Electrical problem need help

[Kaiser2boy]

Heres what happening. Engine starts normal. amp guage normal(in green).
Generator started to whine and got hot. It started to smell like hot bakelite and actually smoked a tiny bit.
Amp guage still normal.
I switched OFF the battery disconect while the engine is running and the whining stopped and the generator cooled off .

Engine runs fine , amp guage in green with batterys off line or on line. No dipping or dimming of lights.

I removed the cover from the regulator with engine off and batterys off and checked for stuck contacts, all are ok with no signs of bunt tips.

Generator has a small sound like a weak bearing but spins freely. The sound may be the brush on comutator.

Any one have any ideas..thank you.
Alan in Pa.

[Gordon Maney]

Here's what happening. Engine starts normal. amp guage normal(in green).
Generator started to whine and got hot. It started to smell like hot bakelite and actually smoked a tiny bit.
Amp guage still normal.
I switched OFF the battery disconnect while the engine is running and the whining stopped and the generator cooled off .

Engine runs fine , amp gauge in green with batteries off line or on line. No dipping or dimming of lights.

I removed the cover from the regulator with engine off and batteries off and checked for stuck contacts, all are ok with no signs of bunt tips.

Generator has a small sound like a weak bearing but spins freely. The sound may be the brush on commutator.

Any one have any ideas..thank you.
Alan in Pa.

If the unit was on the bench and you could turn it by hand — even under normal circumstances — you may hear the sound brushes riding on the commutator. A faint sound.

Your signal is clear, something inside is getting hot. It has not failed yet. Disassemble it and do a careful, visual inspection of all parts including the field windings. You will likely see something.

[Kaiser2boy]

OK, I got it out and apart and I could see where the rotor was hitting two of the fields.
I figured the bearing must be worn. They are fine. No discernible play or noise.
Upon closer inspection I found that some one has been in there prior. I saw punch marks on the end bells and frame as alignment points.
I also found that two of the fields were lose, screws only hand tight. Each one took about a turn and a half to lock up.

I chucked up the rotor in my old South Bend and took about .009 off the rotor to clean it up. The commutator looks very good and required only a few rubs with a scotch brite pad. No groves or wear at all.

I am going to reinstall it and see if the lose fields were the problem.
I also did a Hipot test on the fields and rotor and found no leakes to ground. Monday with fingers crossed it wil go back in.
One thing I still have a question about , the end bells have a V grove around the inside mating surface, should there be an O-ring on them?

[Gordon Maney]

OK, I got it out and apart and I could see where the rotor was hitting two of the fields.
I figured the bearing must be worn. They are fine. No discernible play or noise.
Upon closer inspection I found that some one has been in there prior. I saw punch marks on the end bells and frame as alignment points.
I also found that two of the fields were lose, screws only hand tight. Each one took about a turn and a half to lock up.

I chucked up the rotor in my old South Bend and took about .009 off the rotor to clean it up. The commutator looks very good and required only a few rubs with a scotch brite pad. No groves or wear at all.

I am going to reinstall it and see if the lose fields were the problem.
I also did a Hipot test on the fields and rotor and found no leakes to ground. Monday with fingers crossed it wil go back in.
One thing I still have a question about , the end bells have a V grove around the inside mating surface, should there be an O-ring on them?

Good question on the O-rings. Since it was a submersible unit, that seems very possible. I have no manual here that covers that unit. Someone else here may. On the other hand, if you don't intend to run it under water, it does not matter.

Regarding your field windings and pole screws, you might consider staking them with a center punch, unless you used an impact drive to seat them.

Good job!

[Kaiser2boy]

Thanks, The screws are just shalow slot heads and you really cant wonk them down very tight. I was thinking of replacing them with a real bolt that I can get some leverage on and tacking it with a weld.
The screws were not staked like you would expect, I guess thats why they worked out.
I got lucky that it did not self destruct.

[Gordon Maney]

They are generally not staked, instead they are torqued. If you have an impact driver you can use that. Sears has them for a reasonable price. They are also useful on the screws holding on brake drums.

You can also use the center punch to tighten them that last bit, then stake it. Staking is brutal and crude, but will keep it from loosening. You could also use Loctite. A properly ground drag link socket on a long handled ratchet would work, too.

The screw thread is 3/8?

Years ago we used to take them apart with air chisels fitted with punch tips. You used it to break the screw loose. You can also tighten them that way.

[Kaiser2boy]

The screws are 5/16ths and of course fine thread. Some of them were beat up a little so I bought new ones from Fastenall but I got them with a sockethead so I can do them up right. I bought a new bottle of Loc-tite red. It has been a while since I bought any of that product. I dont know what its made out of but it must be distilled down from gold bars, Jumpin Joe Smith its expensive.

PS. shaving the rotor down .009 of an inch cuts down on its efficincy a bit. I am still in the green but not were it was prior to shaveing it . But its OK it runs smooth and quiet and like I said it is well into the green.

[DrPepper]

The commutator mica....

"I chucked up the rotor in my old South Bend and took about .009 off the rotor to clean it up. The commutator looks very good and required only a few rubs with a scotch brite pad. No groves or wear at all."


did you undercut the mica between the segments so the brass is raised? If not they work for a while then...? A broken hacksaw blade ground narrow on each side and wrapped with tape for a comfortable grip does the trick for a hand tool when needed.
DrPepper

[Gordon Maney]

Good suggestion on the undercutting. I failed to think of that as I read it.

[Kaiser2boy]

Actually the rotor looked new, the comutator end needed no attention at all . There was no wear marks on it at all , no grooves no burnt segments , nothing. Even the brushes looked new and full length. All I did was hold a scotch brite pad on it as it turned on the lathe for about 5 seconds . I checked for any crap inbetween the segments and they are clean.
In the past with other DC generators or motors I have needed to under cut the insulation between the coppers. If you dont ,you get brush bounce and burnt coppers.
I really think the generator had been replaced just prior to me getting the truck. It was probably a rebuilt one and who ever did it failed to lock up the field screws.
The thing that had me was why it stopped whining when I took the batterys off line.
The more I thought about it I figured that when the batterys were off line the load was off the generator and the fields had much less magnetic laod and were not being pulled into the rotor.
I think the slight reduction of output is due to the larger gap between the rotor and the fields. I know shaving the rotors on any motor AC or DC can reduce the output so it must be true for generators also.
Thanks for your input and help. Its good to have this web site to touch base with now and then.

[Gordon Maney]

I realize I am not clear on what you mean by rotor.

[Kaiser2boy]

Ah yes , a rose by any other name ,,Most people call it the armature. I got into the habit of saying rotor because it is the part that spins. I guess I started it working on bigger generators where there is the "ROTOR and the STATOR winding, I am a reactionary, I still say frequency instead of HERTZ too. I never did understand why around 1965 or so we all had to say HERTZ and not frequency.

[Gordon Maney]

You are meaning you machined the OD of the armature's core laminations?

[Kaiser2boy]

Yes.
I just wanted to clean up where it had scraped on the field. It only took about .009 to do that. When you think about it thats only .004 off each side.
When I was done I sprayed it with a thin coat of varnish and let it spin on the lathe until dry.
The funny thing is that when I centered it up the armature was ever so slightly out of concentricity with the shaft. The .009 took that out and it now has no vibration when running.

[Gordon Maney]

OK, I understand now. Interesting, regarding the balance.