Replacing the bearings in a Copal motor

[Johan de Jong]

The rotor of a Copal motor runs in brass bearings/bushings. After a few decades of continuous running the wear of these bearings can start to give problems: the motor becomes noisy or friction becomes too large and the motor (intermittently) stops.

For a while I’ve been looking for a solution. My first attempt to replace them with ball bearings was not satisfactory (too noisy). But now I think I may have cracked it: I replaced the bearings with new porous metal bearings similar to the original. The first clock I did this way has been running perfectly silent for more than two weeks.

Here is how I did it:

First step is to open up the gearbox like described here.

Second step is to remove the pinion gear. With a wooden block for support I used a flattened nail and a hammer to push the axis out of the pinion gear. I also bought a small pinion puller, but that did work out since the gear sits in a recess in the motor (may though still useful to remove the pinion from the axis if the gears give way before the pinion does).



As you can see there is a tiny washer on either side of the motor and also some black stuff. That is I think the remains of old lubrication and wear of the bearings.

Third step is to remove the bearing. This I also did by hammering but using a larger bolt to push the two bearings and spacer out of the motor.



(story continues in next post...)

[Johan de Jong]

The replacement bearings I found here on AliExpress. They measure 1.5 x 3.5 x 1.5 mm (ID x OD x L). That is quite a bit smaller than the original (1.5 x 6 x 2.5) but these were the only ones I could find with an inner diameter of 1.5 mm.

To fill the gap I use a spacer tube that a friend was so kind to 3D print for me. It measures 3.5 x 6 x 11 mm (ID x OD x L). A final refinement using a drill and sandpaper was needed to make it all fit. As an alternative I ordered these spacers but these are still on their way, so I can’t tell yet whether this is a good alternative.



The two bearings then need to be well aligned to let the rotor run smoothly. For this I used the smooth end of a 1.5 mm drill. By grabbing it at both sides and wiggling it around I made the bearings align.



I then added a drop of oil to each bearing and did a test run before pressing back on the pinion gear and reassembling the gearbox.

As said, one clock is running silently for over two weeks now. The second on I have just finished and is also running smoothly. Let's hope it stays that way for a few more decades

[gschmidt958]

Fantastic job, thanks for sharing!

[Johan de Jong]

Small update: that pinion puller I bought is not a good fit for the Copal motor. The pin is a little too thick and the fork is also the wrong size to get a good hold on the gear. That's a pity, but maybe it is handy some other time.

[Johan de Jong]

I was notified that the link to the bearings did not work (anymore).

Here are two new links to the bearings:
Kaifa Electronics Co.: https://www.aliexpress.com/item/33046865723.html
MSM Parts Store: https://www.aliexpress.com/item/1005002302288903.html

I used the bearings from the last link (1.5 x 3.5 x 1.5) but I think they are the same article.

[Johan de Jong]

Update : I tried to remove the bearings from another Copal motor, but these were so firmly stuck that I was afraid my hammering would destroy the motor

So I tried this alternative method that I think is a lot safer.
As shown below I used a small vice, a nut and a bolt to press out the bearings.



This Copal motor also had a little surprise in store: instead of the two bearings and a spacer that I saw with the other motors, this one had four bearings in a row and no spacer. Maybe that explains why they were so badly stuck.

[Johan de Jong]

Another update:
The spacers I ordered from AliExpress (3 x 6 x 12) have arrived and they work very well and are easy to work with!

The outer diameter is exactly 6 mm and fits nicely in the motor.
The inner diameter is 3 mm, but after drilling with a 3.5 mm drill the new bearings fit perfectly.
The length is 12 mm. That is about half a mm more than the original but no problem.

[flipoclock]

I was finally able to do my first successful repair with new bearings and a plastic sleeve, it has been running now for a few hours and it is as silent as Copal motor should be, which is not 100% silent but it has a very soothing and calming running noise, I can't really describe it but when I hear that when a Copal clock is running, it makes me happy because it is an indication that all is well.

I had to wait for my 1.5mm and 3.5mm drill bits to come in, I could not get them locally and had to order them from further away. The final adjustment to the bearings with the 1.5mm drillbit takes some practicing and is a bit tricky but it is the most important bit. Once that is done, you might want to manually adjust the flywheel to ensure it is as balanced as manually possible to prevent the new bearings from wearing out again too soon because I suspect the new bearings are not the same quality as the original Japanese ones but if these last anywhere from 5 to 20 years, essentially I will be happy.

This clock will run for some time to ensure it is ok again and in the meantime I will done one or two more for a test and when they all are running fine, even after a couple of week, I am happy.

At the ends of the bearings I tried some new stuff that I bought, for a bit of lubrication, it is called Molykote DX ( https://www.ebay.de/itm/125795194114 ) and from what I have read it should work well with a situation where you have a small shaft spinning in two bearings but time will tell I guess.

[flipoclock]

I have been tinkering around with a few more motors and found that you have be careful when swapping parts between motors. You would think that the flywheel essentially is always the same, it is not! The length of the shaft can differ.
I was having trouble getting a flywheel to balance nicely and quietly on the new bearings and decided to try another flywheel I had lying around and this worked like a charm but I ran into an issue trying to reassemble the gearbox, it would not fit as a whole, I ended reworking the original flywheel and putting that on (and it now works like a charm).

[Johan de Jong]

Good you got it done! And good to know that there are these differences in the rotors. I have seen so many variations in Copal motors. Finding which parts are exchangeable will always be a matter of trial and error I'm afraid.

BTW: the motors I fixed until now are still running fine