The concept behind the replica Jaeger-LeCoultre Duometre has always been highly interesting, from both a technical and visual side. The entire lineup of watches under the replica Duometre name are coming with a unique Dual-Wing system, including two barrels and two gear trains. One of the main springs powers the display of the time and the complications, while the other mains spring powers, via the second gear train, the regulating organ of the watch. Both are regulated by a single escapement module, although these two are connected.For the SIHH 2016, a new version of the replica Jaeger-LeCoultre Duometre Quantieme Lunaire, now in white gold and with opened dial, has been launched, a very good excuse to look back at this watch.
The idea behind the replica Duometre concept is simple. All starts from a basic observation. In a traditional complication watch, any function not constantly linked to the gear train makes the watch's rate deviate upon its activation: a chronograph as it is switched on, a repeater while ringing or even a calendar function that couples just once a day - each leads to a drop in the amplitude of the balance wheel, and a deviation in timing, as they absorb power for their own requirements. Even if for some of these complications the effect will only be noticeable after days or weeks - in the case of a chronograph, the effect is immediate, in the case of a date, the effect is lower - it will remain in the end a rate deviation, something that isn't likable in high-end watches.
The solution found by replica Jaeger-LeCoultre Grande Complication is the Dual-Wing concept, which features two independent power supplies: one is dedicated to creating a precise timing - regulated by the escapement and the balance - and the other solely for the display of time - hour, minute and seconds hands - as well as date and the age of the moon.The replica Jaeger-LeCoultre Complicated watches feature actually within one single calibre - but with both gear trains being synchronized through the jumping seconds hand mechanism, thus by the same escapement and balance wheel. This construction ensure that the activation of the complication won't affect timekeeping and accuracy.
This twin-construction is clearly visible when turning the watch. One barrel is engraved "Heures / Minutes", this one taking care of the display of the time and the serving the activation of the complications, and the second barrel is engraved "Regulateur", this second one providing power to the balance wheel and the escapement, to ensure a rather constant supply of power - and providing (on paper) a high chronometric rate. These two barrels provide 50 hours of power reserve to the watch. But on the contrary of other watches with two barrels, these two, in the case of the replica Jaeger-LeCoultre Reserve de Marche Quantieme Lunaire, are not mounted in series and wound simultaneously. Both springs are wound through the crown: rotating it clockwise winds the timing barrel (escapment), turning the crown counter-clockwise winds the power reserve of the functions (hour, minute, seconds, jumping seconds, date, moon phase). This is also why the dial shows 2 separated power reserve indicators.