C11KAS automatic overbanking (or is it rebanking)?

[Levine98]

Hi,

I've been working on a mid-1950s Wittnauer C11KAS automatic (based on a Longines 501 and/or Record 1955) and have encountered rebanking (I think) when i do a full or nearly full wind. After a full or nearly full wind, the watch runs fine for a while then the pallet fork gets locked on the wrong side of the escape wheel.

I suspected that it had the wrong mainspring, however it appears that the mainspring is one of those 'sealed' jobs and is probably original. Because it was meant to be replaced whole, I've not be able to find a specification for it so I can compare it to the one in the movement (I've checked the old Ranfft to see and none listed, like other movements that were supposed to have the whole barrel/mainspring assembly replaced during service).

One thing I did notice is the mainspring is bone dry--no lubricant or residuale lube of any kind. I'm wondering if becuase the automatic no longer has useful slipping / breaking grease in left that its possible the mainsrping is getting wound too tight, thus causing too much power to go to the wheel train?

Does anyone have the spec for this mainsrping, or other ideas what might be causing the overbanking?

I've checked the pallet fork and the entry and exit jewels look fine—will check the impulse jewel and safety pin tomorrow. The banking 'pins' are of the type that are milled or cast part of the pallet arbor plate.

THanks in advance

Jay

Edited October 4, 2024 by Levine98
just added more stuff

[Klassiker]

What you are seeing is usually called overbanking, and it isn't a result of too much power from the mainspring. The pallet fork is jumping to the wrong position mid oscillation, without interaction with the impulse jewel, or the impulse jewel is bypassing the fork somehow, then can't get back. Most likely the guard pin on the pallet fork is bent or missing, or the balance or pallet fork has a bent pivot, or too much end shake. Here's a nice article, with a discussion of the terminology too. https://blog.pocketwatchdatabase.com/2022/08/22/overbanking-in-watches-failure-of-the-safety-action/

[oldhippy]

Sorry to disagree but if it is the wrong mainspring and too powerful it can cause overbanking. 

[Levine98]

Anyone know the spec for that mainspring, or should I just order a lesser strength one based on my own measurements after I check out rhe pallet fork guard pin, impulse jewel and escape wheel end shake? 

[Klassiker]

3 hours ago, oldhippy said:

Sorry to disagree

I'm the one who should be sorry, for posting wrong information.  I'd rather post nothing than spread confusion. I don't understand how a too powerful mainspring can cause overbanking though. If you can explain that, I'd be grateful.

[mbwatch]

Is this a confusion between Klassiker's and OH's use of the term "overbanking"? ... Exactly the confusion described in the Terminology section of the PWD blog article Klassiker linked above?

[oldhippy]

The simple answer the power is to strong so the balance is forced to rotate more than it should so the balance, pallets can jam which can force them to overbank. 

[AndyGSi]

How do these mainspring sizes compare to what's fitted?

1.00 / 0.09 / 330

https://www.emmywatch.com/db/part/mainspring_1_00-_09-330_auto--mss-wa11/longines--501/

Just realised it's the 11KA details you're looking for.

1.10 / 0.115 / 325

https://www.emmywatch.com/db/part/mainspring_1_10-_115-325--msn-81/wittnauer--11ka/

Edited October 4, 2024 by AndyGSi

[nevenbekriev]

Guys, if we talk about the situation when the watch has stopped with the impulse jewel outside the fork notch in zero position and it is needed to take the balance out and put it back correctly for making the watch work again, then it has nothing to do with the mainspring. The strong mainspring may be provoking the fault more frequently, but if it is able to happen, then it will happen again and again, until the real reason is rectified. And, the real reason is that the guard mechanism of the balance, which consists of the guard roller and the guard pin, for some reason and in some situation, doesn't work.

[Levine98]

24 minutes ago, nevenbekriev said:

Guys, if we talk about the situation when the watch has stopped with the impulse jewel outside the fork notch in zero position and it is needed to take the balance out and put it back correctly for making the watch work again, then it has nothing to do with the mainspring. The strong mainspring may be provoking the fault more frequently, but if it is able to happen, then it will happen again and again, until the real reason is rectified. And, the real reason is that the guard mechanism of the balance, which consists of the guard roller and the guard pin, for some reason and in some situation, doesn't work.

I can’t speak to the mainspring issue since I’m the OP who asked the question. But the symptom you describe is exactly what is happening.

I did check the pallet fork and the guard pin seems fine (both positionally and not loose).

i also checked the impulse jewel and it also seems fine, but not the roller table. I will take off the balance wheel next week (I’m out starting tonight) to really get a solid look at it without the encumbrance of being connected to the balance cock.

Barring any other ideas thanks in advance for the help.

 

1 hour ago, AndyGSi said:

How do these mainspring sizes compare to what's fitted?

1.00 / 0.09 / 330

https://www.emmywatch.com/db/part/mainspring_1_00-_09-330_auto--mss-wa11/longines--501/

Just realised it's the 11KA details you're looking for.

1.10 / 0.115 / 325

https://www.emmywatch.com/db/part/mainspring_1_10-_115-325--msn-81/wittnauer--11ka/

I’ve noticed her database is all over the place on some movements, this one included.

[AndyGSi]

16 minutes ago, Levine98 said:

I’ve noticed her database is all over the place on some movements, this one included.

Can you clarify what you mean as I don't see anything wrong with this information?

[nevenbekriev]

40 minutes ago, Levine98 said:

... I will take off the balance wheel next week (I’m out starting tonight) to really get a solid look at it without the encumbrance of being connected to the balance cock...

See, The idea to take balance out to check and look at is wrong. Actually, You need the balance and the pallet fork IN the movement to do the checks needed.  It is better to put ONLY the balance and the pallet fork (with their cocks) on the main plate. Then You need to turn the balance in some direction and try to force the pallet fork to the other side. You should try this in different manners, like balance up - fork down and vise versa. Then You should repeat the same when balance is turned to the other direction. Generally, the fork must NOT be able to go to the other side. This should be the same as to lock a drawer so fast that to throw the key inside before it is fully closed. And, if the fork is able to go to the other side, then investigate how, when and why this happens. Generally, it happens if the guard pin is short and passes thru the roller or it passes above or under the roller. Or, the roller doesn't rotate true and there is certain balance position where the roller gets far enough from the pin and lets it pass. The other reason for rebanking is that the impulse jewel is short or it stays up and in certain situation can pass above the fork's horns

Edited October 4, 2024 by nevenbekriev

[SwissSeiko]

In case anyone is wondering, this is how you determine mainspring sizing when you have the mainspring and the barrel. Use the UP/Down Circle. The info at the top is used to determine mainspring length

 

I think George Daniels says it should be 1/3 of the diameter of the barrel when unwound. That will get you close I think.

 

Edited October 4, 2024 by SwissSeiko
added info

[Levine98]

54 minutes ago, AndyGSi said:

Can you clarify what you mean as I don't see anything wrong with this information?

She has different info regarding the Longine 501, Record 1955 and Wittnauer C11K series of movements. These are basically the same movements.  Not the first time I’ve noticed inconsistencies in her data as I’m pretty sure she is just screen scraping another vendors DB (forget whose but US based).

49 minutes ago, nevenbekriev said:

See, The idea to take balance out to check and look at is wrong. Actually, You need the balance and the pallet fork IN the movement to do the checks needed.  It is better to put ONLY the balance and the pallet fork (with their cocks) on the main plate. Then You need to turn the balance in some direction and try to force the pallet fork to the other side. You should try this in different manners, like balance up - fork down and vise versa. Then You should repeat the same when balance is turned to the other direction. Generally, the fork must NOT be able to go to the other side. This should be the same as to lock a drawer so fast that to throw the key inside before it is fully closed. And, if the fork is able to go to the other side, then investigate how, when and why this happens. Generally, it happens if the guard pin is short and passes thru the roller or it passes above or under the roller. Or, the roller doesn't rotate true and there is certain balance position where the roller gets far enough from the pin and lets it pass. The other reason for rebanking is that the impulse jewel is short or it stays up and in certain situation can pass above the fork's horns

Thx for the correction—I will try when I get back and report back for others benefit.

[oldhippy]

As i said it is to do with the mainspring if it is to strong. Thank you Kalle.

 

[Nucejoe]

11 minutes ago, SwissSeiko said:

George Daniels says it should be 1/3 of the diameter of the barrel when unwound. 

George Daniels is right, I thought him that.  lol 

On serious side, he is my favourite legend, Ok must  confes ,like bereguet too. 

Did George say third of  (diameter or of barrel bottom surface area? ).

 

[AndyGSi]

So what size is your mainspring then?

[mbwatch]

This community needs to vote on and then pin the post on what is the agreed definition of overbanking and what is rebanking because this thread is talking about 2 different problems.

What Chronoglide calls overbanking in that video is not what H.B. Fried calls it and not what De Carle calls it. They agree on it meaning the escapement is locked with the impulse pin on the wrong side of the fork, and not about excessive amplitude causing knocking.

[RichardHarris123]

Fried et al are correct. 

[Klassiker]

8 hours ago, mbwatch said:

This community needs to vote on and then pin the post on what is the agreed definition of overbanking and what is rebanking because this thread is talking about 2 different problems.

It seems so. Why not do away with the "...banking" terms, and use out of action and knocking instead?

[Neverenoughwatches]

14 hours ago, oldhippy said:

The simple answer the power is to strong so the balance is forced to rotate more than it should so the balance, pallets can jam which can force them to overbank. 

If this were the case would the movement not exhibit excessive amplitude...the first indication that rebanking is about to occur.

[oldhippy]

Excessive amplitude is caused by to stronger power forcing the balance to rotate more than it should causing the overbanking.  Kalle says in his video you can hear it knocking. 

 

 

[Neverenoughwatches]

11 hours ago, oldhippy said:

As i said it is to do with the mainspring if it is to strong. Thank you Kalle.

 

I mentioned this about a week ago OH and also posted this video......Kalle had the terminology backwards.  Overbanking is the situation of the impulse pin trapped on the outside of opposite fork horm unable to release the escapement.  Rebanking is the situation of too high an amplitude causing knocking of the impulse pin on the outside of the fork horn from too strong a mainspring. But I'm sure you know this, Just Kalle terminology as we understand was incorrect maybe in that area of the world that is the term they use.

If we look at again at the OPs description of the issue " the pallet fork gets locked on the wrong side of the escape wheel" . This is where the confusion begins......what is OP actually meaning here ?   With overbanking the impulse pin is locked on the wrong side of fork........is this what the OP actually means ?

10 hours ago, mbwatch said:

 

 

12 hours ago, Levine98 said:

I can’t speak to the mainspring issue since I’m the OP who asked the question. But the symptom you describe is exactly what is happening.

I did check the pallet fork and the guard pin seems fine (both positionally and not loose).

As Nev tells it, either the safety feature of the fork's gaurd pin ( dart ,finger ) is malfunctioning and slipping past the safety roller possibly from movement of the watch ( a shake , a jar an impact)  or an unsafe lock with the pallet stones allowing the lever to switch banking pin sides, so 2 issues maybe happening.......an unsafe lock and a bent or short fork pin that doesn't tap back from the safety roller..........or the impulse pin and fork heights are poor and are not fully engaged when they meet every time.

Easy to determine a fork pin issue....release all the power.....leave just the lever and the balance fitted.....make sure both palllets are unlocked so the lever is free to move from the escape wheel now carefully test to see if the gaurd finger will pass by the safety roller so an overbanked scenario can take place......it may not quite......but just how close is it to bypassing the safety roller's circumference? 

Edited October 5, 2024 by Neverenoughwatches

[oldhippy]

Neverenoughwatch, I do apologize I didn't know you had already posted that video.  

[Neverenoughwatches]

2 hours ago, oldhippy said:

Neverenoughwatch, I do apologize I didn't know you had already posted that video.  

You obviously know that i hold you in high regard OH, so absolutely no need to apologise for anything at all.