We've all heard of the term overwound or tight with regard to watches. Today I read about a pocket watch being "Over Banked".

New terminology to me, to you?

Hi Stephanie,

OVERBANKED is a condition caused by the roller jewel moving past either side of the pallet fork. The banking pins won't let the fork move any father so the balance wheel is locked up.

To correct the problem the balance wheel "should" be removed and the roller jewel placed into the middle of the fork and reassembled.

There is a reason this happened and that should be solved before reassembly or it will keep on happening. It is more common on single rollers than double rollers.

Good afternoon:

From what I have seen and the terminology that I have used, basically over-banking occurs when the roller-jewel is allowed to slip outside the pallet fork to one side or the other rendering the balance wheel stuck. In my limited experience I have only experienced this with lower grade (i.e. 7J models). I believe the banking pins are supposed to prevent this from happening.
gp

Ah Jim, you type faster!

In many cases "overbanked" is the condition that is the underlying cause of those watches that are described as 'overwound'... and there are other causes

overwound is not a 'correct' term at all....

Stephanie,
Here is a gif animation I did a while back and never posted. Now is the perfect time!
Though the action in the gif may not be absolutely correct it should help clarify the above explanations.

And this shows the roller with proper action.

The "guard" pin on the single roller fork and the "guard finger" on a double roller fork prevent the fork from jumping back into an "overbanked" position when there is a sudden jar to the movement. The pin or finger is in contact with the roller table edge after the jewel clears the fork. It can only move back when it again enters the cutout arc or notch in the roller table edge.
When the pin/finger is broken, bent, or worn it cannot make contact with the roller table and overbanking will occur.

thanks kenny... great graphic sure says a lot...

Although covered in the "Complete Price Guide to Watches" rear section on Watch Terminology, this 185 site just does so much more to thoroughly answer an inquiry. For those not understanding the condition called "overbanked," Kenny's motion graphics are truly worth a thousand words by showing what occurs within the movement!

Kenny,

This is a great way to illustrate "overbanking".
Thanks for sharing, and taking the time to develope the animated picture.

I shall now "pick a nit" with what Kenny has written above: the guard pin (or guard finger on double roller watches) is not in actual contact with the edge of the roller table after the roller jewel clears the fork. The guards are positioned the smallest possible distance away from the edge of the roller table.

If the guard was actually in contact with the edge of the roller table, it would supply a frictional breaking action against the roller table, slowing the balance. By positioning it off the table's edge, there's no friction, but it's too close to allow the fork to jump to the wrong side of the jewel.

This lack of contact is, by the way, why these are called detached lever escapements - there's no contact other than the roller jewel's interaction with the fork.

Those graphics you provided are excellent in showing the meaning of the term "overbanked" (I've also heard people refer to this condition as "roller banked").

Thanks Harvey, for pointing that out! If it were "in contact" it would act as a brake on the table and balance wheel. It would only be in contact at the critical moment when the fork tries to reverse.

Thanks all, for the kind words!

So often I see in the description of a watch that it is "overwound". I always knew that this was an incorrect diagnosis of the condition of the watch but I could never find out what the cause actually was (and therefore unwilling to even contemplate buying it).
Is the overbanking the (major) cause of a watch that is fully wound but not actually working?
If so, what is the remedy? Is there more than one way of correcting the problem?

Mike Snyder

Michael,
There are a host of reasons why a watch that is "fully wound" will not run. The only way to know, for sure what the problem is, is to get inside it. Overbanking is not the major reason a watch will not run, just one of the reasons.
The only remedy for one that is truly overbanked is to repair/correct the guard pin/finger or the roller table if it is bent or otherwise out of whack.

i will put a qualified 'not always' there michael...

i picked up a waltham watch in orlando that was not running..... and was wound...... the cause was congealed oil from having been sitting at least the last 20 years (it had a tag on it dated 1983)...

the balance was free, but the escape wheel would not turn....

after a "bath".. it is running fine as can be for a 15j watch made in 1890...

I will let the true Xperts comment on the major reasons...

While the description of "overbanking" so far matches what I think the term should be used as, I have also heard of "overbanking" used to describe a different problem.

If the balance wheel is moving too quickly, the roller jewel can go all the way around and hit the fork from the wrong side. If it hits hard enough, it can break things, but most of the time, it will just bounce back from the fork, returning quicker than it should. Since it is still moving too quickly, once the balance swings around, it will do the same thing in the other direction.

The net result is a watch that clocks much too quickly. Instead of the term "overbanking", I think the terms "double banking" or "knocking" are better to describe this condition.

Normally, the energy given by the fork to the balance should match the amount of energy lost due to wind resistance and friction on the balance staff. Both of those energy losses increase as the arc of the balance increases so there should be a nice steady state that the balance falls into.

All watches will sometimes do this double banking if you rotate them quickly. Contrary to the images that Kenny created, the fork doesn't actually rest on the banking pins, rather the pallet jewels and escape wheel hold it in place near the banking pins. So, in the rare cases that the balance slightly double banks, the roller pin doesn't actually hit against an unmovable fork/pin, but rather moves the escape wheel backwards a little and, in effect, bounces off the wound up main spring.

Constant double banking can be caused by having a much too strong main spring being put in the watch, or the balance losing one of its weights, or a rusty hairspring, or any of a number of other conditions.

Ok, take everything I've said here with a grain of salt. I really don't know what I'm talking about.

Wayne, I've heard that called"knocking the banking". And of course "overbanking" can also be that state of writing a check on non-existent funds which leads directly to"locking the bank", followed invariably by "locking up the bankee", thus leading to a suspension of time itself as far as the watchmaker himself is concerned. . Oops, my warden has pulled my chain, must off to bed....

quote:

Contrary to the images that Kenny created, the fork doesn't actually rest on the banking pins, rather the pallet jewels and escape wheel hold it in place near the banking pins.

Wayne,
I appreciate your input. My drawings were made only to illustrate the "overbanking" thing and not intended to be to scale or precisely accurate . I didn`t even consider what the pallet and escape wheel were doing. Would make the animation much more difficult and time consuming to create if I tried to include them (if I could, LOL).Your explanation seems logical as to the fork not resting on the banking pin but brings a question to mind; What then is the purpose of the banking pins?
Also take my input with a grain of salt. I`m certainly no expert.

Henry Fried also called this condition "Out of Action", so you may hear some old-timers refer to it this way.

Frank "407" Kusumoto

Thanks everyone for your explanation of "overbanking". Kenny, your gif is great! I now have a somewhat better understanding of the term "overbanking" thanks to you!

Kenny -

With respect to the question of the fork resting on the banking pins, I shall quote George Daniels on the subject:

"The locking faces of the pallets are set at a small angle to the radial tip of the wheel teeth to draw the pallets hard on the banking pins. If the position of the lever is disturbed during the supplementary arc the guard pin will prevent unlocking and the draw angle will pull the guard pin away from the roller." (P. 209, "Watchmaking", by George Daniels).

So, the sides of the fork are in contact with the banking pins, but as a result of the draw between the escape wheel teeth and the pallet jewels, which is caused by a small angle. This action means that the fork continues to move after the tooth is locked, right up until the fork contacts the banking. And if the watch receives a shock that jars the fork loose from the banking pin, the guard will prevent the fork from unlocking the tooth (which would cause overbanking), and the draw pulls the fork (and hence the guard pin) away from the roller until the fork once again rests on the banking pin.

I should note that some watches do not use separate banking pins - on those watches, the banking is built in to the structure of the watch (usually by utilizing part of the pallet fork bridge to act as the banking).

Harvey,
Thanks for the explanation. So the draw actually holds the fork on the banking pin and the guard finger away from the roller table unless there is a jar or sudden shock whereupon the guard finger contacts the table and prevents the fork going into overbank mode. Think I`ve got it!
Pretty close to what I had in mind but had never given it much thought before now.