Bulova 10BM erratic timegrapher trace

[TKM3RD]

Hello! It's been a while since my last post, and I have been having a grand time taking apart and restoring (or irreparably damaging) $1 -$ 10 movements. I hope everyone has been well, and for those in the States, had a nice turkey day.

I have just fully taken apart, cleaned, oiled, and reassembled a Bulova 10BM movement. It came in a very nice, as yet unidentified, watch with 10k GF case and 10k GF Spiedel band I won at auction.

When I put it on the timegrapher, it was a snow storm with ridiculous readings: anywhere from +800 to -750 with just a touch of the regulator arm. I noticed the one regulator pin was sticking up, so I removed the balance, and pushed it back where it belonged. Reassembled the balance and now I get a decent trace...until I don't. But then I do...until I don't again. From what I've observed, there's more good time than snow storm. It always starts with a sudden uptick, then a snow storm, then it just starts behaving. I haven't spent the time to see if there is any consistency in the frequency of the glitch.

Has anyone seen this type of behavior before? If so, any ideas as to the cause?

Here's the technical data on the movement:
https://ranfft.org/caliber/1394-Bulova-10BM

https://www.emmywatch.com/db/movement/bulova--10bm/

Thanks all!

[GPrideaux]

No expert, but here are a few things I'd be looking for.

Perhaps the balance is coming into contact with the centre wheel. Is it worse when you turn it dial up?

Or perhaps the extended fourth wheel pivot is not straight.

Are the hands and dial in place? If so, perhaps the seconds hand it touching the dial.

[nevenbekriev]

It may be galooping (overbanking?)

[HectorLooi]

Try getting the beat error down to 0.3ms first then take it from there.

[praezis]

No, beat error has nothing to do with it and is already fine.

Nev already told you what happens. Amplitude is too high!

Frank

[mikepilk]

Classic rebanking. I just had the same problem - the trace looked just like yours.

Try running it vertically - the amplitude will drop and the plot should look OK.

An easy fix is to try some HP1300 on one, or both pallet fork pivots. If that doesn't work, then a weaker mainspring.

[TKM3RD]

Thank you all so much for the ideas!

I decided to go back to first principles. I took out the balance and pallet fork, then the train of wheels, carefully checking everything for any signs of damage, contaminants, etc. I opened the barrel, and as I was removing the cap... SPROING!... the mainspring did a very favorable imitation of a Xenomorph* chestburster exiting a body. After picking myself and parts off the floor, I found a really beat up mainspring.

Could this mainspring be the culprit? (scroll down a bit to see the spring)

*https://youtu.be/UxqVFmig5AA?si=yoRDQ4fh7ks35Q3N

Thanks again for your help! Have a wonderful weekend!

Edited December 7, 2024 by TKM3RD
clarification

[Knebo]

@TKM3RD, please take the advice everyone is giving. It's "classic rebanking" as @mikepilk said. Textbook. 

One could say you did "too well" on this watch. It's cleaned and lubricated so well that it has too much amplitude. 

Which oils did you use on the train wheels? 

Using HP1300 on the whole train (even escape wheel) would kill a few degrees of amplitude and might just make it run perfectly. 

[TKM3RD]

@Knebo Moebius Synt-A-Lube 9010.
After I get a new mainspring, I will do just that.
Thank you!

Edited December 7, 2024 by TKM3RD
update

[Knebo]

46 minutes ago, TKM3RD said:

@Knebo Moebius Synt-A-Lube 9010.
After I get a new mainspring, I will do just that.
Thank you!

9010 everywhere? Even centre wheel? 

[mikepilk]

[TKM3RD]

20 hours ago, Knebo said:

9010 everywhere? Even centre wheel? 

um, no... yes... a bit? was that a bad thing?

[JohnR725]

On 12/6/2024 at 2:15 PM, TKM3RD said:

Has anyone seen this type of behavior before? If so, any ideas as to the cause?

What's even more interesting than seeing this is listening to this. In the days the paper tape timing machine work would print the dots on paper when this would occur it would sound like a horse galloping.Then starting on page 9 of the PDF attached which has all kinds of interesting information it talks about it. But when it lists the high amplitude what Omega recommends it will vary by manufacturer so typically don't want to go over 300.

1 hour ago, TKM3RD said:

um, no... yes... a bit? was that a bad thing?

Everyone has an opinion when it comes to lubrication. Then 9010 is considered a very light oil typically used on balance wheels sometimes used other places but it is a light oil and seeing as how so many people of asked their probably thinking it's a little too light for the entire watch. Personally because I usually work on bigger watches my light oil of choices 9020 for the most of the watch except the center wheel  where I use HP 1300.

 

8643_WI_81 BASIC CHECKS AND SETTINGS OF A MECHANICAL WATCH_EN cousins UK.pdf

[Knebo]

2 hours ago, TKM3RD said:

um, no... yes... a bit? was that a bad thing?

Hahaha, never a place where a Monty Python reference don't work, innit? 

Well, as @JohnR725 wrote and as @mikepilk diagram shows, 9010 is usually considered too thin for centre wheel and maybe also the slower of the train wheels. The issue with that is that it's easier for 9010 to creep away from where it's supposed to be. 

In my opinion (and lubrication is always contentious), an HP oil (mostly HP 1300, or D5) should be used on the centre wheel. And I usually use thicker oils like 9020, HP1000 or even HP1300 on the 3rd and 2nd wheel as well. But it's contentious. I have a service manual for Rolex 3135 and 2nd/3d wheel are HP1000, whereas a JLC 899 manual prescribes 9010 for those wheels, too. Escape wheel and balance always 9010. 

Anyway, if we focus on your specific problem of this watch which is rebanking (=too much amplitude): here we can either take a weaker mainspring or use heavier oils (i.e. HP1300) for the train wheels. 

 

[JohnR725]

26 minutes ago, Knebo said:

The issue with that is that it's easier for 9010 to creep away from where it's supposed to be. 

Typically any place where 9010 is used you will find epilam to keep it in place.

27 minutes ago, Knebo said:

whereas a JLC 899 manual prescribes 9010 for those wheels, too. Escape wheel and balance always 9010. 

Typically what I've seen the recommendation of 9010 on the balance and escape wheel because are considered fast moving. Although for instance Piguet With quite a few of their watches uses 9020 is the thin oil including the balance and escape wheel. Basically one oil one Greece and the escapement lubrication. 

[TKM3RD]

Wow, all joking aside, this has become an awesome conversation. 

My usual interest leans towards tiny vintage ladies movements (because I can get them dirt cheap, parts are pretty available, and I love the challenge of such a piece of amazing engineering) so when I looked at oils, my thought was the lighter the better. I see that perhaps I didn't take into account using a heavier one when working on a larger movement (and I am always open to the suggestion that I don't have much of a clue as well...)

Anyway, it's a moot point. I lost the pallet fork; the shellac in a replacement I had was faulty, the jewel fell out, and is somewhere - really, it is somewhere, I just have no idea where. I also need to get a proper mainspring but my guy is out of town.

So, this project is on hold for now. Once I have the parts, I plan to take it apart again, give it a quick cleaning, and put it together again using heavier oil as suggested. I will update the post when that's done.

Thank you and Happy Holidays to all!

~~Tom

18 hours ago, Knebo said:

Hahaha, never a place where a Monty Python reference don't work, innit? 

Well, as @JohnR725 wrote and as @mikepilk diagram shows, 9010 is usually considered too thin for centre wheel and maybe also the slower of the train wheels. The issue with that is that it's easier for 9010 to creep away from where it's supposed to be. 

In my opinion (and lubrication is always contentious), an HP oil (mostly HP 1300, or D5) should be used on the centre wheel. And I usually use thicker oils like 9020, HP1000 or even HP1300 on the 3rd and 2nd wheel as well. But it's contentious. I have a service manual for Rolex 3135 and 2nd/3d wheel are HP1000, whereas a JLC 899 manual prescribes 9010 for those wheels, too. Escape wheel and balance always 9010. 

Anyway, if we focus on your specific problem of this watch which is rebanking (=too much amplitude): here we can either take a weaker mainspring or use heavier oils (i.e. HP1300) for the train wheels. 

 

LOL, I drive my wife crazy with Monty Python quotes! You should have heard me when I was working on a Hamilton "Dennis" watch, she about had me committed.

[Knebo]

sorry about your loss (of pallet stone) 

however: "always look on the bright side of life"!