Return-Path: Received: from hawk.mail.pas.earthlink.net ([207.217.120.22] verified) by logan.com (CommuniGate Pro SMTP 4.1.5) with ESMTP id 2629323 for flyrotary@lancaironline.net; Wed, 08 Oct 2003 21:13:19 -0400 Received: from h-68-165-56-67.chcgilgm.dynamic.covad.net ([68.165.56.67] helo=Barry) by hawk.mail.pas.earthlink.net with smtp (Exim 3.33 #1) id 1A7PMj-0004Jr-00 for flyrotary@lancaironline.net; Wed, 08 Oct 2003 18:13:17 -0700 Message-ID: <001701c38e02$8566a000$6501a8c0@Barry> From: "Barry Gardner" To: "Rotary motors in aircraft" References: Subject: Re: EWP - Success at last? Date: Wed, 8 Oct 2003 20:13:16 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01C38DD8.9C2A3510" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 This is a multi-part message in MIME format. ------=_NextPart_000_0014_01C38DD8.9C2A3510 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Guys, let me play the role of skeptic here. I'm not Paul Lamar's = lockstep disciple but I thought his argument sounded good. Can you guys = help me understand why the EWP works with such less power? I looked at the Davies Craig website, which claimed that substitution of = the EWP for the mechanical variety could save "up to 20 HP." A tech = article inside the site looked at the improvement on a drag car which = estimated the HP addition of lessening the load on the crank at 30 HP. = So, the claims are that the EWP saves 20 to 30 HP load on the engine. By Ed's law--I mean Ohm's law--below, the EWP current drain is .134 HP. = So why the difference? 1) The pumps could have differing efficiencies. That's possible but it = doesn't explain the magnitude nor why auto manufacturers would persist = with an inferior pump design if reverse engineering a Davies Craig pump = could yield such superior results. 2) Electric motors are more efficient than internal combustion engines. = While this is true, the 20 HP savings is measured at the crank of the = gas engine so the efficiency loss of the internal combustion engine = (i.e., the heat balance and all that stuff) has already been taken into = account. 3) ??? One interesting datum from the Davies Craig website is that the EWP = pumps less coolant. Maybe you guys saw these lines in there: a.. --"Maximum flow rate of [the EWP is] only 88L/min compared with a = maximum of 240L/min for the same engine using an older mechanical water = pump design. a.. --The extra flow rate is not required and is therefore a waste of = engine power." I'm all for matching my pumping needs to my cooling needs but it seems = to me that all the cooling problems people have had would not argue for = pumping less coolant, off-hand. I realize that a lot of the cooling = problems have been caused by difficulties getting good airflow through = the heat exchangers but still, reducing the coolant rate would not be = first thing I'd propose. So help me out: how can both these claims be true simultaneously? How = can you save 20 HP at the crank but spend only .134 HP on an electric = water pump? I'm pleased that Todd has had this good luck but puzzled why it worked. Please educate me. My physics education must have been lacking. Thanks. Barry Gardner Wheaton, IL Well at 7.5 amps and 13.8 volts the power consumed is approx 100 watts = which equal approx 0.134 HP. A couple orders of magnitude less power = than some "experts" had predicted would be required. Your "experiment" = has debunked another long-held myth about the amount of power required = to keep sufficient coolant flowing. Good work, Todd - a great data = point! Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com From: Haywire=20 To: Rotary motors in aircraft=20 Sent: Wednesday, October 08, 2003 4:31 AM Subject: [FlyRotary] Re: EWP - Success at last Hi Marko; Full specs can be seen at http://www.daviescraig.com.au/ Last = year I did full tests on the current draw, but I can't find that info = handy right now and it's to late to look for it, but IIRC it was approx = 4amps with the inrush current only ~6amps. The web site shows max draw = 7.5amps. If I didn't have so many other things to do in the next few = weeks I'd install a volt/amp meter on the pump/controller to take = readings at various coolant flow rates and plot them on a chart with = temps; engines speed, MAP, etc... but I just don't have the time right = now. maybe in the spring. S. Todd Bartrim Turbo 13B RV-9Endurance C-FSTB http://www3.telus.net/haywire/RV-9/C-FSTB.htm ------=_NextPart_000_0014_01C38DD8.9C2A3510 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Guys, let me play the role of skeptic = here. I'm not=20 Paul Lamar's lockstep disciple but I thought his argument sounded = good. Can=20 you guys help me understand why the EWP works with such less = power?
 
I looked at the Davies Craig website, = which claimed=20 that substitution of the EWP for the mechanical variety could save "up = to 20=20 HP." A tech article inside the site looked at the improvement on a drag = car=20 which estimated the HP addition of lessening the load on the crank at 30 = HP. So,=20 the claims are that the EWP saves 20 to 30 HP load on the = engine.
 
By Ed's law--I mean Ohm's law--below, = the EWP=20 current drain is .134 HP. So why the difference?
 
1) The pumps could have differing = efficiencies.=20 That's possible but it doesn't explain the magnitude nor why auto = manufacturers=20 would persist with an inferior pump design if reverse engineering a = Davies Craig=20 pump could yield such superior results.
2) Electric motors are more efficient = than internal=20 combustion engines. While this is true, the 20 HP savings is measured at = the=20 crank of the gas engine so the efficiency loss of the internal = combustion engine=20 (i.e., the heat balance and all that stuff) has already been taken into=20 account.
3) ???
 
One interesting datum from the Davies = Craig website=20 is that the EWP pumps less coolant. Maybe you guys saw these lines in=20 there:
  • --"Maximum flow rate of = [the EWP is]=20 only 88L/min compared with a maximum of 240L/min for the same engine = using an=20 older mechanical water pump design.
  • --The extra flow rate is = not required=20 and is therefore a waste of engine power."
    •  
    I'm all for = matching my pumping needs to my cooling needs but it seems = to me that=20 all the cooling problems people have had would not argue for pumping = less=20 coolant, off-hand. I realize that a lot of the cooling problems have = been caused=20 by difficulties getting good airflow through the heat exchangers but = still,=20 reducing the coolant rate would not be first thing I'd=20 propose.
     
    So help me out: how can = both these=20 claims be true simultaneously? How can you save 20 HP at the crank but = spend=20 only .134 HP on an electric water pump?
     
    I'm pleased that Todd has = had this good=20 luck but puzzled why it worked.
     
    Please educate me. My = physics education=20 must have been lacking. Thanks.
     
    Barry Gardner
    Wheaton, IL
     

     

    Well at 7.5 amps and 13.8 volts the = power consumed=20 is approx 100 watts which equal approx 0.134 HP.  A couple orders = of=20 magnitude less power than some "experts" had predicted would be=20 required.  Your "experiment" has debunked another long-held myth = about=20 the amount of power required to keep sufficient  coolant=20 flowing.  Good work, Todd - a great data point!

     
    Ed Anderson
    RV-6A N494BW Rotary Powered
    Matthews, NC
    eanderson@carolina.rr.com
     
    From:=20 Haywire=20
    To: Rotary motors in = aircraft=20
    Sent: Wednesday, October 08, = 2003 4:31=20 AM
    Subject: [FlyRotary] Re: EWP = - Success=20 at last

    Hi=20 Marko;
        Full specs can be seen at http://www.daviescraig.com.au/ =20 Last year I did full tests on the current draw, but I can't find = that info=20 handy right now and it's to late to look for it, but IIRC it was = approx=20 4amps with the inrush current only ~6amps. The web site shows max = draw=20 7.5amps. If I didn't have so many other things to do in the next few = weeks=20 I'd install a volt/amp meter on the pump/controller to take readings = at=20 various coolant flow rates and plot them on a chart with temps; = engines=20 speed, MAP, etc... but I just don't have the time right now. maybe = in the=20 spring.
     

    S. Todd Bartrim
    Turbo 13B = RV-9Endurance
    C-FSTB
    http://www3.telus.net/haywire/RV-9/C-FSTB.htm    <= /P>

     

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