Tuesday, April 24, 2007

Jaeger-LeCoultre Duomètre à Chronographe - Brilliant but Pointless

But then are not all mechanical watches? Brilliant but pointless.

Among the concerns I have about this piece, the main one is the obvious one. Is the claim of better timekeeping under chronograph operation achieved?

The barrel and balance wheel package has to be compromised so as to include two barrels and associated chronograph gear train. This leads to a 11.5 mgcm2 balance wheel at 21600 vph (a shocking 1/3 of the balance power of Autotractor) and modest power reserve. Is that trade-off worth it really? I wonder if there is poorer time keeping from the lower performance balance wheel and beat than is created by chronograph operation in a well designed clutch movement with a higher beat and higher inertia balance - take a Rolex 4130 for example.

Remember that under COSC testing there is a 24 our period of chronograph use that must not deviate outside 5 seconds or the criterion for Vmax would be failed (Greatest variation in rates ‘Vmax’ is the absolute value of the greatest of the five variations in rates with regard to the five positions of the watch during the first 10 days of the tests: allowed to be 5s). We debated how JLC's 1000 hour test stacked up against COSC testing here. However, I've never seen a chronograph tested over the MC 1000 hour.

It would need to be significantly better than the above 5s/d standard with/without chrono or it would be a pretty pointless complication. I would suggest that with all this effort it ought to be 0s/d different As ever, it would be nice to see some data from JLC. GAME ON!

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