The tourbillon complication was one of the legendary innovations of 18th century watchmaking. The timekeeping heart of a watch is the balance wheel. Its back and forth oscillation or “swing” sets the watch’s rate and thus determines its accuracy. In turn, the back and forth swing of the balance wheel is controlled by a very fine hairspring, or “spiral” wound around its center. So sensitive is this timekeeping heart of the watch that, as the forces of gravity play upon the assembly of the balance and its hairspring, there is a very slight change of their inertia which results in either slowing down or speeding up of the watch’s rate depending on the position. These gravitational effects depend upon the position or orientation of the watch.
The answer to this subtle physical phenomenon was the tourbillon. Recognizing that gravity had an influence on the watch’s rate, depending upon the watch’s position, the innovation of the tourbillon countered these effects by enclosing the balance wheel assembly (balance wheel, hairspring and escapement) in a cage and rotating it. In its most classic form, the cage rotates one time per minute. Since the assembly will rotate through all vertical positions, it will be equally subjected to periods of speeding up and slowing down. Therefore, the gravitational effects will be averaged out or cancelled.
Although the theory of tourbillon operation is clear enough – rotate the balance wheel, spring and escapement once per minute to cancel out the speeding-up and slowing-down effects of gravity upon the timekeeping heart – the creation of a mechanism to achieve this draws upon the kind of skills that only the most talented and gifted watchmakers possess. A very delicate cage must be constructed to carry the entire timekeeping assembly of the watch, and gears must be designed to rotate this entire assembly around a fixed pinion.
|The Blancpain Flying Tourbillon (ref. 0023-3427-55) circa 1989|
Blancpain introduced its Calibre 23 in 1989, pushing the envelope of classic tourbillon design. As dictated by tradition, Blancpain conceived a delicate cage to carry the timekeeping assembly. But instead of suspending the shaft upon which the cage is attached between two bridges (top and bottom), as common practice dictated, Blancpain made its tourbillon a flying tourbillon. The flying design allowed for removal of the top bridge from which the cage shaft would be supported. Instead, the entire tourbillon cage is supported from underneath, on a single bridge. In order to accomplish this feat, Blancpain’s watchmakers had to develop a miniscule ball bearing assembly to support the rotating tourbillon cage.
What is the advantage of this “flying design”? An unobstructed view of the tourbillon cage, balance wheel and escapement. With removal of the upper bridge, nothing stands between the tourbillon’s fortunate owner and the complex mechanism rotating once per minute. This innovative flying tourbillon design simultaneously achieved several world firsts. It was the first flying tourbillon ever fitted into a wristwatch; and it was the first tourbillon to be supported with ball bearings.Not only did Blancpain’s artisans endow its tourbillon with these groundbreaking flying design features, they garnered two other records as well. When it debuted, Calibre 23 had the thinnest tourbillon cage in watchmaking history.
The second industry leading triumph for Calibre 23 was its 8-day power reserve. An 8-day power reserve meant that the lucky owner of a Blancpain tourbillon could let his watch run without winding for more than a week, before rewinding was required. No wristwatch tourbillon could claim this running autonomy when Calibre 23 was introduced.
Blancpain Calibre 23
The world’s thinnest tourbillon movement
Thickness: 3.50 mm
Diameter: 26.20 mm
Power reserve: 8 days