Tegger wrote:
> jim beam > wrote in
> news >
>
>> if you "clean" the ring with emery, does it go smooth or does it stay
>> rough?
>
>
> 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?

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

>
>
>
>
>> maybe the rings are "loose" sinter cores with a thin solid
>> skin - and the skin's worn through.
>
>
>
> 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.
>
>
>
>> 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.
>
>
> 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?
>
>
>
>> what's the warranty and what's your mileage?
>
>
> 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).

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...