Disassembly of ratchet wheel secured with washer

[oli]

Hi all

I wonder if anyone else has come across this design, where the ratchet wheel is secured on the arbour with a kind of washer.

There is a recess in the ratchet wheel to allow space for the washer, so I do not think I would be able to just move the washer off centre, as it would but against the edge of the recess in the ratchet wheel. There is, as you would expect very little play.

The movement is a Pocket Watch with a chronograph complication, no other ID available other than the "23" and "depose" stamp you can see in the pic below.

I would welcome any advice!

Many thanks

 

 

[Ishima]

I'm guessing you have to budge and pry it upwards, off the arbor that way, I look forward to being told how wrong I am. 

[Chopin]

That's what I was thinking as well. Is it thin and flexible or hard ?

[Mark]

You know. It doesn't matter how long you've been repairing watches. You always see something new from time to time lol.
That's an interesting design. A taper pin is more common.
Looks like a shim which slides out. Please post more pictures as you progress. I am interested.



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[jguitron]

I thought I was simply too inexperienced to not have seen that before but I'm glad to hear this is an unusual fix. I guess the main worry is what's happening in the arbor?

Following along very curious...


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[oli]

Many thanks for all the responses. That is one of the reasons I love watchmaking, it always seems to bring something new as you said Mark. (Especially for me as I am in my early days)

Here are some close up pics of the ratchet and washer. It is quite thick, and not very flexible to answer your question Chopin.

My intuition is telling me as Mark suggested that it will slide out, but I am worried about causing irreversible damage, as the washer sits tightly in the recess, and I am pretty sure that it will get distorted in the process.

Perhaps it is meant to be a sacrificial part, which will get damaged during disassembly no matter what I do? Hence my reluctance to remove it at the moment! I am going to have to sleep over this one...

 

 

 

 

 

 

Edited September 15, 2017 by oli

[Ishima]

1 hour ago, oli said:

I am going to have to sleep over this one...

I cannot endorse this enough, a great idea in general for facing any watchmaking problem, it'll probably be easy the next time you come to sit down with it.

 

Edited September 15, 2017 by Ishima

[Chopin]

Is there a possibility to somehow slightly raise the shaft that's holding the washer and the wheel ? Even a millimeter would probably help...

[Michael]

Possibly an old repair? Is it threaded?

[jguitron]

Could it be screwed into the arbor??





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[Chopin]

We could clearly see that the inner 2 straight edges of the washer are slightly raised. What if you "straightened" the washer and then tried removing it at first from one side and then the other ?

[Ishima]

I see my previous suggestion is impossible. 

if it has no vertical play as it is, as Michael suggests it might, then would it maybe be worth unlidding the barrel, twisting the arbor free of the spring and seeing if the arbor allows itself to be pushed down. Even if it's not the case, it seems looking inside the barrel may yield other clues. 
 

Edited September 15, 2017 by Ishima

[StuartBaker104]

Interesting! The answer is no doubt there if you stare hard enough.

I see 3 things worth noting. First there is a mark to the right hand side of the slot around the circumference of the washer which looks like a lever used against it has slipped at some point. Second, I note that there appears to be a chamfer around the outer edge of the washer. Third, it appears that there are radial rubbing marks along the washer either side of the slot, suggesting it has slid against the square. All these really need you to stare hard with a loupe and see for yourself as photos rarely show these things well. You may see more clues if you look around the parts.

My guess would be, as others have said, that you need to slide the washer off.  I would start by rotating it so that the slot is parallel to the square on the arbour. Then apply a suitable lever (screwdriver) roughly where the marks on the circumference are, and another diametrically opposite to gently lift the washer. If you have enough hands to squeeze the barrel and ratchet wheel together berore or during this (might be a team sport!) then you may see a little movement to ease the operation.

If the washer were fitted the other way up then the chamfer on the outer edge would probably help with this.

[rogart63]

Never seen a ratchet wheel on the dial side of a movement. Between the plate and barrel yes but not on the outside. 

Edited September 16, 2017 by rogart63

[oli]

Hi all , and first of all thank you for all the pointers, it has given me the confidence to progress this.

I applied the "24h rule" and came back to this today, and I am pleased to report I have successully disassembled the ratchet wheel.

It turned out to be much easier than I expected. 

I started by lining up the square. As Stuart pointed out there are wear marks along the edge of the slot, which gave me the confidence to try a bit harder to slide the washer. I applied pressure at the end of the slot with a piece of pegwood to avoid any damage, and eventually the washer did move and its edge went over the recess.

What became obvious only after disassembly  is that the washer was actually dished, and therefore acting as a spring (hence the "no play" I had observed). So it had the ability to flex to go past the edge of the recess of the  ratchet wheel. I was initially very reluctant to even try this as I expected a flat washer, which would have simply butted against the edge, no matter how much pressure was applied.

Mystery solved, I have taken some detailed pictures given the interest this thread generated, so I will let them do the talking!

 

 

 

 

 

[jguitron]

Very nice!!!

How is it related to the arbor?

Thank you for sharing.




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[oli]

Hi 

Forgive me as I am not sure I understand your question, but I will try to answer anyway

The ratchet wheel is secured against the "flat" of the arbour as the washer acts as a spring and effectively maintains pressure against it. Typically a screw would play that role.  The slot in the washer fits neatly into the slot between the two square parts of the arbour which you can see in the last photo. 

[StuartBaker104]

38 minutes ago, jguitron said:

Very nice!!!

How is it related to the arbor?

Thank you for sharing.




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Maybe it isn't immediately obvious but the arbour is still in the barrel in the final picture

[StuartBaker104]

50 minutes ago, oli said:

Mystery solved, I have taken some detailed pictures given the interest this thread generated, so I will let them do the talking!

Thanks for the pictures Oli - every day's a school day!

[jguitron]

Hi 
Forgive me as I am not sure I understand your question, but I will try to answer anyway [emoji4]
The ratchet wheel is secured against the "flat" of the arbour as the washer acts as a spring and effectively maintains pressure against it. Typically a screw would play that role.  The slot in the washer fits neatly into the slot between the two square parts of the arbour which you can see in the last photo. 

Oh no issue at all! I see that the arbor and the the "square" bolt(?) are a single piece... what I was thinking is that the previous watchmaker lost the screw you mentioned to secure the ratchet wheel and so he came up what that square "bolt" to fix the ratchet on to the arbor. In my mind that would make the bolt a separate piece of the arbor but, if I'm understanding correctly, the arbor and "bolt" are a single piece secured with the slotted washer...

I though this was an elaborate fix rather than the original design... is it?

Thanks for the explanation.




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[oli]

Yes the "square bolt" and arbour are one and the same part, the square end is just machined/filed on the arbour.

Difficult to know for sure, but I would say it is the original design, as it is quite complex. If it was a fix it is likely the same result would have been achieved by simpler means, with a screw or a tapered pin. But who knows!