Bulova 10ak balance wheel stuck

[notalkrobot]

Hi all,

 

I'm running into a couple problems repairing a WWII A-11 Bulova with a center sweep second hand.

 

I've cleaned the movement, replaced the mainspring that was broken, and successfully replaced the gear train and bridge as well as the barrel bridge.

 

The watch winds and pallet fork smoothly banks back and forth when little pressure is applied.

 

The first problem occurs when I put the balance cock in with a new balance. Before I tighten the cock, the balance swings freely and engages the pallet fork properly, but when I tighten the cock, the balance stops. If I loosen it, it reengages again. I checked the jewels below and on the cock and they seem to be in order. The balance staff looks straight and the hairspring is nice and flat with no self touching. The staff looks properly seated in the jewel holes.

 

The second problem happens after it is running for a little bit. The balance wheel suddenly gets stuck, like the roller jewel can't get past the pallet fork. It will swing in one direction for a length and then on the back swing it will hit something (the fork?) and stop dead in its tracks. The roller jewel appears to be lined up properly with the hairspring and pallet fork. The teeth on escape wheel and all the other wheels look good. The wheel pivots are all properly seated in jewel holes on the bridge and mainplate.

 

As previously mentioned, when I remove the balance wheel, the pallet fork springs back and forth properly when little pressure is applied.

 

When I remove the barrel bridge, pallet fork, and balance and I spin the mainspring barrel all the wheels engage smoothly and slowly come to a stop.

 

I've tried a couple different balance wheels, even with different balance cocks. Am I placing the balance in improperly? What else could possibly be keeping the balance from swinging back and forth freely?

 

I can attach pictures if it helps, I just thought that someone might be able to point out an obvious misstep that will make all my problems go away. Ha! Any feedback would be great. Thanks!

 

 

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[clockboy]

The thought that comes to me is the cap jewel/s are installed upside down. If the watch was free running before then either something is being put back incorrectly or damage has occurred during assembly. For example bent a balance staff pivot can easily happen and it is not obvious until assembled. Strong magnification is best for the detection work. 

[oldhippy]

It sounds funny as all you have checked should have sorted the problem out. Did you remove the end stones if so have you put them back right, make sure the top one went back as the top, are you using the correct screws, nothing from below pointing to high and rubbing and the escapement oiled properly. Is the balance a new one as it sounds as if its to high, are the jewels clean. Has the balance cock been bent?

If you could post close ups that hopefully will help. 

[WatchMaker]

When I had a similar problem it turned out to be a damaged jewel for the pallet fork. Loosening off the balance bridge slightly would appear to alleviate the issue so the natural assumption was that it had to be a balance issue. It took a while of false trails for me to disassemble everything again and, under magnification, spot the pallet fork jewel issue. Presumably all that was happening was that with the impulse jewel making slightly less contact and me manually swinging the balance wheel then the pallet fork would seat itself differently for a short time and the watch would appear to work; until it got scuppered by the damaged jewel and the watch stopped.

As the guys mention above ... some super close ups of parts around the offending area (particularly jewel holes and pivots) could help pinpoint the actual issue.

 

[notalkrobot]

Thank you all for your replies. I definitely need help determining the condition of these parts. I'll check the cap jewels and I'll try to get some close-up photos for you this evening.






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[notalkrobot]

So I started with the cap jewels and found that they were properly aligned. Then I swapped the balance cock for a different one and the balance wheel started up immediately... but only for a few seconds before it got stuck again. Damnit.

I removed the balance and put pressure on the pallet fork. It was stuck. I messed around with it a little and the fork freed up, but the escape wheel wasn't moving forward. It would just bounce back and forth in the same position as the pallet fork swung back and forth. (I swear I even saw it got backwards a couple ticks!) So I kept messing with it and then suddenly the escape wheel started to advance smoothly again... until it stopped. Damnit.

So I swapped out the escape wheel and Boom! Thanks to all your suggestions, the watch is working again ... turned out to be a classic balance cock/ escape wheel swapsidoodle case. Ha!

That being said, I'm still a little confused about what happened exactly. I examined the escape wheel after the fact and couldn't identify the problem spots.

Here are some close ups:




Any ideas? Also thank you all again for your help. I was a frustrated mess before I posted. This forum is a godsend for beginners like myself.





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[clockboy]

The escape wheel might not have been seated correctly in its jewel.

[RyMoeller]

Interesting.  I would check the pivots on the escape wheel too.  If one is bent then there may have been a bit of wobble introduced that could have kept the pallet from unlocking.

Glad you've got the piece running again though!  I have a small container of "cursed" parts; they look fine but when you put them in a movement, the movement won't run properly!

[notalkrobot]

The escape wheel might not have been seated correctly in its jewel.

That makes sense... you're probably right. I think I was secretly hoping for a cool explanation like the angle of wear on one of the teeth caused the hang up with the pallet jewel... then I could justify buying a new set of microscopic hand files. Ha!


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[notalkrobot]

Interesting.  I would check the pivots on the escape wheel too.  If one is bent then there may have been a bit of wobble introduced that could have kept the pallet from unlocking.
Glad you've got the piece running again though!  I have a small container of "cursed" parts; they look fine but when you put them in a movement, the movement won't run properly!

That's funny. I think part of my problem is that I keep reaching to my drawer of problem parts to fix things... then I wonder why the movement still won't work. Maybe I need to treat that drawer like I do an ex girlfriends phone number and label it "Do not answer!" Ha!


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