Thread: Alternator bearing Shagged

Originally Posted by Old Farang

Hmm, do not quite what you mean with this? If you are only replacing the bearings the slip rings do not have to be disturbed. If you are replacing the slip rings maybe you mean to cut the old ones off in a lathe?

I was assuming that reconditioning included renewing brushes and slip rings. Of course there is no need if you are just doing bearings. Ones I did, the slip rings went on as one unit, that is, a single 'sleeve' and then they were separated using a cutter on a lathe. I worked for an auto elec for a time in the dark ages, and that's how he did it. He sold changeover units, rather than fixing the one the customer presented with, and everything was replaced, including rectifiers. Bodies were polished, and fans painted.
He trusted me to take them off the car, and sometimes to cut the slip rings, or turn down and undercut the commutators on DC stuff, but only sometimes.

Ones I did, the slip rings went on as one unit, that is, a single 'sleeve' and then they were separated using a cutter on a lathe.

Hmm, not sure just how that works? I served a 5 year apprenticeship as an electrical fitter / armature winder, albeit a bloody long time ago! Automotive alternators were not around then, but big electric motors with slip rings were common, and they are constructed as one piece on an insulated metal sleeve. Although I have never done an automotive one the ones that I have looked at are of the same construction. It is not unusual to put the rotor in a lathe and take a VERY light skim off them after mounting to ensure they are running true. But they are not "split" or separated. There is also usually enough material on a worn set to also take a light skim off them and reuse them.

Originally Posted by Pub247

Looks like ill need a new alternator...

Put a wanted ad in the markets for an old alternator or the wreckers. Stuffed alternators are cheap if you only need the front casing.

That alternator looks like it has had a pretty hard life, A new one would probably be a good option

Originally Posted by Old Farang

Hmm, not sure just how that works? I served a 5 year apprenticeship as an electrical fitter / armature winder, albeit a bloody long time ago! Automotive alternators were not around then, but big electric motors with slip rings were common, and they are constructed as one piece on an insulated metal sleeve. Although I have never done an automotive one the ones that I have looked at are of the same construction. It is not unusual to put the rotor in a lathe and take a VERY light skim off them after mounting to ensure they are running true. But they are not "split" or separated. There is also usually enough material on a worn set to also take a light skim off them and reuse them.

Can't answer, and you are more knowledgable than me, but I vividly recall the blistering ticking off I got from the sparky when he had pushed the ring on, got me to turn the thing in the lathe to split the split ring, and impatient me pushed the tool in too fast and spun the ring, tearing off his carefully soldered leads. It was some time before he let me do it again. Maybe it wasn't standard practice, but he did it all the time.

Originally Posted by trout1105

That alternator looks like it has had a pretty hard life, A new one would probably be a good option

No idea how old it is but it had an easy life up until i owned it it looks in a bad way as its full of dirt from recent trip away offroading for a week

Originally Posted by johntins

Can't answer, and you are more knowledgable than me, but I vividly recall the blistering ticking off I got from the sparky when he had pushed the ring on, got me to turn the thing in the lathe to split the split ring, and impatient me pushed the tool in too fast and spun the ring, tearing off his carefully soldered leads. It was some time before he let me do it again. Maybe it wasn't standard practice, but he did it all the time.

Sorry to keep this going, but it needs to be cleared up for everybody's benefit.

I have no idea what it was that you were working on, but I do know that it was not a slip ring in a modern alternator. You keep calling it a "split ring", which is an entirely different part, and is in fact a commutator.

Now, maybe if it was so long ago, there may have been an item in a first generation alternator that was supplied in a semi-finished state, or the brush surface was supplied with a protective coating on it that needed to be removed, I do not know. But I do know that all the slip rings that I have ever seen come ready to use and comprise at least 2 separate rings, all insulated from each other and the mounting sleeve, and there is no requirement to "split" anything. Even slip rings on AC motors, or mains voltage alternators, are constructed that way. Very early slip rings were built up on an open metal carrier and bolted together with insulated bushings around the bolts.

Automotive dynamos are an entirely different matter. The commutator WILL have to be skimmed after either rewinding or replacing, or just to dress the surface. That needs to be done in a lathe followed by undercutting the insulating mica between the bars. Also a demanding job to ensure that the commutator is not damaged.

The following is a slip ring for a Magneti Marelli alternator as found on a D1, and the 2 separate rings are obvious:

NEW MAGNETI MARELLI ALTERNATOR SLIP RING FORD TRACTOR,JCB,JOB MANN,LAND ROVER | eBay

Cheers

Originally Posted by Old Farang

I have no idea what it was that you were working on, but I do know that it was not a slip ring in a modern alternator. You keep calling it a "split ring", which is an entirely different part, and is in fact a commutator.

I don't care how long you want to keep it going. The alternator in question would be one of these, or similar:
834c0e771b9f469c99ab3f1dae288c66.jpg
May mot be "modern", but it is most certainly an alternator.

There may be a difference in terminology, but the rings I am speaking of are the com, but I was taught that a com was the segmented connector on the end of DC generators and motors, and the rings on an AC device were split rings. I would suggest taking that up with the people that taught me that, but I imagine they are most likely dead.

The rings in that Marelli pic are what I'm speaking of, but there was no raised insulation between them. It's a fairly simple concept then to grasp that a single copper ring could be pushed onto the end of the armature, the connectors soldered on, and then the ring be cut to make two rings.

Sorry if this process offends you in any way, but I can assure you that that is the way he did it.