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Date: Mon, 10 Jul 2006 09:34:44 -0600
From: Bob White <rlwhite@comcast.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: EWP Power - Was: Re: Nothing to do with Rotary Engines, but....
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I don't think so George.  The power consumed by the mechanical is
around 2 hp.  The electric wp is running around 1/4 hp max.  This
difference is way to much to be attributed to any rating difference
between the two.  The 2 hp was measured by Paul L at a pump speed of
7000 rpm.

My theory is the mechanical pump is designed to provide adequate cooling
on a hot day in stop an go traffic and as a result consumes more power
than required at high power.  The power required by the pump increases
as the cube of the rpm, but the flow is proportional to rpm.  So if the
engine goes from 800 rpm to 3000 rpm, the power used increases by a
factor of 50.  My pump is drawing 12-13 amps at 14V or almost 1/4 hp.
I'm using a Mezerie pump.  The Davies-Craig pump seems to produce
about the same flow with less current.

I also think the EWP is somewhat marginal or inadequate for continuous
high power.  The only data point I have for my system is that on a 60F
day with no cowling my oil and water temps stabilize at 190-200F up to
4000 rpm or so.  I ran it up to 6000 rpm for short periods of time and
the temps started creeping up.  The one time I couldn't maintain those
temps was on a day when the wind was blowing 30 mph and I turned
downwind.  I was taxiing about 10 or 15 and the temps started up
immediately.  After turning back into the wind, temps were running
lower than normal.  (so the WP doesn't do any good if there's no air
flow) :)

I'm almost finished with the cowling work so I"m looking forward to
finding out how well it cools on a 90F day with the cowling on.  That's
assuming I can get everything finished up before it turns cool again. :)

Bob W.


On Mon, 10 Jul 2006 16:29:30 +1000
"george lendich" <lendich@optusnet.com.au> wrote:

> I'm wondering if any of this sort of information is relative 
> (donkey reference aside) to use of electric water pumps and how they run with reduced HP but seemingly provided  sufficient coolant transfer, even if they appear borderline power wise.
> 
> George (down under)


-- 
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