<VV> Air vs Water HP

[Nick Elzinga]

Having given this a quick bit of thought I have come to the following
conclusions....

In a water cooled car the fan only runs for brief periods to reduce
temperature to within a certain range.  Cars equipped with air conditioning
would have the fan run permanently and sometimes at a higher speed with the
air conditioning switched on, but therein lies the problem - I think.  The
fans are 12v DC and to the best of my knowledge are of the type that have
carbon brushes, which wear out.

If an electric fan were to be used to cool an air cooled car, it would have
to run permanently and at high speed and I think the lifespan of the brushes
is the limiting factor.  If the fan were to stop working because the brushes
had worn out, you'd be stuck and I think it is because of the reliability
factor that air cooled cars use either a fan mounted directly on the
crankshaft as in the VW type 4, Citroen 2CV and Citroen GS, or belt driven
as in the Corvair.

If one were willing to check and replace brushes at regular intervals, then
I don't see why one couldn't use an electric fan.

Nick Elzinga

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org] On Behalf Of Bill Elliott
Sent: 08 July 2005 11:04 PM
To: virtualvairs at corvair.org
Subject: Re: <VV> Air vs Water HP

I've pretty much bought into this reasoning...until recently.

Rich and I assembled the bits to put together a vertical fan for my track
car (using items similar to how other Corvair racers do it).

The fan that's most often used in this application is the 11-blade plastic
Austin America fan.  Now this appears to me to be a pretty standard fan and
not 
one particularly suited to building up a head pressure to push air through
the engine. (And it's not even particularly powerful.... and is often
replaced with a 
metal fan with fewer blades for "tropical" applications despite the greater
noise.)

And beyond that,  in it's original Mini/America application (where it pushes
air through a sideways radiator) it is very often replaced with a standard
1000-
1100cfm electric fan which is seen as a performance upgrade since it pulls
less HP.

So my question is... what makes the vertical fan assembly as used by Corvair
racers cool the engine when it uses a fan most often replaced with electric
in 
its original application, yet the same electric fans can't directly replace
the Corvair fan?

I'll admit I haven't sat down and thought this carefully through, but at
first blush it doesn't make much sense. What am I missing?

Bill