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Date: Thu, 31 Mar 2005 18:08:52 -0500
Subject: Re: [FlyRotary] Davies-Craig EWP Test Results
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From: Jerry Hey <jerryhey@earthlink.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Bob,  thanks for the test.  I wish you could convert everything to 1.25 
  hose.  The reduced sections must have a significant  negative effect.  
I am not a pump expert but I think the EWPs are intended to move a 
large volume at low pressure and probably do not do well with 
restrictions.  If  you wanted to change out the fittings on your rad to 
1.25s, I am sure Ed Klepeis could do the job.

   I am converting my rad from AN16 to 1.25 hose which will be the only 
size in the system.  This is easy for me as I have a C& R rad in which 
the inlets and outlets of choice can be simple screwed in place.   
After reading the mixed results from your test,  I goggled Davis, Craig 
and spent an hour reading one good report after another.

Thanks for the effort.  We all appreciate it.  Jerry


  I note that Paul L. again today pointed out that only a certified fool 
would use an EWP.


On Wednesday, March 30, 2005, at 10:36 PM, Bob White wrote:

>
> I spent the afternoon at the cold and windy airport.  There must have 
> been some
> 50 mph gusts, typical New Mexico spring.  Temp in the hanger was a 
> little over
> 50 F.
>
> But here's what you're interested in.  I put Rusty's Davies-Craig pump 
> on the
> same setup I've been using to measure flow on the Meziere pumps.  It's
> difficult to keep everything the same because each pump has a unique 
> input/
> output configuration.  All pumps were tested with aproximately the 
> same input
> hose size, and output hose size.  The lengths varied by what I had 
> available,
> and adaptors were fabricated to match to the pumps.  The hose from the 
> water
> container to the flow meter was 3/4 inch for all.  The hose from the 
> flow
> meter to the pump was 1 inch for the D-C and WP337, and 3/4 inch for 
> the WP136.
> This hose was shorter for the D-C test.  Output from the pump to the 
> container
> was 1 inch for the D-C, two 0.69 inch for the WP337, and 3/4 inch for 
> the WP136.
>
> First attachment is a photo of the test setup for the D-C pump.
>
> Second attachment is a photo comparing the D-C and WP337 pumps.  The 
> D-C pump is
> quite a bit smaller, and lighter.
>
> Third is the plot comparing the D-C, WP337, and the one data point I 
> have for
> the WP136.
>
> The tiny D-C pump outperforms the WP136.  I believe both of these 
> pumps have
> the same flow rating from the manufacturer of 20 GPM.  The D-C pump is 
> probably
> benefiting from larger hoses, however it has a _much_ lower current 
> draw.
>
> The WP337, rated at 55 GPM, does a little better but with a much higer 
> current
> draw than the D-C.
>
> I did note one difference.  The D-C motor seemed fairly warm, so I put 
> a
> Thermocouple on it.  Running at 14 V, the motor temperature was 138 F 
> with OAT
> in the low 50's. I didn't measure the temperature of the WP337 because 
> I hadn't
> noticed it being particullarly warm.
>
> My conclusion is that the Davies-Craig pump outperforms the Meziere 
> pump, but
> the Meziere pumps appear to me to be of higher quality.  The thing that
> concerns me the most is the small size of the motor and it's high 
> operating
> temprature.  I will check the WP337 running temperature after it's 
> installed.
> Even though the WP337 is consuming more power, it has quite a bit more 
> mass to
> dissipate the power in.  That isn't to say I think the D-C won't last, 
> as we
> have examples in use, just that the Meziere pumps seems more robust.  
> Another
> thought, the Meziere pump may heat up to the coolant temperature when 
> in
> operation because of the conductivity of the aluminum.  The D-C pump 
> motor is
> isoltated from the impeller by an air gap.
>
> I don't believe I have enough data to determine what the WP337 flow 
> rate will
> be when installed.  I need to know the static head pressure to 
> estimate that. I
> will just measure the flow when I get it in the plane.  I'm sure it 
> won't be as
> much as I wanted. :)
>
> Another interesting thing to do is look at this data compared to the 
> data Todd
> has previously reported.  Todd's measurements were at 12 V, so 
> comparing with
> my measurement:
>
> My Flow:       12 V, 4.8 A, flow 10.9 GPM
> Todd's Flow:  12 V, 4.3A, flow 9.3 GPM thru engine and parallel Ford 
> Evap cores.
> Todd has larger hoses, so it seems my test setup is almost as 
> restrictive as
> his entire cooling system.
>
> Bob W.
>
> -- 
> http://www.bob-white.com
> N93BD - Rotary Powered BD-4 (real soon)
> <Test_Setupa.jpg><D-C_vs_WP337a.jpg><WP_Performance.jpg> Homepage:  
> http://www.flyrotary.com/
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