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Watch gaining time, process of elimination?

MyFavoriteObsession
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MyFavoriteObsession Watch Enthusiast

MyFavoriteObsession

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Hello again, I have a 1950 Bulova 10BM movement that is running extremely fast. I do not know the watch's history. So far, I have demagnetized, cleaned, and lubricated, and it is still gaining time. The hairspring is clean, not bent, coils are not stuck together or magnetized. I was wondering, when a watch is gaining vast amounts of time and you've demagnetized and cleaned but you don't know the watch's history, what are the next steps you would take to determine the cause?

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VWatchie Distinguished Member

VWatchie

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1 hour ago, MyFavoriteObsession said:

I have a 1950 Bulova 10BM movement that is running extremely fast.

I have no suggestion at this time, but it would be interesting to know what you define as "extremely fast"? If you have a timing machine it could possibly tell us a lot. Anyway, that would be my next step, just to make sure it isn't re-banking, completely out of beat, or the poising (amplitudes) being all over the place.

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Nucejoe Distinguished Member

Nucejoe

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If all visible signs are OK, then you check the non-visible.

You have done demag, one cause could be wrong someone slapped a hairspring on balance which didn't belong or the balance wheel doesn't.

I suppose it gains in all positions. 

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oldhippy Distinguished Member

oldhippy

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Have you checked to see if the hairspring is correctly between the regulator, it should be free to move no matter what position the regulator is at. Have you removed the complete balance from the cock and touched the hairspring to see if it sticks, if the tools you are using are not anti magnetic make sure they are not magnetized, have demagnetized   the whole movement. Are you sure it has the correct mainspring, if its to strong that will cause it to gain. How much does it gain in 24 hours?

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Nucejoe Distinguished Member

Nucejoe

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2 hours ago, MyFavoriteObsession said:

when a watch is gaining vast amounts of time and you've demagnetized.

That has to do with hairspring, either sticking or too short or the wrong one.

Sticking can be intermitent and sometimes hard to spot, can you show top view vid of running.

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MyFavoriteObsession Watch Enthusiast

MyFavoriteObsession

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1 hour ago, VWatchie said:

what you define as "extremely fast"?

The movement has a beat rate of 18,000A/h and my timegrapher auto-detects it as 21,6000A/h. 

 

1 hour ago, Nucejoe said:

someone slapped a hairspring on balance which didn't belong or the balance wheel doesn't.

This is what I suspected, as I have no idea who has worked on this watch before me. 

 

The hairspring is correctly positioned in the regulator, I tested the hairspring with pegwood to check for sticking/magnetism, and the entire watch and my tools have been demagnetized. 

1 hour ago, oldhippy said:

Are you sure it has the correct mainspring

I am not sure at all. The 10BM uses a 10AK hairspring and I have some here that I can test with. I'll try this step next. Thank you all for your advice. 

 

 

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Nucejoe Distinguished Member

Nucejoe

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2 minutes ago, MyFavoriteObsession said:

The movement has a beat rate of 18,000A/h and my timegrapher auto-detects it as 21,6000A/h.

 

Considering distinctness of 21600a/h , your balance complete or its hairspring  is highly likely to be off of different variant.

Doesn't belong would not vibrate to the watch.

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jdrichard Distinguished Member

jdrichard

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7 hours ago, MyFavoriteObsession said:

Hello again, I have a 1950 Bulova 10BM movement that is running extremely fast. I do not know the watch's history. So far, I have demagnetized, cleaned, and lubricated, and it is still gaining time. The hairspring is clean, not bent, coils are not stuck together or magnetized. I was wondering, when a watch is gaining vast amounts of time and you've demagnetized and cleaned but you don't know the watch's history, what are the next steps you would take to determine the cause?

I would look for some anomaly with the hairspring. Is it touching the balance arms at all. Is there a small hair touching the hairspring. Is it bunching up under the balance coc and you can’t see it?

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rduckwor WRT Addict

rduckwor

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I'm currently working on a Bulova 8AE with the same problem.  I had a prior Bulova that someone had shortened the hairspring on and then removed the regulator arm to make it a free-sprung balance in an effort to get it to run.  Run it did!  It gained several hours/24 hours.

 

The problem with the current movement, the 8AE is that the amplitude is really crappy, not even 180 degrees.  This despite a cleaning, demag, new MS, and a completely clean hairspring.  One clue is that with a fully wound mainspring, additional pressure on the crown in the winding direction will improve the amplitude.  Thus, the power is not being generated or not making it thru the train to the escape wheel.

 

This movement runs and gains 1 hour/12H.  Check your amplitude.  Good Luck.

 


RMD

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jdrichard Distinguished Member

jdrichard

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So I had a similar issue with the Rolex I was working on. After cleaning the balance with hairspring, I noticed that some of the leaves were actually sticking together but were impossible to see as they were under the balance cock. I disassembled it all and looked at the hairspring under my stereo microscope and immediately saw that there was oil of some sort between 2 leaves, thereby shortening the length and speeding up the watch. This also impacted the amplitude. I place the hairspring in lighter fluid for 30 min, then grabbed the stud and moved it around a bit. When examining it again, perfect results and no indication of any remaining oil. I think this is in the end of my video. 
Assembly - Rolex Oyster Everest Precision 1957 https://youtu.be/7AqT-bL7wcc

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