Puzzling ETA oscillating weight bearing

[VWatchie]

This ETA oscillating weight bearing belongs an ETA 2772 movement (also found in the following ETA calibres: 2770, 2773, 2776, 2778, 2779, 2780, 2781, 2782, 2783, 2784, 2788, 2789, 2790, 2791, 2793, and 2798).

I have two of these bearings. One came on a Candino watch (see above) I bought at an auction and one I bought used to replace the one that came on the watch. Both are functioning equally poorly. When testing them the oscillating weight stops swinging within a second or so. When I’ve previously tested healthy oscillating weights (Russian Vostok calibre 2415/16) they have been swinging for well over 30 seconds and sometimes even close to 60 seconds.

Unlike the more modern ETA ball bearings (2824-2), the balls aren’t visible. This makes me suspect that this type of bearing isn’t meant to be serviceable but meant to be replaced by a new part when needed. And that is basically my question. Can it be serviced to work properly again, or does it need to be replaced by a new part?

If it can be serviced, I’d really need some advice about how to go about it. All I’ve done now is clean it, but it doesn’t seem possible to oil it, and even so, a bit of oil wouldn’t make much of a difference, I guess?

If it can’t be serviced but needs to be replaced, then the problem is finding a new part. Luckily(?) I just found this bearing NOS on eBay, but as I was about to press the ”Buy it now”-button, I started to think about it a little more deeply. This bearing could well be 50 years old and any oil inside that bearing must now have dried up, possibly putting a brake on the bearing balls.

So, I don't know how to deal with this situation. I’d really like to get that watch fully working again. Winding it manually (after having serviced it and having replaced the mainspring) gives it its full power reserve, approx. 47h.

Edited March 20, 2020 by VWatchie

[jdm]

9 minutes ago, VWatchie said:

Can it be serviced to work properly again, or does it need to be replaced by a new part?

A new, or used but efficient bearing is needed.

9 minutes ago, VWatchie said:

ll I’ve done now is clean it, but it doesn’t seem possible to oil it, and even so, a bit of oil wouldn’t make much of a difference, I guess?

It will not. The more oil, the less efficient it becomes. I can search (again) an old topic here and link here.

9 minutes ago, VWatchie said:

This bearing could well be 50 years old and any oil inside that bearing must now have dried up, possibly putting a brake on the bearing balls.

More likely than not there is no oil at all. But even if it there is one can clean it with simple soaking in the usual liquids.

[VWatchie]

I found a lot of 7 NOS oscillating weights with this type of bearing on eBay advertised as for "ETA 2783 2789" and according to the "JBC Watch Parts Database" these should be interchangeable with my 2772 calibre. So, I've ordered them and hopefully at least one of them will be performing well. Keeping my fingers crossed. In correspondence with the seller they have never been used. The seller only wanted £25 incl. shipping for the entire lot from Portugal to Sweden. So if they're good it will be a bargain.

[VWatchie]

Having received my lot of seven NOS oscillating weights for ETA calibres 27XX I tried them all and they all performed equally poorly. My guess is that the material of the bearing oxidises over time creating some friction, or that it’s simply an inefficient type of oscillating weight bearing.

As I was testing these oscillating weights using a carved piece of peg wood, I unintentionally applied to much pressure on the peg wood and the innermost section of the bearing came apart with a pop. As my brain anticipated the sound of steel balls bouncing on my work bench (and eventually floor) I was, and very surprisingly, only met with silence. The reason? This type of bearing does not contain any steel balls! I guess ETA must have decided that they could do away with the steel balls and still get a “satisfactory” automatic winding functionality. In the future, I will likely stay away from any calibre not using steel balls in its oscillating weight bearing.

Anyway, I decided to try to polish the bearing to see if it would make any difference.

After a lot of work the rocking of the weight felt somewhat smoother but didn’t seem to have any effect on its efficiency. 

Looking back on this work I now realise that I probably should have polished the inner rim of the bearing. I will try that next, but if it doesn’t improve the efficiency, I will probably think that this type of bearing without steel balls simply isn’t any good.

What’s your experience of these bearings? Good, so-so, substandard? Perhaps these bearings are only designed to work when the watch is worn 24/7!? Surely, those of you being professionals must have encountered this type of oscillating weight bearing lacking steel balls at some point, no?

[nickelsilver]

When you say it is less efficient do you mean swinging on a piece of pegwood, or actually winding the watch? All plain bearings will be less efficient than ball bearings, but they are still used in many applications because they are either better in actual use or more reliable.

 

I've actually never had an issue with these ETA rotor bearings. I run the rotor through the machine, add a small amount of oil, and off they go. The other primary "plain" bearing rotor design using a post and usually jewels also work quite well, but in my experience are more prone to wear than these ETA ones. The ETA bearing with the conical portion on the rotor and corresponding screw can be more fiddly (I think it was you that posted on adjusting these a while back?), but tend to be pretty good too. I actually haven't needed to adjust one yet.

 

Just a work of caution- the parts you are lapping there are made from beryllium copper, which can be toxic. In particular dust from grinding/lapping...   But- don't freak out- you need to inhale the dry dust, and particle sizes around 20 microns are bad while somehow smaller and larger particles are less bad. The alloy is about 2% beryllium (the bad stuff), the rest being mostly copper. As an alloy it's safe enough, but over time the body breaks down the copper leaving the beryllium. All that said you'd need to be around dry airborne dust daily for quite some time for it to be a problem, but just an FYI. It's mostly an issue in industrial machining settings. I work with it frequently and just keep things wet and clean up after.

[anilv]

They're not as efficient as ball bearings but a clean and lube with just s drop of thin (9010) oil works. Too thick oil an dit will drag.. not to mention turn to paste and gum things up further.

If you've bought NOS rotors, you can press out the bearing and press it into your old rotor if you want to keep it looking original.

Cheers

Ailv

[VWatchie]

 

On 4/15/2020 at 5:00 PM, nickelsilver said:

When you say it is less efficient do you mean swinging on a piece of pegwood, or actually winding the watch?

Well @nickelsilver, I'd say both! That is, less efficient swinging on a piece of pegwood and less efficient winding the watch. When swinging on a piece of pegwood it comes to a complete stop after about a second and after the polishing the swinging action has deteriorated even more as can be seen and heard in the above video. I now believe polishing should be avoided as I am suspecting it ruins the polished surfaces and creates friction. Before the polish and after a full manual wind and wearing it for about 15 hours per day for about five days it stopped during the night indicating a power reserve of about 7 hours from the moment when taken off the wrist.

In the above video I am trying to determine if any “unnatural resistance” can be felt in the automatic device framework. However, all wheels seem to be moving freely. I should mention that the mainspring probably had a lot of power in it when I did this test. Looking at the video, can you please tell me if you (any of you) think the action looks OK?

 

I decided to follow @anilv's suggestion to replace and oil the bearing with the most efficiently swinging NOS bearing I could find in my lot. I first thoroughly cleaned it, gently tapped it into the original rotor, and then applied a drop of Moebius 9010. As can be seen in the video, it is a pretty dramatic improvement. However, I simply lack the experience to tell if it is swinging freely enough. It sure still is a far cry from the ball bearing rotors swinging for well over 30 seconds. Please let me know if you think it looks good enough!?

 

In the above video I’m trying to show how well or how poorly (?) the rotor swings when mounted to the automatic device framework. Again I should mention that the mainspring had a lot of power in it when I did this test and I believe that could affect the swinging of the rotor as I suspect the ratchet wheel to be more resistant when the mainspring already has a lot of power. However, again, I’m guessing as I simply lack the experience to tell if it looks OK, so please let me know your opinion!

On 4/15/2020 at 5:00 PM, nickelsilver said:

The ETA bearing with the conical portion on the rotor and corresponding screw can be more fiddly (I think it was you that posted on adjusting these a while back?), but tend to be pretty good too. I actually haven't needed to adjust one yet.

Yes, you’re right about that and it all worked out well in the end. The rotor of that watch is now doing a great job on my brother's wrist.

Never heard about beryllium copper so interesting and useful “bonus information”. Thanks!

Edited April 16, 2020 by VWatchie

[HSL]

How could I have missed out on this one.. The oscillator looks fine for me, but are you sure your reversers in that automatic bridge is healty? seems to be a dramatic change from the pegwood test to the actual installed one..
Following this with interrest.. Just like Nickelsilver I just cleaned and lubricated these ones so this is a learning opportunity for me too !

Edited April 16, 2020 by HSL

[VWatchie]

8 minutes ago, HSL said:

The oscillator looks fine for me

Great! 

8 minutes ago, HSL said:

but are you sure your reversers in that automatic bridge is healty?

No, not at all! I've cleaned them and I have treated them with Lubeta V105 but maybe they need to be replaced? Anyway, that's why I included a video showing what it looks like when I gently manipulate the reversers with tweezers and my blower. They feel free but I just haven't got the sufficient experience to tell for sure 

12 minutes ago, HSL said:

seems to be a dramatic change from the pegwood test to the actual installed one..

Indeed! I was thinking it could be the result of the mainspring having a lot of power in it making the ratchet wheel resisting the automatic winding wheels. Again, that is just a wild guess as I really don't fully understand the mechanics.

Cleaning and oiling definitely seems to be all that is needed. The polishing I did only made matters worse.

So, new reversers?

[HSL]

11 minutes ago, VWatchie said:

Cleaning and oiling definitely seems to be all that is needed. The polishing I did only made matters worse.

But you did a nice job to get them shiny

[anilv]

For really dirty reverser wheels I clean them in alcohol jar followed by ultrasound..

Some reverser wheels have jewels and some dont. Those without jewels usually need the alcohol treatment.

Anilv

[VWatchie]

 

To assess if the somewhat sluggish action of the oscillating weight (seen in this video), was due to the mainspring being almost fully wound, I let the mainspring down completely, wound it up some, and then moved the watch around again while observing the oscillating weight. The result can be seen in the above video.

My conclusion is that if the mainspring is fully, or near fully wound, the ratchet wheel will be resisting the wheels of the automatic winding device making the oscillating weight somewhat sluggish. I think this will be especially true for rotors having this type of plain bearing, unlike ball bearing rotors which swings more freely.

Also, trying to reduce friction by polishing the bearing as demonstrated in my previous post paradoxically seems to increase friction, so I will not be doing that again. All that is required seems to be a good cleaning of the bearing and a drop of Moebius 9010.

So, all that remains now is to wear the watch for a few of days, then let in wind down completely and see if the automatic winding has been able to wind the watch fully. For anyone interested I will let you know.

[HSL]

Thank you for sharing this, makes me want to test this theory with different lubrication in the barrel to see if it could be the lubrication or something else causing too high friction or if it is just to tense as you say, better write this up on my mile long todo list  
 

[VWatchie]

2 hours ago, HSL said:

Thank you for sharing this, makes me want to test this theory with different lubrication in the barrel to see if it could be the lubrication or something else causing too high friction or if it is just to tense as you say, better write this up on my mile long todo list  
 

According to Ranfft Watches the power reserve of this movement (ETA 2772) should be 47h. When fully wound I actually get a little less than that, 44h, but I haven't used an original ETA mainspring (as they are so difficult to get hold of) but a Generale Ressorts replacement spring (GR4006X). The explanation for the difference could be that the specifications of the replacement spring differs from the original spring (I wouldn't know), but it could also be that the replacement spring slips slightly too soon. If that is the case my barrel causes less friction than an original spring and hence should affect the rotor friction even less. (It could also be that Ranfft is wrong about the 47h I guess)

I should mention that when completely wound down and fitted to the movement, the rotor swings nearly as freely as when fitted to a piece of pegwood. However, having swung the rotor around for awhile I pretty soon start to notice a slight resistance (that's when I recorded the video).

I'm not sure, but I think/hope this friction problem has been solved but I will know for sure in a few days and will report back. If you do get to test with different lubrication in the barrel I'll be an ardent reader of you findings!

Edited April 20, 2020 by VWatchie

[VWatchie]

Just a short update to let you know that the automatic winding of my ETA 2772 plain bearing oscillating weight is now working perfectly. So, I'm now fairly convinced that the sluggishness we can see in the oscillating weight of a healthy watch is perfectly normal and should be expected as the ratchet wheel will resist the automatic winding device gears the more power the mainspring has.

I made a two minute video about this...

 

[jdm]

2 hours ago, VWatchie said:

should be expected as the ratchet wheel will resist the automatic winding device gears the more power the mainspring has.

Yes for these ETA, but is not so for Seiko and possibly other mov'ts. 

[VWatchie]

1 hour ago, jdm said:

Yes for these ETA, but is not so for Seiko and possibly other mov'ts. 

That's interesting. I would definitely have assumed that this phenomena would manifest itself in movements using the magic lever design as well, such as in the SEIKOs and the ORIENTs. After all, they too drive the ratchet wheel in the end but it may not be as palpable as in the ETAs. Perhaps because the oscillating weight of the magic lever movements only operates on the ratchet wheel effectively for about 50 % of its circumference, whereas in the ETAs any movement of the rotor will drive the ratchet wheel. Well, JM2C, but I'd be very interested to learn more, so please elaborate if you feel like it.

Anyway, the main point of my video was to let the viewers know that a sluggish oscillating weight shouldn't always and automatically be interpreted as a problem but is an expected and natural consequence of the automatic winding design (at least for the ETAs). Before having looked into this, I was very much under the impression that a sluggish rotor was faulty. Thankfully, now I know better!

[VWatchie]

On 5/14/2020 at 6:39 PM, jdm said:

Yes for these ETA, but is not so for Seiko and possibly other mov'ts.

I forgot to report it, but I did investigate the oscillating weight behavior of a "magic lever" watch, an ORIENT Calibre 46E40 and it behaves exactly like the oscillating weights of the ETAs. So, you were mistaken. Perhaps it was just an assumption on your part?

[jdm]

15 hours ago, VWatchie said:

I forgot to report it, but I did investigate the oscillating weight behavior of a "magic lever" watch, an ORIENT Calibre 46E40 and it behaves exactly like the oscillating weights of the ETAs. So, you were mistaken. Perhaps it was just an assumption on your part?

No assumptions. Seems like that your Orient has trouble making the mainspring slip under static weight of the rotor. Seiko normally do not. Not the end of the world, you watch should work fine anyway.