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

[Tools]

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..

[f16570]

Nice one Tools, informative and educational.
Thanks

[Tony-GB]

Fascinating. Thanks for posting.

[SS Oyster]

Great information. My GMT IIc, though worn daily gets a good wind every once in a while and after checking it after 4 days against standard time, it only gained 2.5 seconds. That's +0.625 secs/day --- absolutely amazing and well within COSC standards.

[dubeagle]

Great info.

I read somewhere that as the mainspring is tighter (or more) wound, the watch slows down and that as the reserve is reduced, that the watch speeds up. Can this be?

[Tools]

Originally Posted by dubeagle

Great info.

I read somewhere that as the mainspring is tighter (or more) wound, the watch slows down and that as the reserve is reduced, that the watch speeds up. Can this be?

Yes... that tends to be true..

A tight mainspring provides maximum pull to the gear train so you have maximum friction, and you have a pallet yoke that has a stronger "push" on the hairspring jewel to give maximum amplitude to the hairspring....maximum amplitude means that it is swinging back and forth at about 300 degree arcs.. it is the timing and speed of this swing that locks and unlocks the escapement wheel....tick-tock, at exactly 8 per second.

When the mainspring winds down, there is less torque in the system, less friction, and the hairspring does not get quite as big a "push" from the system..the amplitude drops to less than 240 degrees per swing (swings shorter and faster), there by speeding up when the mainspring is unwound.. perhaps 8 1/2 to 10 ticks per second..

(There are other forces as well, but this is a key point)

[Wooddog44]

Originally Posted by Tools

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..

So if I wear my watch everyday for at least a few hours do I still need to give it any "extra" winding?

How much, how often?

Thanks!

[JJ Irani]

Originally Posted by Wooddog44

So if I wear my watch everyday for at least a few hours do I still need to give it any "extra" winding?

How much, how often?

Thanks!

Even if you wear your watch for 7~8 hours on a daily basis, that should suffice to keep the watch going.

JJ

[buz-lh]

Another very informative post. Thanks.

[acce1999]

And to add to this interesting issue:

The state of the mainspring tension has an amazing impact on accuracy. In the large number of postings we see here on the theme accuracy I am pretty certain very few take the state of the mainspring into consideration.

I have observed that with full (maximum) tension most Rolexes are dead on, but after 24 hours (even less) of sitting still they start to drift: Caliber 30XX and 313X starts to gain time, and during the last 4 to 8 hours they behave differently: 30XX slows dramatically and loses seconds per hour, whilst the 313X picks up a second or two more every hour.

My caliber 3186 (my guess) Ex II (M serial) is the most consistent one. Just losing fraction of seconds as tension drops. Perhaps helped by the new Parachrom balance spring.

Best,

A

[acce1999]

Originally Posted by JJ Irani

Even if you wear your watch for 7~8 hours on a daily basis, that should suffice to keep the watch going.

JJ

Yes that's true, but if you expect maximum accuracy you need to keep it at maximum tension. See my post above.

Best,

A

[karmatp]

Larry, you da man, I love reading stuff like this. Very entertaining and informative, thanks.

[JJ Irani]

Originally Posted by acce1999

Yes that's true, but if you expect maximum accuracy you need to keep it at maximum tension. See my post above.

Best,

A

I read your interesting post above, but it's OPTIMUM tension you need to be looking out for. That's the correct tension that will keep your watch very, very accurte at all times.

Works for me, my friend!!

[acce1999]

Originally Posted by acce1999

... and during the last 4 to 8 hours they behave differently ...

The last 4 to 8 hours of total available tension... most likely hours 40 to 48...

[Andad]

Thanks for the info Larry.

My 14060M is my daily wearer. During the week Monday - Friday I wear it 7.00am - 4.30pm - no winding at all, during this period it gains just less than 1 sec / day. When I take it off on Friday I give it a full wind before putting it away for the weekend. Over the weekend it looses 4 - 5 seconds then the whole cycle starts again.
I set it to timeticker on the 13th of October and today it is 2 seconds slow as we head for the weekend. Winding it up certainly slows it down and I can adjust the gain/loss by winding or not winding.

Can the auto winder wind a Rolex up to the 'clutch slip' point? If not what % of full winding will the auto winder achieve?

[JJ Irani]

Originally Posted by directioneng

Can the auto winder wind a Rolex up to the 'clutch slip' point? If not what % of full winding will the auto winder achieve?

Hmmmm....interesting question, Eddie. Never thought of that.....but I doubt a winder would be able to give any watch a FULL MAXIMUM wind. By my thoughts, it would be just over the optimum level.

JJ

[Tools]

Eddie,

I would think that a watch winder is going to only give it the winding power that you have set..and it will vary... If you put an already well wound watch on the winder, it will keep it there for quite some time..

If it is not wound at all, then it will wind it to a point, and it will tend to stay at that point as long as the winder is working......it could be to the point of clutch slippage since that is the watches safety feature, after, if the rotor is turning, it is trying to wind the watch... however, most winders are designed to just keep it running until needed...

As to wearing vs. letting it sit either in a winder or on a desk.... a worn watch will usually run faster than one that just sits.........The movement of your wrist and activities tend to change positions and amplitude of the hairspring off optimum so it gets a lot fewer full amplitude swings than it would just sitting....therefore, it will gain a few fractions of a second..

[golfball123]

the panerai has reserve upto 10 days ! how did they do it ? bigger n stronger spring ?

[Tools]

Originally Posted by golfball123

the panerai has reserve upto 10 days ! how did they do it ? bigger n stronger spring ?

The 10 day has multiple mainsprings........ I think, but the correct answer to your question is an absolute YES....

As a rule, the IWC 8 day, and the other watches with a high power reserve have huge, long alloy mainsprings.. The IWC mainspring and barrel is almost 3 or 4 times the size of the typical 48 hour spring..


It takes a big watch to be able to install one of these massive springs....

Personally, I fail to see any benefit in having a wrist watch with an extended power reserve... A mantle clock, sure..... but a wrist watch........

[Perdu]

I've not tested my Rolex but my Omega is spot on if worn and can loose 8 seconds if I leave it off 24 hours on it's side. I suspect Rolex will do much better (not tested yet) but I've learned by experimenting the way to keep your watch as accurate as possible is to wear it. And Larry, thanks for explaining Isochronism, I never really got it before. I guess one test of accuracy could be the accuracy rate as the spring unwinds.

[Tools]

We like to say that our watch is designed to tell time...

But, really ...it isn't....

The hands only give us an indication of the rate at which the mainspring is unwinding... and there is a bunch of stuff attached so that rate is consistent, and at a rate we can relate to...... the rotation of the earth..

[acce1999]

Originally Posted by JJ Irani

I read your interesting post above, but it's OPTIMUM tension you need to be looking out for. That's the correct tension that will keep your watch very, very accurte at all times.

Works for me, my friend!!

Hmmm... yes you're right, optimum is probably a better word than maximum (to avoid misunderstanding since overbanking could be a problem with too much tension).



Best,

A

[Singslinger]

Useful information - thanks guys!

[DanP]

Great postings everyone! Very informative! Thanks

[marshallr47]

Good stuff Larry. Thanks.