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Lawren5

What Could Be Causing Low Amplitude

Question

Prior to servicing, the Hamilton pocket watch I received had an amplitude of only 130 degrees. During servicing, the mainspring was found to be weak and was replaced. After a routine cleaning and lubing, the amplitude had only risen to 166 degrees.
Looking at possible causes, I could detect no binding in the gear train, pallet fork or balance wheel and the timegrapher line looks clean. There is, however, a significant difference in position:

    DIAL UP           +7 sec       166 degrees amplitude              0.2 ms beat error
    CROWN UP    -34 sec       126 degrees amplitude              0.1 ms beat error

I'm running out of ideas at this point. Could a weak hairspring or worn pivots cause low amplitude or am I overlooking something?

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Well, a few posts back I was referring to the fact that a lot of American pieces have the escapement in tatters because the thing that gets adjusted (mis-adjusted) straight away is the banking pins.

It would be worth seeking out Fried's book on the lever escapement, and I think his main book the Watch Repairer's Manual also gets into adjusting. In a nutshell: with power on the watch, balance in, stop the balance and rotate it by hand slowly just until and escape tooth falls on a pallet stone. Observe the amount of lock right at this moment, this is drop lock. Go the other way, the locks should be equal or near it and definitely not more than about 1/5-1/4 the width of the stone. Do it again, and at the moment of lock, move the fork toward the balance and check that the escapement doesn't unlock, then continue rotating the balance and continue checking. You're checking that the fork horns are supplying safety and as you continue to rotate that the guard pin is providing safety.  When all that checks out you can look at total lock. If you have an abundance of lock still when the horns are against the roller jewel and guard pin against the roller table, you can pull the pallet stones in a little bit. Go through the checks again.

Total lock is drop lock (what you saw above) plus the run to the banking, which is what the fork does after drop lock. There must be some run to the banking. Drop lock must be safe. Now you can get to your banking pins. If the total lock is more than about 1/3 the width of the stone, you can close the banking a bit. Check that you still have run to the banking, and that there is freedom between the fork horns and roller jewel and the guard pin and roller table at all times.

Keep in mind that moving a stone affects the other. If you move the entrance stone into the fork, you will reduce drop lock on that stone, and on the exit stone. Total lock will be reduced on the entrance and be unchanged on the exit. Pulling the stone out will increase drop lock on both stones, total lock on the entrance, and total still remains the same on exit. And vice-versa if moving the exit stone.

 

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Have you checked staffs axial end play? Check for Worn short  staff pivot.

Pivot coming to rest on pivot shoulder impedes balance wheel's motion ( amplitute).

Which at this point sounds to be the case with your watch.

 

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Agree with Joe end shake is the most likely culprit. It could be the balance staff with too much end shake or the train wheel pivots. If so adjusting the height of the jewels is required BUT without the correct tools this is difficult task. 

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I just have to agree with nucejoe in this; I have encounter this phenomena many times in 100+ years old pocket watches. One have to keep in mind the area of wear and tear is quite much bigger in the pivot areas than on wrist watches. If one think about carry on with repairing or servicing pocket watches one should buy a good jewel staking set.
Even though I been servicing pocket watches for many years I recommend Marks third watch repair course, everything he goes through there applies on pocket watches too.

 

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How did you check the train freedom? Did you peg the holes, in particular the pallet fork hole jewels? Are the pallet fork slot and the roller jewel impeccably clean?

One think that's frequently seen on American pieces is the escapement is completely maladjusted. With the eccentric banking pins, many would be repairers start moving them immediately if the watch isn't running as it should be. From there the pallet stones may get moved to compensate for the errors introduced by the bankings being wrong. And finally the watch runs very poorly. Do you know how to check the escapement?

To answer your questions- weak hairsprings are a myth, and even if a hairspring weakened over time it would contribute to too much amplitude (and a slow rate) if anything. Worn pivots can very much be a problem. As can worn holes in the plate or bridges, though I think Hamilton only made fully jeweled movements, but cracked or damaged jewels can be an issue.

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Clean, assemble, oiled and timegrapher indicates something is wrong, lawren modestly states" I am runing out of ideas at this point" 

    This point we often ran out of ideas is where fault finding starts and I have seen a lesson with this title by mark. Don,t tell anyone I havn,t yet taken the course either, what I know I have learned through the expensive approach of watch destruction.

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With crappy amplitiude, I usually start looking at the fast end of the train, and test the balance wheel for freedom and end-shake first:

Remove pallets and excite the balance until it starts to oscillate. Does it take a reasonably long time to gradully stop oscillating? Then, with a fine oiler or tweezers, push the balance wheel while static upwards and downwards and judge the amount of shake by eye.

If that all looks ok, then remove the balance and inspect the locking/unlocking of the lever.

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All advice given hereinbefore. Plus

A pic of the movement? How about dial down?  Slows down? Stops? a pallat of lighter fluid on each cab temporarily eases possible excess friction on pivots, you may see substantial amplitute.

Grab in tweezers one side of the BW, gently pull up to see if the pivot jumps out of jewel hole ( Excercise cautin,  not to force it out , not to bend the pivots.)

 

 

 

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Thanks to everyone for your inputs. Upon further examination I found significant endshake, not so much in the vertical direction but rather from side to side. In the attached video, I'm gently touching the balance wheel and you can see the play with the pivot.

To me, this endshake looks pretty serious and that I'll have to replace both jewels and balance staff. Any thoughts on this?

?

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in my experience low amplitude is due to too much end shake and sometimes the cause of this is a flattened pivot. over the years grime mixes with old oil and turns into like a grinding paste which flattens out the pivot end. a healthy pivot end should have a domed or cone shaped tip not flat. the flat pivot causes more friction and yields a higher amplitude. this can be easily overlooked because a powerful microscope is needed to really see the shape of the pivot traditional eyeloops will not do the job. the pivot can be reshaped with a pivot polisher, jacot tool, and burnisher. setting jewel height may not fix the issue alone.

 

BTW the pivot looks pretty flat in your video

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Traditionally American companies would use flat ends on their balance pivots. This tends to equalize the horoizontal and vertical amplitudes. It was a cause of some serious rebanking when watches were restaffed with Swiss made replacements, as they had the more typical rounded ends.

As for checking the escapement, it's fairly involved, have you read up on it at all or completely new?

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I checked that the pallet fork jewels were properly engaging the escapement wheel and that the pallet fork snaps from side to side when nudged. Information that I found on the internet for setting up the escapement seems to focus on the banking pins. Is this what you're referring to?

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If the pivot jumps out of jewel hole, due to side shake, same difference as end shake.      pivot jumps out= fault

Video shows bad enough condition to let the pivot out of jewel hole.

 So please inform us that you performed my proposed test and the highly likely result can be foreseen that pivot dose indeed jump out of jewel hole.

I think Nickelsilver then best knows what to do. I,ll be aboard assissting.

 

 

 

 

 

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Sideshake and endshake are not the same, endshake is axial play, and sideshake is radial play. Excessive sideshake wouldn't allow the pivot to come out of the jewel, and in my view the sideshake apparent in the video is acceptable.

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The end shake in the video does not immediately appear bad. However, I’d be more interested to see the balance rim moving rather than the end of the pivot as it’s difficult to judge by looking at the pivot. 

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Nickelsilver - Thank you for the explanation on how to check the escapement. I found it difficult, however, to perform some of the checks, particularly the fork horns and safety which I could not observe on a fully assembled movement.

Below are two photos of the pallet fork jewels as they engage the escape wheel. There is power to the movement but the balance wheel is removed. The first photo shows the entry jewel and the second the exit jewel. Not sure if these photos indicate much but I will try to get some measurements and better photos within the next several days.

entry_pallet.jpg.25239162a9ab6065af752b78ea394b34.jpg

exit_pallet.jpg.62bbea282e8b7cb6174a996d50329c60.jpg

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That's a tremendous amount of total lock on both stones. Easily the cause of 100 degrees of missing amplitude. To find out whether to move the stones or bankings or both depends on the drop lock.

A shortcut to get you in the ballpark is to check fork horn safety; with the roller jewel just out of the fork slot bring the horn in contact with it. Check the lock. In a good escapement the lock should be very very small here, almost nothing. If it is excessive, in theory you can move the stone in until it is just a tiny amount.

If the horn safety is already very small, it's a clear sign that the bankings have been moved.

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resetting the stone requires you to use a bluing pan. a small metal pan which is put under a flame ( a candle or alcohol lamp) and heat just enough to soften the shellac then you must remove it quickly from the flame. reset the stones in the pan and once stones are reset you have to let it cool off slowly. this can be a pain esp knowing when shellac is soft so usually i take a tiny piece of shellac and place it in the pan as a reference to know when it is ready.

Edited by saswatch88

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Ideally you do these checks looking straight down at the movement under a microscope. You won't see the horns or guard pin interacting with the roller, use an oiler to move fork and feel when it makes contact and observe the pallet stones.

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I am afraid this may drive both Nickelsilver and lawren insane, I once spent days trying, I don,t know what I did wrong but ended giving up in desperation.

A video was posted on the thread titled  citizen 8110A data sheet or let the strip down begin, by wdc. Video explained the proceedure well.

I think the video helps prepare lawren for the task and easier understand Nickelsilvers approach.

Following this thread with interest.  Joe

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