it doesn't use any more power, it just adds more friction

Hi Dynamic Turtle,

It's something of a misconception to think that chronographs use more power when they're on, and you can prove it to yourself experimentally with a simple test. Run a watch with the chronograph on until the watch stops. Then turn the chronograph off and the watch will start up and continue to run for several more hours. The power has not gone anywhere, it's just that the additional friction in the chronograph train has raised the minimum power requirements to keep the watch running.

The main source of friction in a chronograph mechanism is the friction spring that smooths out the running of the sweep second hand. In most cases this will reduce the running amplitude by somewhere between 15 and 30 degrees at full wind and the power reserve by 5 to 7 hours or so (let's say roughly 10 percent of the power reserve). This is of course NOT the case where some vertical clutch chronograph designs are concerned and a source of great pride for some Blancpain enthusiasts, but that is another discussion entirely.

_john

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7750 question for all you techies

By: Dynamic Turtle : October 5th, 2009-08:58

I recently bought a triple-register 12 hour chronograph (gulf war camo style thing - Meccaniche Veloci for anyone who cares) with a 7750 base. Still a horrid thing that reminds me of dark IWC GST days! Assuming a fully wound mainspring and engagement of t...

Normally, the reduction of the power reserve ....

By: Marcus Hanke : October 6th, 2009-01:46

... by the chronograph function is not too drastic, maybe two to four hours, normally even less. So a fully wound 7750 should still run about 40 hours. For longer road trips, I do use the chronograph for several hours, and there is also sense in using it ...

Thanks

By: Dynamic Turtle : October 6th, 2009-02:52

Very interesting point re the psuedo GMT function! I'm suprised the chrono doesn't use more juice. DT

The energy consumption is not so high ....

By: Marcus Hanke : October 6th, 2009-03:09

... the main chronograph hand has a very low mass, and the two tiny subcounter hands are also not so consuming. Of course things are entirely different with special kinds of indications, such as the numeric display of the Porsche Design monster. For this,...

it doesn't use any more power, it just adds more friction

By: ei8htohms : October 10th, 2009-01:04