Message text written by Randall Young
>David Massey wrote :
> If you
> look at a fan blade from the side you will see that it is not
> straight.
Actually, many (most ?) aftermarket radiator fan blades _are_ straight, to
give equal (if somewhat diminished) efficiency for either direction of
rotation. My Hayden has a blind hole in the blade assembly, so it can't be
reversed on the shaft anyway.
If you do find an automotive electric fan with cupped blades as Dave
describes, I'd be cautious about reversing it. Many purpose-built fan
motors (computer 'muffin' fans being one good example) only have adequate
thrust washers/bearings in one direction. Reversing the airflow will cause
them to wear rapidly, or even bind up.
Randall
<
Straight bladed fans are less efficient than those optimised for a given
flow. That is the compromise for a fan that works equally well (poor?) in
either direction. But an aftermarket fan with curved pitch fans will be
reversible. I believe this is what Joe was referring to.
And I would think that any motor designed for a high vibration environment
such as an engine bay fan would survive quite well being reversed. I
mounted a VolksWagon rabbit fan on my TR6. I converted it to a pusher and
had to modify the fan hub a bit to do so. It is still working fine
(although it gets only occasional use).
Dave
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