St 36 MOVEMENT

[cannon]

Hi all hope you can help me? Just fitted a new st36 movement into a new watch case,nipped off the second hand pivot as the dial is just for two hands,it's been running plus four seconds s day so no problems there,the problem is as soon as I put it on within half an hour it stops.i have had it in every position for three days and no problems,checked the train right down to the escapement,everything runs fine,the balance is oiled at the end stones as I can see under the microscope, put the balance back on runs brilliant, until I again put it on,can anyone offer any advice as I'm stumped, regards Steve

[watchweasol]

Hi    So what you are saying is it runs on the bench ok but stops when you wear it, is that correct..   I should have a look at whether the hands are fouling due to the case being flexed when worn, strapped on. when you tested the watch was it cased up or just the movement.

[eccentric59]

When it stops, will it start right away if you nudge the balance, or do you have to pull out the stem and reset the time? 

[cannon]

Hi it works fine cased up on the bench,but when worn it will stop after some time,when i try to flick the balance there is very little movement,the hands don't  foul ive checked they turn freely with gaps in between,i have pulled back the click to let the mainspring down,it does not backwind with any power ,when I take off pressure from the crown completely it unwinds very slowly,regards Steve

[HectorLooi]

I suspect the seconds wheel. Can you show us a very close up photo of the end where you nipped of the second hand pivot?

Sometimes there is a jewel in the tube of the centre wheel. If you cut off the second hand pivot completely, there isn't any pivot left to seat in the jewel hole. 

[RichardHarris123]

Since it doesn't work when worn, I'm guessing the  heat from your wrist is making the components expand and one of them is binding. 

[watchweasol]

Hi definitely check out Hectors suggestion, when it’s on the bench it may e just running in the jewel.

[Nucejoe]

 Isn't this sweep seconds arbour attached to  minute gear ?   So a solid test is to replace the sweep arbour- gear with a new un- nipped one and see how your watch behaves. 

At least dress/ polish the cut end end of the arbour.

Rgds

[watchweasol]

To get it back on if it is you will need a press as some of these can be tight.

Is this the original bezel , as it came back in bits. Have you any pictures of it before it went for a battery change or can you confirm it’s original.

[cannon]

I have checked the seconds wheel there is enough on the pivot to keep it in both jewls fine,the watch is running perfect on the bench in face up,face down and on either side with no problems keeping acurate time,its a strange one as everything looks perfect under the microscope, i have a spare seconds wheel I'll nip off the pivot slightly longer and see what happens.

[eccentric59]

14 hours ago, cannon said:

when i try to flick the balance there is very little movement

Could it be overbanking?

[HectorLooi]

What does the timegrapher trace look like?

Another thing to check is the hairspring. It might be out of flat or out of round. Touching the hairspring stud. Check that the hairspring is centred properly too.

Check aldo, the endshake and sideshake of all the wheels, from the barrel to the balance.

[Nucejoe]

2 hours ago, cannon said:

I have checked the seconds wheel there is enough on the pivot to keep it in both jewls fine,the watch is running perfect on the bench in face up,face down and on either side with no problems keeping acurate time,its a strange one as everything looks perfect under the microscope, i have a spare seconds wheel I'll nip off the pivot slightly longer and see what happens.

 Replacing the wheel with a good one is to find out  is it or is it not the culprit. The process of elimination is a relatively conclusive test, which you will not conclusively  find out by replacing another part thats tampered with.

 

[JohnR725]

4 hours ago, cannon said:

everything looks perfect under the microscope

Maybe you need more power to see things better? One of the problems with the microscope is sometimes you don't see the big picture. I don't suppose you have a timing machine? Because something that visually looks like it's running great on the bench may not actually be  running that wonderful.

[cannon]

The watch is running at +5 sec a day,beat error is 0.6ms don't think it's overbanking as it runs flawless on the bench in the case,I am wondering if the mainspring is not pushing in enough power through the train when it's on my wrist and I'm moving about? Is this a possibility any suggestions will be most appreciated regards Steve 

[eccentric59]

What's the amplitude? Overbanking is certainly a possibility if it's +300°. All you need is one extra degree to overbank which is entirely possible from moving your arm about. Your description of "very little movement" suggests something is in direct contact with the balance. If there were something stuck in the train, you'd still be able to get pretty good oscillation of the balance with a puff of air. It just wouldn't continue.

[JohnR725]

2 hours ago, cannon said:

+5 sec a day,beat error is 0.6ms

As you have nice numbers I assume you have a timing machine what's the amplitude? Then ideally the timing results in more than one position not just dial down may be crown down and a picture of whatever you using for timing machine often times we might see something you don't

 

 

 

[Nucejoe]

 As said it can be overbanking, symptoms you describe certainly suggest overbanking , but new movements are not suppose to overbank unless you have tampered with the escapement.

Amplitude please.

 

[Jon]

On 10/14/2023 at 11:24 PM, cannon said:

Hi it works fine cased up on the bench,but when worn it will stop after some time,when i try to flick the balance there is very little movement,the hands don't  foul ive checked they turn freely with gaps in between,i have pulled back the click to let the mainspring down,it does not backwind with any power ,when I take off pressure from the crown completely it unwinds very slowly,regards Steve

When you say 'very little movement' what does that look like? You need to be a little more specific. Does the balance rotate freely when given a puff of air both ways? Is the pallet jewel fully locked with the escape wheel tooth when you try to rotate the balance, as the escape tooth might be caught on the pallet jewel impulse face and the guard pin is left touching the safety roller because the pallet stone is slightly too short, or rather the lock isn't deep enough with the escape wheel. If it is overbanked the balance will only turn in one direction, as the impulse jewel is on the wrong side of the horn and would need taking out and re-fitting it again. Is this the case? 

I'm curious when you take power off the mainspring, you say the crown rotates very slowly. Is this with the mainspring fully wound and then taking off power? Did you check the end shake of the barrel when seated between the barrel bridge and the mainplate and did you check the end shake of the barrel arbor inside the barrel? If there is no end shake this would do exactly what you have described, as the mainspring is binding, but it wouldn't explain the watch running on the bench and not on the wrist. But just because you find one problem doesn't mean there aren't several

Have a look at this discussion from a couple of weeks ago week regarding pallet stones:

 

13 hours ago, eccentric59 said:

What's the amplitude? Overbanking is certainly a possibility if it's +300°. All you need is one extra degree to overbank which is entirely possible from moving your arm about. Your description of "very little movement" suggests something is in direct contact with the balance. If there were something stuck in the train, you'd still be able to get pretty good oscillation of the balance with a puff of air. It just wouldn't continue.

This is called 're-banking', also known as 'knocking', not overbanking. An easy mistake to make. It looks like this on the timegrapher when the movement is close to being fully wound

[eccentric59]

2 hours ago, Jon said:

This is called 're-banking', also known as 'knocking', not overbanking.

Yes, but re-banking would not cause the movement to stop, just run poorly. If the impulse jewel taps the outside of the horn with enough force would it not "bounce" the pallet fork into an overbanked state making the movement stop altogether? That's what I was getting at.

[Nucejoe]

 A video showing the issue be nice then your sure to get excellent diagnos .

You can post the vid on youtube and give the link here.

Rgds

 

 

[JohnR725]

1 hour ago, eccentric59 said:

Yes, but re-banking would not cause the movement to stop, just run poorly. If the impulse jewel taps the outside of the horn with enough force would it not "bounce" the pallet fork into an overbanked state making the movement stop altogether? That's what I was getting at.

I always find the terms confusing. So if you have too much amplitude the roller jewel hits the backside of the fork. It makes a very audio noise that sounds like a horse galloping. On the timing machine you get the effect that shown above it's very distinctive. It never as far as I know causes the roller jewel to end up on the other side that is purely a safety problem. Unlikely to find it on the new watch not impossible but just unlikely and we didn't get any observations of my watch sounds very bizarre.

17 hours ago, eccentric59 said:

Overbanking is certainly a possibility if it's +300°.

One of the problems with the discussion like this is assumptions versus proper field observation. In other words we were relying on description of the person who has the watch is new to watch repair and has zero idea what exactly is looking for instance.

On 10/14/2023 at 9:25 AM, cannon said:

Hi all hope you can help me? Just fitted a new st36 movement into a new watch case,nipped off the second hand pivot as the dial is just for two hands,it's been running plus four seconds s day so no problems there,the problem is as soon as I put it on within half an hour it stops.i have had it in every position for three days and no problems,checked the train right down to the escapement,everything runs fine,the balance is oiled at the end stones as I can see under the microscope, put the balance back on runs brilliant, until I again put it on,can anyone offer any advice as I'm stumped, regards Steve

We have a brand-new watch which typically we can expect should work fine. We do see that the movements been modified as the fourth wheel pivot has been shortened to eliminate it sticking up into the dial. This might presents some issue of is it too long and still touching the dial sometimes if it is bent when it was trimmed off.

Then we see that everything is 100% perfect except eventually when it was worn. Except a lot of things can't be seen  including with a microscope that's would be really nice if we had some timing machine diagnostics including amplitude that for some reason were not getting. Plus pictures of the timing machine results often times we see things that somebody else doesn't sometimes we don't though sometimes it looks fine. Oh and be really nice to know if the watch actually runs 24 hours on the bench.

On 10/14/2023 at 3:24 PM, cannon said:

Hi it works fine cased up on the bench,but when worn it will stop after some time,when i try to flick the balance there is very little movement,the hands don't  foul ive checked they turn freely with gaps in between,i have pulled back the click to let the mainspring down,it does not backwind with any power ,when I take off pressure from the crown completely it unwinds very slowly,regards Steve

We get this report that's a bit confusing. We see that the hands aren't the issue except depending upon the case it's in and we don't have any pictures of that is possible the secondhand could be too close to the crystal.

releasing the power is interesting it tells us it's probably binding upon the crown. In the lack of pictures the case I guess which is waterproof crown with no silicone grease and it's not nicely turning on the case Tube. In other words when the powers released it has no place to go shouldn't be a running issue though.

Then I'm going to repeat suggestions that other people of made. If you hold the watch in your hand and just move your arm back and forth like you going for a stiff walk does the watch stop and how fast? If your watch had pathetic amplitude for instance it might still run on the bench but it wouldn't possibly may be run if it's moving rapidly. We don't know how much wrist movement you have for instance a desk job that would be equivalent of sitting on the bench. On the other hand if you're running a jackhammer for instance that's very hard on the watch or if you're out playing golf that's very hard on the watch.

 

On 10/15/2023 at 5:50 AM, cannon said:

I have checked the seconds wheel there is enough on the pivot to keep it in both jewls fine,the watch is running perfect on the bench in face up,face down and on either side with no problems keeping acurate time,its a strange one as everything looks perfect under the microscope, i have a spare seconds wheel I'll nip off the pivot slightly longer and see what happens

Then we keep seeing everything is perfect on the bench but still be nice to have timing machine results because visually perfect in real perfect or not always the same thing. By the way when you nipped off the pivot was the wheel in the watch?

It's a shame you didn't have a electron microscope we would see things much much better or would we? One of the reasons I keep fussing about the microscope is that depending upon what you have your field of view may not include the entire watch. Did you know in the old days watchmakers didn't use microscopes? Yes I know they let you see specific things better but they also allow you not to see things. Like you're looking straight down on the watch are not looking at an angle where you can see things like you would be if you're sitting at a bench with a loop. You really do need to look in the watch sideways it do need a much bigger field of view and typically cheap microscopes have. Like when you look in sideways how does the hairspring look?

Oh and then a course were back to the other problem you're new to watch repair you have no idea what you're supposed to be seeing or not. That is not helped with the microscope at all.

18 hours ago, cannon said:

The watch is running at +5 sec a day,beat error is 0.6ms don't think it's overbanking as it runs flawless on the bench in the case,I am wondering if the mainspring is not pushing in enough power through the train when it's on my wrist and I'm moving about? Is this a possibility any suggestions will be most appreciated regards Steve 

Then just to be 100% clear. When the watches running on the bench it's fully cased up in the exact same condition it would be as on your wrist it just is not on your wrist?

Then we get partial timing results no pictures of graphical displays and the amplitude which is the obsession of this group is totally missing. While others are concerned about too much amplitude I'm actually concerned about too little amplitude even if it is a brand-new watch. For instance if you had pathetic amplitude it might actually run and keep time on your bench but it would be very unhappy if was moved around.

Then I'm repeating what other people of set up above I'm just putting everything in one place was easy to see. When the watch stops what does it take to get started again and when it starts again how long does it run before it stops again on your wrist? Or when it stops if you set it on the bench will continue to run fine?

Then pictures we like pictures like a picture of the watch in the case which case did you choose will bill the see that maybe a picture of the movement when you take the back off so we can see how you're holding it.

 

Edited October 16, 2023 by JohnR725

[eccentric59]

One other thought. Since you mention the movement is an ST36, are you sure it's a genuine Sea-gull or the listing only said it was. The Chinese are rather lax with respect to branding. And I've made it a practice to clean even new clone movements. They are usually over-oiled and often got fibers and fingerprints everywhere. The smallest hair trapped under a bridge plate or screw head could easily stop a movement.

As @JohnR725 has pointed out, fixing the problem is usually straightforward, but identifying the problem can be elusive.

[Jon]

 

2 hours ago, JohnR725 said:

We have a brand-new watch which typically we can expect should work fine.

I've had brand a new ST 36 that had the escape wheel get stuck on the impulse face of the pallet stone and the guard pin hard against the safety roller, stopping the watch. One can only tell when doing guard pin shake and horn shake tests, as mentioned above. I never assume that just because a movement is new all is well. It depends on the quality control at the factory. I've had a brand new Sellita SW500 movement with a jewel presses in upside down.  Assumptions are the mother of all f-ups.

3 hours ago, eccentric59 said:

Yes, but re-banking would not cause the movement to stop, just run poorly. If the impulse jewel taps the outside of the horn with enough force would it not "bounce" the pallet fork into an overbanked state making the movement stop altogether? 

err... No

[eccentric59]

46 minutes ago, Jon said:

err... No

I think Sherlock Holmes was working his pocket watch movement when he coined the adage "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."