9300 Winding Question

kaereachi · Dec 21, 2015

Hello.

I recently bought a Grey Side of the Moon watch, my first automatic. Was reading about the 9300 movement and that it contains two mainspring barrels, and from what I understand one barrel is wound by the crown and the second barrel is wound by the rotor, with a slipping clutch to prevent over-winding. I have read that the barrels are used sequentially, but can't confirm this. The movement claims to have a 60 hours power reserve.

My question is that given the nature of each mainspring, is it necessary to wind the crown regularly to maximize the power reserve and accuracy? Otherwise the natural winding of the rotor will only offer half the power reserve at best? I feel as though doing this will put strain on the winding mechanism if done regularly. I have read that not winding the crown and relying on the rotor only can decrease the accuracy of the movement, but have not read that specifically to this movement. But I have also read that automatic watches really are not meant to be hand wound regularly and are more susceptible to breakage by doing so.

What do you recommend? And can anybody confirm whether these mainsprings are used sequentially and whether hand winding is necessary on a regular basis?

Horlogerie · Dec 22, 2015

Hello and welcome,

I don't have access to the technical data on this particular movement, but since I am a watchmaker I do have an understanding of how movements work and did some research, I think the following should help you understand.

There are two barrels, both can be wound either by the crown or the roto, it makes no difference what method is used, the results are identical.

The design is such that the first barrel that gets wound has a mainspring that is hooked solid to the mainspring barrel, in the same fashion that a handwind movement is designed, once this first mainspring is fully wound, the winding motion is then transferred to the second barrel, via the first barrel, continued winding winds the second barrel which has a clutch that releases when the mainspring is fully wound, as is found in an automatic movement.

Handwinding or automatic winding produces the same results, there is no requirement to hand wind the watch along with having it wind itself automatically.

Both mainspring feed the train, at full wind the torque comes from the second automatic barrel, once it's depleted the first barrel takes over and powers the movement.

Rob

OmegaSean · Dec 22, 2015

Very informative post thank you Rob, does the 8500 that has 2 barrels work the same ?

Thank you in advance

OmegaSean

Horlogerie · Dec 22, 2015

Yes, from what I can glean from the 8500 tech documents, the same principle applies.

The barrels are connected in series and only barrel two mates with the train, having looked at the drawings and read the functional description I am not 100% sure if both barrels wind simultaniously or if as I described above the 1st barrel winds fully, then it winds the second.

In the description they state "...the upper winding torque on barrel 1 is slightly lower than the barrel 2 torque..." then it states "...there is a balanced torque between the two barrels during winding..." but it sounds as if the first one winds the second only once fully wound and locked by the mainspring bridle.

Rob

OmegaSean · Dec 22, 2015

Thanks Rob.

OmegaSean

Horlogerie · Dec 22, 2015

My pleasure, hopefully I got most of it right... 😀

Rob

Archer · Dec 22, 2015

Horlogerie
Hello and welcome,

I don't have access to the technical data on this particular movement, but since I am a watchmaker I do have an understanding of how movements work and did some research, I think the following should help you understand.

There are two barrels, both can be wound either by the crown or the roto, it makes no difference what method is used, the results are identical.

The design is such that the first barrel that gets wound has a mainspring that is hooked solid to the mainspring barrel, in the same fashion that a handwind movement is designed, once this first mainspring is fully wound, the winding motion is then transferred to the second barrel, via the first barrel, continued winding winds the second barrel which has a clutch that releases when the mainspring is fully wound, as is found in an automatic movement.

Handwinding or automatic winding produces the same results, there is no requirement to hand wind the watch along with having it wind itself automatically.

Both mainspring feed the train, at full wind the torque comes from the second automatic barrel, once it's depleted the first barrel takes over and powers the movement.

Rob

Hi Rob,

The 8500 and 9300 system does not work in the way you have described, so I'll try to explain it here for you and others...

One barrel has the regular end mainspring that is attached at both ends, and the other barrel has the slipping bridle automatic spring.

The winding of both barrels is simultaneous, and not sequential as you have indicated. The ratchet wheel on top of the first barrel meshes with a ratchet wheel transmission wheel, and then the ratchet wheel on the second barrel. When the first barrel is wound the torque is transmitted along to the second barrel as the first barrel is being wound. The torque between the two barrels is constant during winding.

The final torque of the barrel that has the slipping bridle is slightly less than the barrel with the fixed spring. So when the fixed spring is fully wound the bridle slips in the automatic barrel and excess torque that might cause rebanking is not transmitted to the train.

Unwinding happens in a similar fashion, so the barrel that has slightly higher torque is driving the first wheel, but as that torque decreases to a point where it matches the torque of the other barrel, both barrels then unwind simultaneously, and the link between them means the torque between both barrels is even as they unwind.

Of course as you have mentioned, there is no need to wind the watch manually, because both barrels are wound regardless of the winding method used.

Hope this helps you understand the system better.

Cheers, Al

Horlogerie · Dec 23, 2015

Thanks for that Al.

What the tech docs state doesn't match the simultanious winding that you describe. Unlike a conventional layout where you are winding the ratchet wheel, in this set up you are winding the barrel.

So we have barrel 1 being wound (the barrel directly, not the ratchet wheel). As barrel 1 winds up, the fixed spring transfers torque to the barrel 1 ratchet wheel, which through the ratchet wheel transmission wheel, applies this torque to the barrel 2 ratchet wheel, which winds up the barrel 2 slipping spring. Barrel two is meshed with the center 1st wheel.

For both barrels to wind together, shouldn't barrel 1 mainspring have to have more torque than barrel 2, in order for barrel 1 to overcome the torque and wind the barrel 2 spring. But according to the technical description, that isn't the case:

The technical description states "The upper winding torque on barrel 1 is slightly lower than the barrel 2 torque".

So how does a mainspring with less torque (1) wind a mainspring with more torque (2)? I could see it winding once the barrel and ratchet locked when the spring was fully wound, but not before.

This I can't figure out, if I had one in the shop I would be able to watch the winding in person, but I don't...

Rob

Archer · Dec 23, 2015

It clearly says that both barrels wind simultaneously. The reason it does so is right in the statement that you quote as proof that it can't. It refers to the "upper" winding torque, so when fully wound or at maximum torque. Of course that is not the case when the watch is fully unwound or in the process of being wound. If you start at a fully unwound state (as much as each barrel can unwind in an assembled watch) as soon as barrel 1 is wound at all, it has more torque than barrel 2 does, so the torque is transmitted to barrel 2 via the ratchet wheels and the ratchet wheel transmission wheel.

I think if you spend a few more minutes thinking about this it will become quite clear...

Cheers, Al

Horlogerie · Dec 23, 2015

I have thought about it, and re-read that tech docs, and it doesn't at all tell me that both barrels wind together. A weaker spring able to wind up a stronger one just doesn't add up.

I still maintain that barrel 1 winds first and then barrel 2 winds once barrel 1 and it's ratchet wheel are locked due to the fixed mainspring reaching it's full wind position...

Clear as mud, but there you have it.

Rob

Archer · Dec 23, 2015

Okay, you can believe what you wish, but I personally think this statement makes it quite clear...

"The barrel one torque is transmitted to barrel two by the ratchet wheels and ratchet wheel transmission wheel. There is balanced torque between the two barrels during winding."

The torque between the two barrels can't be balanced if one is being wound and the other is not...

Cheers, Al

guelerct · Dec 23, 2015

Thanks for the info
If one of these models lies dormant is it better to prime the spring by winding it manually vs just wearing it?

Archer · Dec 23, 2015

With any watch that can be wound manually, most companies recommend that the watch is wound via the crown from a dead stop before you put it on for the day. If you just strap it on without any winding, the timekeeping will be pretty wonky to start typically.

Cheers, Al

ScubaPro · Dec 23, 2015

This is why none of my watches has more than one barrel. The ensuing confusion of the multi barrel system travels up my arm, and upon reaching sufficient torque enters my brain and causes chaos. I have enough to handle with a single barrel movement.

kaereachi · Dec 24, 2015

Thanks Al and Rob for your help bringing light to this question and discussing it. If I am correct, it seems that regardless of whether the barrels wind simultaneously or sequentially, the crown winding mechanism and the automatic rotor mechanism are both connected to the same mainspring winding mechanism? This would imply that it is possible to achieve a full wind to the 60 hour power reserve either by hand winding fully, or wearing the watch sufficiently long enough that the rotor alone could wind both barrels fully. Does that make sense and do you agree?

Horlogerie · Dec 24, 2015

K kaereachi
Thanks Al and Rob for your help bringing light to this question and discussing it. If I am correct, it seems that regardless of whether the barrels wind simultaneously or sequentially, the crown winding mechanism and the automatic rotor mechanism are both connected to the same mainspring winding mechanism? This would imply that it is possible to achieve a full wind to the 60 hour power reserve either by hand winding fully, or wearing the watch sufficiently long enough that the rotor alone could wind both barrels fully. Does that make sense and do you agree?

Your welcome, more discussion to come as more folks with actual hands on experience with this watch join in. Unfortunately I haven't had one on the bench, yet...

After all that back and forth, you are correct in that hand or automatic winding produces the same results and both are connected to the same gears to wind the springs. If putting the watch on and it's not running, best to give it a handwind and get some charge built up, before you wear it. I don't know how many rotations of the automatic winding rotor are needed for a full wind, but I expect that it's quite a few. The automatic winding is bi-directional so it's very efficient.

Great question, you forced me to look at a movement I was not familiar with.

Happy Holidays!
Rob

Horlogerie · Dec 24, 2015

Archer
The torque between the two barrels can't be balanced if one is being wound and the other is not...

Cheers, Al

Good morning Al,

I think you are confusing torque with the actual winding action.

Because both barrels are joined by a gear, it stands to reason that torque between them will always be balanced, it has to be because of the gear. But even though the torque is balanced, it doesn't result in both barrels winding at the same time.

The 1st barrel mainspring is weaker than the 2nd barrel, as the 1st winds the torque between both barrels is the same even with the 2nd ratchet remaining stationary, the 2nd spring doesn't wind up, not until the 1st reaches close to full wind where Hooks law deviates and the force increases, then it can overcome the stronger 2nd spring and cause it to wind along with the first.

At full wind of the 1st barrel, the mainspring fixed end causes the barrel and ratchet gear to become one and there is no more winding, at this stage the torque between both barrels is the same even as the 2nd barrel continues to wind, yet the 1st barrel remains fixed = equal torque, but only one barrel is winding.

Rob

Horlogerie · Dec 24, 2015

One last post.

Christian has recently serviced one of these movements, so I asked for his view and what he observed, here's his reply on my PM:

As the mainsprings have different strength, it definitely has to be the manual (1.17mm x 0.095mm) mainspring that is wound first. It does of course wind the automatic mainspring slightly as it's wound, but only to a small degree. But as you get towards the manual mainspring being fully wound, the automatic mainspring (1.49mm x 0.08mm) is getting wound to a certain degree, too. So when the manual mainspring is fully wound, the automatic one will be wound quite a bit, too, and if you continue winding, you will then get to the slipping of the automatic mainspring.

You are of course correct that the winding power flow goes through the manual mainspring first, and from there to the automatic mainspring. They definitely aren't wound at the same time, e.g. to the same amount of rotations together, as the gears aren't fixed that way. It's the manual mainspring winding the automatic one.

All that makes perfect sense, too, if you think what should be achieved, e.g. a long power reserve without a huge barrel. The mainsprings can't be too different in their power, as you would otherwise have a huge decrease in amplitude once the stronger one is unwound.

ChrisN · Dec 24, 2015

Hi Rob

I just saw this thread and scanned your and Al's comments without trying to follow them in detail but, "Hooke's law". My goodness, this is getting technical😲. I'll throw in Young's modulus (E) and tangent modulus (Et) just to muddy the waters further 😉 - hey, I'm on holiday now but still feel the need to write a few Engineering terms😀.

Enjoy your Christmas.

Cheers, Chris

ChrisN · Dec 24, 2015

Hi Al and Rob

You've written a lot here and I still didn't read it all but, a picture paints a thousand words. Took this picture from Christian's website:

It appears the auto barrel is the one on the right and the crown wheel is acting on the other barrel (not ratchet wheel. Aha, so this is how you make a two barrel watch!). Assuming both have no reserve at the start, it seems obvious unless I'm missing something?

So, once you turn barrel 1 (left hand), there is a torque on it's ratchet wheel because the spring inside wants to unwind. There's that intermediate ratchet wheel which is now suffering a torque and so, logically, barrel 2 (right barrel) ratchet wheel is as well. If so, then barrel 2 is being wound at the same time as barrel 1 (there must be a slight lag as there's a bit of friction to overcome so you need a little torque on barrel 1 ratchet to overcome that).

Surely, it's no more complex than that?

I assume the click is only on barrel 2? I also suppose that the second wheel is only connected to barrel 2?

Interesting, cheers, Chris

Edit: so, I read what you both wrote again.
I seem to have reproduced a lot of one of Al's posts but, hey, my stolen picture makes it clear😉

I think that what you're saying, Rob, would be true in an ideal world where the torque reaction of the mainsprings would be constant for any state of wind. But, if that was true, then why are my balance amplitudes lower at 24H than 0H? (Please, don't say it may be my poor oiling regime😗) Seriously, these mainspring designers aim for a constant torque release but it's not possible as you know. I make the auto barrel spring some 7% higher nominal strength than the fixed one. I bet that when the auto one is 50% wound, it's resistance is only equal to the fixed one at 49%. I think you know what I mean - A picture would help!

9300 Winding Question

kaereachi

Horlogerie

OmegaSean

Horlogerie

OmegaSean

Horlogerie

Archer

Horlogerie

Archer

Horlogerie

Archer

guelerct

Archer

ScubaPro

kaereachi

Horlogerie

Horlogerie

Horlogerie

ChrisN

ChrisN

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