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Discussion Starter · #1 ·
I posted some pictures and description in my build thread regarding the state of the brushes in my new-to-me FB1-4001A motor. The motor is now out of the engine bay, and I was able to remove the end cap and get a better look at things. I'd appreciate any input on diagnosing its bench test failure (didn't spin under 12V power), aka, determining if I should go ahead and replace the brushes or if there's something else wrong that I need to dig into first.

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I've seen that brushes getting stuck in the holders is common from carbon build-up after sitting for a long time, but that doesn't explain why half of them are popped up like that, and several having chunks missing from them. Does that white residue around the brushes provide any hints as to what happened or why they're so stuck?

The brush I successfully removed measured within 0.1mm of the new spec length, so they can't have been run for long. I assume the 7-14-09 on the nameplate indicates a 2009 build date, which means it was pretty new when the half-finished conversion took place by the PO.

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While blowing out dust and cobwebs, a couple small shards of what looks like foil/paper insulation fell out. I couldn't spot anything missing or torn, but sitting for that long, it wouldn't be a shocker if critters got in there.

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The debris needs to be blown out and removed for sure. The strips may have been something used to hold the brushes back during installation and was not removed properly.

The brushes are not making contact with the commutator so it won't run. The white residue is likely some oxide from the coating on the brush holders reacting to moisture over a long time. Remove the brushes and rub them lightly across some 400 grit to remove the white if it doesn't just blow off. Clean out the inside surface of the brush holders. The brushes should easily move in and out against the spring pressure.

Did you ever try to rotate the shaft by hand when it was assembled, was it locked up or free to turn?

It looks like there is an opening to insert the brushes after the end cap has been assembled, that would be easier than trying to hold the brushes back.
 

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Discussion Starter · #3 ·
The shaft spun freely and smoothly in either direction with the transmission in neutral ... and didn't spin in gear, so I knew the coupler was engaged properly. That had me hopeful it would pass the 12V bench test, once I learned it's possible to test a higher voltage DC motor that way.

Yeah, the brush holders are accessible with the screen removed (with the end cap on), but the lower ones sit right above the engine mount crossmember, so getting in there isn't particularly easy. I would probably have to unbolt the driveshaft, loosen the tranny mount, and lift the motor several inches to do so with it in the engine bay. I wanted to remove it to get a better look at the motor-tranny coupler setup, though, so it was worth pulling the motor in this case.

Currently, all the brushes I've tried removing, other than the one that did come out, are totally seized up. They were crumbling under plier and channel lock pressure. Now that I can get to them from the bottom, I can hopefully apply more pressure. It doesn't look like any of them are going to be salvageable, judging from the number of chunks missing from them along the comm surface, so I guess I can be a bit extra forceful... It may be worth testing your theory of it being an oxide and see if it cleans up with medium grit sandpaper, though. Acetone should clean up the holders, but probably wouldn't be great for brush experimentation.

The bigger concern is why they're so seized, are the holders messed up, were the brushes ever seated properly, what caused half of them to pop up like that (they're not all in the same row, so it's not like they hit debris and were all affected in that path), and did something else go awry in the process?
 

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The only thing I can think of that could make a white film like that is that the motor was exposed to salt spray or somehow got exposed to chlorinated water (or rodent urine) and the brushes absorbed that moisture then cooked it off. Nothing else is corroded, though, apart from some modest white splashes of aluminum corrosion.

If it was my rebuild, I'd replace the brushes and springs. Be careful not to sand off that cadmium plating on the holders.
 

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Discussion Starter · #5 ·
The truck is so rust-free, salt spray seems unlikely. Although, assuming it actually was running at some point after the conversion (seems unlikely, given the state of things), a single test drive could have gotten it salty before sitting for years. Rodents doing their business is plausible.

Some of the motor mount was done with stainless steel. I've never worked with stainless, but I know it's a lot more complicated with oxygen control and what not. I wonder if, a) that welding was done with the motor in place, and b) if the shielding gases used could have had any effect on the brushes?

Ooh, one other question I forgot to ask in the first post, are there any trusted brands and vendors for brushes? I found several options under the various part numbers (A91-112E, etc.):


There's not a huge range in price, so if some are better than others, that would be worthwhile.
 

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Shielding gases are either CO2 or Argon - neither would affect the carbon brush chemistry.

It looks like the brushes were somehow soaked (maybe WD40 if they were sticking, lol), then the stuff got cooked off.
 

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Discussion Starter · #7 ·
Shielding gases are either CO2 or Argon - neither would affect the carbon brush chemistry.
Mild steel and aluminum are, but SS is a tri-mix that escapes me off-hand... Probably still not the answer, just a possible explanation that came to mind.

It looks like the brushes were somehow soaked (maybe WD40 if they were sticking, lol), then the stuff got cooked off.
That could well be. WD40 ... 1,001 uses, all of them the wrong application!
 

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You could try vinegar to possibly dissolve the oxide, use acetone at reassembly at the end to dry everything out. i might use some wooden dowels or blocks against the brushes as you punch them out with a hammer. If the old ones won't be salvaged then it doesn't matter so much.

i would imagine that the coating is gone on the inside surfaces of the brush holder. Not sure what would be a good repair solution for that.
 

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Discussion Starter · #10 ·
I spent a couple hours on Monday hammering the brushes out and cleaning up the holders. To get an idea of how seized they were, it took a comparable amount of force to driving in a substantial nail.

Acetone had no discernible effect on the corrosion and carbon accumulation on the holders, and I'm not sure carb cleaner fared any better. It took a lot of tedious scraping with an x-acto to smooth them out enough for the brushes to move relatively easily. Once I had them to that point, working the brushes in and out was actually the best remedy for the remaining crud. They all slide freely now.

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The state of the brushes once removed was not good... But, it got me thinking, they're all intact and probably good enough to re-run the bench test to verify condition of the motor before ordering new brushes.

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And finally, cleaned up pretty good:

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As kennybobby predicted, the surface doesn't look so hot. In searching fruitlessly for whether lubes (white lithium?) can be used on brush holders, I ran across this thread:


Deja vu... I'm thinking brush removal should be listed as preventative maintenance for DC motors if they'll be sitting for a while!

All I could find was stuff saying to not use lube between the brushes and commutator. I can't see any harm in lubing the holders lightly, unless it were to run down and make its way onto the comm...which I guess is bound to happen as the brushes wear down and pull the lubed portion closer. I also struck out in finding replacement holders. It looks like the whole assembly would need to be replaced, as the holders appear to be riveted to that inner ring with those dimpled brass heads.

But, to the more important point, I put the sketchy brushes back in and hooked it up to 12V power ... and it runs! The brushes sounded a bit clunky, not surprising with those chunks blown out, but it ran smooth and quiet.
 

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Discussion Starter · #12 ·
Graphite might work as a "lubricant, but I have no idea what it would do under arcing or high current conditions.
One of the things I read, as far as not lubing the brush faces themselves, is that graphite is the primary component so they're self-lubricating. As such, I could see an argument being made for either: a) don't bother lubing them with graphite because it's redundant, or b) it couldn't hurt to lube them with graphite, because the comm wouldn't see it as any different.

I would try to maybe polish or lap the copper brush holder. Super smooth might help.
Yeah, I'll try getting them smoother still before putting new brushes in. Access isn't the easiest, but maybe additional disassembly of the end cap will help.
 

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I was referring to lubing the brush holder walls to get rid of the sticking and get a consistent force against the commutator.

I would not mess with lubing the commutator and would let the brushes break in on them dry.
 

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Discussion Starter · #14 ·
I was referring to lubing the brush holder walls to get rid of the sticking and get a consistent force against the commutator.

I would not mess with lubing the commutator and would let the brushes break in on them dry.
Right. I was applying the logic of the brush face argument for not lubing, to also being redundant as far as lubing the holders with graphite.
 

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Did you happen to try Vinegar to dissolve the white deposits?

Is the brush holder made of steel (magnetic) or is it copper?

If you decide to try cleaning some more, Maybe try some Brasso or other brand metal polish on the inside surfaces to remove the yellow spots. Wrap a cloth on a wooden dowel and scrub that muther out. It may work just fine for years as is, just depends upon your OCD level.

The brushes look ok and will work fine once they seat in to a fresh surface; Did all the white residue come off the sides?
 

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Discussion Starter · #16 · (Edited)
I did use vinegar on the brushes after scraping the deposits down a bit, and it did seem to help with the white residue. I also tried it on the holders and it had no effect, as far as I could tell. But, it might be worth another round of that now that all the buildup is removed.

The holders appear to be copper, but I hadn't thought to check if they're magnetic... I checked just now and they're non-magnetic.

I have Mother's aluminum polish; which looks like it might work. I'm not familiar with Brasso, but the name implies it's more suitable to copper and brass.

You think the brushes are still usable, huh? That's a pleasant surprise! Oh yeah, I did take one more photo of them after cleaning them up:

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Graphite is porous so they will now be acidic as heck. Bad juju in motors. I suspect they got wet and the white powder is ash remains of arc burning because they were too loose in the holders. Should be a nice slip fit like gapping a set of points in the olden days, but no wobble anywhere, perhaps about 1lb of drag force to move them in the holders. If they are bouncing, perhaps a very light stoning of the comm when you get new brushes then a long seating run
 

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Make a paste of baking soda and water to dip or brush on the brushes to neutralize any acid, then wash with soap and water, then rinse with alcohol or acetone for remove any water or oil residue.

Could the brush holder be made of brass? It appears to be stamped plates held together with pressed joints, no fasteners. Just wondering what metal would produce white oxide like that.
 

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The prior owner may have used aluminum foil shims - aluminum oxide is white. Salt water will leave a white residue, as will chlorinated tap water.

It's merely a curiosity at this point -- the main thing is getting the brush holders restored and I think polishing them is the right move.

At first I thought the holders were cad plated steel, but copper for cooling would make sense. Conductivity should be through the copper braid of the brush in any case.
 

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Discussion Starter · #20 ·
All of a sudden, this thread may have to get stickied for DC brush info. :)

Graphite is porous so they will now be acidic as heck. Bad juju in motors. I suspect they got wet and the white powder is ash remains of arc burning because they were too loose in the holders.
That theory would explain the blown-out chunks on the faces of the brushes. My lingering question was, were they afflicted by arcing, and if so, is that a sign of any other issues on a motor that appears to have been fairly new and not run long? If the issue was isolated to the brushes themselves, that eases any such concerns.

Should be a nice slip fit like gapping a set of points in the olden days, but no wobble anywhere, perhaps about 1lb of drag force to move them in the holders. If they are bouncing, perhaps a very light stoning of the comm when you get new brushes then a long seating run
The way I've got them now, with more cleaning/polishing still to be done, they require very slight pressure to move and don't have any play in the holders.

Make a paste of baking soda and water to dip or brush on the brushes to neutralize any acid, then wash with soap and water, then rinse with alcohol or acetone for remove any water or oil residue.
Will do, thanks.

Could the brush holder be made of brass? It appears to be stamped plates held together with pressed joints, no fasteners. Just wondering what metal would produce white oxide like that.
Other than brass usually being darker, I'm not sure how to tell it apart from copper...? The holders are definitely darker than the copper lugs that the brushes bolt to, so I could buy them being brass. Or maybe some sort of plating over copper. The areas I cleaned up look more like copper to my untrained eye.

The prior owner may have used aluminum foil shims - aluminum oxide is white. Salt water will leave a white residue, as will chlorinated tap water.
That could explain the two pieces of foil looking shards that left the case when I blew it out with compressed air.

At first I thought the holders were cad plated steel, but copper for cooling would make sense. Conductivity should be through the copper braid of the brush in any case.
That raises an interesting question of what isolates the brush conductivity from the case? I'll have to take a closer look at that when I remove the end cap for more holder cleaning. Copper braids conduct through the brushes, so wouldn't the brush contact with the holders also conduct? Or does the slight air space act as enough of an insulator?
 
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