Hi All, Apologies if this has been asked before. So I recently bought a brand new Speedmaster Professional Moonwatch (wanted one for years and finally pulled the trigger). Absolutely love it but just wondering about the power reserve. So since purchasing it last week I’ve been testing the reserve as if there were any faults I figure it’s best to get them sorted out under warranty sooner rather than later. On it's first full wind (without using the chronograph) it managed 51hrs before stopping (so I’m pretty sure I’m fully winding it). On the second full wind it only managed 41hrs - however this time around I started the chronograph and let it continue to run the whole period. I’m by no means an expert on the mechanics of the movement but is it normal for the power reserve to be so largely affected by the starting/stopping/continual running of the chronograph? Many thanks for your replies in advance.
Correct Remember the Chrono does not take power away faster. But running the Chrono requires more torque to function as the power gets lower the torque drops. So runningnthe Chrono will cause the watch to stop sooner but stopping the Chrono May restart the watch.
Perfectly normal - if you let the watch run down with the chronograph running, and after it stops turn the chronograph off, the watch will start ticking again. If you then let it run down and add the time it ran in both cases together, it will very likely still equal 51 hours that you had on the initial test. From a technical perspective, the power reserve is baked into the design of the watch - length of the mainspring, number of turns of the barrel, and gear ratio between that and the center wheel. However a watch will stop when the torque required to overcome the frictional loads exceeds the torque that the mainspring is putting out. When watches run down and stop there is still power on the mainspring, and in a watch that is in good condition it will be some fraction of a turn of the barrel - in normal use it never runs all the way down to zero torque being supplied by the spring. Anyway, the loads that can stop the watch can be from things like added complications, such as chronographs running, or date change mechanisms. If the time when the watch runs down happens to be near the date change, you will often find a watch that is running down stops around the time of the date change. But if you advance the hands through the date change, it may run for a few hours after. The running time can also be reduced by worn parts, gummed up oils etc. as the watch nears a service interval. But the basic geometry that determines how many turns of the center wheel will happen never change, unless the physical characteristics of those parts are changed - for example installing a longer or shorter mainspring. Cheers, Al
Hi All, Many many thanks for all your responses! Al, in particular your response is fantastic and a good explanation for a layman such as myself! This puts my mind at rest with regards to the power reserve and I can continue enjoying the watch.