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Date: Sat, 02 Jul 2011 00:17:12 -0400
From: Ernest Christley <echristley@att.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Test prop/club needed
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On 06/30/2011 02:14 AM, Andrew Martin wrote:
> Ernest, I thought the calculation for a test club was X section = 
> 1/15th of length, means a 90mm square should be 1350mm or 54” in your 
> language. mine is 90x1350mm calculated to absorb 190hp@2450rpm. do I 
> have this wrong, or do you have a more up to date equation? only 
> problem I can see with using a test club is needing supplemental air 
> for the heat exchangers or very short runs.
> I used the attached spreadsheet.
>
>
I took the calipers to my dyno-prop today.  After the glass and micro, I 
have a cross section of 88mm all around.  With my 3.18 gear reduction, 
it will only absorb 123Hp at 7000 RPM, according to the spreadsheet.

The second page suggests having several bars.  This one wasn't to hard 
to make, so I guess making a few more will be in my future.  I need to 
get out to 100mm before I'll have a bar that the spreadsheet says will 
absorb over 180Hp.

Brian, I'll be cutting this bar down to 52" (1320mm) tomorrow or 
Sunday.  With a 2.85 reduction, 6500RPM will require 137Hp to spin the 
bar at 2281.