Re: 5 blade cooling fan mod

["Mark Rutherford" <mark@afnetinc.com>]

I thought that this might be relevant to you modification.  This is a
paragraph from "The Design and Tuning of Competition Engines" by Philip H.
Smith, published by Robert Bentley Press.

    "Multiblade fans are quieter that two blades fans;  sometimes
multiblades are set at irregular angles to one another to limit the further
the possibilities for resonate frequencies that passengers might find
objectionable.  In a competition car, therefore, it is often possible to
reduce fan drive losses  by using  a fan with fewer blades or a smaller
diameter"

It continues to discuss horsepower losses due to fans in the later
paragraphs and makes these points.

1.  Electric fans are used over belt driven fans due to fact that electric
fans are tuned to a specific RPM making them much more efficient to use.

2.  The main reason for using multiblade fans is not to increase airflow but
to eliminate noise.

So any fan that was designed for a higher air flow will help in cooling
regardless of the number of blades so long as the engine RPM and the fan RPM
are designed to work together.

mark@anetinc.com


-----Original Message-----
From: Huw Powell <human@nh.ultranet.com>
To: quattro group <quattro@coimbra.ans.net>
Date: Thursday, August 06, 1998 9:54 PM
Subject: Re: 5 blade cooling fan mod


>> The reason I was told is that the fan with more blades actually pushed
>> less air when turned too fast
>
>I think fans / windmills do have an optimum rpm.  (That's why electric
>generating windmills have windspeed adjustable pitch.)
>
>Before mounting the 5 blade fan I was going to try to verify that the
>motor it was on (unless I'm stuck using it) is similar to my stock
>motor.
>
>--
>Huw Powell
>
>http://www.thebook.com/human-speakers/audi-main.htm
>
>"This is the place where death rejoices to teach those who live."
>
>Usually it is written in Latin.
>