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How to separate third wheel from bridge?


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I have successfully disassembled and restored a number of movements, but all have been with sub second hands. I'm working on my first sweep seconds hand movement and am unclear on how to remove the third wheel from its bridge. It's held in place (keeping gears together on both sides of the bridge) by a small circle plate, pictured and pointed to here:

img_2476.thumb.jpg.33bd33ecd490ce0fe5bca818b054c38c.jpg

Can anyone tell me how to remove this, or how to separate the gear(s) from the bridge?

Thanks!

Seth

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30 minutes ago, SethL said:

I have successfully disassembled and restored a number of movements, but all have been with sub second hands. I'm working on my first sweep seconds hand movement and am unclear on how to remove the third wheel from its bridge. It's held in place (keeping gears together on both sides of the bridge) by a small circle plate, pictured and pointed to here:

img_2476.thumb.jpg.33bd33ecd490ce0fe5bca818b054c38c.jpg

Can anyone tell me how to remove this, or how to separate the gear(s) from the bridge?

Thanks!

Seth

When I've done Bulova's with center seconds, I leave that wheel on the bridge for cleaning.

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I have seen the many times on watches where it is the seconds wheel, driving the seconds shaft pinion. Please see attached example of one on my bench now. The wheel is a friction fit and I use two long modelling blades to act as a lever.

Hope this helps?
6815848831eaaa4699493f9b057f0dcd.jpg


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Has to be a seconds wheel. To be a third wheel it would need an elongated pinion gear connected to two wheels? Interesting but pointless.
I have come across a Chinese movement with a centre seconds and a sub seconds all on the same movement. Must of been some sort of sales gimmick

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Isn't this type of wheel connected/tied to the plate underneath it via a circlip or some sort of a pin/spring which has to be unscrewed to free the wheel itself ?

That's how I remember it... Either way you have to take it all apart and underneath the plate you will probably see how you get to remove it.

The wheel itself won't come out like normal parts do where you just pull them out.

PS: That small "circle plate" that you talk about is part of the wheel just like the long shaft beneath it (on the other side).

Edited by Chopin
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What you have is an indirect centre seconds configuration where the third wheel has an extended staff that comes up through the bridge to the back of the movement. An intermediate centre seconds drive wheel is friction fit onto the extended staff which couples with the centre seconds pinion. you will probably find there is a friction spring sitting on top of the centre seconds pinion to control the inevitable stutter that these design suffer from. This was the how all centre seconds configurations were executed when centre seconds first became a thing. It's a perfectly good way to achieve centre seconds without bu$$ering about too much with the rest of the movement but it has a couple of drawbacks. The stuttering is one of them, the other is it makes the movement quite thick.

Anyway, the circular plate that you refer to is not a separate part, it is a thickening of the hub of the intermediate wheel in order to provide enough meat for a competent friction fit on the staff. There is a Presto tool specifically designed for removing these, and I have also seen some very nice pullers that people have made, but a pair of very thin levers or blades usually does the trick if you are careful. And you do have to be careful. The extended staff does not take kindly to anything other than a perfectly vertical lift; cant the wheel off of erpendicular to the staff and the staff will snap. Reinstall using a staking tool to keep everything nice and true.

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Personally I've always called this a sweep wheel. It's frictions on as others have said above it also has an up and a down so pay attention after he remove it. So the tool mentioned above I have another link showing how it's used. It also comes in a different number of fingers apparently there is different arm crossing so you needed tool that correspond to the number of arms you have. Then the tool found At the second link comes in three different sizes color-coded. All you do with this is slide this gently under the wheel rotate and lifts the wheel up. However you lift the wheel up make sure you lifted straight you do not want to bend the post that it's on.

http://www.drsjewelry.com/cgi-bin/LTT1.pl?Sub-NSP=Removesandhandpress&Description-NSP=PRESTONo3SWEEPWHEELREMOVERBERGEON&template=1LVC&method=perfect

http://www.julesborel.com/products/tools-hand-tools-hand-removers/bergeon-6016-wheel-remover-1-2mm

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What you have is an indirect centre seconds configuration where the third wheel has an extended staff that comes up through the bridge to the back of the movement. An intermediate centre seconds drive wheel is friction fit onto the extended staff which couples with the centre seconds pinion. you will probably find there is a friction spring sitting on top of the centre seconds pinion to control the inevitable stutter that these design suffer from. This was the how all centre seconds configurations were executed when centre seconds first became a thing. It's a perfectly good way to achieve centre seconds without bu$$ering about too much with the rest of the movement but it has a couple of drawbacks. The stuttering is one of them, the other is it makes the movement quite thick.
Anyway, the circular plate that you refer to is not a separate part, it is a thickening of the hub of the intermediate wheel in order to provide enough meat for a competent friction fit on the staff. There is a Presto tool specifically designed for removing these, and I have also seen some very nice pullers that people have made, but a pair of very thin levers or blades usually does the trick if you are careful. And you do have to be careful. The extended staff does not take kindly to anything other than a perfectly vertical lift; cant the wheel off of erpendicular to the staff and the staff will snap. Reinstall using a staking tool to keep everything nice and true.

Lovely explanation thank you. I have often noted the stuttering and put it down to wear or slight eccentricity of the mating gear train.


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I have seen the many times on watches where it is the seconds wheel, driving the seconds shaft pinion. Please see attached example of one on my bench now. The wheel is a friction fit and I use two long modelling blades to act as a lever.

 

Hope this helps?

6815848831eaaa4699493f9b057f0dcd.jpg&key=4ee58aa93a8ef917113d45e769eefb5c076a39ff47c8230df284b32ea2d6e0d0

 

 

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Here’s another photo with the centre jewel removed for clarity. Please note the beryllium copper leaf spring (slotted to accept the seconds shaft) with pinion on the top.

4de9eee3b07140205f568bbed85e0478.jpg&key=577b28604534886b5c371b12434de36d6ca7b5c10a49f45ee70cd5d2cbedf543

 

 

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Thanks so much, everyone (especially Marc, John, and Deggsie). Very helpful. I was able to remove it with two blades. I've attached the before and two afters (the gear with the tension fit center piece and the movement with the pinion from the other gear sticking through) for anyone who wants to see the details.

5ac2fdd7edd4d_2018-04-0220_32_39.thumb.jpg.09ab0bad1b993381bdfeaa3aeae73d2e.jpg

5ac2fdd98a477_2018-04-0220_33_23.thumb.jpg.a1535e91fce4b45ff22fe374b16cbc60.jpg

5ac2fddb2246b_2018-04-0220_34_51.thumb.jpg.a56b83cf0fa16dafd339c3890fddd2b0.jpg

Thanks again,

Seth

p.s. For those really into details, note that my first photo was taken from the web because it was easier. These three are from the actual movement I'm working on.

Edited by SethL
added p.s.
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