One of the fundamental challenges in the world of watchmaking has always been the management of mechanical power and the regularity of the watch. It is an age-old mission for watchmakers to seek better methods to relay energy efficiently, especially so when complications are involved and the energy needed amplifies; with more parts, more friction is generated in a movement. We also need to contend with the influence of the diminishing torque as the mainspring unwinds, directly influencing the chronometric performance of the movement. These are all part of the power challenge imparted by the nature of physics.
In 2007, Jaeger-LeCoultre took inspiration from a pocket watch calibre dating back to 1881, the 19/20RMSMI with two barrels, and introduced the Duomètre collection as a testament to the maison’s inventiveness. The concept is to segregate the energy source and consumption to timekeeping, and to everything else than timekeeping, which the maison has dubbed the “dual wing” concept.
To demonstrate how such a design guarantees the constancy of the power supply, the maison implemented a chronograph complication on their very first model. This is because actuating a chronograph, typically for those with a horizontal clutch, engages an extra set of gear trains and introduces new loads to the movement. This would in turn cause the amplitude of the balance to drop which impairs the accuracy of timekeeping. However, separating the power source and the train using two individual sets of barrel and gear trains can prevent the impairment despite utilising only one escapement. So whether or not the complication is engaged, the power delivery and regularity remain the same.
Jaeger-LeCoultre has now revisited the Duomètre collection with four new models to the lineup, one of which is the Quantième Lunaire seen here. Mostly consisting of precious metal cases in the past, this is the first time we see a Duomètre in stainless steel, matched with a blue dial, one of the most versatile combinations of all time.
The four models are also introduced along with a new case design, inspired by the savonette pocket watches created by the maison back in the 19th century. While the French word “savonette” essentially means a small disc of soap that fits in the palm of a hand, the essence of such a shape is now translated into the new Duomètre case. The gently rounded bezel matches the curvature of the convex crystal, and the crown is also redesigned with rounded notches for the ease of use. It is quite a contrast compared to the previous Duomètre, which showed a relatively refined edge on the case, and the new contour goes rather well with the natural thickness of the watch while giving a nice presence when holding in hand.
Another notable feature of the case is the mix of finishing techniques, easily perceivable once turned to the side. It is achieved with a complex structure, consisting of a total of 34 parts of different finishing, including polished, brushed, and micro-blasted. The lugs are also designed to be screwed in rather than integrated, so the side profile of the watch is more coherent and satisfying to look at.
Visible via the transparent case back is the calibre 381AA, a reworked movement from the original 381 with the quality finishing details one would expect from the maison, including a sunray Côtes de Genève, radiating from the escapement, the chamfering on the bridges and plates, and the blue screws. The two mainspring barrels are also marked accordingly, “minutes / heures” and “régulateur”, denoting that one barrel is responsible purely for timekeeping, and the centre seconds since it is part of the first gear trains, while the other one is responsible for all the displays in the front. Including the hours, minutes, centre seconds, date, moon phase, and, of course, the lively foudroyante skipping at all times.
The foudroyante, skipping at a rate of 1/6th of a second, is merely for show but a vital part of the Duomètre movement construction. Underneath the dial, there is a foudroyante star that connects to another wheel beneath the escape wheel and runs at the same cadence as the watch, it essentially connects the second set of gear trains to the escapement. And, because the foudroyante force couple is 160 times inferior to the one in the escape wheel, in theory, the impact on the energy transmitted is close to zero.
Other than the aesthetically pleasing symmetrical layout, and perhaps the constantly animated foudroyante on the dial side, the technicality is also what makes the Duomètre collection so interesting, and while the Duomètre Quantième Lunaire is the least complicated among the four current models, the case material and the new design make it more wearable in the daily settings. One thing though is that the bridges and plates are no longer made in nickel silver but now in brass, perhaps a disappointment to the more ardent enthusiasts, though it avoids the yellow tint from oxidation over time. However, that is a detail that will probably not detract those who are discovering the Duomètre concept for the first time with this new collection. We certainly look forward to how the maison will continue to expand on the concept in the near future.
