<VV> Fan Belt Tension

[jvhroberts at aol.com]

 Jim, the issue here is, it's not the rubber, it's the tension members! And they very much do expand when hot, a lot more than the metal parts do. 

Probably the only way to put this to bed is to get an infrared thermometer and a GOOD belt tension tester, and correlate tension to temperature over a bunch of points. 

 

John Roberts
 

 

-----Original Message-----
From: Jim Simpson <simpsonj at verizon.net>
To: Virtual Vairs <virtualvairs at corvair.org>
Sent: Fri, Apr 13, 2012 3:25 pm
Subject: Re: <VV> Fan Belt Tension


Actually, fan belts tighten as they get hot.  Sort of mind-boggling, but
stretched elastic polymers (i.e. rubber) shrink as they are heated.  This
has been known since at least 1805 -- here's a good reference if you want
to look into the phenomena:
http://tpt.aapt.org/resource/1/phteah/v48/i7/p444_s1?bypassSSO=1

By the way, the shop manual has a tension spec for the fan belt.  In my
opinion, it's way to high.  I have a fan belt tension measuring device and
if I actually tighten a fan belt to the shop manual spec, it's almost like
a violin string.  I, like most other Corvair owners, subscribe to the "just
tight enough so you can move the alternator" approach.  That's worked for
me for several decades.  I suppose it works because as the fan belt is run,
the flexing and friction heat it up and tighten it.

Jim Simpson
Group Corvair
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