[T3] cooling fan engineering

[Jim Adney]

On 26 Apr 2014 at 11:14, Dave Pallo wrote:

> Since I wasn't going to use this fan anymore - I drilled out the rivets.
> What an amazing amount of engineering that went into the cooling fan! I
> never knew there were rubber bushings with what I'm assuming are shim
> plates. I'll bring this fan to display at the Invasion so everyone can see
> just how complicated our metal cooling fan really is, and so y'all can help
> me figure out what went wrong with it!

I've been tempted to do the same, but never had a fan that I was 
willing to sacrifice. I had a talk with the folks at Gene Berg, 
however, and got an earful about what was going on there. If you send 
your type 3 or 4 fan to them for balancing, they tig weld the parts 
together, because they have had trouble with the parts shifting and 
going out of balance. They use different welding rod for the Type 3 
fan compared to the Type 4 fan, because the hub materials are 
different. I forget the details, but they seemed to know what they 
were doing. They do a very nice job of it.

If you mount the fan on a crank and then put the crank in a vise, you 
can wiggle it around and see the movement. I suspect the rubber 
bushings are in there to absorb vibrational energy, so the fan acts 
as a vibration damper.

I had to replace a fan once on another guy's car, and the only fan I 
had at the time had a bit more looseness than I was happy with. I did 
not have a tig setup, so I brazed it. That worked well, but it takes 
a lot more time and heat, so my main memory from the experience was 
the acrid smell of burnt rubber that came out as I was doing the 
brazing.

I look forward to seeing what the inside parts look like. I'd like to 
be able to fix these without completely disabling the damping 
function. Do you see any possibility of doing that?

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