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Date: Tue, 31 May 2011 16:31:42 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Blower design
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Pat Panzera wrote:
> Here's more info that was sent to me:
>
>
>
>
> Hi Pat,
>
> As you might already know, the stock cooling fan gets discussed 
> (sometimes cussed) quite a bit in Corvair car circles.  Chevy did 
> tests on the fans, so the HP use isn't a guess, it's documented - you 
> do have to extrapolate the curve, but at 3400, it takes about 7 HP to 
> drive the fan.
>
> The later magnesium fans were made to help keep the belt on during 
> enthusiastic driving of a stick shift car, the earlier fans actually 
> flow a little more air per HP.  The later fan does use a little less 
> HP total, but it also flows less air, the fan design suffered a bit so 
> it could be a cast rather than a built up assembly.
>
> More info on my site at:
>
> http://autoxer.skiblack.com/fan.html
>
> Hope that helps.
>
Not to be glib, but...not really.
Talking about Hp requirements without stating head pressure and flow in 
the same sentence tells you very little.  Up at 18,000ft, it won't take 
nearly as much power to drive any fan for a given rpm.  Dunk that sucker 
in a pool of water and spin it up to 6000rpm, and THEN take a reading Hp 
requirements.  The numbers Chevy give, and what all the Corvair guys are 
quoting, are with a very low restriction output section.  They are 
basically quoting full flow numbers.  The numbers we're interested in 
will be much closer to the static pressure, no-flow end of the scale.