Mechanical WW Bulova 10COAC offset center wheel question

klevay

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Jan 24, 2010
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(Originally posted on new message board site, but it cannot be seen from here)

This is my first time overhaul of Bulova 10COAC self-winding movement made in 1970 and while disassembling it I was puzzled by the offset center wheel mounting. It's pivot goes through a plate center jewel and press-fitted into pinion on the dial side (don't know the correct part name). At least I think it was a press fit because it was really hard to pull off. This pinion has an elongated "neck" on its bottom side. Finally, I was able to carefully remove it without damaging anything, although it took me some time.
Now is my question. What would be the correct way to reassemble it? How do I press fit the dial side pinion? Any help is greatly appreciated. Does anybody have a Technical Bulletin for this movement?
 

Roland Ranfft

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Feb 10, 2011
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Hi klevay,

It's pivot goes through a plate center jewel and press-fitted into pinion on the dial side
This is by no means a press-fit junction. It is a set of minute arbor and cannon pinion, else found in the center of conventionally designed movements, thus the necessary friction clutch between hands gear and train.

If you push the cannon pinion onto the minute arbor, make sure to support the pivot on the back side. Else you will likely crack the jewel. Another method is gripping the cannon pinion with a pin vize, and turning it while pressing it down.

Anyway, this junction should be lubricated, not only for easier slip the cannon pinion down, but also to prevent wear to this clutch.

Regards, Roland Ranfft
 

klevay

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Jan 24, 2010
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This is by no means a press-fit junction.
Thank you for reply, Roland. That's why it was so hard to remove then? Could it be due to old/lack of lubricant? It maybe be easier to slip on the pinion after the center wheel is supported by the train bridge on the other side, but there's another jewel to watch out for. I'll try to do it the way you suggested.
 

Roland Ranfft

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Feb 10, 2011
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Hi klevay,

.... That's why it was so hard to remove then?
In principal it is designed like a normal center cannon pinion, i.e. in the tube on top of the wheel there is a dent for both, supply friction between tube and post, and to keep the tube on the post.

But compared with a conventional cannon pinion this one is very short. This means, the inclination from the thinner portion of the arbor post to the thicker top is much stronger. And this makes it difficult for the friction dent to pass the thick end of the post. It is recommendable to drop some oil into the hole on the top and set the hand gears some turns before pulling the pinion off.

Regards, Roland Ranfft
 

klevay

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Jan 24, 2010
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Roland, thanks again for clarification. Reassembly was not a problem.
Cheers,

P.S. BTW, I really enjoy your website. Tons of useful information.
 

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