The inherent challenge in crafting complex mechanical timepieces arises from the power drain caused by their complications on the mainspring. This consumption can interfere with the consistent power flow essential for the escapement's precise timekeeping.

In response to this challenge, the early 2000s saw Jaeger-LeCoultre's development of the innovative Duometre mechanism. Officially unveiled and patented in 2007, this mechanism distinguishes itself by employing dual barrels and gear trains within a unified calibre. One set is dedicated to the escapement, ensuring accurate time measurement, while the other powers the watch's various complications, both operating under a shared escapement. This design ensures the watch's isochronism—or the consistency of its timing oscillations—remains unaffected by the activation of any additional functions.

The choice to debut the Duometre concept through a chronograph in 2007 was strategic, considering the chronograph's significant impact on timekeeping precision. Over the years, Jaeger-LeCoultre has expanded the Duometre's application to encompass a variety of complications, such as moon phase indicators, world time functions, and tourbillons, further testament to its versatility and ingenuity; and this year's Watches and Wonders releases are no exception. Let's take a closer look:

Duometre Chronograph Moon

Powered by the new Calibre 391, the Duometre Chronograph Moon presents an intriguing contrast between the lightning-fast operation of the chronograph – which can time intervals as small as 1/6th of a second – and the slow rhythm of the moon as it passes through its cycle in 29.53 days, complemented by a Night and Day display. For Calibre 391, Jaeger-LeCoultre’s engineers started from the ground up to develop a fully integrated movement that combines a manually wound mono-pusher chronograph with moon phase and night-day complications, as well as two power reserve indicators and a seconde foudroyante (flying second) display. The seconde foudroyante is displayed in a sub-dial at 6 o’clock, flanked by the two open-worked areas that reveal parts of the mechanism. The two power reserves (50 hours for each barrel and gear train) are displayed on an arc-shaped bridge on each side of the sub-dial. Both barrels are wound by a single crown – forwards for the barrel that provides power for the timekeeping function and backwards for the second barrel, which provides power for the complications.

On the dial side of the Duometre Chronograph Moon, two open-worked sections offer intriguing glimpses of the mechanism, hinting at the mechanical beauty of the calibre. On the reverse side, fully revealed beneath the transparent crystal case-back, much of the movement is open-worked and an array of bridges seems almost to be floating above the levers and wheels, drawing the eye deep into the mechanism. Creating visual unity across the entire expanse of the movement, the bridges are decorated with sunrayed Geneva stripes. It’s a challenging technique that demands absolute precision because the components must be decorated one-by-one, and yet radiate from the centre of the regulating organ to the edge of the calibre in perfect alignment once the movement is assembled.

The open-working of Calibre 391 serves two purposes: not only does it greatly enhance the aesthetics, it also serves a technical purpose, enabling the watchmakers to more easily assemble some parts of this highly complex calibre. This is a fine example of Jaeger-LeCoultre’s philosophy of marrying mechanics and aesthetics in such a way that each serves the other. Being a manually wound calibre, there is no winding rotor to conceal the chronograph levers.

Duometre Heliotourbillon Perpetual

Yet another watch with an innovative new calibre under the hood, the Heliotourbillon Perpetual's Calibre 388 features an entirely new tourbillon construction: one that spins on three axes to create a ‘spinning top’ effect. Beating at a frequency of 4Hz (28,800 vph) to further enhance chronometry, Calibre 388 also incorporates a perpetual calendar with a grande date indication.

Incorporating almost eight decades of accumulated expertise in the tourbillon regulating mechanism, the Duometre Heliotourbillon Perpetual, features a newly developed tourbillon configuration that rotates on three axes. In doing so, it creates a completely new kinematic effect for Jaeger-LeCoultre resembling a spinning top. Fitted with a cylindrical hairspring, the Heliotourbillon takes this thinking further, with a newly developed construction comprising three titanium cages rotating on three axes. The first cage is set at a 90-degree angle to the balance wheel and rotates perpendicular to it. The second cage is set at 90 degrees to the first (thus, on the same plane as the balance wheel). Together, these two cages are constrained by an axis tilted at 40 degrees and make a full rotation in 30 seconds. The third cage is perpendicular to the second and makes a full rotation in 60 seconds. Supported on ceramic ball bearings to minimise friction, the tourbillon consists of 163 components and weighs less than 0.7 grams.

A neat feature of Calibre 388 is that the hours and minutes can be set either backwards or forwards without compromising the perpetual calendar. In Calibre 388, the relationship between the winding and calendar assemblies is such that the perpetual calendar mechanism moves forwards only and cannot be dragged backwards when the time is set backwards. Other notable features of Calibre 388 include a Grande Date display: a classical yet rare complication sought-after by watch connoisseurs, it is set at the 3 o’clock position on the hours-and-minutes sub-dial, ensuring great legibility. The year indication shows the last digit of a leap year in red – a Jaeger-LeCoultre patent – and the moon-phase indication is accurate to 122 years.

Measuring 44 mm in diameter, the case is a complex structure of 34 separate parts and the lugs are screwed rather than integrated, to enable multiple finishing techniques. A mixture of polished, brushed and micro-blasted surfaces creates a fascinating play of light with every movement of the wrist. The apparent simplicity of the case belies its complexity of detail, which perfectly complements the complexity of the calibre within. 

The Duometre collection has always been distinguished by the powerful symmetry of the dial layout. On the dial of the Duometre Heliotourbillon Perpetual, the triangular arrangement that directly expresses the underlying mechanism with its two barrels and gear trains has been turned 90 degrees, as if the winding crown forms the apex of the triangle, the time display is flanked by the two power reserves, and the ‘base’ of the triangle is formed by the moon-phase indicator and days on one side and the months and years on the other. The tourbillon is set above a background of deep blue lacquer representing a starry sky and, as it spins, red triangles set on the third cage indicate 20-second intervals marked on a sapphire crystal arc that floats above the starry blue background. On the main dial refined finishes abound, with applied hour indexes and frames around the date and year, and a mix of opaline, brushed and azuré surfaces creating subtle contrasts between the different indications. 

Duometre Quantieme Lunaire

The first Duometre piece to be offered in steel, its eye-catching blue dial, paired with a new case, lends a decidedly contemporary air to a timeless and distinctive design. On the deep blue dial of the Duometre Quantieme Lunaire, the long and very fine hands are a signature of all Duometre watches, as is the symmetrical layout, with three sub-dials forming an inverted pyramid. 

The sub-dial at 3 o’clock shows the time, with the cardinal hours marked by applied Arabic numerals; the sub-dial at 9 o’clock displays the date with a hand and the moon phase set against a blue sky. The seconde foudroyante sub-dial nestles beneath them at 6 o’clock. Making a complete revolution in one second (versus a ‘standard’ seconds hand, which rotates in 60 seconds) with six ‘jumps’ per rotation, the foudroyante hand makes it possible to observe intervals of precisely one-sixth of a second.

The dial is made in several sections, with different finishes to create visual interest and contrast. The opaline main dial has the very soft glow and sense of visual depth characteristic of that decorative technique. The lower section of the dial is sunray-brushed and, in an added touch of refinement, the two power reserve indicators are distinguished from this sunrayed background by an opaline arc.