Synchronous motor bearing issue on M3

[blugatchtube]

I bought an M3 a while ago and have been trying to get it running. I oiled and freed up the TWG first. That turns fine if decoupled from the run motor but if it's connected to the run motor, the whole TWG slows to a halt when it switches from the start motor to the run motor.

Looking at the run motor I notice that the oil thread coming down toward the flywheel from the tub is broken. What appears to have broken it is that the bearing it is tied to is spinning WITH the flywheel. I'm not sure if it's tied to the wrong place or the bearing is seized but here is a video: https://www.youtube.com/watch?v=FitKoSVfV4Y

I also moved the run motor / scanner assembly back to take a look inside the coupling. I found a lot of hardened gunk inside the coupling and it takes a little scraping to get it off. Maybe the same gunk is in the run motor? It's also not clear if the ball in the middle of the flywheel coupling is supposed to be free-rolling like a ball-point pen. It is very stationary in mine. Here are some pics of the coupler gunk.




Hoping someone can give me a little guidance here.

[enor]

Yes, that bearing is seized and has let go from the motor housing. This is one of those (rare) cases where even I would say motor replacement is the best option.

[muckelroy]

I agree with Enor. If you aren’t in a hurry to see this come back to life, you could tie new threads to the motor and start a generous oil regiment. Naptha MIGHT help speed the process along, but if there is corrosion inside the motor bearing it may be a lost cause.

Getting these motors apart is a difficult job.

[geoelectro]

This is a common occurrence. Whenever you encounter a stuck generator you MUST determine if it's the generator or run motor. This is easy to do by gently turning the motor flywheel with a finger. If the motor is not stuck, it will turn freely. It it doesn't turn easily, it's stuck. Otherwise, if it turns freely but the generator doesn't turn then it's the generator. The reason this is important is because forcing a stuck run motor to turn WILL break the oiling thread.

With a stuck run motor drop some oil on the front bearing. Drop some oil on the threads going into the motor's rear bearing and scanner. Without turning the shaft, gently pry the shaft in and out. Continue to move it in and out until it is free. There is a good amount of lateral play with these motors. Adding the oil and sliding the shaft back and forth will free it up without turning any bearings that may be stuck which will break oiling threads.

Slide, not turn.

Geo

[blugatchtube]

I'll try to see if I can free up the bearing but it's a little late for that thread unfortunately. Even if I do free it up though, is this bearing a lost cause? Like enor said, it appears to be seized but still rotating in the bearing's housing like it has been detached/broken off. It's hard to get a close look at it since the flywheel is in the way and I'm not quite sure what the construction of these bearings is like.

[enor]

I'll try to see if I can free up the bearing but it's a little late for that thread unfortunately. Even if I do free it up though, is this bearing a lost cause? Like enor said, it appears to be seized but still rotating in the bearing's housing like it has been detached/broken off. It's hard to get a close look at it since the flywheel is in the way and I'm not quite sure what the construction of these bearings is like.

I had a similar thing happen to a scanner. Oiled it and soldered the bearing back so it wouldn't rotate in the chassis hole... but alas, the results were very disappointing and I ended up replacing the scanner instead.

[tiredoldgeezer]

There should be about a 1/4" of axial play in the shaft. No resistance to finger pressure in either direction (axial or radial).
Sometimes, an easy solution is a hair dryer or heat gun.
There exists a chemical buildup in the motor known by the technical term as "gunk". This gunk, when heated, can become "goo". Heating the motor to very warm temps and moving the shaft about both directions will free the armature from the gunk and goo.
Suddenly, it all works, again.

It will run just fine with no oiling threads at all. You'll want them back for the long term, but for now you needn't sweat it.

The 'bearing' you provided pictures of is designed to NOT transfer rotational forces -- that the job of those two little springs. The ball is an alignment and decoupling device to prevent phasing and vibration transfer, so the surface is not exactly critical, though it's always good to keep it clean.

[Sweet Pete]

I still have two seized up run motors here.
Maybe I'll break out the heat gun and try to coax some axial movement out of the things.
Have replaced a few seized wheel bearings....heat(torch) really makes teardown happen!
At 4 bucks apiece,I use new....
Teeth are all fine on the scanner gear one (CV) and the tremulant box one (BCV chorus gen) so who knows?
I never forced anything,just replaced them with working parts.
Can't hurt to give it a try?
Would a rubber mallet be safe to tap on the axle?