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The Precision of Complications
The fundamental requirement for accurate timekeeping is that the power supply delivered from the movement’s barrel to the regulating organ should be absolutely steady, in order to maintain isochronism – the perfect regularity of the mechanism’s ‘heartbeat’.
Requiring a watch movement to drive an additional complication carries the risk of jeopardising its timekeeping accuracy – for the simple reason that the complication itself requires power in order to function. Moreover, while displaying the time accurately, the watch must also ensure that the complication’s indications – for instance, a moon phase, a celestial map, elapsed seconds – are displayed on the dial with the greatest possible precision.
Some complications create a slow and relatively steady drain on the power supply over time – for example, calendars of varying degrees of complexity. Other complications – including chronographs and minute repeaters – require a high burst of energy for a very short period. The chronograph poses an added challenge to precision because its entire purpose is to accurately measure and display precise, and very small, intervals of elapsed time.
Since the early days of the Manufacture, our watchmakers have not only mastered the chronograph but also have associated it with other complications, devising ways to successfully manage the transfer of energy between the timekeeping function and the operation of the complications, while minimising its effect on isochronism.
In their search for a solution to the conflicting demands of timekeeping and complications, Jaeger-LeCoultre’s engineers developed the Duometre concept. Patented by the Manufacture and introduced in 2007, a Duometre mechanism features two barrels, each with a separate and independent gear train, housed within a single calibre and linked to a single regulating organ. One gear train is responsible for powering the time indications, and the other for driving any additional functions. Because it ensures that the operation of the complication does not compromise the timekeeping function, and thus guarantees operating accuracy, this concept has opened the door to continuously expanding horological complexity.
For the first application of the Duometre concept in 2007, Jaeger-LeCoultre watchmakers set themselves the hardest challenge: to develop a chronograph watch that would be as accurate as a chronometer. The result was the Duometre à Chronographe, fitted with Calibre 380 – a fully integrated column-wheel chronograph movement. The Duometre mechanism has since been employed for other complications, including moon phases, a GMT function, a classical tourbillon and, in 2012, a spherical tourbillon.
In 2024, Jaeger-LeCoultre introduces two new Duometre movements: Calibre 388, which powers the Duometre Heliotourbillon Perpetual, features an entirely new tourbillon configuration, which rotates on three axes and creates a ‘spinning top’ effect. And Calibre 391 unites a chronograph with a moon-phase display in the Duometre Chronograph Moon.
Incorporating almost eight decades of accumulated expertise, the new Duometre calibres represent another step forward in the Maison’s continuing quest to master precision. And thus, the story begun by the founder continues…
