This week thanks to Montblanc North America, we had two pretty spectacular timepieces from the very highest end of the Montblanc horological ecosystem in the office. On Monday, we went hands on with the Montblanc Collection Villeret Tourbillon Cylindrique Geosphères Vasco da Gama, with its combination of a very artistically done world time/GMT function and a very large, 18,000 vph tourbillon with a cylindrical hairspring, and we talked about the relationship between navigation at sea, the marine chronometer, and the development and purpose of the cyclindrical hairspring. Today, we’re going to go hands on with another very technically unusual Montblanc watch: the Villeret ExoTourbillon Rattrapante. This isn’t a completely new watch, of course – it was originally unveiled back in 2013 – but that was at Watches and Wonders in Hong Kong, and while we’ve seen the watch “in the metal” once or twice in the interim, this was really our first chance to spend an extended period of time with it.
The ExoTourbillon Rattrapante is, like the Tourbillon Cylindrique Geosphères Vasco da Gama, built around a pocket watch scale movement; it’s a quite large wristwatch, with a 47 mm diameter, 17.5 mm thick case. The balance is the same size as that on the Tourbillon Cylindrique Geosphères Vasco da Gama: 14.5 mm, and the beat rate is the same (18,000 vph). The name of the watch raises two questions, of course – what is a rattrapante chronograph, and what is an “ExoTourbillon.”
The first question is probably the easiest to answer so we’ll start there. A rattrapante chronograph is also known as a “split seconds” chronograph (not to be confused with a flyback chronograph) and it gets its name from the action of its two chronograph seconds hands. There are two central chronograph seconds hands in a rattrapante; one is superimposed over the other, and they actually look like a single hand. Now, imagine you want to record the times for two horses racing against each other. When you start the chronograph at the start of the race, the two hands travel together. As the first horse crosses the finish line, you push the “split” button on the watch. One of the two hands will now stop, showing first horse’s finishing time. The remaining seconds hand – “split” from the first, and it’s this phenomenon that gives the split seconds chronograph its name – will continue to travel until, as the second horse crosses the finish line, you push the chronograph stop button. Now the remaining seconds hand stops, and you can record the second elapsed time. (If you’ve ever used a digital watch with this function you know that the somewhat confusing “split time” terminology is retained even in quartz digital watches, even though there is no longer anything that splits!)
One of the features of a rattrapante chronograph is that if you push the split button a second time, the first hand will actually move so as to “catch up” with the second chronograph hand, and the two will start traveling together again. The mechanism that allows this is visible in this watch through the transparent case-back. You can clearly see the central wheel for the second chronograph hand, placed in between the scissor-like jaws of a clamp, and the two lyre-shaped springs that allow the jaws of the clamp to close. When you push the split button for the first time, the jaws are released and hold the wheel still; this causes the first chronograph hand to stop. When you push the split button a second time, the jaws of the clamp let go of the wheel, which starts to turn again – it “catches up” to the first hand thanks to a very delicate mechanism using (to simplify the mechanism considerably) a ruby roller and heart-piece, which in traditional watchmaking is considered one of the most challenging complications to make and adjust. This is the reason the rattrapante chronograph was traditionally considered one of the “high complications,” along with the perpetual calendar and the minute repeater.
The ExoTourbillon is so-called because there is no traditional tourbillon cage in the construction of the watch. Normally, a tourbillon consists of a rotating cage, inside which the escape wheel, escapement, balance, and balance spring all rotate together; as most of us know, the tourbillon was originally invented by Breguet and patented by him in 1801 and its purpose was to negate the deleterious effects of gravity on the accuracy of a watch (again, an oversimplification but correct in broad outline). The single biggest problem with a tourbillon, however, is that the gear train, instead of just making the balance oscillate, now has to generate enough power to make the entire cage assembly and all its components move as well; this is a huge additional load and to cope with it, the tourbillon historically had to be constructed to very high standards of precision in order to reduce energy losses due to friction to an absolute minimum.
It would be great, however, if you could eliminate as much of the extra mass as possible, too. The usual approach was to just make the cage as gossamer thin as possible (and, starting in the 1980s, with Audemars Piguet, manufacturers began using extra light alloys as well, like titanium.) The ExoTourbillon Rattrapante, however, essentially does away with the cage entirely; it has been reduced to a small rotating platform underneath the balance, just large enough that the lever and escape wheel can be carried on it. When the ExoTourbillon first came out (as part of a simple chronograph watch from Montblanc, in 2010) there was some initial confusion as to whether it was a “real” tourbillon and the answer is, of course, yes – all the escapement components still rotate through 360 degrees, just as in a more conventional construction.
Finally, the ExoTourbillon Rattrapante also has a dual time-zone function; you can see the pusher for adjusting the second time zone indication at 8:00. And, as the sharp-eyed amongst you have probably noticed, this is a monopusher rattrapante chronograph as well – the start/stop/reset button is co-axial with the winding/setting crown, with the split-seconds button at 2:00.
As with the Tourbillon Cylindrique Geosphères Vasco da Gama, this is obviously a major horological showpiece, not an every-day wearer. At the same time, though, it is for its size quite comfortable on the wrist, and it shares the same generally approachable ergonomics of the Tourbillon Cylindrique Geosphères Vasco da Gama in terms of wearability. It’s perhaps a bit less overtly dramatic (the Vasco da Gama’s visual pyrotechnics, with its two hand-decorated hemispheres, would be tough to beat) but it’s got a tremendous amount of visual punch of its own, with a creamily beautiful gold and grand feu enamel dial. And the view through the case-back of the movement is one of the most breathtaking we’ve seen in a long, long time.
The Montblanc Villeret ExoTourbillon Rattrapante, as show, in 18k white gold; 47 mm x 17.5 mm. Movement, Montblanc manufacture caliber 16.61, 38.4 mm x 11.9 mm. Split seconds monopusher chronograph with two column wheels, and second time zone indication. Cageless “exotourbillon” with 14.5 mm balance, four minute rotation; balance spring with mathematically correct Philips terminal curve. All plates and bridges of maillechort (German silver). Power reserve approximately 55 hours. 18 pieces worldwide; price available from Montblanc on request.