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Date: Fri, 21 Dec 2007 09:15:55 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: superchargers electric
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Steven Boese wrote:
> Ernest,
>
> I apologize in advance if you have taken the following into
> consideration already:
>
> The units of manifold pressure that are usually used are inches of
> mercury.  To convert inches of water to inches of mercury, divide by
> 13.6.  That means that the highest pressure that was generated was less
> than 2 inches of mercury over atmospheric pressure of about 30 inches.
> I'm not sure this is the amount of boost you were hoping for.
>
> Steve Boese
>   
Not what I'm hoping for in the final product.  It was more just to see 
what a centrifugal blower will produce.  Some people on this list know a 
lot about them, and have worked with them a lot.  I'm not one of those.  
I found out a 5" fan can give 2" of mercury. I ?believe? that is 
significant.  I could be wrong, but that would give a measurable 
increase in Hp, even after taking into account the power lost to 
producing it.

The next step in this particular sub-plot will be to get my bellhousing 
finished, get a fan and build a shroud.  I can attach it to the gearbox 
and drive it with my drill press from the propeller drive.  Running the 
3.17 reduction in reverse, I should be able to get 6000RPM on the fan 
side.  Then I can run through this same set of experiments.  Adding in 
an airspeed measurement and knowing the exit tube size(s) will give me 
an idea of the airflow.  Graph the results, pick out the head pressure 
at 277CFM and I'll have a reasonable chance of making a good SWAG at how 
much power I can expect to pick up.  The only piece I'd like to add in 
is a power meter on the drill press so that I could more accurately 
determine how much power I'm putting into it.

I'd expect the whole thing to take no more than a couple days.  One to 
rig up a shroud, and a couple hours the next to take measurements.  All 
the parts involved that require careful construction would have to go on 
the airplane anyway, so there isn't going to be much time lost.