Just replaced balance staff, now watch runs wildly different depending on orientation.

[Max50916]

I've just replaced a balance staff on a Bulova 10AK movement from WWII with a NOS Bulova 7AK staff (according to jules borel, these should be interchangeable.) I also had to replace the roller jewel (I sourced a roller jewel from an AS 1194, again, interchangeable). Now the watch is running wildly differently depending on which side is up. I've attached some photos, keep in mind my timegrapher is just a phone app which uses my phone microphone , so some of the random blips may be outside sounds. Back side up the movement can be regulated pretty close to accurate, but when the dial side is up it runs CRAZY fast. Could anyone explain what went wrong/what may be the issues and potential solutions? Thank you for any help you can give!

 

 

[Nucejoe]

Variation as large as your saying , points to hairspring issue or something rubbing , hairspring rubbing, pivot shoulder seat runbbing due to unadjusted end shake or defective end stones, perhaps even defective pivot end of the new staff. 

  I noticed you made no mention of having poised the balance or balance complete, though poise issue would not cause  large variation between FU & FD positions. 

Regs

[Nucejoe]

TG prints just openned on my device, dial side is all over the place.  More discusssion to come.

[jdrichard]

2 hours ago, Max50916 said:

I've just replaced a balance staff on a Bulova 10AK movement from WWII with a NOS Bulova 7AK staff (according to jules borel, these should be interchangeable.) I also had to replace the roller jewel (I sourced a roller jewel from an AS 1194, again, interchangeable). Now the watch is running wildly differently depending on which side is up. I've attached some photos, keep in mind my timegrapher is just a phone app which uses my phone microphone , so some of the random blips may be outside sounds. Back side up the movement can be regulated pretty close to accurate, but when the dial side is up it runs CRAZY fast. Could anyone explain what went wrong/what may be the issues and potential solutions? Thank you for any help you can give!

 

 

Where did you get this meter, iPhone?

[JohnC]

Just looking at the movement shot, I am wondering if you placed the roller in the same position you found it. Usually the impulse jewel is at 90 degrees to the balance arms. If that was the case here the watch would be very out of beat, perhaps to the point that it wouldn't run at all. Just something to check, although not really germane to this problem. It would also throw off the poise, to Nuce's point.

I can't really read the second timegrapher shot - it looks to me like it's barely running at all, more than a case of it running fast. My guess is that the amplitude is dropping a lot on that side, which is not really a question of the rate but more of the watch stalling out on that side. My guess is the hairspring or something else is rubbing.

[JohnC]

I can't really see if it's an overcoil - I think it is from the position of the stud. But if it is one thing to check is that the overcoil is not hitting the centre wheel when the watch is dial up. It could be that you have the stud depthed incorrectly, which may pull the overcoil toward the centre wheel. Another thing is that the hairsprings on these tend to be super soft, and can be distorted if you don't support the balance wheel when removing it. Just the weight of the wheel can put the hairspring way out of wack. You may want to remove the hairspring, stud it in the cock, and just check that it's flat.

[Nucejoe]

Sharp eyes John, judging by short length of regu arm I'd say its an overcoil, also agree if the roller is poisitioned right then mpulse jewel seems is co siderably out of beat. Would you vote for possible rebanking? 

Regs

[JohnC]

@Nucejoethat is one theory but my uninformed guess is that it is low amp and barely on the threshold of being readable OR some amplitude but hairspring is bouncing off centre wheel and getting effectively shortened and increasing the rate. Could be neither though, I am just spitballing.

[nickelsilver]

The hairspring isn't centered, that could be the reason it looks so out of beat. If it isn't centered then there is a good chance it isn't flat too, try to get the hairspring sorted out as a start. It would be nice to see a pic of the balance itself from the side, top and bottom.

[oldhippy]

I have just had a look at the photo after magnifying the photo and the hairspring is't right it is all gathered at one side. It should have even gaps between coils all the way around. That's the cause of your problem.   

[clockboy]

It looks like a hairspring issue but did you poise the balance after fitting the new balance. 

[jdm]

11 hours ago, Max50916 said:

when the dial side is up it runs CRAZY fast.

Dial side up, hairspring weight pulls toward balance cock, touches there (as others said) and makes it run fast.

[praezis]

According the photo, the 1st (over-)coil lies outside the regulator pins!

[dadistic]

Wow, good eyes. I could see it once you told me where to look, but I would have never spotted it otherwise.

The OP owes you a beer

[rodabod]

Also check balance end-shake as this can interfere with how the roller interfaces with the lever which can cause timing oddities in certain positions. And the roller itself if it's a replacement.

[Max50916]

Thank you everyone for your help! As many of you suspected, it was indeed an issue of the hairspring running, it wasn't perfectly flat and after some adjustments it is now running great!!

[Max50916]

On 10/28/2021 at 7:21 PM, jdrichard said:

Where did you get this meter, iPhone?

It's called "watch accuracy meter" I have an Android but believe it is for iphone as well. For a free app it actually works quite well