Bulova mainspring issue

[Fleslie]

I have now had two Bulova movements, (10 BTC) and (10BU) have the same issue. If I wind both movements up and gently nudge the balance wheel it will run for about 5 seconds. If during the 5 seconds of movement I keep pressure on the spring via the stem, the balance will keep running indefinitely until I let pressure off of the stem. I have removed both springs, cleaned and lubricated them and re-installed with the exact same issue. At this point I am assuming they are bad springs, although they both appear to be intact and good. Is there something else that can cause this that's unrelated to the mainspring? In both cases I have cleaned the parts and have seen no wheel or pinion issues. Many thanks to all advice.

[Poljot]

37 minutes ago, Fleslie said:

I have now had two Bulova movements, (10 BTC) and (10BU) have the same issue. If I wind both movements up and gently nudge the balance wheel it will run for about 5 seconds. If during the 5 seconds of movement I keep pressure on the spring via the stem, the balance will keep running indefinitely until I let pressure off of the stem. I have removed both springs, cleaned and lubricated them and re-installed with the exact same issue. At this point I am assuming they are bad springs, although they both appear to be intact and good. Is there something else that can cause this that's unrelated to the mainspring? In both cases I have cleaned the parts and have seen no wheel or pinion issues. Many thanks to all advice.

Remove Balance, take it apart and clean balance pivots & jewels and oil balance jewels (at least).

But since you will have to remove the hands and dial, you might as well clean every jewel.

Edited January 23, 2021 by Poljot

[Graziano]

1 hour ago, Poljot said:

Remove Balance, take it apart and clean balance pivots & jewels and oil balance jewels (at least).

But since you will have to remove the hands and dial, you might as well clean every jewel.

Ageed ,and don't forget the pallet folk ,as they can be gummed up .Sometimes ,for some reason ,someone lubricates the pivots and they are like glued to the pallet bridge.And will stop a movement on its own.Have come across this problem many times,all it was was the pallet pivots glue to the bridge.

 

Edited January 24, 2021 by Graziano

[Fleslie]

Thanks, I will proceed with your suggestions. Many thanks

[JohnC]

How's the running of the train without the pallets installed? If you turn the crown a few clicks, does it run down smoothly or jolt to a stop?

[JohnR725]

Background history of the watches? Were they running before you attempted to service them? 

10 hours ago, Fleslie said:

I have removed both springs, cleaned and lubricated them and re-installed with the exact same issue. At this point I am assuming they are bad springs, although they both appear to be intact and good.

From my interpretation of the quoted above you appeared to views the Springs that were in the watch? What color were they blue or white? What did they look like were they a really tight spiral or did it open up quite a bit. Even if they were  set that means there were a really tight spiral you still should Be able to wind them up a little bit and what should run at least for a while not the problem you're having.

11 hours ago, Fleslie said:

Is there something else that can cause this that's unrelated to the mainspring? In both cases I have cleaned the parts and have seen no wheel or pinion issues.

Maybe you should explain your cleaning procedure and lubrication procedure? It sounds like a watch that has super friction somewhere between the mainspring and including the mainspring all the way to the balance wheel.

 

[Fleslie]

If I take the pallet fork out, all of the wheels freely spin. The watch will fully wind without issue. At the end of the wind the balance will move and stay moving with the pallet forks operating as they should including the escape wheel but only if I keep pressure on the stem as if I were still winding.

On both movements I removed the springs, (white) and they appeared to have a normal expected shape with no damage. I cleaned them both with rubbing alcohol and lubricated with Mobius 8200. None of this changed the issue that is why I am wondering if there is an issue not related to the spring at all. I will try and clean Poljot suggested above. All suggestions are greatly appreciated.

[Marc]

If you're really stuck try installing each wheel in isolation and check that each spins freely with no more than a puff of air from a blower. If they do then build the train up one wheel at a time, testing freedom with the blower after each wheel. If you get to the point where the complete train is installed up to and including the escape wheel, then with the pallet fork and click out you should be able to spin the whole train (including the M/S barrel) in both directions using a puff of air on the escape wheel. Next install the click and wind just one or two clicks of power into the M/S, no more. The train should spin freely, and if you're lucky you should see the escape wheel reverse maybe a half turn before it stops. This systematic approach should help to identify exactly where in the train the losses are occurring, if that is where the problem lies.

Before you install the M/S into the barrel you should try installing the arbor and the lid (empty barrel) and check the end and side shake of the arbor in the barrel. The barrel should spin freely on the arbor, but with minimal end and side shake, any excess of which would indicate excessive wear.

If you get to this point and the M/S is correct and in good order then it's fairly safe to assume that the excessive power loss is associated with the pallet (check pivots which should be run dry and undamaged, pallet stones which should be spotless and not scored, and lubrication), or with the balance pivots.

A quick check for losses in the balance can be made by installing the balance without the pallet fork. From its rest position carefully turn the balance wheel through about 300 degrees of rotation and then release it. Time how long it takes to come to a complete rest, you should be looking at times in the order of two to three minutes or more, and its decrease in amplitude should be gradual and consistent until it stops. If it comes to a sudden stop or comes to rest in much less than a couple of minutes then end shakes, side shakes, and condition of jewels and pivots need checking.

If all the above is good and the problem persists then it's just possible that there is an issue with the escapement geometry (position of banking, position of pallet jewels, height of engagement between the pallet stones and the escape wheel teeth, engagement of impulse pin with pallet fork, roller and guard pin, etc) however, these are things that would have been sufficiently correct for the movement to have performed to factory specs when it was new, and which don't normally go out of adjustment unless someone else has been playing with them, which is a whole other can of worms.

[JohnR725]

1 hour ago, Fleslie said:

I am wondering if there is an issue not related to the spring at all

We rely on your eyes to make diagnostics but your eyes aren't seeing the problem yet. Could we have a picture of each of the watches looking straight down set it over the balance wheel. That another picture looking inside ways at the balance wheel. It's amazing how much energy you can lose at the hairspring isn't quite where it's supposed to be. In addition to all the things above but. Sounds like your gear train is free by your own description. So it could be related to the balance wheel.

With no power at all the balance wheel should be very very free to move is it? In other words if you manually with your finger wind it one turn it let it go what happens?

 

[Fleslie]

[JohnC]

I think that unless the mainspring is badly deformed that is unlikely to be the issue. If the rundown of the train is okay - or at least not awful - most likely problem is in the escapement or balance wheel. Check the hairspring is not hung up on the centre wheel - easy enough to do and easy enough to miss. Also check the hairspring is not out of flat and rubbing something.

[Nucejoe]

I fully let the power down. Turn the barrel by finger, you get a feel of the torque the movement takes to start running . That would give you an idea if you get inadequate torque out of both spring( unlikely).

Next check turning( by spoke) wheels of the train.

Make a habbit of this tests to get the hang of it.

I didn't get to read all said so far, but agree with JohnC. 

1-Oscilators grously out of beat wont self start.

2- Bad pivot.

3- Fork pallets badly out of adjustment.

4-No end shake on staff, fork arbout and escape wheel.

Make a habbit of checking the oscilator, 

See if pivots jump out of jewel holes as you gently raise one side of the balance wheel.

Good luck

[Fleslie]

Many thanks to all, I will begin all of the suggested tasks and post what I found, could take awhile.