Power Reserve.... What Is It.... ?? (my views)

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OK... I'll tell you...

Power Reserve on most Rolex watches is 42-48 hours.. The Daytona is 72 hours, and the Ladies watches are around 35 hrs because of the limited space and smaller mainspring..

But, that isn't what I mean... My question (which, of course, I will answer) is...Why ??? If we wear a watch all the time, why do we need a 2 day power reserve...

Well, it all goes to optimum mainspring pull and isochronism. Isochronism (completely in balance) attempts to achieve the same hairspring amplitude (watch tick tock timing) throughout the entire time the mainspring is unwinding.

Of course, this cannot actually be accomplished.... at some point, there just isn't enough oomph to keep things the same.

Mainsprings are made much bigger and stronger than necessary (for a days worth of ticking) to be able to keep the pull of the mainspring in its upper power curve. On an automatic watch, activity keeps it "topped off"; if you are inactive and mainspring pull drops below optimum, your watch timing is whacky. A manually wound watch takes 50 from a dead stop, but only 25 each morning... Watch engineers expect that both will stay in the top-half of the power curve for most of it's operating time.

So, the next time that you have your watch off for a couple of days and slip it back on........give it a few winds first to get it back in it's best operating curve.....the entire drive train will thank you..