[T3] Fan Blades

[Tim Keohane]

On 30 Nov 2010 at 10:02, Tim Keohane wrote:

> The fan blades are located in a venturi/throat/nozzle arrangement.
> With the fan out I powered the unit and watched the blades as the
> lower portion of the throat is scuffed/abraded. I can manually move
> the fan blades ever so slightly (less than .01") and the contact
> ceases. I suppose the "squeal" could still be the bearings, sounds
> like bearings, but I suspect the fan starting under load  will be more
> prone to failure down the road ( because of the contact ). I inverted
> the fan and started it up and I have no noise. Still could be
> bearings. A few drops of oil won't hurt.

Interesting. It sounds like something warped slightly over time, but I  
haven't
seen that before. If the fan blade was that close at the bottom, how  
much
clearance was there at the top? Was there side play in the fan shaft?

When I looked at the blade positions they appeared slightly off-center  
toward the bottom, the area that was scuffed/abraded. I could shift  
the blade unit as a whole and get the appearance they were then  
centered. It seemed as if there may be some play in the bearing socket  
if there is one. It really didn't feel that way. The idea of some  
external stress didn't occur to me.
Oil will certainly help center the shaft a bit better, but that's only  
by the
thickness of the oil film, which I wouldn't expect to be more than a  
couple
thousandths. It's still a good thing to do.

Were there any signs that this fan housing had been subjected to  
unusual forces
over a long time? Examples could be mis-installed at the top, so that  
the
gasket was folded or out of place, or a poorly installed radio that  
pushed
against the housing.
The fan housing seemed to fit into the fresh air box/housing well  
enough. I did notice the top gasket wasn't properly seated, not  
folded, but certainly miss-aligned. That may have accounted for the  
squeal. It will be a bit more effort to install the gasket/seal  
properly, but now is the time to correct it. Thanks
Tim
Jim Adney
jadney at vwtype3.org
Madison, WI USA
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