Zenith calibre 3841 Pocket Watch (shock protection)

agemo

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Thank you Agemo that is very informative! What does it mean "without the racket"? Is it the characteristic Zenith regulator that looks a bit like a tennis racket?
Yes, it is the characteristic racket of Zenith, your watch is one of those to collect, all my congratulations!!!

Amicalement GG
 

svenedin

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I think I spoke too soon about this watch. It has been running continuously for 5 days and I have been using it. It was keeping good time. In the middle of the night it stopped whilst it was sitting on a table. This morning I discovered it stopped and it would not re-start even with a gentle shake.

I though initially that perhaps a hand was catching but this is not the problem. I found that the balance was for want of a better term, jammed. It would not rotate with a little shake or a puff of air. I removed the balance, looked at it, could find nothing wrong and put it back in the watch. The watch took off and is still running apparently fine.

I cannot really work out what went wrong. I think the most likely explanation is that I did not tighten down the balance cock screw, it worked loose and the balance came out of a pivot. I am nervous of damaging a pivot and very careful to ensure they are in place before final tightening so perhaps I just forgot. We will see!

At the moment the movement is in a plastic box running on my desk but I must do some of my actual job now!
 

gmorse

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Hi Stephen,

It sounds as though it was 're-banked', (aka 'over-banked'), which can happen if the safety dart doesn't engage with the safety roller properly for some reason, and the impulse jewel ends up on the outside of the fork. When you replaced the balance you clearly did it properly and ensured that the jewel was in the fork, so off it went.

Regards,

Graham
 

svenedin

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Hi Stephen,

It sounds as though it was 're-banked', (aka 'over-banked'), which can happen if the safety dart doesn't engage with the safety roller properly for some reason, and the impulse jewel ends up on the outside of the fork. When you replaced the balance you clearly did it properly and ensured that the jewel was in the fork, so off it went.

Regards,

Graham
Thank you Graham. What I can say is that when I first put the watch back together it was very out of beat which may have had something to do with it. Surprised though that it ran 5 days in normal use without issue.

Since I've had the balance out just now should I re-clean the balance jewels and re-oil the endstones? I am reluctant to do this as it involves the dreaded Kif springs! :emoji_laughing:
 

gmorse

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Hi Stephen,

If you need to do this, before replacing the balance it's worth looking closely at the staff pivots to see whether they've picked up any debris from the bench covering, because anything sticking to them will get back on the jewels. Strictly speaking, you should re-clean and lubricate everything in these circumstances, but while there's a question mark over the stability of the watch I should carry on with the testing.

Regards,

Graham
 

svenedin

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Good. I thought that too. I have put the dial and hands back on, it's back in the case and in my pocket and I shall give it an extended test of real life use. If it overbanks again then I will have to investigate further.
 

svenedin

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So far so good. The watch running normally for 24 hours. It ran 5 days before overbanking first time round. I think my provisional diagnosis is that I forgot to tighten down the balance cock screw. The screw loosened over 5 days carrying the watch around in my pocket. Then when I put it dial up on my bedside table the balance cock tipped down allowing too much endshake on the balance and the dart missed the safety roller probably with the minor impact of putting the watch down. I did notice a strange metallic pinging from the watch as I was going to sleep but ignored it only to find the watch stopped in the morning. That pinging was presumably the balance hitting the wrong side of the fork as it came to rest after overbanking.

Having to partially take the watch apart again has been a learning experience. I used too much oil on the shoulder of the barrel arbour (my book recommends HP1300) and I found a little oil on the back of the dial. I also used a bit too much grease on one or two posts of the keyless works and some creep was evident (but not much). I think the hand tension is a bit "light". It's very smooth but perhaps too easy. The hands don't slip but again I may have been over generous with canon pinion grease. Having said all that, there was far more oil and grease around the watch when I first received it! Under the crown wheel looked more like the inside of a motor car wheel bearing.....

I'll keep the watch on test for now but I think I'll be heading towards a full strip down again as I am too obsessive and fussy to tolerate my sloppiness!
 

Skutt50

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If the movement has a tendency to overbank, one situation when this happens is when the mainspring is worn down and the watch comes to a halt.
 

svenedin

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If the movement has a tendency to overbank, one situation when this happens is when the mainspring is worn down and the watch comes to a halt.
Yes. Thank you Skutt. I actually read some of your old posts on this. When the watch overbanked it stopped at 11pm so it was at roughly half-wind (assuming 30 hour run time). It should not have been low on power at that point.
 

Chris Radek

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Just a few thoughts:

If the hand setting is loose, that's not because you've used too much grease. Too much grease causes a mess, but not looseness. Looseness is because the cannon pinion is worn from there NOT being proper lube previously, and now it needs to be tightened.

If it overbanks, that is a fault in the safety mechanism of the escapement, which is made up of a roller with a cutout for passing (the one with the jewel, on single roller; the small one on double roller) and corresponding pin or dart, and also the general condition of the jewels and pivots that keep the safety parts in their proper places with respect to one another. When you service the escapement, check it for safety - try to pass the lever to the wrong side throughout all the balance's positions. Concentrate especially on the positions where the fork and jewel are interacting. In a correctly functioning escapement it will not be possible to move the fork to the wrong side in any situation.
 
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svenedin

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This watch stopped. It had overbanked again and was making an odd noise but this time the cause was really very obvious indeed and rather silly on my part! I had not tightened one of the pallet bridge screws and I found it loose in the movement.

I fixed that and then on further testing the mainspring has started to slip on the arbour. I have had very limited success trying to tighten the centre coil of a mainspring before and have ended up breaking them or deforming them out of round. I will try to tighten the centre coil by squeezing it with pliers whilst it is around the tapered arbour from my spring winder. It may break so before I do that I have ordered another spring...Quite a nuisance to have to get the spring out again but the barrel will pass underneath the centre wheel so no need for too much disassembly.

Does anyone have any tips they could share about how to tighten the centre coil of the mainspring to ensure a tight, secure fit on the arbor?

IMG_8652.jpeg
 
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gmorse

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Hi Stephen,

You can buy curved jaw pliers, which have one convex and one concave jaw. To make a permanent bend in a spring you have to bend it past its elastic limit, (without it fracturing!), so bending it on an arbor probably won't work. The centre coil is particularly vulnerable because of the hole where it hooks on.

Regards,

Graham
 

svenedin

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Thank you Graham. I have investigated and the spring was in fact securely hooked on the arbor. I am thinking that in fact the spring was slipping on the barrel hook. It would take about a 1/4 wind and slip. I think the hook end of the spring was squashed so flat as it fed into my winder that it was no longer an effective hook. The barrel hook looks fine. Then again maybe it was slipping on the arbor with sufficient tension in the spring. I am not sure. Needless to say I did try to tighten the inner coil and........I broke the spring through the hole.

Thank you for the link to the pliers. Would their profile achieve a tight enough curve?

As well as ordering the "correct" mainspring by dimensions (Zenith will not sell the branded mainspring) I have ordered a slightly shorter (40mm shorter) of the same height and thickness but for a 15 barrel rather 16. I am hoping the spring for the smaller barrel may have a tighter inner coil already. Just a guess!
 
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gmorse

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Hi Stephen,
Would their profile achieve a tight enough curve?
That does depend on how tight it needs to be! If it's the hooking in the barrel wall that's suspect, it may be the hole itself or the hook that's at fault, as well as the final curve; have you any pictures?

Regards,

Graham
 

svenedin

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Hello Graham. Yes the hook from the original spring and replacement look different. For want of a better term, the "barb" of the original spring is obvious but in the replacement it is ineffective. The original spring has the hook end almost flat but in the replacement it is curved.

Original spring:

IMG_8653.jpeg

Replacement spring:

IMG_8654 2.jpeg
 
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gmorse

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Hi Stephen,

IMG_8654 2_crop.jpg

The end of the bridle ringed in red, where it engages with the hooking in the barrel wall, may need chamfering so that the outer edge is sharper and bites better in the hooking. Is the hooking in the barrel wall a stud or just a step in the metal?

Regards,

Graham
 

svenedin

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Thanks Graham. It’s a stud. Too small for me to photograph. From the outside of the barrel there’s a hole/slot that the internal stud is fitted into somehow.
 

gmorse

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Hi Stephen,
It’s a stud. Too small for me to photograph. From the outside of the barrel there’s a hole/slot that the internal stud is fitted into somehow.
If it's a separate piece, these are usually either screwed and/or riveted in place, although in some cheaper watches they aren't separate, they're just punched into the barrel wall.

Regards,

Graham
 

svenedin

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I had another look today. The mainspring is definitely slipping on the barrel hook not the arbour. If I wind the watch until it slips then let down the spring the tail end has clearly slipped past the barrel hook. Unfortunately, the barrel hook is not a stud as I first though but punched into the barrel wall. If I could get parts I would replace the barrel but parts are near impossible to find for this rare movement. There is a scrap movement on the well known auction site but it is rather expensive for what it is and there is no way of knowing whether the barrel is in good condition. I used a punch to punch the barrel hook from the outside of the barrel so that it protrudes slightly more into the barrel. This has actually worked and the spring now holds but I don't like my crude "bush fix" very much. I will keep looking for a new barrel as one may turn up eventually.
 

Skutt50

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It probably is not a problem. Sometimes these barrel hooks are worn or damaged and needs a bit of help to function properly. As Graham pointed out earlier it may help to chamfer the outer edge so it grabbs better. Also bending the outer edge slightly "outwards" can do the trick.
 
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svenedin

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Thank you Skutt and thank you to everyone for your patience with my adventure with this watch. If the spring slips again I will try these suggestions. At the moment the watch is ticking away in my pocket. About time too!
 

svenedin

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Just to finish off this thread I did manage to find a used barrel complete.

This has the advantage of not only a good condition barrel with a hook that works but the original Zenith spring. None of the generic springs that I bought had the same form as the original spring nor did they appear to be made of exactly the same material. Whether this actually matters I do not know.

I cleaned up the replacement barrel and spring. Fitted it. Tested and all was good. Then (tempting fate perhaps) I re-oiled the balance endstones (since the balance had been out), lost a Kif spring (again), found the Kif spring and re-fitted. Re-oiled the pallet stones (they been out too and degreased) and the centre wheel bottom pivot (bridge had been off).

Just for interest here are 3 springs. The top one is the Zenith spring. The bottom 2 are both Generale Ressorts springs with exactly the same dimensions as the original spring. As can clearly be seen, they are NOT of the same form nor are they consistent between each other!

I had thought that as long as a spring was the same dimensions then happy days but no.......

IMG_8696.jpeg IMG_8569.jpeg IMG_8570.jpeg
 
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svenedin

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Since I replaced the barrel (which also had the correct Zenith specification mainspring) the amplitude is significantly better. It just needs some adjusting for rate now. I am now getting 345 degrees DU and 325 DD compared with around 280 DU before the barrel swap. This is based on default 52 LA on the machine which I know is too high but this is about relative amplitude rather than absolute.

The old barrel was significantly worn, not just the barrel hook which was unreliable and started letting the spring slip (the hook is the type that is a little tab that has been pushed out from the wall of the barrel leaving a little hole). Although it didn't seem to have too much side shake or end shake I suspect it did actually because clearly the watch has more power. Then again it may be the spring too. The springs were exactly the same dimensions but not the same shape or on visual inspection exactly the same material (both alloy). I suspect the Zenith spring is stronger (it feels stiffer and more springy).
 

svenedin

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I went to regulate the watch today. Popped the case open and put the watch on the timing machine. Nothing. Switched machine off and on several times and nothing. Then looked at the watch which had stopped. Deep sigh. What has gone wrong now?!!!!! For crying out loud! :mad:

Looked at watch in case, balance would swing but escape wheel not moving. Totally puzzled.

Took watch out of case. Looked at hands, seems fine. Moved hand around, not catching. Took hands off in preparation for getting dial off. Watch now working I notice. Hands? No. This..................(notice my avatar; it's a white German Shepherd Dog hair)

IMG_8720.jpeg
 

svenedin

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Hi Stephen,


She's just making sure you haven't forgotten her!

Regards,

Graham
Yes indeed! I do have the current, boy, white GSD but my avatar is still the old girl. He never lets me forget about him. He’s far too noisy for that!
 

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