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Testing the train wheel

jguitron

By jguitron
in Watch Repairs Help & Advice

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jguitron WRT Addict

jguitron

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Hello all,

I'm servicing a CYMA 234 and have found a few gremlins. First the mainspring was jimmied badly and was slipping with minimal tension. Then, I found what I thought was a worn or broken staff. I was able to source one and realize that the pivots look just the same, therefore concluding that my initial assessment was wrong. Something nagged me to remove the pallet fork and put a little power in the mainspring and while the train gear spins "freely" at the very end it has somewhat of a sluggish end. This is a movement that I washed and oiled just a few days ago. 

So, I tried looking up more specific info on how to best assess the train but I'm not coming up with anything specific. I recall in the past there is this minute retrograde spin that the escape wheel does when there's truly no friction on the train corresponding to the mainspring fully releasing and then a tiny overstretch recoil that makes the train go backwards a hair.

Well, I can't find that reference and I'm not feeling very good about my train wheel, but before I take it apart again I wanted to consult with wiser peeps here and learn something.

Thank you!

 

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watchweasol Distinguished Member

watchweasol

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Hi  what you suspect is usually correct with a free running train but not always, from your description It sounds more like the mainspring not delivering the power required and is a candidate for replacement. when cleaning did you check and clean the jewels and use the correct lube.   I have attached the tech sheet for the cyma  !!!! a bit scruffy

2047_CYMA 214,215,216,217,234,235,237 (1).pdf

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jguitron WRT Addict

jguitron

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15 hours ago, watchweasol said:

Hi  what you suspect is usually correct with a free running train but not always, from your description It sounds more like the mainspring not delivering the power required and is a candidate for replacement. when cleaning did you check and clean the jewels and use the correct lube.   I have attached the tech sheet for the cyma  !!!! a bit scruffy

2047_CYMA 214,215,216,217,234,235,237 (1).pdf 869.03 kB · 2 downloads

Thank you for your reply! I was able to get a proper part mainspring that fit properly and looks to me right on. I'm mainly troubleshooting the poor balance wheel function and fit and I wanted to start checking with the wheel train, which is where I'm a bit stock not able to determine if it's free enough to proceed downstream or if it's something I need to address before I move on.

Julian

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jdm Distinguished Member

jdm

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Another test, less violent than spring running which in the ends does something the mov't isn't really designed for, remove click or ratchet  wheel, blow air,  train must spin easily and stop kind of slow.

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