1956 Bulova 10BPAC 23 jewels service

[Levine98]

8 hours ago, GuyMontag said:

Perhaps try increasing the tension that the sweep seconds tension spring is providing on the sweep second pinion. I've never personally seen "backlash" that the tension spring is supposed to control, but what I've read makes it sound like this.

 

EDIT: was the tension spring broken? It looks like it in the movement photo but in the parts tray it doesn't

that is the way it is supposed to be, i..e, the spring has a notch. 

Regarding the giddy up problem, I've experienced the same condition on a 10BPAC.  In that case, I had a very slightly loose sweep second hand that was losing contact with the pinion. 

You have to work your way back in the chain from the sweep second hand then the pinion etc to find the problem.

Have you tried another sweep second hand?

Have you checked the pinion to make sure it is true and not bent? 

Does it always do it in the same spot? Check a full rotation between the wheel and the pinion and watch to see where the hesitation happens at that level.

Does it do this in multiple positions?

Have you observed that the sweep second hand driver wheel and pinion are close to level and meshing with no wobble?

And so forth down the chain.

 

Edited May 9, 2023 by Levine98

[ManSkirtBrew]

10 hours ago, GuyMontag said:

was the tension spring broken?

No, it's just the lighting in the picture. There is definitely good tension on the pinion (thank you for putting the right word to it for me!).

 

3 hours ago, JohnR725 said:

Do you know what was rusting in the watch?

Much of the keyless works were rusted, but since I have two movements I used the parts from the not-rusted one. I just took the nicer-looking dial, which happened to be from the rusty movement.

 

3 hours ago, JohnR725 said:

can you see the bushing?

I can, and it looks very worn to me, but since both movements look the same I didn't want to assume it was incorrect right away.

 

I will take the second hand pinion spring off and check it for tension again, but I did notice something else this morning that's probably important. When I pull the crown out to setting position and turn it to set the time, the balance stops spinning--but only when I turn the crown clockwise. If I turn it counterclockwise, the balance continues running.

Also when I turn the crown clockwise, I see the seconds hand rotate counter-clockwise a few degrees.

I've never seen that before, so I assume it's significant to our diagnosis here.

2 hours ago, Levine98 said:

Have you tried another sweep second hand?

I have, and it looks the same.

 

2 hours ago, Levine98 said:

Have you checked the pinion to make sure it is true and not bent? 

After you suggested it, yes, and it looks dead straight.

 

2 hours ago, Levine98 said:

Have you observed that the sweep second hand driver wheel and pinion are close to level and meshing with no wobble?

Yes, after removing and re-seating the driver wheel.

 

2 hours ago, Levine98 said:

Does it always do it in the same spot?

It did seem to be worst around 4-6 o'clock, but after removing the pinion and reseating things it seems to be running smoothly.

The problem with the balance stopping when I set the time persists, though, so I'm not ready to button it up yet.

[JohnR725]

4 hours ago, ManSkirtBrew said:

I will take the second hand pinion spring off and check it for tension again, but I did notice something else this morning that's probably important. When I pull the crown out to setting position and turn it to set the time, the balance stops spinning--but only when I turn the crown clockwise. If I turn it counterclockwise, the balance continues running.

Also when I turn the crown clockwise, I see the seconds hand rotate counter-clockwise a few degrees.

I've never seen that before, so I assume it's significant to our diagnosis here.

one of the things you're seeing is specifically the stopping. If you set a watch and depending upon the particular watch and how tight the Canon pinion is you can stop the watch. Basically if you can rotate and cancel out the force the mainspring the watch.. The same as if you turn in the other direction carefully you can kick the amplitude up a little bit it's not really an issue because you're setting the watch

the problem would be as the amount of play between the gear driving the pinion. That's why the spring is there. Gear trains tend to produce pull stations up our that you normally wouldn't see you look at how that gear meshes with opinion you'll see that it might actually be a position where it's not actually touching at all and in that moment the secondhand can move back and forth as why the spring is there to just make sure it doesn't flop around in the in between positions. It's a common problem for that style of design which is why they have Springs. Also in manufacturing if the gear and pinion were sized properly. also if the poster gear rides on is bent conceivably it may go in and out of meshing properly and you may see it worse in some positions

Alan I think I might have mentioned it up above but if I didn't make sure that there is no lubrication on the spring. As it's supposed to be holding something in place and lubrication would make it more slippery and then your hand flop around a little bit.

[ManSkirtBrew]

4 hours ago, JohnR725 said:

Alan I think I might have mentioned it up above but if I didn't make sure that there is no lubrication on the spring. As it's supposed to be holding something in place and lubrication would make it more slippery and then your hand flop around a little bit.

I did make sure of this when I reassembled, and it seems to be behaving well now.

I just ordered a new center wheel, but at least it was only $14. If there's a significant difference in the fit of the seconds pinion shaft, I'll swap it out.

But for now I might just put it together and wear it for a bit

[Jon]

To make sure you have the correct amount of tension on the sweep second pinion, run the watch without the sweep second pinion or brake spring in place and note the amplitude after at least 48 hours after lubricating. Let's say it is 300 degrees amplitude. Then fit the sweep second pinion and brake spring and set the tension so it is just enough to stop the flutter/backlash of the second hand, but not so much tension to reduce the amplitude by more than 10 to 15 degrees amplitude. That is the Goldilocks point. No flutter, but not a ridiculous drop in amplitude. If the spring is dented or damaged, that will decrease the amplitude radically, making you think it is something else, so make sure that isn't the case. Any bigger drop than 20 degrees using this method, then you need to backtrack the problem, such as a bent sweep second pinion, bad lubrication, over lubrication, dirty pinion leaves, too much side shake, etc...

Also, I always advise to fit a new mainspring, so you can rule out any power output problems because you aren't using an old spring.

Edited May 9, 2023 by Jon

[ManSkirtBrew]

Thanks again to everyone for the advice. It's running well now, and really looks great. I'll keep an eye on it and see how it runs on my wrist.

[Levine98]

1 hour ago, ManSkirtBrew said:

Thanks again to everyone for the advice. It's running well now, and really looks great. I'll keep an eye on it and see how it runs on my wrist.

Wow, that’s a beauty—well done.  

[mikepilk]

That's a nice looking watch, what a lovely dial.

Good work.