The "ExoTourbillon"
January 18th, 2010 at Salon International de la Haute Horlogerie Geneva - The newest creation in Montblanc’s Collection Villeret 1858 features a delightfully surprising and trailblazing innovation. The new ExoTourbillon Chronographe is a regulator watch with a large centrally axial minute-hand, a distinct hour display, an indicator for the time in a second time zone (with day/night display), a subdial for the seconds, a chronograph with a counter for 30 elapsed minutes, and an absolutely unprecedented tourbillon with a balance larger than the tourbillon’s rotating cage and positioned outside it.
The ExoTourbillon Chronographe is the first watch in Montblanc’s Villeret 1858 Collection to unite two of the most avidly admired horological complications: a chronograph function and a tourbillon. Mastery of the difficulty of crafting these complications numbers among the distinguishing characteristics of the Institut Minerva, which has here combined the two complications in a highly unusual fashion: the chronograph upholds the lovely tradition with a column-wheel and horizontal coupling, and the four-minute tourbillon boasts a never-before-seen innovation.
But what exactly does a tourbillon accomplish? Due to the subassembly’s architecture, the center of gravity of the balance and balance-spring in every mechanical watch is never absolutely collinear with the center of the balance’s axis of rotation. This off-centeredness causes a disadvantage when the watch is in a vertical position: the oscillations of the balance are disturbed by the influence of gravity on its eccentric center of gravity. The ingenious tourbillon mechanism was invented to solve this problem: the balance is borne inside a cage that continually rotates around its own axis. The eccentric center of gravity accordingly orbits the tourbillon’s axis of rotation at this same rate. The accelerating effect caused by the Earth’s gravity on the center of gravity during the first 180° of the tourbillon’s rotation is compensated by an analogous de-accelerating effect during the second 180°. The long-term result is a movement that runs at a regular rate.
This clever mechanism underwent further optimization for the ExoTourbillon Chronographe: the balance has been separated from the cage to isolate it from the disturbing movements of the escapement. This separation made it possible to create the world’s first tourbillon in which the rotating cage is smaller than the balance, which oscillates outside the cage and on a higher plane. This architecture also inspired the watch’s name, which includes the Greek prefix exo, meaning outside. The balance in this unconventional configuration is borne between two jewels - it is neither cantilevered (“flying”) nor is it borne between two bridges - while the tourbillon turns at the foot of the axis in a two-point bearing.
The reason for this most elaborate construction is that the traditionally large and massive balance would have required a comparably large rotating cage if it had been positioned within a conventional tourbillon. A smaller tourbillon has less mass and consequently requires less energy for its rotations. The rotating cage is also freed from the weight of the balance, which further reduces the amount of energy it consumes. This architecture requires about 30% less energy than conventional constructions. The energy saved here can be used to power the chronograph’s functions.
Another essential advantage: Being separated from the rotating cage, the balance is not adversely affected by the inertia of the cage and consequently oscillates with greater precision. This innovation is entirely in accord with the statutory task of the Institut Minerva: namely, to cultivate the authentic Swiss watchmaking tradition and to combine it with ongoing innovation, thereby assuring a bright future for this noble and artful handicraft. It goes without saying that this invention has been registered for patent protection and that it will be used exclusively in the timepieces which comprise Montblanc’s Villeret 1858 Collection.
The owner of an ExoTourbillon Chronographe can enjoy the spectacular vista of a large balance (with weight screws along its rim) that’s free to oscillate in all its beauty and turns around its own axis, without being cramped inside the narrow confines of the tourbillon’s cage. With commensurate self-confidence, it proudly presents itself in a large aperture cut into the dial at the “12 o’clock” position and above a plate that has been manually embellished with circular graining.
Tourbillon Chronograph with Regulator Dial
The watch’s face boasts a typical regulator configuration. A large minute-hand and the chronograph’s elapsed seconds-hand share a common axis at the center of the dial. The subdial for the hours is shifted out of the center and occupies the lower half of the watch’s face. Additional displays portray a miniature solar system with a golden sun (the tourbillon) at the “12,” the Earth at the “6,” the moon in the form of a small 24-hour dial between the “4” and the “5” (as a day/night display for the time in a second time zone), and two other heavenly bodies in the form of the small seconds at the “9” and the chronograph’s counter for 30 elapsed minutes at the “3.” The last-mentioned display is semicircular, with two differently colored scales calibrated for 0 to 15 and 15 to 30 minutes, respectively. The tips of two unequally long and differently colored hands each serves its designated scale.
Monopusher Chronograph with Column-Wheel Control
The Calibre 16.60 is a chronograph movement with a large and centrally axial counter for the elapsed seconds, a counter for 30 elapsed minutes, a classical column-wheel and horizontal coupling. The chronograph lever is elaborately finished by hand, and the mise en fonction is likewise accomplished manually: the surfaces where the chronograph lever contacts the column-wheel and the heart disc are observed through a watchmaker’s loupe during the operation of the chronograph’s functions and are gradually and meticulously abraded to a tolerance in the hundredths-of-a-millimeter range. The steel parts and the chronograph bridge (in the “V” shape typical of Minerva’s products) are manually beveled and polished.
A finely grained stone is used to polish the lever; the bridges are manually adorned with Geneva stripes. The large and massive balance, with weight screws along its rim and a Phillips curve at one end of its balance-spring, oscillates at the classical frequency of 18,000 semi-oscillations per hour (2.5 hertz), which makes it possible to measure brief intervals to the nearest fifth of a second. The chronograph’s start, stop and return-to-zero functions are operated sequentially by depressing a button in the crown.
Second Time Zone and Day/Night Display
Frequent flyers will appreciate the fact that the ExoTourbillon Chronographe can display the time in two different time zones. The skeletonized hour-hand on the hours subdial indicates the local time, while the tip of the blued steel hour-hand points to the hour in the wearer’s home time zone. When the watch is worn in the home zone, these two hands are always positioned one atop the other; when the wearer travels to a different time zone, he or she can press the button at the “8” to advance the local-time hour-hand in single-hour increments until the hand indicates the correct local time. The current time at the wearer’s home is shown on the little 24-hour dial with day/night indicator and blued steel hand.
Collector’s Items in a Limited Edition
Also because they’re manufactured in strictly limited editions, the chronographs in Montblanc’s Villeret 1858 Collection are ardently sought rarities. This distinction is further enhanced by the extremely unusual combination of a chronograph and a tourbillon, and even further refined by the presence of a unique tourbillon construction. Only one unique piece of the ExoTourbillon Chronographe will be manufactured in platinum, along with limited editions of 8 pieces each in 18K white gold and in 18K red gold (5N).
The watches with white or red gold cases have massive gold dials on which the slender grooves of manually applied guilloche embellishment invite incident lights to dance. Delicately shimmering mother-of-pearl is inset into portions of the dial on the one-of-a-kind platinum watch. Each of the impressive 47-mm-diameter cases is high-gloss polished and fitted with an arcing bezel that securely holds a highly domed sapphire crystal with vertically falling flanks (forme chevée). A pane of sapphire crystal is integrated into the back, which is screwed to the case and protected by a hinged cover which is opened by a patented mechanism concealed between the horns.
Each watch is engraved with the words “Edition Limitée,” “Montblanc” and “Fait main à Villeret” (i.e. handmade in Villeret). The interior of the hinged cover is signed “Demetrio Cabiddu Maître Horloger,” thus identifying by name the technical director of the manufacture, who led the team that developed the Calibre 16.60. This bears the gold-filled engraving “Minerva Villeret” and can be admired by peering through the pane of sapphire crystal in the back of the watch when the cover is opened. Naturally, the Montblanc logo hasn’t been forgotten: the familiar six-pointed star, which symbolizes the six tongues of the glacier that covers Europe’s tallest mountain peak, has represented the utmost in European handcraftsmanship for many decades. The same stellar emblems, executed in genuine mother-of-pearl, grace the watches’ winding crowns.
These new collector’s items in Montblanc’s Villeret 1858 Collection are affixed to alligator-leather straps, each of which is equipped with a pronged buckle made of either 18K white gold, 18K red gold or 950 platinum, depending upon the material of which the model’s case is made.
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