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Bunn Special stopping in Pennant Down

jdrichard

By jdrichard
in Watch Repairs Help & Advice

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jdrichard Distinguished Member

jdrichard

Posted
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Quick Question. Just serviced a 24 Jewel Illinois Bunn Special Pocket Watch. It now has an amplitude of 260 deg, however, it stops when placed in Pennant Down position. It has a right angle escapement. Any hints?

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Repivot Member

Repivot

Posted
Posted (edited)

Based on the position of the stem to the pallet, pendant down would place the balance above the pallet. My guess would be to check the interaction of the fork and guard pin with the roller table and jewel. There could be enough play in the pivots that the guard pin is touching the roller table, but only in that position. Or that the jewel doesnt have sufficient corner clearance to enter the fork, again only in that position.

Edited by Repivot
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WellAdjusted Member

WellAdjusted

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Agreed. I have worked on many of these, and when the watch fully stops when the balance wheel is directly above or below that pallet, the issues you've heard are almost always the reason.

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WellAdjusted Member

WellAdjusted

Posted
Posted

Although it probably isn't the fault in this case, a chip in the edge of a balance hole jewel can cause this behavior as well.

It happens when the jewel is intact enough for respectable amplitude dial-up and dial-down and in most vertical positions, but in one vertical position the pivot falls into the chipped area, causing it to stop.

WellAdjusted Member

WellAdjusted

Posted
Posted

Those full-plate watches can be a trial. (I have an Illinois 18s Model 2 that is giving me fits right now.)

You might consider removing the hairspring, replacing the balance, and then observing the watch. The movement will still send an impulse to the balance in the good positions, and it is easier to see how the guard pin and roller are interacting.

Some of the old-time repair books called this "running in half-time" and recommend it for troubleshooting after a balance staff replacement.

 

jdrichard Distinguished Member

jdrichard

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12 minutes ago, WellAdjusted said:

Those full-plate watches can be a trial. (I have an Illinois 18s Model 2 that is giving me fits right now.)

You might consider removing the hairspring, replacing the balance, and then observing the watch. The movement will still send an impulse to the balance in the good positions, and it is easier to see how the guard pin and roller are interacting.

Some of the old-time repair books called this "running in half-time" and recommend it for troubleshooting after a balance staff replacement.

 

I like your name by the way:)  I have done this before where the top of the palate fork was rubbing against the bottom of the roller table.  I have also observed the action in my microscope.  Will try that out...

Again thanks all.

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nickelsilver Distinguished Member

nickelsilver

Posted
Posted

I wouldn't touch anything until I was sure it was working toward a solution. It could be that the guard pin is rubbing in that position, but why? Did it get bent, or is something else causing it to rub? It plays an important role in the safety action of the escapement, maybe bending it fixes your pendant down issue, but then the escapement unlocks when it shouldn't in other positions.

 

For sure vertical guard pins are very sensitive. One thing they are renowned for is wedging against the roller table when they have too much freedom. So do you move it closer, or further away? Just randomly trying things is like praying for abundance- you might get an abundance of mosquitoes!

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Nucejoe Distinguished Member

Nucejoe

Posted
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43 minutes ago, jdrichard said:

ALL Exceptional advice.  Very hard to see on a full plate watch.  Would you recommend i adjust the guard pin?

Hi jd, as equipped as you are, I was expecting a video of the roller table and guard pin in action.

I imagine adjusting the guard is easier than painting the roller with ink to check it for signs of rubbing in PD versus PU position.

Wont this full plate let you check side shakes?  

Have you check staff pivots and jewels for wear? 

Do you see a sign of guard pin having moved or bent?   

Has the fork been replaced?    I guess you don't know if it ever run with this fork.

 

jdrichard Distinguished Member

jdrichard

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1 hour ago, Nucejoe said:

Hi jd, as equipped as you are, I was expecting a video of the roller table and guard pin in action.

I imagine adjusting the guard is easier than painting the roller with ink to check it for signs of rubbing in PD versus PU position.

Wont this full plate let you check side shakes?  

Have you check staff pivots and jewels for wear? 

Do you see a sign of guard pin having moved or bent?   

Has the fork been replaced?    I guess you don't know if it ever run with this fork.

 

Wont this full plate let you check side shakes?  

Answer: Yes i can check the side shake and I did...all looked good.

Have you check staff pivots and jewels for wear? 

Answer: I did make a cleaning video and did check all jewels with my microscope and all looked good.

Do you see a sign of guard pin having moved or bent? 

Answer:  Did not check the guard pin as there was no obvious issue...but that may be the guilty party.  I am hoping I dont have to take that full plate off again as getting the pivots in the holes with a 24J full plate is almost impossible. Took be 30 min of frustrating nudging the last time.

Has the fork been replaced?

Nucejoe Distinguished Member

Nucejoe

Posted
Posted
2 minutes ago, KarlvonKoln said:

Man, judging the interaction between roller and lever fork and guard pin.. on a full plate watch!  My sympathies. 

yes I agree.

  Jd makes some real tough to capture videos, shows upclose how he makes staffs, I thought  a close up vid of roller table- guard pin should be easy for him. oh well. 

I am certainly not for messing with the guard pin unless he has solid reason to.

1 hour ago, jdrichard said:

Wont this full plate let you check side shakes?  

Answer: Yes i can check the side shake and I did...all looked good.

Have you check staff pivots and jewels for wear? 

Answer: I did make a cleaning video and did check all jewels with my microscope and all looked good.

Do you see a sign of guard pin having moved or bent? 

Answer:  Did not check the guard pin as there was no obvious issue...but that may be the guilty party.  I am hoping I dont have to take that full plate off again as getting the pivots in the holes with a 24J full plate is almost impossible. Took be 30 min of frustrating nudging the last time.

Has the fork been replaced?

ya, you nudge one pivot in and two pivot slide out.

Repivot Member

Repivot

Posted
Posted

In my world, checking these things on a full plate means using a mirror or holding the movement over my head or some awkward contortions like that. But it can and needs to be done from time to time. Good lighting helps. Eventually the problem shows itself. 

What I do prior to installing the balance is test the pallet under low power. Is the guard pin straight? Does the fork come to a lock equally on both sides in relationship to the hole of the balance jewel? If not, there needs to be an adjustment to one of the banking pins. These two checks go a long way in addressing any issues between the balance and pallet.

Let us know what you find.

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