Why the CHS GMT movements are failing

[KJ2020]

Another one bites the dust. Really not sure what I'm going to do to try and fix this, but what a pain. I'm half considering fabricating a new spring from higher quality metal. Should be interesting and blinding to try.

Go for it bro, its not just the spring though there are protrusions that stick up through holes in the upper plate. Need a good machinist with a good shop. Someone should be able to do this, we know the Chinese did.

 

[Duckguy]

Right, I noticed that for sure. There is a video where the watch repair course guy fabricates a spring from flat spring steel stock. It does not have tabs but I wonder if they could be bent. It's likely out of my league given the small size, but maybe I'll try it sometime. Not much investment for a piece of flat stock spring steel that I could sand to thickness. But...I'm not speaking from any experience, only ambition.

 

[KJ2020]

Looks to me like that spring could be stamped out of slightly thicker metal with the tabs included and then bent up like you said. Might take a few tries to find the right combination of material and thickness but this definitely is not rocket science.

 

[Dr Fun Socks]

Looks to me like that spring could be stamped out of slightly thicker metal with the tabs included and then bent up like you said. Might take a few tries to find the right combination of material and thickness but this definitely is not rocket science.

I think the thickness needs to stay the same as the spring is essentially a spacer between the two gears. Maybe just wider but you would need a punch and a die to stamp it from sheet? I think it could get very expensive.

 

[KJ2020]

I think the thickness needs to stay the same as the spring is essentially a spacer between the two gears. Maybe just wider but you would need a punch and a die to stamp it from sheet? I think it could get very expensive.

I think it could handle a little more height, have you seen this post?

https://forum.replica-watch.info/forum/modification-repairs/7448328-spring-for-chs-wheel

You're right about it needing a custom die but that's a one time expense. Someone could recoup that cost selling these on ebay, I think ppl would pay $40 - $50 for one of these if it was bullet proof. Small price to return you paperweight to action.
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[Duckguy]

A stamp would be great, but I think it could be traced, cut, and filed by hand for a one-off. I mean, that's how they all used to be made. That would be my strategy, but if I knew anyone with the tooling if be keen to make a replacement and sell the damned thing.

 

[molivio]

Hey, would like to propose something. If someone takes the time to provide such valuable insight, can we propose a "donate" function where we send a $1 that after a while can be used say towards purchasing a used watch on the site ? I mean this shouldn't go unrewarded and can help drive sales this way?

 

[Dr Fun Socks]

Hey, would like to propose something. If someone takes the time to provide such valuable insight, can we propose a "donate" function where we send a $1 that after a while can be used say towards purchasing a used watch on the site ? I mean this shouldn't go unrewarded and can help drive sales this way?

As in purchasing a used gen? The design is just completely different. The tiny little spring used in the rep is just too thin and snaps. Even if a thicker one could be made, it may over stress the rest of the components making yet another problem, or prevent the gmt function from working all together. Despite all this as a tool maker im kind of keen to give it a go

 

[Tickleshoes]

Ok so it seems the hour wheel must have an issue. I havent taken it apart yet, im off on holiday for a couple of weeks so it will have to wait, but the time setting function is fine, but when running only the hour hand stops. I find this very weird because im pretty sure the gmt hand runs from the hour hand (at least in the setting mode it does) so no idea whats happening! The guy I bought the watch from tried to glue the stem back in because of the keyless issue.... probably related!

depending on the epoxy, that little spring might be slipping leaving the hour wheel behind. It should be one piece as you say. The only real solution will be a better quality replacement spring. Good luck.

 

[KJ2020]

No solid fix yet. Glueing the wheels didn’t last very long either. Plus it means you’ve gotta advance the date by turning the hands through 24 hrs. Not fun

Hard to picture why gluing the wheels together wouldn't be a permanent workaround solution, albeit with reduced functionality. What else could cause this besides the glue bond not holding? If the two halves were really solidly acting as one, wouldn't that imply a successful workaround? Maybe a better glue and wait longer for full cure? JB Weld and 7 days for example.

If the two halves are to be bonded, seems like neither the spring nor the inner gear even need to be present. Except maybe as a spacer, for which a substitute could easily be used - even just a thicker bed of glue.

 

[Dr Fun Socks]

Hard to picture why gluing the wheels together wouldn't be a permanent workaround solution, albeit with reduced functionality. What else could cause this besides the glue bond not holding? If the two halves were really solidly acting as one, wouldn't that imply a successful workaround? Maybe a better glue and wait longer for full cure? JB Weld and 7 days for example.

If the two halves are to be bonded, seems like neither the spring nor the inner gear even need to be present. Except maybe as a spacer, for which a substitute could easily be used - even just a thicker bed of glue.

I pretty much glued the shit out of mine. It seems to be holding well but as mentioned my hour hand and gmt hand arent synced some how. I havent had a chance to take it apart and have a look because ive been away but ill let you know how it goes. I used bsi 30 min slow cure epoxy with a 24 hour cure. The whole area inside the spring was full of epoxy, but i used the spring as a spacer.

 

[Dr Fun Socks]

depending on the epoxy, that little spring might be slipping leaving the hour wheel behind. It should be one piece as you say. The only real solution will be a better quality replacement spring. Good luck.

Im not particularly bothered about independently adjustable gmt hand, if the glue fails i think my next port of call will be essentially a thick circle with either two or four triangle teeth to interlock the two wheels. I just want something reliable! If it does come to this does anyone have a spring to hand they can measure the thickness on so i can order some spring steel or possibly d2 sheet as the spring element will be kind of redundant for what im aiming for.

 

[KJ2020]

I pretty much glued the shit out of mine. It seems to be holding well but as mentioned my hour hand and gmt hand arent synced some how. I havent had a chance to take it apart and have a look because ive been away but ill let you know how it goes. I used bsi 30 min slow cure epoxy with a 24 hour cure. The whole area inside the spring was full of epoxy, but i used the spring as a spacer.

Understood, but if there is no play between the two halves then maybe we need to look somewhere else for a gearing ratio issue

 

[Dr Fun Socks]

Understood, but if there is no play between the two halves then maybe we need to look somewhere else for a gearing ratio issue

As tickleshoes said maybe the glue has just given up? Theres no other reason the gmt and hour hand would run at different times. The 24 hour hand is powered by the hour hand as far as i can see so maybe even what im taking was a good 80% glue coverage isnt enough. I know the forced arent high but i dont think epoxy sheer strength is that great.

My thoughts are as below (the top is Tickleshoes original pic, bottom is my proposal)

Get some sheet steel at whatever thickenss the spring is (got to be 0.5-1mm). Drill out the center to the distance between the two ‘teeth’. Attach that to a mandrel and mount it to a lathe if you have one or a drill/dremel in my case. Use a set of grinding stones to turn the outside diameter to just less than the teeth of the smaller wheel (hour iirc). File out either two opposing teeth or possibly even 4 at 0, 90, 180 and 270 if im feeling particularly bored than day. Then by some miracle, fold up both sides, use a file or a set of stones to create the flappy slotty bits to attach to the top wheel, check, fit, finalise etc. Then in theory there is no where for the wheels to separate. If this doesnt fix it, A. Ill be very upset because i know it will be time consuming and stressful. And B. I might give up on the CHS movement as depressing as that is

 

[KJ2020]

As tickleshoes said maybe the glue has just given up? Theres no other reason the gmt and hour hand would run at different times. The 24 hour hand is powered by the hour hand as far as i can see so maybe even what im taking was a good 80% glue coverage isnt enough. I know the forced arent high but i dont think epoxy sheer strength is that great.

Get some sheet steel at whatever thickenss the spring is (got to be 0.5-1mm). Drill out the center to the distance between the two ‘teeth’. Attach that to a mandrel and mount it to a lathe if you have one or a drill/dremel in my case. Use a set of grinding stones to turn the outside diameter to just less than the teeth of the smaller wheel (hour iirc). File out either two opposing teeth or possibly even 4 at 0, 90, 180 and 270 if im feeling particularly bored than day. Then by some miracle, fold up both sides, use a file or a set of stones to create the flappy slotty bits to attach to the top wheel, check, fit, finalise etc. Then in theory there is no where for the wheels to separate. If this doesnt fix it, A. Ill be very upset because i know it will be time consuming and stressful. And B. I might give up on the CHS movement as depressing as that is

I have one of these to work on, I can measure the spring thickness. What's the safest way to separate the halves, a staking tool?

 

[KJ2020]

Also it looks like I may be missing a gear - in one of Tickleshoes' pics I can see the gear present. Is it the same gear the ICHS movement uses? A previous modder may have removed this to prevent position 2 from working, as without it nothing can happen in position 2.

 

[Dr Fun Socks]

I have one of these to work on, I can measure the spring thickness. What's the safest way to separate the halves, a staking tool?

You just need to remove the tiny circlip at the top end using tweezers! Should just fall apart after that. Its under the gold wheel, will be obvious when you see it.

Yeah the small floaty one is definitely missing. Sorry for my poor terminology... Ive got no idea if the ICHS uses the same one but it’s definitely different to a normal a2834 gear in the same position.

 

[KJ2020]

You just need to remove the tiny circlip at the top end using tweezers! Should just fall apart after that. Its under the gold wheel, will be obvious when you see it.

Yeah the small floaty one is definitely missing. Sorry for my poor terminology... Ive got no idea if the ICHS uses the same one but it’s definitely different to a normal a2834 gear in the same position.

OK mine didn't have a circlip, that's why I didn't see an obvious wat to open it up. I pried it open gently and it appears this one had already been glued. There was no spring to measure but it should be the same thickness as the inner gear wheel. I measured that at .15mm

The missing gear is called a double corrector, it's for quicksetting day and date, or day and GMT hand on an ICHS. The CHS includes an extra intermediate wheel to reach the shorter radius GMT wheel where ideally the spring would release the GMT wheel from moving while the gear connected hour wheel would flip.

I put one in and am confident this is the same part as the ICHS (top and bottom views).

Since I have no spring to try to fix, all I can really do is try a better glue job. With that attempted solution, there is no need for the other two GMT intermediate wheels either.

After examining this more closely, I think if the two parts of the GMT wheel can be permanently locked together, the GMT and hour hands should be able to be synched. An offset could be done between GMT and local time manually when setting the hands. After that, there also should be no reason why the quickset date function can't be restored since the two GMT wheel intermediate wheels are removed.

 

[Ossenaar87]

Hi guys mine chs is broken to, but it still runs i only cant move my minute hand. I can move the houre hand and set date and when i pull the crown out it wont stop running is this typical when de movement is broke?

 

[Dr Fun Socks]

OK mine didn't have a circlip, that's why I didn't see an obvious wat to open it up. I pried it open gently and it appears this one had already been glued. There was no spring to measure but it should be the same thickness as the inner gear wheel. I measured that at .15mm

The missing gear is called a double corrector, it's for quicksetting day and date, or day and GMT hand on an ICHS. The CHS includes an extra intermediate wheel to reach the shorter radius GMT wheel where ideally the spring would release the GMT wheel from moving while the gear connected hour wheel would flip.

I put one in and am confident this is the same part as the ICHS (top and bottom views).

Since I have no spring to try to fix, all I can really do is try a better glue job. With that attempted solution, there is no need for the other two GMT intermediate wheels either.

After examining this more closely, I think if the two parts of the GMT wheel can be permanently locked together, the GMT and hour hands should be able to be synched. An offset could be done between GMT and local time manually when setting the hands. After that, there also should be no reason why the quickset date function can't be restored since the two GMT wheel intermediate wheels are removed.

Dude you have probably forgotten more watch lingo than ive ever learnt but i think i get where your coming from. If the gluing keeps failing i think my idea i showed in the pic should work as its a permanent mechanical lock that in theory cant fail. I dont need independently adjustable gmt as im sure most people dont. Which wheels are you looking to remove? Are you thinking make it so the quickset just makes both the hour and gmt spin around quicker together? Its a pain in the ass trying to set a date using just the normal time setting method (crown all the way out). If its 0.15mm i could probably just get some shim and have a crack but i know making things that tiny will be a nightmare.