Tudor c. 390; Rebanking, low amplitude

[mzinski]

Hi all! 

I'm looking for some advice on a Tudor caliber 390 I'm working on. I'm finding when worn or placed on my autowinder it rebanks. I suspected this was the case after seeing it would gain so much time so quickly compared with it's timegrapher readout.

I tested my theory and observed this by rotating the watch in my hand and listening to the movement after a few rotations. Note, not aggressive shaking or rotating. I could hear the rebanking. 

Normally, I'd chase after the mainspring as I'd expect the amplitude to be too high. In this case, it's not. 

DU: +3, 274, 0.6

6H: +8, 209, 1.1

9H: +20, 199, 1.2

12H: +15, 197, 1.3

3H: -16, 199, 0.8

DD: +1, 266, 0.7

I obviously have some poising and positional error to work through but my bigger question is why I'm getting rebanking on such low amplitudes? 

Please let me know your thoughts. 

Thanks! 

[mikepilk]

3 minutes ago, mzinski said:

I'm finding when worn or placed on my autowinder it rebanks.

Normally, I'd chase after the mainspring as I'd expect the amplitude to be too high. In this case, it's not. 

How can these two statements be true?  Either you have too much amplitude and it's rebanking, or the amplitude is OK and there is another problem.

Do you have a timegrapher pic of the 'rebanking'

[Jon]

51 minutes ago, mzinski said:

my bigger question is why I'm getting rebanking on such low amplitudes? 

Your timegrapher readings aren't inferring in any way that there is knocking (rebanking) is occurring, in fact, quite the opposite.

I would trust your readings more than your ears. What are you hearing? And what is the trace on your timegrapher?

[Neverenoughwatches]

20 minutes ago, Jon said:

Your timegrapher readings aren't inferring in any way that there is knocking (rebanking) is occurring, in fact, quite the opposite.

I would trust your readings more than your ears. What are you hearing? And what is the trace on your timegrapher?

I thought the same after reading what appears to be contradictory information.  But the OP does say when the watch is on his winder ' it gains so much time so quickly ' .

[mzinski]

I hear you guys - it didn't make sense to me either. I'm accustomed to rebanking presenting itself on a watch that might be at rest 320+ amplitude, then when it moves it rebanks. I've never experience rebanking on a watch at rest at 270. 

So here is the timegrapher:

Photo 1: Watch at rest, dial up, amp 270

Photo 2: I removed the watch from timegrapher, rotated in my wrist 4-5 times (imagine warming up for physical activity or how a watch rotates on an autowinder, rotating my wrists), placed on timegrapher. Amplitude spikes, timing goes crazy

Photo 3: Amplitude is high but coming down, it does create another rebanking event

Photo 4: Amplitude is continuing to come down until it comes back to rest at 270

My ear - I can hear the galloping after watch is rotated. I cannot hear galloping when it is at rest. 

The heart of my question, how am I getting a 60+ amplitude bump from common movement of the watch (on the wrist, rotating in an autowinder, etc)? 

 

[Neverenoughwatches]

31 minutes ago, mzinski said:

I hear you guys - it didn't make sense to me either. I'm accustomed to rebanking presenting itself on a watch that might be at rest 320+ amplitude, then when it moves it rebanks. I've never experience rebanking on a watch at rest at 270. 

So here is the timegrapher:

Photo 1: Watch at rest, dial up, amp 270

Photo 2: I removed the watch from timegrapher, rotated in my wrist 4-5 times (imagine warming up for physical activity or how a watch rotates on an autowinder, rotating my wrists), placed on timegrapher. Amplitude spikes, timing goes crazy

Photo 3: Amplitude is high but coming down, it does create another rebanking event

Photo 4: Amplitude is continuing to come down until it comes back to rest at 270

My ear - I can hear the galloping after watch is rotated. I cannot hear galloping when it is at rest. 

The heart of my question, how am I getting a 60+ amplitude bump from common movement of the watch (on the wrist, rotating in an autowinder, etc)? 

 

I'm not quite sure what you mean ' watch is at rest 320 amplitude ?   So the tg readings and trace are showing signs of rebanking, previous figures supplied didn't indicate that.  I'm a bit confused now. 

At rest , do you mean held stationery ? 

[mzinski]

Sorry. 

At rest = watch left in one position for 30-60 seconds to stablize and continues to be in that single position

The initial read out is a programmed test with 30 seconds pause between positions for stabilization than 60 seconds of timegrapher reading to determine average performance. 

The subsequent photos demonstrate watch in dial up position, stabilized. Then watch moved (rotated), set back on to timegrapher, and the following ~60 seconds of amplitude jump, rebanking, and settling back down to 270 amplitude. 

Make more sense? 

[AndyGSi]

Strange that the values aren't as high as you think as lift angle should be 50 Deg.

What have you done to the movement.

Edited February 21 by AndyGSi

[mbwatch]

Does it do this at less than full wind? I wonder if what you're seeing is similar to what happens if you crank a manual movement all the way to the end of the mainspring where it may have crazy amplitude for the first 5-10 minutes while the ratchet eases up on the barrel arbor. On an automatic at full wind that could mean your mainspring isn't slipping like it is supposed to.

[Neverenoughwatches]

49 minutes ago, mzinski said:

Sorry. 

At rest = watch left in one position for 30-60 seconds to stablize and continues to be in that single position

The initial read out is a programmed test with 30 seconds pause between positions for stabilization than 60 seconds of timegrapher reading to determine average performance. 

The subsequent photos demonstrate watch in dial up position, stabilized. Then watch moved (rotated), set back on to timegrapher, and the following ~60 seconds of amplitude jump, rebanking, and settling back down to 270 amplitude. 

Make more sense? 

Yes it does thank you. So small winding of the watch causes it to rebank ? Can the watch also be hand wound, can you tell how close it is to being fully wound ?  It's starting to sound like the bridle is not slipping soon enough, so the bigger question of why you are getting rebanking at low amplitudes is answered....you're not. 

[mzinski]

@Neverenoughwatches lol - I know I'm not getting rebanking at a low amplitude. My phrasing could have been better. I'm trying to understand how I jump to rebanking from a low amplitude so easily. 

It's an automatic movement that can be manually wound. I gave it a full wind and more, place it immediately onto the timegrapher. The amplitude started at 316, dropped to 300 within 15-20 seconds, and continued to dropp to 290 within 60 seconds. About 120 seconds in it settled to 270.  

42 minutes ago, AndyGSi said:

Strange that the values aren't as high as you think as lift angle should be 50 Deg.

What have yo done to the movement.

PS. yes, my bad in my haste I didn't adjust. Reading should be considered 10 degrees less than stated. 

[mikepilk]

I've had similar very confusing results on the timegrapher in the past, where amplitude was all over the place.

It turned out that the hairspring collet was loose. I've also had odd results and found the staff was loose in the balance.

I notice in your plots that beat error varies from 0.4 to 0.7ms, which might suggest something could be moving?

[AndyGSi]

So what have you done with the movement?

[mzinski]

@Neverenoughwatches I'm going to experiment with the mainspring and winding. See if there is too much tension on the bridle when wound. That's a good theory to look in to. 

@mikepilk I did not restaff the balance but I will look into the assembly to movement. 

@AndyGSi I received it barely running, subsequently cleaned, replaced mainspring, and started in on adjustments/time testing. 

[AndyGSi]

14 minutes ago, mzinski said:

I received it barely running, subsequently cleaned, replaced mainspring, and started in on adjustments/time testing. 

So what mainspring did you use and how did you grease the barrel.

[mzinski]

1 hour ago, AndyGSi said:

So what mainspring did you use and how did you grease the barrel.

Mainspring = MSN-29, 1.3 x .095 x 266 auto

Grease = 8213 around barrel wall for braking, 8141 oil for spring, and 1300 for the arbor at the barrel holes. 

Edited February 22 by mzinski

[mikepilk]

Check that the hairspring collet is secure - I've had a loose collet a couple of times. It can suddenly slip and give odd timegrapher readings.

[AndyGSi]

18 hours ago, mzinski said:

Mainspring = MSN-29, 1.3 x .095 x 266 auto

Grease = 8213 around barrel wall for braking, 8141 oil for spring, and 1300 for the arbor at the barrel holes. 

For me that spring is a little too powerful for the old movement and would be interested to see what the barrel is doing during these spikes.

[nevenbekriev]

This is a regular problem - rebanking while fully wound and continuing winding by autowind. This is bigger than needed friction of the spring bridle on the barrel wall. What is the bridle shape? Is it well polished (sometimes it is not and friction is due some bad edge or burr)

[mzinski]

Sorry for the long gap, took me a little bit to get back to this project. 

I started chasing down the idea of the bridle or barrel wall causing too much friction so when fully wound OR automatically wound, it would keep hitting that point of high tension and high amplitude, hence the rebanking. But when left to it's own, it would settle into it's natural state of amplitude. 

What I've noticed in the process, that standard loose bridle for a MSN-29 (same as WA80) is too short for the barrel. As you can see in the picture, it does not appropriately overlap itself. The rest of the spring is getting caught up under the bridle and causing issues! 

Further that, I noticed Tudor 390 lists a "MAINSPRING BRIDLE ONLY" in the parts list, A/1396. I'm suspecting, though I don't know until I get one, the bridle only is a special length to be substituted in. 

More to come when I get this piece. 

[AndyGSi]

Just looking back at your earlier responses and you say you've used an MSN-29 Auto Mainspring.

If that's the case then why is that bridle still in the barrel?

[mzinski]

19 minutes ago, AndyGSi said:

Just looking back at your earlier responses and you say you've used an MSN-29 Auto Mainspring.

If that's the case then why is that bridle still in the barrel?

MSN-29 = WA80

I have two WA80's on hand, both have a split bridle. 

Bridle is in there for posterity sake and photographic evidence of what I observed. 

[AndyGSi]

So all the details I've found for both the MSN-29 & WA80 show attached bridles?

Also the WA80 is even stronger again at 0.10 thick which won't help.

[mzinski]

46 minutes ago, AndyGSi said:

So all the details I've found for both the MSN-29 & WA80 show attached bridles?

Also the WA80 is even stronger again at 0.10 thick which won't help.

When I get home I'll look at my packaging again, see if I can recall where I got the WA80. I took it out just yesterday and it was a split bridle. 

[Nucejoe]

On 2/21/2025 at 10:30 PM, mzinski said:

I obviously have some poising and positional error to work through.

   Number one suspect.

On 2/21/2025 at 10:30 PM, mzinski said:

my bigger question is why I'm getting rebanking on such low amplitudes? 

Are you sure what you are hearing is the sound of rebanking? 

Shake the watch to hear the sound  and immediately take a  slow mo video, should shows the sound  is/isn't rebanking. 

Good luck.

Edited yesterday at 03:11 AM by Nucejoe