[T3] Whining noise with new gen belt

Jim Adney jadney at vwtype3.org
Sun Sep 21 10:25:23 PDT 2014


On 20 Sep 2014 at 22:24, Phil Hof wrote:

> 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. 

It's actually amazing how long an old belt will last, especially if 
they are not particularly tight, as you described yours.

> 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 oepopping out of the groove as it exits the pulley during rotation.  Maybe that is the noise?  I canTMt see any easy way to machine it  smooth, and even if I did, it would be weakened from being thinned.

I've heard 2 different noises from generators: bad bearings and dirt 
on the field pole pieces that builds up to the point where it rubs on 
the rotating commutator. I've never heard belt noise like you 
describe, but it's possible since your new belt is probably riding on 
a partly worn/partly new area of the pulley. I'd look for a different 
belt anyway; something like 10 x 1005 or 10 x 1008, or 3/8 x 39.5".

> 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? 

If you're willing to put the old belt back on, that would tell you 
whether the noise is actually coming from the belt or not. The 
pulleys often break when people continue to drive with failing 
voltage regulators, so I'm reluctant to suggest that you consume a 
pulley just to get rid of a noise. It might help to sand yours a bit, 
to get rid of a sharp edge.

If you swap your old belt back in, keep your spare and necessary 
tools in the car so you can replace the belt on the road if 
necessary. FYI, I once drove 150 miles home with no belt and no 
problems. That was a nice day, no headlights, no wipers, no radio. 
And the battery still had plenty of juice to start the car several 
times after I got home!

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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