I’m getting a lot of sparks out of the back housing of this 12v Delco remmy generator.. I have seen brushes spark on slotcars but the sparks coming out of this generator seems excessive? Is this normal or is something inside the housing grounding the brushes?
The commutator needs to be cleaned up with a toothbrush and rubbing alcohol. Prolly can use new brushes too. Jack E/NJ
I just did a Model A generator. Pulled the armature and cut the commutator. Installed a new set of brushes and lubricated it, worked great.
Seen that when the brushes are getting towards end of life(replacement time) and/or the commutator(copper) is so worn it is causing the brushes to jump/skip. Which, if there is acceptable tolerances left, you will need to cut down the mica between the copper.
This is the correct answer! Best case you would chuck the armature in an armature lathe and true the commutator up. Then you would use the little cutter wheel that is on the lathe and back cut the mica so that it is a bit below the level of the copper .015 to .02o if even that. What I have done for the past 30 years since I no longer have an armature lathe available is take a strip of sand paper and clean up the commutator and take a razor saw like you use on model cars for radical mods and cut the individual strips of Mica. A real thin fine tooth hack saw blade (half of one so you can cut back past the contact area of the brushes) will work too but you don't want to get into the copper. I've done this both on Generator and starter armatures.
I’ve stuck the small bushing end in my drill press and held a strip of 220-240 sandpaper on the com. Check to see if you have high mica. Use a broken 18 tooth hack saw blade to undercut it......carefully.
I mentioned Armature lathe earlier in the thread, here is one in Holland MI That is on Craigslist. A search showed several around the country for sale.
I have a armature lathe like that , its missing the electric motor but everything else is there, infact my uncle just called yesterday to ask if I wanted to put it in there garage sale this week end , I said what , then he informed me that I brought it to the sale they had two years ago ...apparently it hasn't sold..I had forgot about it...so if anyone needs one there's one at a garage sale this weekend in Longview Washington. Sent from my SM-T387V using The H.A.M.B. mobile app
The old manuals always specified "garnet" sandpaper for the commutator. The orange stuff, ordinarily used for woodworking basically. The idea being that wet-dry or emery paper would leave particles embedded in the mica or elsewhere, that are conductive. Maybe, they oughtta know. Lighter fluid or Naptha works pretty good to clean them up, Carbon Tet and Trike being on the Bad List these days. I bought a rebuilt generator that was otherwise pretty good, except for the fact the brushes had never been sanded, something I wasn't aware of. I "assumed" a rebuilt generator would be squared away. Oops. Brushes are supplied square. If they don't conform to the curve of the commutator and present a full contact patch, only a small part of the brush will actually make contact, and they will arc and burn up real quick within a few hundred miles. No, they won't "wear in".
Over the last 60 years I've put a lot of brushes in slot of devices & never sanded any of them , they obviously wear , otherwise they wouldn't need replacing . JMO
Commutator and brush wear as mentioned in the previous posts will cause sparking, and so will a heavy current load.
Of course they wear, but it is extremely gradual. The reason for sanding or seating the brush is to prevent arcing, sparks, and burning. I didn't even get maybe 500 miles or so on the rebuilt genny before the brushes were trashed. Most of the current flows through only one brush to begin with, in this "unseated" condition the load is now concentrated through just a small corner of the brush. This defect over time can also permanently damage the voltage regulator itself.
Lot of new alternators seem to get bad reviews, 'alt light came on/not charging correctly/etc' Picked up one for the OT car. Popped off the back cover to check the brushes. Brand new unmolested, not seated brushes. No wonder they are dying early.
As it happened I had to cut short a road trip and head back home. The charge voltage started to sag on the way back and the GEN light illuminated when I got home or soon after iirc. By mileage calculation figured had I continued on with the road trip as planned it would have instead failed somewhere in rural SE Wyoming, in a blizzard.
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