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I have a small 12 volt bilge pump for my birdbath/fountain. Mfr claims it moves 640 gph of water. If I divide gallons per hour by 60= gpm should work out to around 10.66 gpm. This is a tiny 12 volt bilge pump that my photovoltaic cell runs, with no battery. (only works when the sun is overhead). You can hold it in the palm of your hand nearly close your hand around it. Seems like it wouldn't take much larger of a motor to push 30 gpm if this puny thing will pump 10+ gpm. It will empty a bilge pretty fast. I realize this is unrestricted water, but still, it has to move all that water out of a boat bilge, and does a fine job. It pumps the water in my fountain too high, had to put a restrictor on it. Paul Conner

----- Original Message -----

From: Jack Ford

To: Rotary motors in aircraft

Sent: Sunday, February 27, 2005 3:00 PM

Subject: [FlyRotary] Re: [FlyRotary]Belt rumnations; soliciting Opinions of racers please....

I had a 3/4 horsepower pump that moved 13 gallons per minute of water out of a 100' deep well, 40' head minimum.

It was a lot faster than that until I drew the well down to it's production rate, but I only measured the production rate.

Extrapolating from that, 3 horsepower will move 52+ GPM. Different kind of pump, different environment.

Data point.

Jack Ford
----- Original Message -----

From: Jim Sower

To: Rotary motors in aircraft

Sent: Sunday, February 27, 2005 12:36 PM

Subject: [FlyRotary] Re: [FlyRotary]Belt rumnations; soliciting Opinions of racers please....

Al,
I made a quick analysis from facts obtained elsewhere. I surmised that PL was right about the 10 hp at high rpm because I've heard that number from so many sources over the years. How considerably off do you think PL was and why? I seem to recall that PL's case against EWP was that since water pumps require 10 hp, you'd need a 10 hp motor to drive the EWP. As for the 0.1 hp of EWP, I'm pretty sure someone on this list that's using one reported that his EWP draws about 5 amps in operation. Starting from there, the math is pretty straightforward.
Anyway, I'm a believer until I hear something really compelling ... Jim S.

Al Gietzen wrote:
The case for EWP for example is performance.  PL insisted that an EDWP absorbs over 10 hp at 6000 rpm.  He is probably damned close.  He then made the unfortunate leap that therefore an EWP must absorb the same power.  Not true.  EWP conservatively absorbs 14V x 5 A = 70 W =~ 0.1 hp.  He was off by about two orders of magnitude or about 9.9 hp.  Don't know about you  but I can always use an extra 9.9 hp.
 
PL may have been considerably off; but at .1hp with the EWP you will be getting only a fraction of the flow of the belt driven pump; even if it were 100% efficient.  Keep in mind that converting power into electricity is about 85% efficient, as is converting electricity back into power. 0.85 x 0.85 = 0.72; so you have lost 28% of the power in the process.  Pumping coolant against even a small pressure head takes power.  Any ‘performance improvement’ you may see with EWP vs belt driven pump comes from lower flow rate.  
Al
 
  
 
  
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