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Discussion Starter · #1 · (Edited)
​I often hear about how much to wind a 2824-2 or STP1-11 through the stem to get accurate time keeping without over doing it since the auto winder will keep it powered up throughout the day. Use this information based on your daily arm/wrist movements to judge for yourself. For this example I'm using the STP.

To start we need some facts. It takes 8 turns of the mainspring arbor for a full wind. The arbor wheel has 63 teeth, the intermediate wheel has 26 but only engages every other tooth on the mainspring wheel. The winding pinion on the stem has 10 teeth. The math works like this 31.5/26=1.211, 26/10=2.6. 1.211x2.6=3.15 or more simply 31.5/10=3.15. It takes just over 3 full turns of the stem to wind the mainspring arbor 1 time. 3.15x8=25.2. To get a full wind you need to turn the stem 25 full times.

winder8.jpg

gear.jpg

​The auto winder works the same but uses compound wheels. The rotor has 38 teeth, the reverser has 39 with a small pinion that has 11 teeth. The other reverser was not calculated because of a 1:1 ratio. The next wheel has 47 and 9 followed by a 61 and 9 wheel that send power to the mainspring wheel at 63. The math works like this, 38/39=.974, 11/39=.282, 9/47=.191, 9/63=.142. .974x.282x.191x.142=.0074. One rotor rotation turns the mainspring wheel .0074 times. 1/.0074=135, it takes 135 rotor rotations to wind the mainspring wheel 1 time. 135x8=1080, 1080 rotor rotations gives a full wind.

Here are photos showing power transmission through the rotor to the mainspring wheel.
winder0.jpg

winder4.jpg

winder3.jpg

winder5.jpg

winder6.jpg

winder7.jpg

So what does this all mean? First we start with stem winding facts referencing timegrapher readings.

1/4 wind or just over 6 full turns of the stem,
242 degrees amplitude, +8s.

​1/2 wind or 12 full turns on the stem,
289 degrees amplitude, +4s.

3/4 wind or 18 full turns,
​312 degrees amplitude, +2.

Full wind or 25 full turns,
320 degrees amplitude, +1s.

Giving a run down movement 12 full winds through the stem will give accurate timekeeping. If you are moving very frequently throughout the day, the movement will stay powered up and keep excellent time.


RFG

 

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Discussion Starter · #3 ·
What an amazing post! Super fascinating.
Thank you. I'll do a Miyota 9015 next but need to partially disassemble the barrel to see the mainspring go to full wind. The 2824-2 and clones have a certain feel and sound to them when the mainspring slips inside the barrel. The Miyota is very smooth.

RFG
 

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Whatcabout the seiko nh35
 

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No one said there'd be math.


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A COSC certified movement will spare you from all those mathematical calculations.
 

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A COSC certified movement will spare you from all those mathematical calculations.
I believe his point is related to isochronism, which affects all mechanical watches, even COSC certified chronometers, which go through testing involving being wound every 24 hours, or, about 1/2 of full power for a watch with a 44 hour power reserve (what the STP has).


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Interesting stuff, especially the accuracy difference from half wind to full. Any thoughts on the often mentioned weakness of the winding pinion teeth on the 2824 that stokes fear that it could suffer early damage by hand-winding?
 

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I believe his point is related to isochronism, which affects all mechanical watches, even COSC certified chronometers, which go through testing involving being wound every 24 hours, or, about 1/2 of full power for a watch with a 44 hour power reserve (what the STP has).
But how could he prove that the power reserve is the main factor affecting isochronism? How about other factors like hairspring material/construction, balance positions, temperature variations...?
 

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But how could he prove that the power reserve is the main factor affecting isochronism? How about other factors like hairspring material/construction, balance positions, temperature variations...?
Uhm... I can't tell if you're serious or joking.

Do you know what isochronism is? It's only about power reserve.

Like, that's what isochronism specifically refers to, the phenomenon of losing accuracy as a watch loses power.

Are you just throwing out a bunch of watch-related words here? The thread is about power reserve and accuracy. What do any of those other things have to do with the thread topic?


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Uhm... I can't tell if you're serious or joking.
Why do you think that I'm joking?

Do you know what isochronism is? It's only about power reserve.
Isochronism

The property, in an oscillator such as a pendulum or balance, of having a period that is independent of oscillator amplitude. In layman's terms, a pendulum or balance that takes the same time to complete a swing no matter how big the swing is, has the property of isochronism. An isochronal oscillator, whether a balance and balance spring, a pendulum, or a quartz crystal in a quartz watch, is essential – without one there is no timekeeping.

"Isochronism" is derived from Greek roots (iso + chronos) and means, literally, "in the same time."

All a watch or clock really is, is a machine for counting swings of an oscillator. Since no mechanism can deliver exactly the same amount of push to an oscillator each time it gives the oscillator energy, and since external disturbances can cause bigger or smaller amplitude in the swing of an oscillator, if the oscillator is not isochronous, it can't keep accurate time.


Source: https://www.hodinkee.com/watch101/isochronism

Like, that's what isochronism specifically refers to, the phenomenon of losing accuracy as a watch loses power.
Power losing is the last thing you should care on an automatic watch, those watches are made to always have a full power reserve, so accuracy has very little to do with losing power. Of course if you take the watch off its power reserve will decrease, but it's intentional because an automatic watch needs XXX rotor turns per day.
 

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Why do you think that I'm joking?



Isochronism

The property, in an oscillator such as a pendulum or balance, of having a period that is independent of oscillator amplitude. In layman's terms, a pendulum or balance that takes the same time to complete a swing no matter how big the swing is, has the property of isochronism. An isochronal oscillator, whether a balance and balance spring, a pendulum, or a quartz crystal in a quartz watch, is essential – without one there is no timekeeping.

"Isochronism" is derived from Greek roots (iso + chronos) and means, literally, "in the same time."

All a watch or clock really is, is a machine for counting swings of an oscillator. Since no mechanism can deliver exactly the same amount of push to an oscillator each time it gives the oscillator energy, and since external disturbances can cause bigger or smaller amplitude in the swing of an oscillator, if the oscillator is not isochronous, it can't keep accurate time.


Source: https://www.hodinkee.com/watch101/isochronism



Power losing is the last thing you should care on an automatic watch, those watches are made to always have a full power reserve, so accuracy has very little to do with losing power. Of course if you take the watch off its power reserve will decrease, but it's intentional because an automatic watch needs XXX rotor turns per day.
Okay, you're serious.

No idea what you're talking about, but whatevs.


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Okay, you're serious.

No idea what you're talking about, but whatevs.
Is my English that bad?

I said buying a COSC certified watch will spare you from such complex calculations. Regardless what you do the watch's accuracy will remain within specs.
 

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Is my English that bad?

I said buying a COSC certified watch will spare you from such complex calculations. Regardless what you do the watch's accuracy will remain within specs.
I read what you said. You're incorrect, about all of it.

COSC chronometers are highly accurate - when fully wound. But just like all mechanical watches, they will lose accuracy as they lose power (or be less accurate on low power) due to isochronism, or the phenomenon of a watch losing amplitude - and accuracy - as it loses power, due to the lessening amplitude.

No matter how accurate they are when fully wound, as the watch loses power, the amplitude lessens, and the watch becomes less accurate. This is also true for COSC chronometers, just as it is for all mechanical watches, so your comment is somewhat baffling, if you understand this (and it appears that you did not, given your further comments).

Notice how the OP provided both accuracy and amplitude numbers for the same movement, at varying states of power reserve? Notice how the watch is less accurate when the amplitude is lower? That's the point of the thread - how power affects accuracy, the result of isochronism.

In point of fact, those complex calculations were in fact necessary to calculate the number of crown turns needed to reach the varying states of power, and it's EXACTLY those complex calculations movement manufacturers do in order to determine the same thing for their own movements.

As I said, the thread is about accuracy as it relates to power reserve, and the phenomenon of isochronism. It's got nothing to do with
other factors like hairspring material/construction, balance positions, temperature variations...
I literally just wrote a detailed blog piece about this exact subject - Watch-geeks and the Zen of Accuracy - Janis Trading Company.
 

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@lvt - You should read up on COSC testing if you're going to talk about it, so you know what you're talking about. The testing requires daily winding of the movements at precisely the same time each day, in order to avoid the effects of isochronism.

In other words, a COSC movement will NOT remain within specs, no matter what you do to it, if one of the things you do to it is letting it run down to the point it begins to lose accuracy due to being low on power.
 
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Discussion Starter · #17 ·
I read what you said. You're incorrect, about all of it.

COSC chronometers are highly accurate - when fully wound. But just like all mechanical watches, they will lose accuracy as they lose power (or be less accurate on low power) due to isochronism, or the phenomenon of a watch losing amplitude - and accuracy - as it loses power, due to the lessening amplitude.

No matter how accurate they are when fully wound, as the watch loses power, the amplitude lessens, and the watch becomes less accurate. This is also true for COSC chronometers, just as it is for all mechanical watches, so your comment is somewhat baffling, if you understand this (and it appears that you did not, given your further comments).

Notice how the OP provided both accuracy and amplitude numbers for the same movement, at varying states of power reserve? Notice how the watch is less accurate when the amplitude is lower? That's the point of the thread - how power affects accuracy, the result of isochronism.

In point of fact, those complex calculations were in fact necessary to calculate the number of crown turns needed to reach the varying states of power, and it's EXACTLY those complex calculations movement manufacturers do in order to determine the same thing for their own movements.

As I said, the thread is about accuracy as it relates to power reserve, and the phenomenon of isochronism. It's got nothing to do with

I literally just wrote a detailed blog piece about this exact subject - Watch-geeks and the Zen of Accuracy - Janis Trading Company.
I could not have said it better myself.
 

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Discussion Starter · #19 ·
Interesting stuff, especially the accuracy difference from half wind to full. Any thoughts on the often mentioned weakness of the winding pinion teeth on the 2824 that stokes fear that it could suffer early damage by hand-winding?
The old saying is, "Anything manmade is prone to failure." I think the winding pinion failure fears are over exaggerated, but I don't want to re-hash that here. If you are like me you may have several watches in rotation, I have over 30 at any given time, about 10 ETA's or clones are included. If a 2824-2 is run down will you make sure to wind it through the rotor at least 500 revolutions? No. Just give it a half wind and you are good to go.

About accuracy, if that is the main consideration for buying a watch then I suggest a quartz or better yet an atomic watch. I like mechanical movements and don't expect them to perform like a quartz. I have over 100 mechanicals and one quartz.

Last week I had a patient in my lab. He always brags about his Rolex. He just spent $1500 for a service. I let him know the crown did not screw down. He said that was an additional charge to fix. I happened to have my timegrapher with me that day. I put his Rolex on the machine, 243 degrees amplitude, -15s. I put my NTH Nacken on the machine, 300+ degrees, +1s. That's a Japanese movement I said. He almost fell over.
 

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Ahh, yes, terminology and how it differs from one field to another...

Generally speaking, isochronism is a physics phenomenon, which for any oscillator such as the balance wheel in a watch movement, can be affected by numerous different factors.
In the field of watchmaking though, the term isochronism seems to have taken on the more specific meaning of how well a movement can keep regular timing as the mainspring winds down.

For myself, I look at all those pictures, especially all the tiny gear teeth, and the following thought comes to mind: Design is one thing, and execution another.

Generalizing that thought to other things/equipment besides watches. One may copy another's design and produce something that's (almost) exactly the same. But if your tolerances aren't as good, or your metallurgy isn't up to snuff, performance and durability will suffer.

*grumbles something under his breath about crappy aftermarket parts while leaving*

Edit: Not to say that's always true, but for some things, sometimes you can't beat the original manufacturer, while for other things, sometimes the aftermarket stuff does better; do your research!
 
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