ETA movts

Tourbillon needs extra power, so you cannot use normal mainspring. There are two ways: to use stronger mainspring or to use two barrels. As a result - better performance and 3 days power reserve.

Fig 5. There are two barrels to give extra power

Fig 6. Mainspring bridges. Design is common to ETA 2892-А2

Let's jump to the most interesting device - the cage. As I told before - it is fixed to the bridge in the only point. Pay attention to the fig.7. Central jewel is a car jewel of the balance wheel with Incabloc shock protection. The cage is set in ball bearing and fixed with a special bolt very common to oscillating weight bolt of ETA 2892A2 movt. The ball bearing has 7 ruby balls.

Fig 7. The ball bearing is based on 7 ruby balls

The hairspring is flat and mounted in not moving stud. The index has device very common to ETACHRON, so if you want to adjust a gap between pins you can simply turn this brass device to some angle.

Fig 8. The part of cage and index are look like a small second hand

Second wheel is fixed firmly to the bridge. The escape wheel pinion moves among it and rotates the whole cage. There are teeth on the outer part of cage. With these teeth the cage interacts with the wheel train.

Fig 9. Dismounted tourbillon

The balance wheel is a bit strange, with enlarged axle. In this way producer placed cap jewel to the level of bridge surface - easier to maintain.

Fig 10. The balance is with strange rim and long axle

The cage is disassembled. Escapement bridge is dismounted. The pallet fork is made as a lever - for the better composition (also to place the balance in the center of the cage). Both banking pins are from the one side of the pallet fork - very original decision.

Fig 11. Banking pins are from the one side of the pallet fork

In conclusion I would like to say that I like this movement. It has the most modern decisions, passed thru many years of trials. The cage is fixed easily and safely, the balance can be adjusted easily and quickly. Cannon pinion with driving wheel have the best design, ever used. There is a very reliable movement. The only minor thing - there are no slots for easier bridge removing - there is a risk to scratch a main plate.