3k st alternator just stopped mid work

[dieselgman]

From your pictures the brush alignment looks off a bit... and one slip ring does not appear very clean. I would clean up those ring surfaces and align the brush holders carefully. You should be able to spin the unit by hand and work it with some crocus cloth or similar fine abrasive... diamond dust (in stick form) used to be the best tool for this purpose, not sure if it is in common use or available today.

dieselgman

[BruceM]

I've had a bad brush situation recently on a new ST-3 from CGG with brand new brushes, properly aligned.  Sanding the brush surface by slipping some 400 grit sandpaper between brush and slip ring would fix it only  briefly, then it would fail open circuit (confirmed by ohm meter) again after spinning for just a minute.  I think some contaminant in the brush graphite material or binder is to blame.  I switched to one of the spare brushes and it solved the problem.  I normally shape the brush somewhat via sandpaper on the slip ring, in order to get a broader contact area on new brushes, since the ST-3 has only 2 brushes.

This can be a frustrating problem to identify, since the brush looks fine and it will measure well when first set up (but not after it fails).  Check your brush resistance from wire lead to slip ring first, is my best advice.  It should be no more than 0.2 ohms more than your test leads, checked immediately after failure, before you clean or adjust anything.

[Tom]

sounds like good advice.

[tyssniffen]

MORE crazy.  it's working again. 

ok, so, two things:
one, I swapped ONE of the brushes out for the OLD brush.  who knows, I was just trying stuff.

two, given my ignorance about that rectifier thing, I should have maybe mentioned that as part of my rewiring this, I put longer wires on it, to organize the thing. so, that rectifier now has 4 18" (thicker) wires coming off it, rather than the what, 5" it had.  Could I have messed up the activation voltage needed by creating a longer loop or something???   

I ask, because after swapping back that old brush, I was just staring at it running at 82.3v ... and decided to play with the speed. I sped it up beyond 650, and the thing jumped up to 120v and then as the speed settled back, it stayed.     

thoughts?

[BruceM]

Your wire length change did nothing.  Wire length issues are for radio frequencies and perhaps some high speed data, not the extremely low frequency 60Hz power or the 120Hz harmonic excitation.  You could run the wiring around the room a few times without issue.

You also seem to have gotten some bad new brushes, as I did.  Once the contaminant was worn off the slip ring a bit- bingo, you were back in business.  I suspect there are going to be a LOT of these out there.

Either that or you have some sort of intermittent problem...the bane of troubleshooting.  Time will tell.

If you don't have one, get a cheap volt-ohm meter and learn how to measure resistance in ohms. It can help you with electrical troubleshooting greatly, and would positively confirm this bad brush issue. 

[tyssniffen]

I continue to struggle with this low to no power issue.   I've played around with speed, checked all connections, and I continue to feel it's the brushes, though I can no longer make a change by swapping out different brushes.

running at good speed - 650ish, but I'm not sure - I'm now getting about 50v.  last week, before I started messing with it, I was getting 80something, and hardly any amps.  Sometimes, I could get it up over 100v but cannot any longer.

can someone talk to me about glazing? how do I fix it? could that be it?  here's photos taken today, after much fiddling.  surprising to see how it looks lined up well from one side, and off-kilter from the other.

"front"
http://1.bp.blogspot.com/-5Gaq-Z2jYfI/Vhh7U3HJyxI/AAAAAAAAGmU/wqNLzKsT4tc/s1600/2015-10-09%2B17.07.53.jpg

"back"
http://4.bp.blogspot.com/-ngmUKZQ-0AA/Vhh7UsyImNI/AAAAAAAAGmQ/jrqE7OWerCo/s1600/2015-10-09%2B17.08.04.jpg

also, there is no more fixing the alignment, at least with the stock parts. They are at their maximum already.

I need to get this thing ready for winter! 

[tyssniffen]

From your pictures the brush alignment looks off a bit... and one slip ring does not appear very clean. I would clean up those ring surfaces and align the brush holders carefully. You should be able to spin the unit by hand and work it with some crocus cloth or similar fine abrasive... diamond dust (in stick form) used to be the best tool for this purpose, not sure if it is in common use or available today.

dieselgman

is this saying I should use some abrasive on the RINGS or the BRUSH?  I've run 6 different brushes in and out, both with sanding them to shape and not.  still not getting there.

No, I haven't checked OHMs yet.  not clear how. check the resistance, when it's not running, from the ring to the lead off the brush, or where?

[dieselgman]

Sorry if that was not clear. The diamond dust (in stick form) would be used to re-surface the slip-ring and commutator surfaces while manually spinning the rotor. Resistance checks would be taken from brush lead to any accessible point on the slip ring in question. Replace brushes if in doubt.

dieselgman

[merkland]

Looking at your pictures it looks as if the brush holder needs adjusting as the brushes are lying at an angle and not square with the rings. The brushes consequently are not making even contact with the rings, as you can see by the shiny contact area on the rings. This may have nothing to do with your voltage problem but it certainly won't help. If, as you say, no further re-alignment is possible I can only assume that someone has fitted the wrong brush holders or something has moved that should not have. I hardly think that any reputable manufacturer would put out a unit in that state.

merkland

[tyssniffen]

Looking at your pictures it looks as if the brush holder needs adjusting as the brushes are lying at an angle and not square with the rings. The brushes consequently are not making even contact with the rings, as you can see by the shiny contact area on the rings. This may have nothing to do with your voltage problem but it certainly won't help. If, as you say, no further re-alignment is possible I can only assume that someone has fitted the wrong brush holders or something has moved that should not have. I hardly think that any reputable manufacturer would put out a unit in that state.

merkland

I will continue to try and straighten that up... but I'm sure you know what I mean - there is some adjustment possible built in to the design of the piece that holds the brush holders... but I've maxed it out.  if I tighten down the bolts, it ends up slightly off.

most annoying about this is that I never had a problem for the first 7 years of running this thing. (only ran it 20-30 hours a year, but still)

[tiger]

maybe time to check rotor bearings and shims if fitted, for end slop

[tyssniffen]

maybe time to check rotor bearings and shims if fitted, for end slop

how and where do I do that? in the Alt? do I have to pull the whole axle?

[tyssniffen]

attempted to check Ohms.  that was confusing.  completely random numbers from all 6 (!) of my brushes.  some of which have never been installed.


check out my test numbers, using the digital meter, with points on end of wire and end of chunk:

http://1.bp.blogspot.com/-V40LG7KS17Q/Vhnde81dzRI/AAAAAAAAGmo/_yiVscRxMe0/s1600/2015-10-10-16.png

what the what?

[BruceM]

Were these measured by just touching the brush with the tip of the meter probe?  If so, this is why your readings are so varied. You need to put the brush in the holder and measure it from connector to the slip ring.  Spin the head a bit first.

When there is contaminant in the graphite mix, the brushes may measure OK, but after spinning a bit, not.

[tyssniffen]

I was doing the measurements with it all hooked up too, with one probe on the ring, one on the end of the wire (connector end) and getting lots of different numbers.  I guess I might not have been spinning it first. 

is it really supposed to be as low at .2 ?    I was seeing 4.1 from ring to connector.    still, I'll do it again. with all 6.

thanks for the patience people.