Too much lock? Causing low amplitude?

[VWatchie]

This newly serviced Unitas movement calibre 6380 suffers from too low amplitude. Dial up about 225°, dial down about 245°, and about 200° in all other positions. I’ve went through my list of possible causes but couldn’t find anything obvious. Then I remembered that Mark Lovick in his watch repair lessons mentions that “too much lock may reduce the power available for impulse” and I suspect this could cause too low amplitude?

I don’t have enough experience to determine if what I see in the pictures is too much lock, but I assess that the amount of lock to about 1/3 to 1/2 of the width of the impulse face, and I believe that could be too much even for this calibre?

So, if there’s too much lock and it affects the amplitude, two questions arise; what could have caused it and what would be a practical remedy?
 

Edited October 26, 2019 by VWatchie

[watchweasol]

Hi  Probably been like it from the day it was made being acceptable at the time, as the escape wheel and fork position are fixed the only movable part is the fork jewels, and that's job and a half getting them right.

[nickelsilver]

The lock looks very heavy. Whether it's due to the jewels being too far out or the bankings being too open is impossible to say just looking like that. Does it have banking pins? Are they straight?

[VWatchie]

33 minutes ago, nickelsilver said:

The lock looks very heavy. Whether it's due to the jewels being too far out or the bankings being too open is impossible to say just looking like that. Does it have banking pins? Are they straight?

Fixed banking! So, would you assess that the heavy lock is the likely culprit for the low amplitude? I would assume so but I want to make sure. Any suggestion for a solution?

[VWatchie]

58 minutes ago, watchweasol said:

Hi  Probably been like it from the day it was made being acceptable at the time, as the escape wheel and fork position are fixed the only movable part is the fork jewels, and that's job and a half getting them right.

Hmm... Interesting! So, do you mean to say that the amplitude (dial up 225°, dial down 245°, all other positions 200°) could have been the same when it was brand new and that it was considered acceptable?

[nickelsilver]

Fixed banking! So, would you assess that the heavy lock is the likely culprit for the low amplitude? I would assume so but I want to make sure. Any suggestion for a solution?

If you've eliminated other causes then yes you will increase amplitude by decreasing lock.

You have to check it to see if the stones could/should be moved, or if the only option is closing the bankings.

This is something you spend weeks on in school, I would suggest checking something like the Chicago School of Watchmaking course or Bulova School course (both can be found for free online I believe) for insight.

[AndyHull]

You could of course try a different fork and see if that has any effect.

I don't see any evidence of other damage that might cause the fork to be out of alignment, but I guess it is possible that the fork is either out of tolerance (though I have never heard of shellac swelling, but I guess that might be a possibility), or the fork and/or balance and/or escape wheel have been replaced at some stage with a defective part, and the movement hasn't run correctly since. 

[JohnR725]

2 hours ago, VWatchie said:

Dial up about 225°, dial down about 245°, and about 200° in all other positions.

Ideally your dial-up and dial down amplitude should be the same. If it is not it can be an indication of pivot problems. Then from your pictures of the fork it looks like there's a little room behind each of the stones you just have to move them back a little bit.

Then if you know what the look for its amazing what you can find by doing a search in case you don't know what the tool looks like for moving a pallet stones.

https://www.watchrepairtalk.com/topic/8699-pallet-stone-replacement/

[Nucejoe]

We don,t know if the fork is a replacement. 

Escape wheel and pallets look unlevel to me.     QUESTION:     Can such unlevelness be the cause?

 

 

[praezis]

First, the shown deeper lock (esp. 2nd photo: too deep) seems not very likely to reduce the amplitude so much.

If it is a pallet or a banking pin issue, is not difficult to find:
essential is the point, where the wheel tooth hits the pallet jewel. The pallet fork must move a bit more then for security, until stopped by the banking "pin". If this movement is considerable, the banking pins (hrer: gap) are too wide else the pallet jewels are too long.

Frank

[watchweasol]

Bearing in mind, ' according to Ranfft it was manufactured in 1970, if thats right the watch is 39 years old,  If its never had any parts changed in that time the first statement would be true. But in 39 years it will have been serviced and repaired but not knowing its history one can only guess at what has been changed over the years, Balance staff, balance complete even the fork its self, therefore the problem may have been introduced unwittingly by some previous repairer. The logical method would be change the fork if still same the balance. As the banking is fixed therefore not adjustable other than filing, but once material is removed it cant be put back, so that's a non starter, or moving the fork jewels

[VWatchie]

Thanks for all input!

This pallet fork comes from a Unitas calibre 6325 that I recently serviced. It has perfect amplitude.

This pallet fork comes from the Unitas calibre 6380 with the inadequate amplitude.

Searching CousinsUK.com for this part it becomes clear that these two calibres (6325 and 6380) share the same pallet fork (restricted, of course). However, as you can see, the guard pins differ. That makes me wonder if the pallet fork of the 6380 (having the poor amplitude) has been replaced at some point, or if the different guard pins are of no importance?

At this time, I do not have the skill or tools to relocate the pallets, and for that reason I haven’t even investigated if that would be an option. However, a new pallet fork for the 6325 is available on eBay. So, what do you think, would it be worth taking a shot at, hoping it would solve the problem?

EDIT: Looking at the pictures again, the staffs also differs, right? Hmm...

Edited October 26, 2019 by VWatchie

[watchweasol]

From your observations its imminently possible the pallet/fork has at some time been changed in the past. If the replacement supplied by Cousins is the same as the one which gives you correct readings ie (guard pin) and depending on cost,  myself I would change the fork/pallet, that being the logical thing to do as moving the jewels is an art and could lead to further problems. I am afraid the choice is yours, 

[jdm]

11 hours ago, VWatchie said:

This newly serviced Unitas movement calibre 6380 suffers from too low amplitude.

Sorry I can't suggest a solution but would you share what equipment was used for the most excellent pictures?

[VWatchie]

11 hours ago, jdm said:

Sorry I can't suggest a solution but would you share what equipment was used for the most excellent pictures?

Thank you! It's nothing special really. Just an iPhone 6s with a $10 macro lens. For background I use a gel cushion. I don't use a tripod but I do support my hands against the table and I often take several pictures while slightly moving the camera to and fro the part to get the best possible focus. For light I have a well lit room from the ceiling and then I move around the work lamp until it "looks good".

[jdm]

3 hours ago, VWatchie said:

It's nothing special really. Just an iPhone 6s with a $10 macro lens.

Thanks, I'm impressed, I have the cheap lens and it's awful on my Sony. 

[jdrichard]

What about the strength of the mainspring?

Sent from my GT-N5110 using Tapatalk

[VWatchie]

6 hours ago, jdrichard said:

What about the strength of the mainspring?

Sent from my GT-N5110 using Tapatalk
 

Interesting question and now that you mention it there's a story to tell which could possibly be, or be part of the problem! I always replace the mainspring with a new mainspring if I can find one. In this case however the cousinsuk.com search function did not yield a result for calibre 6380, but I noticed that ranfft.de listed the same mainspring dimensions for calibre 6325 which was available (Generale ressorts GR5171).

However, the diameter of the inner coil was too wide to fit the barrel arbor so I had to adjust the inner coil by pressing on it with the wide section of my brass tweezers. However, I only noticed that the inner coil was too wide after I had pressed it into the mainspring barrel, and at that point I couldn't reach the inner coil sufficiently with my tweezers. So, I had to take it out, put it on a mainspring winder (K&D), adjust it (while in the winder barrel) and press it back in to the mainspring barrel. In the process I slightly deformed the inner coil but didn't think much of it. Now that you mention it, I wonder if that could be part of the problem?

[rodabod]

It does look like quite deep locking, but I wouldn't assume that it isn't normal without a comparison. Don't compare it to any Chinese copies as I tend to find that these have a very shallow lock.

I would doubt your mainspring is the culprit, from what you have described.

[jdrichard]

Interesting question and now that you mention it there's a story to tell which could possibly be, or be part of the problem! I always replace the mainspring with a new mainspring if I can find one. In this case however the cousinsuk.com search function did not yield a result for calibre 6380, but I noticed that ranfft.de listed the same mainspring dimensions for calibre 6325 which was available (Generale ressorts GR5171).
However, the diameter of the inner coil was too wide to fit the barrel arbor so I had to adjust the inner coil by pressing on it with the wide section of my brass tweezers. However, I only noticed that the inner coil was too wide after I had pressed it into the mainspring barrel, and at that point I couldn't reach the inner coil sufficiently with my tweezers. So, I had to take it out, put it on a mainspring winder (K&D), adjust it (while in the winder barrel) and press it back in to the mainspring barrel. In the process I slightly deformed the inner coil but didn't think much of it. Now that you mention it, I wonder if that could be part of the problem?

But you did adjust the mainspring and it could be slightly obstructed. You could use a toothpick and press lightly against the inner arm/spoke of the center wheel and see if it significantly improves the amplitude of the balance. I do this with pocket watches usually then iPhone record it in slo mo to see the resulting amplitude.


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[VWatchie]

8 hours ago, jdrichard said:

But you did adjust the mainspring and it could be slightly obstructed. You could use a toothpick and press lightly against the inner arm/spoke of the center wheel and see if it significantly improves the amplitude of the balance. I do this with pocket watches usually then iPhone record it in slo mo to see the resulting amplitude.


Sent from my iPhone using Tapatalk Pro

That sounds intriguing. Can you elaborate a bit more? I’m just past being a beginner and I’m thinking that interfering with any wheel in the train would reduce (not increase) amplitude, no?! And why record the amplitude with a camera and not a timing machine? Sorry for sounding confused! 

[VWatchie]

On 10/28/2019 at 11:55 PM, jdrichard said:

But you did adjust the mainspring and it could be slightly obstructed. You could use a toothpick and press lightly against the inner arm/spoke of the center wheel and see if it significantly improves the amplitude of the balance. I do this with pocket watches usually then iPhone record it in slo mo to see the resulting amplitude.


Sent from my iPhone using Tapatalk Pro

Edited this:

"You could use a toothpick and press lightly against the inner arm/spoke of the center wheel and see if it significantly improves the amplitude of the balance."

to this and it started to make sense (guess I'm a bit slow ):

"You could use a toothpick and push lightly against the inner arm/spoke of the center wheel in its rotating direction and see if it significantly improves the amplitude of the balance."

Anyway, iPhone slow motion would still be too fast for 21600 beats, I guess!? Hopefully, it would work with the timing machine set to 2 sec average.

[Nucejoe]

Hi, Generously apply kerosene or diesel fuel to escape teeth like you do lubricants. This will dilute the oil, reducing drag, you are very likely to see much enhanced amplitude.

If you see 280 degree amplitude you can conclude the deep lock was,nt much of impedenace. 

That the easy part. The tough part starts if you accept to grind the pallet to shorten the length using my approach. 

Best

[jdrichard]

Slow mo on the iPhone should work well.

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[VWatchie]

19 hours ago, jdrichard said:

Slow mo on the iPhone should work well.

Sent from my GT-N5110 using Tapatalk
 

Any particular reason to why you use slo mo instead of a timing machine? I've recorded a few slow mo videos of the balance previously just for the fun of it, but I find it near impossible to determine the amplitude. Its so fast even in slo mo, and I guess the pallets must be included to determine the exact point the impulse pin is hit by the fork.