Mailing List flyrotary@lancaironline.net Message #42518
From: Michael Silvius <silvius@gwi.net>
Subject: Re: [FlyRotary] Electric Water pumps - Interesting
Date: Sun, 27 Apr 2008 10:56:10 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Ed:
 
I have been thinking about a similar set up as those electric water pumps but more on order of a remote mechanical water pump in order to get rid of the original heavy cast iron cartridge and the tall housing. I have been unable to locate a water pump that would be like those electric stand alone units but minus the electric motor. My thought would be mounting it as one perhaps would mount an alternator. In my case I seem to have a god bit of room on the lower back end of the engine. An other thought on installation was a direct drive with a coupling of the back pulley. My natural apprehension is messing with a system that we know works. So I may wind up with a bump or two on my cowl to accommodate it as well as the distributor.
 
Michael in Maine
Falconar F-12 progressing at glacial pace.
 
 
 
----- Original Message -----
Sent: Sunday, April 27, 2008 9:31 AM
Subject: [FlyRotary] Electric Water pumps - Interesting

I was just thumbing through a recent catalog from Summit Racing and came across a couple of pages on electric water pumps.  There has always been a degree of interest (and some debate {:>)) regarding the use of electric water pumps in aircraft.   It was interesting to read some of the descriptions, but basically the current consumed ranged from 4 - 9 amps and the quoted flow rate (presumably without back pressure) was from 16-35 gpm.
 
So if you take 9 amps at say 14 volts = 126 watts = 0.167 HP to get that flow.  However, some of them indicate you can save 15 - 20 engine HP at HIGH rpm.  So why the difference?
 
  Apparently (my best guess) is that they are advertising their product to best advantage (surprise?).  I would suspect that the flow rates shown are without back pressure and that when attached to a real engine coolant system that :
 
1.  The flow rates would decrease
2.  The current requirements would increase. 
 
 However, not to the point the electric pump would be required to make 10HP or more to provide the required flow.  I suspect there are considerable losses (such as pump cavitation and pressure drops through the cooling galleys)with mechanical pumps  at high pump rpm as driven by a high revving engine which accounts for the high power requirements.  Whereas the electric driven pumps may operate at lower and more efficient rpm without the majority of those losses.
 
That said, the pumps cost range from around $200 - $400 and while no weights were given, basic on the photographs showing the heavy electric motors and additional plumbing  would not appear to offer any significant weight savings over the proven, reliable mechanical pumps most of us are using. 
 
 So while certainly interesting and perhaps of value in some aircraft installations(how would you like to gain an additional 10 HP on takeoff?), I remain confident in my old 86 13B water pump housing and cartridge which is still going strong after 10 years.  I have moved it from my first 86 N/A engine to my current 91 turbo block, so it has performed for over 10 years in two different engines without any problem.
 
Interestingly, of  the  11 electrical water pumps advertised, only one was specified for drag race use only - and it had the lowest current drain - 3.5 amps.
 
Ed
 
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