[T3] Whining noise with new gen belt

Phil Hof phil.hof at ostronic.org
Sat Sep 20 22:24:45 PDT 2014


I was doing a few repairs and maintenance on Clementine in prep for the Rally in a couple of weeks.  One of the things I did was replace the fan belt, which was a little loose and cracked on the outside.  I figured a 500 mile or so trip was not prudent with a flakey belt.

The correct size is 9.5x1000, according to the owners manual and also the 30 year old spare belt cardboard thingy.  However, the spare belt I actually had was too long, so I went to a could of FLAPS in sear of the correct belt.  No dice, but they came close with a 10x980.  Being shorter, I had to add shims, but it seemed to fit with the right tension and off I drove.  The old belt wasn’t slipping while driving, but I could turn the gen and have it slip, so I had to push down on the belt to give it a little more tension in order to turn over the engine.  It’s been that (with they same belt) for many years.

A new noise appeared with the new belt.  It’s a high-pitch whistling that is at generator speed.  Anyone had this happen?  I have a few theories:
1) The new belt has a surface that needs to wear-in/work/stretch, and the noise will go away.
2)  I need generator bearings.  But I’ve had then fail before and this is not the noise.
3)  This is the interesting one:  the halves of the pulley are worn.  There are ridges and it is definitely shaped in a wear pattern.  You would not expect metal to wear when pushed on by rubber, but I suppose after a hundred billion or more revolutions anything will wear.  I wonder if the belt is being squeezed as it moves around the worn pulley, slipping into the worn part, then sort of “popping out” of the groove as it exits the pulley during rotation.  Maybe that is the noise?  I can’t see any easy way to machine it  smooth, and even if I did, it would be weakened from being thinned.

Anyway, has anyone heard this noise, and did they figure out what caused it?

I am thinking of putting the old worn belt back on and keeping the new one in case of breakage.  But if #3 is correct, I am looking for NOS (or at least unworn) pulley halves for a ’71 12V gen.  Anyone have one for sale?

Thanks,
-Phil



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