Tourbillon bi-cylindrique

With the new Tourbillon Bi-Cylindrique, the Montblanc Collection Villeret 1858 again presents an exclusive innovation that differs in many respects from anything that modern haute horlogerie has created until today. Not only is this the first wristwatch with a tourbillon escapement and a cylindrical double balance-spring, the newcomer also delights connoisseurs by revealing the mechanisms and the mode of function of the legendary Heures Mystérieuses display. This new timepiece epitomizes the working philosophy cultivated at the Montblanc manufacture in Villeret, according to the best Swiss watchmaking tradition, of which constant innovation, which always searches for the new and the unprecedented, is a vital part. This manifests itself once again in the new Tourbillon Bi-Cylindrique, for which master watchmaker Demetrio Cabiddu and his colleagues pursued a daring idea. Would it be possible to miniaturize and transplant the precisely beating “heart” of an 18th-century ship's chronometer into a tourbillon rotating inside the case of a wristwatch? This steadily beating heart is an escapement with a cylindrical balance-spring, thanks to which ship's chronometers were able to tick so steadily and so precisely two centuries ago that, despite turbulent waves and extreme temperature variations, mariners could rely on them to navigate across entire oceans, erring by only a few nautical miles in their calculated positions.

The Cylindrical Balance-Spring as the Renaissance of a Great Achievement
The new Tourbillon Bi-Cylindrique earns new honors for an invention that had already set the pace in the world of timepieces centuries ago. The mechanism is a cylindrically shaped balance-spring: unlike the vast majority of contemporary balance-springs, this one doesn't swing to and from in a single plane, but expands and contracts along a vertical axis as though its gyres were the threads around a bolt. Like a conventional balance-spring, a cylindrical balance-spring is a concentrically wound strip of elastic metal; but instead of being wound side by side, at increasing distances from a common center and all on the same plane, its individual turns are all of equal diameter and are wound one atop the other. This eliminates the slight eccentricity of the center of gravity, which has always been the Achille's heel of spirally coiled balance-springs. The second advantage of a cylindrical balance-spring is that it develops absolutely concentrically and symmetrically.
The new Tourbillon Bi-Cylindrique in the Montblanc Collection Villeret 1858 ticks with two cylindrical balance-springs positioned concentrically one inside the other, each with its own diameter, but both with identical torque. The springs develop in opposite movements while the torque remains the same, thus further optimizing the isochronism. For this fascinating new development, the Montblanc manufacture in Villeret benefited from the ability to produce its own balance-springs.
The bi-cylindrical constellation has never before been used in a wristwatch, to say nothing of its being mounted inside a tourbillon escapement.

Unveiling the Secret of “Heures Mystérieuses”
The Tourbillon Bi-Cylindrique solves the heures mystérieuses mystery by revealing the hidden mechanism. The new wristwatch eliminates the dial that formerly concealed the mechanism which powers the paper-thin sapphire disks with their printed black hands.

A Case like an Icon
A watch's case rarely evolves into a veritable icon. One exception to this rule is the shape of the cases of the Grand Tourbillon watches in the Montblanc Collection Villeret 1858. Their most noticeable characteristics are a teardrop shape which tapers toward the “6 o'clock” position, a slightly cambered profile which cuddles comfortably close to the wrist, and a bezel with a concave cross-section from the “8” through the “12” to the “4,” where it transitions into a convex curvature from the “4” to the “8.”
The new Tourbillon Bi-Cylindrique will be available as a unique piece in platinum and in strictly limited series of eight wristwatches with 18 carat white gold cases and eight timepieces with 18 carat red gold cases.