Tegger replaces his alternator

What puzzles me more than anything is what (if anything) was going through
the mind of the hillbilly that let that one past a basic quality check.

There is NO way that assembly should have been reused, and the fact that it
did is a condemnation of aftermarket parts in general. Keep in mind this
was my SECOND aftermarket alternator. The first one also failed early, but
I didn't get a chance to find out why.

 

i wonder about that too. my thought is cynical. i know that life
limitation is front and center in most domestic component manufacture.
"rough" rings like that are going to produce the results you have. you
have therefore to suspect the remanufacturer's design choice. a solid
electrical copper ring is not going to have a wear face like that
naturally. certainly not when abraded by a graphite brush. and even if
the brush had grit in it, wear would be streaked, not pitted. offhand,
unless there was severe arcing [which would cause extensive collateral
heat damage to the brush holder housing], i just can't think of a way it
could end up pitted like that without life limitation coming into design.

if you "clean" the ring with emery, does it go smooth or does it stay
rough? maybe the rings are "loose" sinter cores with a thin solid skin
- and the skin's worn through. that would make brush replacement futile
and keep a purchaser of this remanufactured alternator keep returning
for new ones, hopefully outside of the warranty period. what's the
warranty and what's your mileage?

 

Warranty or no, I still think he needs to just take it back and drop it on
someone's toe...

 

On careful inspection, it looks like the bad patch (the part I showed in
the photo) only covers about 40-45 degrees of rotation. Past that, the
ring is pretty good, close to the appearance of the other ring. The
lathe-bit marks are nice and even all over.

Crocus cloth removes the black carbon deposits, showing even lathe marks
all over except within the bad patch.

To see what was happening within the bad patch I had to inspect with a
very bright light and a special magnifying glass similar to a jeweler's
loupe. The copper there definitely looks rough. The lines left by the
lathe bit are not smooth and even, but almost look randomly peened-over,
as though they'd been bead-blasted...but ONLY within the brush contact
area. Crocus cloth changes the apparent color, but the roughness
remains.

I wonder what happened within the rough patch that did not happen
outside of it?

Maybe. It's hard to tell. The rings consist of machined copper sleeves,
maybe 20-thou thick, riding on a thick plastic sleeve that's pressed (or
molded) on to an iron center bar.

I think it's just plain copper tubing, but your notion would explain the
roughness only being in the brush contact area.

I am certain that's their goal.

Other than speed of assembly and total absence of quality control, how
else can they sell these things so cheaply?

The warranty was one year, no mileage given. I average about 20K miles
per year these days, so the first aftermarket alternator lasted me about
18K (eleven months) and the other about 8K (five months).

 

No, I'd like to throw it, HARD, at someone's toe.

The thing weighs over five pounds, so it should make a nice big dent.

 

if it's a porous sinter core with a solid sleeve, once the sleeve wears
off, that's what it'll look like.

i think national average mileage is about 14k miles, so a design life of
20 will keep the punters coming back to be regularly fleeced. 8k is the
problem you get with designing to fail - it's hard to get it right.

o.e.m. dude - it's the only way to go on stuff like this. decent rings,
decent windings, decent bearings, decent diodes, decent solder...

 

I mis-typed before: the rough patch is about 90 degrees, not 45. When I was
studying it, I was thinking "quarter way around", and somehow that got
transliterated into "45 degrees" when I typed my report.

As to the roughness, it's burned. Melted, more accurately.

I just took apart my old microscope from when I was a kid, this so I could
look more closely at the scarring. The eyepiece says "6x". I have three
lower lenses, 10x, 20, and 30x. I tried 10x first, then went to 30x. All
hand-held, mind you. I had to brace against the bench and alternator, and
stop breathing, so I could control my shaking and keep things in focus.
Plus I had to hold my bright light just so...

The unused portions of the slip rings look kind of like furrows in a
freshly-cultivated field, only a lot smoother. They have sort-of rounded
peaks and hollows. Lots of machining scars.

The good sections of both rings under the brushes look the same. The furrow
peaks are a bit flattened, and the hollows are filled with a solid river of
carbon, which looks like melted plastic.

The rough section looks chaotic and blobby. The furrows are almost
obliterated. It looks like something's been arcing over a long period of
time in that area. The metal is not blackened, and the surface is not
sunken compared to that in the swept area that's still good.

I wish I could get pics of this. But to do so I'd have to spend more time
than I care to rigging up a proper stand and lighting. This textual
description will have to suffice.