Rebanking on a Valjoux 72

[Delgetti]

Hello,

I'm working on a Valjoux 72, medium quality I think, and after cleaning and lubrication it shows very high amplitude (about 330 DU). Sometimes it passes 335 and starts rebanking.

 

I tried the following solutions:

- weaker mainspring. The next weaker mainspring I could find lowered the amp to 270 DU. But that meant in a hanging position and with the chronograph running amplitude dropped to 190, high loss of accuracy -> not acceptable for me.

- HP 1300 lubrication for the balance -> no effect.

- HP 1300 lubrication for the anchor pivots -> no effect.

 

The target is to get the watch to an amplitude of about 310 DU. On the net and in some books I read about 2 possible further steps.

1. Slightly bend the banking pins to the outside. This is discussed very controversial and seems to be some kind of collaboration with the devil?

 

2. Move the pallets towards the escape wheel. I didn't work with shellac so far and do not have the special tool to move and measure the pallets. I think I don't want to buy that tool for about 800 Euros. Is the job possible without the tool and are there tutorials?

 

Opinions about my options? Or even other ideas to lower the amplitude? Thanks in advance, gentlemen.

[JohnR725]

I don't suppose you could give us a picture of the timing machine results? It also is nice to see the watch in another position other than dial down a dial up whichever you're currently using. In other words crown down to be really nice.

 

[Delgetti]

Hello, sorry, some family issues over here right now. I ll be back with timegrapher pics on monday. 

[rodabod]

Is the positional variation not good enough at 270 degrees? I wouldn’t worry about the chronograph running amplitude too much  

I wouldn’t recommend altering the escapement action - if you increase the lock then this is effectively making your lever escapement less “detached”. I would have a look at alternative mainsprings. 

[nickelsilver]

For reference the GR mainspring for the 72 is 3357, 1.30 x 0.14 x 360 11.5

 

This caliber is a particularly good runner, but if you were getting enough amplitude to rebank you probably did have the wrong spring. I have gotten springs from old suppliers where the spring was in a hand marked envelope, no size or ref other than "Val 72" and they've been way too strong. Don't remember the measured thickness but they were too strong.

 

This caliber, with 270 horizontal, should drop around 40 degrees to 240 give or take. If it's dropping to 190 there are other issues. If the escapement is set up with heavy locks, either from opening the bankings or pulling the stones out, that can have a more noticeable affect on the verticals than horizontals. If the balance pivots are rough, same. Too much endshake on balance, same. I am thinking you got it with the strong mainspring; perhaps a previous repairer tried increasing the lock to drop the amplitude. When you're back at the bench, some close up picks of the escapement locked on both sides, and if possible, some video, would help.

 

Yes, you can adjust an escapement without the expensive tools, but it can be a lot of back-and-forth trial to hit the sweet spot.

[Delgetti]

Thank you for all the replies. Not back at the bench, but at the breakfast table. 

Some more information. I ordered 2 GR 3357 from cousins, new in sealed pack. Tried both, same result, too high amplitude. Next mainspring I tried was 1.3 x 0.13 … but the cubic influence of the thickness reduced amp to 270 DU and 220 in hanging positions. Before service I measured an additional drop of amp with engaged chronograph of about 30 deg. So I think with the weaker mainspring and chronograph engaged it would all end up in 240 DU and 190 hanging. I do not like that.

 

Another description of the current situation: Fully wound movement runs with 330-335 amp DU, sometimes rebanking (typical timegrapher reading for the issue). Rotated to hanging positions amp drops to about 280. Hm, while writing this I ask myself if a difference of 50 deg DU to hanging is suspicous? Could this be the point where I should think about flatening the balance pivots (uh, another collaboration with the devil…)?
 

To clarify: If I could find a solution without touching the escapement I would absolutely prefer that as such work could be beyond my skills.

 

As mentioned I ll be back with timegrapher pics tomorrow and will also try to make the escapement pics nickelsilver asked for.

[JohnR725]

4 hours ago, Delgetti said:

To clarify: If I could find a solution without touching the escapement I would absolutely prefer that as such work could be beyond my skills.

 

As mentioned I ll be back with timegrapher pics tomorrow and will also try to make the escapement pics nickelsilver asked for.

always best to not modify things in a undesirable way until we know it's going on and we see the timing machine results preferably in more than one position as I asked for like dial-up and dial down at least one crown position like crown down photographs of the machine

4 hours ago, Delgetti said:

Another description of the current situation: Fully wound movement runs with 330-335 amp DU, sometimes rebanking (typical timegrapher reading for the issue).

timing procedures? If you line the watch up nice and tight and put it on the machine that's not what you want to be doing need to let it run about 15 minutes to an hour then you can put it on the machine. Because it's always possible to get that last little bit of announced not good is not supposed to be wound up supertight

4 hours ago, Delgetti said:

Some more information. I ordered 2 GR 3357 from cousins,

 

5 hours ago, nickelsilver said:

or reference the GR mainspring for the 72 is 3357, 1.30 x 0.14 x 360 11.5

I thought I was onto something but never mind? 3357 is what the mainspring book indicates  the website below is usually very reliable except in this case they have a mainspring number that doesn't seem to exist? fortunately the size is right maybe nobody notices?

http://cgi.julesborel.com/cgi-bin/matcgi2?ref=qWI_h

4 hours ago, Delgetti said:

Could this be the point where I should think about flatening the balance pivots (uh, another collaboration with the devil…)?

this is why we need timing machine pictures. Yes if somebody got carried away and polished your pivots really nice and round that could be an issue. But always best to make proper diagnostics before modifying the watch.

 

 

 

 

[Delgetti]

Here are some pics:

Fully wound (until I can feel force rapidly increasing, not supertight).

DU

Sometimes changing to this:

CU (right wrist wearer )

CL

Escapement:

 

 

Any thoughts?

[rodabod]

It’s been discussed here before regarding how different spring metallurgy affects force - I had an issue with finding a suitable spring for an Omega bumper one which was a bit overenthusiastic. 
 

Can you maybe try a 1.35 spring as a compromise? I can look through my spares if Cousins don’t stock them. 
 

[nickelsilver]

The escapement looks great from the pics (to really know it has to be checked with balance in, under microscope etc.). What was the thickness of the weaker mainspring you used? I wouldn't hesitate to pull the entry stone out perhaps 0.01mm; that should drop it enough it's not rebanking anymore. You could also move the entry banking a tiny bit to increase the lock. Both are totally reversible and won't hurt anything to try; I suggest the entry as it has quite a small total lock now, and moving that stone has a greater effect than the exit.

 

GR lists a spring 1.30 x 0.135 x 360, ref 3348, but that doesn't mean they are available.

[Nucejoe]

Doesn't the guard pin look too long? 

[nickelsilver]

23 minutes ago, Nucejoe said:

Doesn't the guard pin look too long? 

Not really, but that's easy to check (with the balance in).

[Delgetti]

Thanks, gentlemen. 

@rodabod: Yes, 0.135 would be my favourite choice, but I only found one 1.3x0.135x520x14 and I think this is too much volume for the barrel. 

@nickelsilver: Didnt find that GR3348, but will further try,specs sound perfect. 

In case of manipulating the right banking pin: I understood I have to push it a very tiny way to the right? Of course I dont have the special bergeon tool for that purpose. So what tool should I use and how?

Once again: Thanks for the discussion and the help. 

[rodabod]

For a banking pin tool, I turn small brass rod (2mm or so?) into what looks like a small hollow staking punch. So, it tapers toward the end, and you drill it hollow so it’s just large enough to slip over the pin. Really handy for checking uprightedness - sometimes the pins will be bent in all directions and this makes it much easier to see. 

[Jon]

20 hours ago, Delgetti said:

Thanks, gentlemen. 

@rodabod: Yes, 0.135 would be my favourite choice, but I only found one 1.3x0.135x520x14 and I think this is too much volume for the barrel. 

@nickelsilver: Didnt find that GR3348, but will further try,specs sound perfect. 

In case of manipulating the right banking pin: I understood I have to push it a very tiny way to the right? Of course I dont have the special bergeon tool for that purpose. So what tool should I use and how?

Once again: Thanks for the discussion and the help. 

I would be very cautious of moving a banking pin to alleviate the problem, as this is going to increase the guard pin shake and horn shake, which could unlock the escapement if it receives a shock, so if you are going to move one or both banking pins, do it slowly and check with the balance in place that when the balance is turned in both directions, that when you try to pull the pallet away from the banking pin, the pallet stone doesn't unlock and the guard pin touches the safety roller before that happens, otherwise you could have the escapement mislocking or totally unlocking. These slides will help understand the principles as well as what you would check and adjust. Hope it helps. I have got a lesson on making a pallet stone warmer and spirit lamp as well as how to set pallet stones using shellac, but it has a lot of videos in and the server won't take it

 

]

[nickelsilver]

Moving the banking will only increase the total lock,  it won't make the escapement unsafe. Moving a stone in can possibly cause an unsafe escapement that can unlock accidentally, if it's moved in enough that the guard pin shake allows it, and can also reduce the drop lock enough that that is unsafe as well.

 

 

[JohnR725]

8 hours ago, Jon said:

These slides will help understand the principles as well as what you would check and adjust.

out of curiosity where did the image's come from?

 

[Klassiker]

Hi Jon, thanks for posting this. I have a problem with how you explain horn shake though. Your diagrams show a position and a measurement which would not be affected by banking pin position, and so I don't see how moving the pins can increase or decrease the risk of accidental unlocking.

 

[Jon]

8 hours ago, Klassiker said:

Hi Jon, thanks for posting this. I have a problem with how you explain horn shake though. Your diagrams show a position and a measurement which would not be affected by banking pin position, and so I don't see how moving the pins can increase or decrease the risk of accidental unlocking.

 

If the banking pins are brought together to be a smaller distance from each other, creating a smaller lock, then when you pull the pallet away from the escape wheel, as the balance is turned, the pallet may unlock before the guard pin touches the safety roller. If you bring the banking pins apart then you may have the guard pin constantly rubbing on the safety roller. The pictures say it all really.

Also, if the horn shake is too big, the pallet may unlock from the escape wheel. The notch of the pallet fork maybe worn creating a bigger gap, therefore unlocking, or a loose roller jewel, or one the wrong size roller jewel, or a bent pallet.

On 5/4/2022 at 2:54 PM, nickelsilver said:

Moving the banking will only increase the total lock,  it won't make the escapement unsafe. Moving a stone in can possibly cause an unsafe escapement that can unlock accidentally, if it's moved in enough that the guard pin shake allows it, and can also reduce the drop lock enough that that is unsafe as well.

 

 

I agree

Edited May 5, 2022 by Jon

[nickelsilver]

16 minutes ago, Jon said:

I have to disagree. Moving the banking pins out has the same effect as pushing the pallet stones in. There is a smaller lock. If that lock is smaller than the guard pin or horn shake the escapement will unlock given a shock without a doubt

I think if you have a look at a watch and manipulate the fork and balance you'll see where you're getting confused. You can remove the banking pins completely and the safety action of the guard pin and fork horns relative to the pallet stones remains the same.

 

If I check my horn/guard pin shake, and observe the position of an escape tooth on the pallet stone, the banking pin is not in action. If that shake is safe, moving the banking will affect total lock, nothing more. If I move a stone in, I might not have safe action with the guard pin/horns. I might not have safe drop lock. I will have reduced the total lock for the stone moved in (moving in a stone decreases drop lock for both stones though).

Edited May 5, 2022 by nickelsilver

[Jon]

Just now, nickelsilver said:

I think if you have a look at a watch and manipulate the fork and balance you'll see where you're getting confused. You can remove the banking pins completely and the safety action of the guard pin and fork horns relative to the pallet stones remains the same.

 

If I check my horn/guard pin shake, and observe the position of an escape tooth on the pallet stone, the banking pin is not in action. If that shake is safe, moving the banking will affect total lock, nothing more. If I move a stone in, I might not have safe action with the guard pin/horns. I might not have safe drop lock. I will have reduced the total lock for the stone moved in (moving in a stone decreases drop lock for both stones though.

Sorry @nickelsilver I edited my response, as I misread what you wrote

2 minutes ago, Jon said:

Sorry @nickelsilver I edited my response, as I misread what you wrote

I also said pulling the banking pins apart reduces the lock, when in fact it increases it.... duh!

[Klassiker]

4 hours ago, Jon said:

If the banking pins are brought together to be a smaller distance from each other, creating a smaller lock, then when you pull the pallet away from the escape wheel, as the balance is turned, the pallet may unlock before the guard pin touches the safety roller.

I don't understand this. It seems to me  that if the guard pin to safety roller interaction prevents unlocking, then it will do this wherever you move the banking pins to. If you move the banking pins too far inwards, you will trap the guard pin against the safety roller, but the pallet stone will still be in lock.

 

4 hours ago, Jon said:

If you bring the banking pins apart then you may have the guard pin constantly rubbing on the safety roller. The pictures say it all really.

The pictures say the opposite to me. Very confusing!

4 hours ago, Jon said:

Also, if the horn shake is too big, the pallet may unlock from the escape wheel. The notch of the pallet fork maybe worn creating a bigger gap, therefore unlocking, or a loose roller jewel, or one the wrong size roller jewel, or a bent pallet.

This all makes sense, but I still don't see how you can change it by moving the banking pins.

[JohnR725]

For those that want more knowledge and more confusion I'm attaching a PDF.

I've also snipped out an image found in the PDF. It shows the consequence of doing things what happens if. Ideally you would follow procedure you Properly adjust your escapement and you'll be fine. If you don't properly adjust your escapement you have consequences that's what this page shows.

A vaguely recall at the start of this discussion somebody is trying to improperly screw up their escapement to deal with a problem that's not the escapement's problem? So how are we going with solving that?

Escapement handout wostep nscc.pdf