<VV> Fan Belt Experience

Tue Jul 2 01:44:09 EDT 2013

Okay - My two cents. On Sunday I went through a day of Autocross belt  
problems. This experience will be applicable to only a few folks. You will see  
why. On my race motor, I am running one of the LeVair half-speed fan kits. 
The  kit replaces the drive pulley with a smaller pulley that bolts to the 
center of  a disassembled late model dampener. (They is a good supply of 
these, by the  way.) The system also uses a larger pulley at the fan. There is 
also a modified  mount to provide a better alignment for the alternator and 
the idler  pulley.  The two changes of the pulleys offset each other and the 
design  uses a stock-length fan belt. I ran the complete set-up at a track 
event and a  bunch of autocrosses last year with no belt problems. I have been 
using a  Corvair Underground spring loaded idler as well. At the last event 
of 2011, I  ran several runs, the last of which, it turns out was without a 
belt. Due to my  negligence the idler setup had come adrift, followed 
shortly by the belt.  Continued running loosened up a valve seat, and the season 
was over. In  preparation for going to Kalamazoo, I prepped another 140, and 
moved the belt  drive system over - except for the belt, which had been 
damaged, I used a new  Clarks HD belt. I re-assembled the Idler, assuring that 
it would not come loose.  Now I wanted to make sure the car would work for 
the long-haul back to  Kalamazoo. In an event two weeks ago, I had no 
problems, but the small lot  didn't really tax the systems, really no shifting. On 
Sunday we ran a fast, fun  event at Marina, top of second gear for me and a 
few shifts. On my second run,  the light comes on, the belt had departed. I 
installed a new  identical belt, lubed the crap out of it - and it came off 
at the  first shift. I cruised slowly back in, put the seemingly undamaged 
belt back on,  ran my fourth run - actual 2/3's of it, Light on, shut off. 
After I brought the  car back to the pit area, I put the belt back on, hitched 
it up and towed home. 
I talked a bit with Warren last night, we went over the possibilities. He  
is running the exact same set-up. He mentioned one possibility, the  belt, 
when restrained by the idler, is pulled back to the rear of the car a  bit 
more than vertical. He said that both he and Michael had found that whenever  
the belt is leaning back from vertical, there is a tendency to come off. A  
wider belt might functionally run as a longer belt, because it would ride 
higher  on the pulleys.  One other note, I was running an early version  of 
the Underground idler. I also had a new one sitting on the shelf. The  spring 
in the pulley on the newer ones is definitely longer  (stronger?) that the 
early one. 

This morning I removed the idler and swapped the heavier spring on. I  went 
through the dozen or so fan belts, looking for a shorter one. The Current  
Clarks HD and their Otto Parts Super belt were all the same length, allowing 
the  belt to lean backwards. I did have new pair of older Otto Parts belts 
marked  C8704. They are definitely shorter and, when installed, feed 
vertically up to  the idler.  

In the past, I have run the Gates 3VX560 belt (Notches on the bottom) and  
the Dayco Top Cog belt. Those are listed as 56" length belts. I noted that 
both  of these belts are available as 55" lengths as well. This morning I  
ordered one of each and they will be the next test. 

There is another Autocross this Sunday at Marina. If the belt survives, the 
 car goes to Kalamazoo!

The jury is still out on whether the belt length is THE factor. We shall  
see. - Seth Emerson

In a message dated 7/1/2013 7:01:39 P.M. Pacific Daylight Time,  
RoboMan91324 at aol.com writes:

Bill,

I believe that the only time a properly adjusted belt  will  slip is under 
high acceleration/deceleration conditions on the  motor RPM.   This happens 
during shifts.  The motor changes  RPM very quickly at these  shift points. 

You want the fan to  slip a little at these points or the fan  belt will be 
more likely to  fly off.  Unless the belt is too loose, I don't  think the 
fan  
will freewheel other than the mentioned accel/decel  situation.   This is 
especially the case when everything has warmed up to   operating levels.  
Once 
the belt and pulleys are warm/hot, the  contact  friction increases.  Also, 
the 
engine will have grown  due to thermal  expansion.

Just my opinion,

Doc

1960  Corvette, 1961 Rampside, 1962 Rampside, 1964 Spyder  coupe, 1965  
Greenbrier, 1966 Canadian Corsa turbo coupe, 1967 Nova SS, 1968   Camaro 
ragtop

~~~~~~~~~~~~~~~~~

In a message dated 7/1/2013  4:51:52 P.M. Pacific Daylight Time,  
virtualvairs-request at corvair.org  writes:

Message:  1
Date: Mon, 01 Jul 2013 15:16:18  -0700
From: Bill & Chris  Strickland  <lechevrier at q.com>
Subject: Re: <VV> Fan Belt   Physics
To: virtualvairs at corvair.org
Message-ID:   <51D1FFB2.5060603 at q.com>
Content-Type: text/plain;   charset=ISO-8859-1; format=flowed

> Belt is too  tight!   When the engine is COLD...using your HAND ONLY pull 

back on the idler/  tensioner pulley..   lock it and leave  it..
>
>
>  You should be able to slip the alternator  fan with a finger...

Well,  that is one opinion and it seems to  work for lotsa folk, but it is 
not the  only opinion.  I don't  like the idea that I could be loosing a 
lot 
of  cooling air in an  already inefficient system by fan belt slippage due 
to 
the  belt  being too loose.

Fan belts are now made a lot tougher than they   were in the sixties -- use 
good ($$$) belts!

Bill   Strickland

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