Now that we have wound the watch, let's play with the chronograph function and get a better understanding of the mechanism. The Duometre is a monopusher chronograph, a bit of a rarity these days but very classic.
Starting the chronograph via the push piece located just above the winding crown sets the chronograph into motion. In this illustration above (as well as the next two illustrations), the push piece works by pushing the main chronograph-operating lever in the direction of the red arrow, (upper left of the drawings). The hour, minute, and seconds recording hands are immediately set into motion because the hook that was holding the chronograph gear train in place has released the flying-seconds 6-point star wheel (see insert).
Pressing the push piece a second time stops the chronograph function as the hook latches on to one spoke of the 6-teeth star wheel (see insert). This stops the chronograph and the precise hours, minutes, seconds, and fractional second of an event are recorded.
Press the push piece again, this time holding it for one second. This action brings the chronograph function back to zero. Perhaps, you have noticed that one spoke of the flying seconds 6-teeth star wheel looks slightly different from the other 5. This "special" tooth is the only one, out of the six, that is capable of engaging the hook when it has been slightly retracted, as shown in the insert.
It is only when the hook has engaged this special tooth that the hammers are allowed to drop to their heart shaped cams located on each of the hour, minute, and seconds hands, thus returning all chronograph recording hands to their zero positions.
The Duometre is finished to the exacting high standards of Jaeger-LeCoultre. I particularly like the blue screws, which add a nice contrast to the rhodium-plated bridges and ruby jewels. A sunburst damascene pattern radiating from the center of the balance wheel decorates the bridges in place of the more commonly seen Côte de Genève pattern – a nice touch in my opinion.
Duometre is based on a new Jaeger-LeCoultre movement (ebauche), aptly named the Dual Wing. I’m told that the Dual Wing will form the base for further watches in the Jaeger-LeCoultre stable and I am waiting eagerly to see what comes next.
