Jump to content

Two parts or a split roller-table ??


Recommended Posts

I disassembled a balance assembly of a 1930's CYMA 797 in order to replace the broken balance staff.

S20230226_002.jpg.2951ecc458a9190781dec7e75e5e80d9.jpg

I carefully removed the roller table and the safety roller, which I thought were both one solid piece. The roller-table was pushed off the balance-staff from in between the roller-seat and the roller-table, so the safety roller hasn't seen any force, apart from compression.

To my surprise they were separate, a roller table and a safety roller.

S20230226_003.jpg.8c686448ce2b50850e37e196e2440189.jpg

S20230226_004.jpg.8478f485d297c659cb6bc33416a51a3e.jpg

S20230226_006.jpg.9e3f72d772faf35827a4aeb7da582b6b.jpg

There are two indents in the roller-table, but not much to see on the bottom edge of the safety roller.

Did they become separated or are they separate by design ??

Do I have the same as Mark has in his video "Fitting a new balance staff to a vintage 1940s CYMA"?  Coincidentally also a CYMA movement with the same shape roller-table & safety roller, also from the '30's / 40's.

Starting from the 3:30min mark;

 

Is this the "joy of watch repair", as Mark remarks at 15:15min when assembling the roller??

 

Edited by Endeavor
Link to comment
Share on other sites

2 piece rollers do exist, roller table and safety roller, and I think Mark is mistaken that his has split; from your photos the grained surface on the main piece is uniform up to the hole, with no sign of breakage (and the hole in the safety roller is chamfered on both ends).

 

More commonly with two piece rollers the two pieces fit on distinctly different diameters, and the safety roller doesn't have the tube section. Very tricky to get the fit just right on those.

  • Thanks 1
Link to comment
Share on other sites

I just can't believe my luck !! 🤩

First time ever to change out a balance staff and meet nearly all the complications there are!

When assembling, how does one line the roller-table and the safety roller up, eyeballing or is there a more sophisticated method?

  • Haha 1
Link to comment
Share on other sites

6 minutes ago, Endeavor said:

I just can't believe my luck !! 🤩

First time ever to change out a balance staff and meet nearly all the complications there are!

When assembling, how does one line the roller-table and the safety roller up, eyeballing or is there a more sophisticated method?

Eyeballing is fine- eyes are pretty good at lining things up!

  • Thanks 1
Link to comment
Share on other sites

So the roller table is friction-held in place by the bottom edge of the safety-roller?

I carefully replaced the roller-table and it doesn't fully bottom out on the roller-seat, so maybe the roller-table is also held in place by friction on the staff? I didn't try to push it any further, didn't want to enlarge the hole unnecessarily.

Anyhow, I'm already happy that it wasn't me, but it was by design ..... 🤗

 

Edited by Endeavor
Link to comment
Share on other sites

With a steel roller, you want it to go almost to the hub, maybe 1/2 to 1 (max) thickness of the roller away, before pressing all the way. The safety roller similar. If it seats too far from the hub initially there's a big risk of bending or breaking something. With your two piece roller both parts need to be a friction fit.

 

Same really goes for a one piece roller, you want it to seat about one thickness of the roller- the part with the roller jewel- from the hub. They are most often brass or similar, and can crush easily if they seat too far away and then get forced down.

Edited by nickelsilver
  • Thanks 1
Link to comment
Share on other sites

The roller, gently pushed, sits indeed about between 1/2 to 1 of its thickness above the staff's roller-seat. So, I guess, that will be fine ...... that is, when the new staff is 100% identical in dimensions ...... for that we have to wait until the new balance staff's arrive. The Danish PostNord is very, very slow .... from the moment CousinsUK ships it, at least 3 weeks, perhaps 4 weeks !

Thanks for your help so far ! ...... 😉

 

Edited by Endeavor
Link to comment
Share on other sites

9 hours ago, nickelsilver said:

 

2 piece rollers do exist, roller table and safety roller, and I think Mark is mistaken that his has split; from your photos the grained surface on the main piece is uniform up to the hole, with no sign of breakage (and the hole in the safety roller is chamfered on both ends).

 

More commonly with two piece rollers the two pieces fit on distinctly different diameters, and the safety roller doesn't have the tube section. Very tricky to get the fit just right on those.

 

Yes, much to my surprise when I removed the roller on a Waltham- I thought I had broken it as well…

Edited by rehajm
Link to comment
Share on other sites

  • 3 weeks later...

Yes. It is a two part, I’ve seen exactly the same since although the roller (not plate with impulse) did seem to be spread out on that watch - I did that video 9 years ago and have not looked at it since until today 😁 

  • Like 1
Link to comment
Share on other sites

  • 3 months later...

I just ran into this tonight while doing a balance staff replacement on an Elgin 478.  It surprised me for sure, and I initially thought I had broken something.  On closer inspection it didn't appear that I had, and thankfully I found this thread afterwards.  Thanks to all.  My blood pressure is coming back down now!

  • Like 1
Link to comment
Share on other sites

1 hour ago, thor447 said:

Elgin 478.  It surprised me for sure, and I initially thought I had broken something.  On closer inspection it didn't appear that I had, and thankfully I found this thread afterwards. 

Here's something that Elgin had on the subject.

image.png.cbe611260fbc2e68d8da342f8df88bf5.png

Then we have Waltham Where sometimes it's a little confusing over what exactly your disassembling. Fortunately friction staff's typically have a blued steel hub.

image.png.2cb7d3e85bf884af04d881dbb25e27d7.png

 

 

image.png

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



  • Recently Browsing

    • No registered users viewing this page.
  • Topics

  • Posts

    • Yes, barrel size.  A 11mm spring will push out into a 11mm barrel, no need to go 0.5mm smaller. 
    • Hello All, I’m looking for advice about how to interpret the mainspring specs described in the GR documents and in the catalogues of online sellers such as cousins.  My problem relates to interpreting the value describing barrel size - I’m unsure what the last number REALLY refers to.   For example: 1.10x.0105x360x11  (This refers to GR2628-X) Does the “ 11 “ here refer to the barrel inside diameter of the calibre OR to the diameter of the wound mainspring before insertion? For example if my measured barrel inside diameter to 11mm, I would normally select a wound spring size a little smaller, say 10.5, wouldn’t I?  Or, does the barrel diameter described in the catalogue specifications take that into account and I would therefore order a catalogue size 11 for an 11mm barrel ID? Hope this makes sense. I can’t find clarification of this anywhere. Many thanks for any enlightenment. Cheers, John
    • Let's say, like in a watch, you have  a 70 tooth 4th wheel, which needs to make a turn in one minute, with an 18,000 beat escapement. 15 tooth escape wheel as usual, and a 7 tooth pinion on it.   70 x 15 x 2 /  = 300  That's 300 beats, and there are 5 beats per second, so divide and you get 60s, one minute- all is well. If we do 70 x 15 x 2 / 8 that equals 262.5. With an 18K balance, which will let the escape wheel move one turn in 6 seconds, the 4th wheel will have made like 1.14 turns. So the time display is running fast. But this comes to like 7.5 seconds over per minute, which is about double your gain (maybe I'm wrong- I'm mathing on my phone while writing on my phone 😄) but pretty sure the gain is more than you are observing.   A possible culprit is that crown/4th wheel isn't running true, and a tooth is slipping past a pinion leaf once per revolution. I've seen this. If the platform is original and it's a nice piece they are often pinned, so the depthing isn't an issue. If the platform isn't pinned, check the depthing. And at any rate check the crown wheel between centeres and make sure the teeth are running true.
    • Fast responses - thank you. Yes, I mentioned the 18000bph to illustrate that it's not a matter of touching coils, over banking, shortened hairspring etc. I even took off the platform and temporarily fitted a another NOS one also with 8 leaves and beating 18000 but the colossal gain is the same. I'm resigned to buying and fitting a new Gorge platform plus a 7 leaf pinion escape wheel but only if I think it will work; otherwise it's a waste of £200 and a couple of hours work. Hence the underlying question is: all other things being equal, what would the timekeeping effect be? Is it a simple 7/8ths as fast? Logic tells me it is but can it be that linear?
    • Sorry to jump in here guys, but I've read through this whole thread and it seems there are a lot of people who think joining Facebook means everyone will have access to their lives. You could make a Facebook account with a fake name. You could even use your real name if you wanted to and set it to completely private so people can't even find you in a search and you don't have to add anyone as a 'friend', so you won't see anyone's posts. Literally use it to join a group full of members of this site. Admins could even set the group to private and require a password of some sort to gain acceptance into the group, so you can be sure that it's only members of this site that get in. @tomh207 is right, the form with email addresses and names is a bad idea. That will be abused by scrapers. Facebook is only as personal as you let it be. You can be completely anonymous on there if you wish. Don't think of it as Facebook. Just think of it as a watch repair group as that's all you'd use the account for. It doesn't even have to be set up with your current email address. Make a random one on Gmail or any other free provider just for the Facebook account. Tagged you by accident and now it won't let me remove it 😂 @Neverenoughwatches
×
×
  • Create New...