Return-Path: Received: from fed1rmmtao01.cox.net ([68.230.241.38] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 480492 for flyrotary@lancaironline.net; Wed, 20 Oct 2004 13:54:36 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.38; envelope-from=ALVentures@cox.net Received: from BigAl ([68.107.116.221]) by fed1rmmtao01.cox.net (InterMail vM.6.01.03.04 201-2131-111-106-20040729) with ESMTP id <20041020175405.XQMH22340.fed1rmmtao01.cox.net@BigAl> for ; Wed, 20 Oct 2004 13:54:05 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: EWP Date: Wed, 20 Oct 2004 10:54:07 -0700 Message-ID: <000001c4b6cd$cbc8ec70$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C4B693.1F6C8570" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C4B693.1F6C8570 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable > Al =20 Al, =20 I wonder if you misunderstood the nature of the question=20 and of my reply. I keep saying that I shouldn't reply to=20 messages at 0-dark-30 when I can't sleep, but I keep doing=20 it. Still, the question wasn't whether to convert or not=20 but whether or not to use the controller. =20 Oh, I may have been answering some combination of e-mails on the = subject; but I thought some point had been made in relation to power requirements = and using the controller; or maybe I was just blabbing =20 The belt-driven water pump has to be able to provide=20 cooling flow under worse-case conditions: low-speed city=20 traffic. Therefore, it is way over capacity at 6500 RPM. This can be mitigated somewhat by changing pulley sizes,=20 but at the risk of the cooling at idle and taxiing. =20 =20 Looking at the relationship between speed, flow and power dissipation, I come to a different conclusion. The pump output curve goes up = relatively linearly with speed and bends over toward flat as the back pressure = builds. The power dissipation required (with a prop) goes up roughly as the cube = of the speed (parabolically), so it goes up slowly at first and then heads = up pretty steep as you get past 3-4000 rpm. At some point out there the = curves for flow produced and the flow required cross, and beyond that you have = a cooing problem. So the greatest excess flow with the belt driven pump = is probably somewhere in there around 3000 +- (where you probably don't = care if you are wasting a couple of horses), and at the power output at = 6000-6500 needs all the flow you get; and then some if you have marginal cooling capacity. =20 The electric pump allows demand-based flow, using only=20 as much energy as necessary to provide adequate cooling at=20 that moment. =20 Not using the controller, leaves three basic options:=20 (A) wire direct, pumping full flow all the time and using=20 a thermostat to maintain minimum heat. (B) wire direct, with no thermostat, and run cold during=20 decents and other low-load conditions. (C) Put in a manual speed control. =20 Rusty's concern - inadequate "minimum" flow speed - can=20 be dealt with fairly easily. =20 I'd go with the controller. Probably at cruise the EWP can save a bit = of pumping power. =20 Al ------=_NextPart_000_0001_01C4B693.1F6C8570 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

> Al

Al,

I wonder if you misunderstood the nature of the question =

and of my reply. I keep saying that I shouldn't reply to =

messages at 0-dark-30 when I can't sleep, but I keep doing

it. Still, the question wasn't whether to convert or not

but whether or not to use the controller.

Oh, I may = have been answering some combination of e-mails on the subject; but I thought some = point had been made in relation to power requirements and using the = controller; or maybe I was just blabbing

<= /font>

The belt-driven water pump has to be able to provide

cooling flow under worse-case conditions: low-speed city

traffic. Therefore, it is way over capacity at 6500 RPM.

This can be mitigated somewhat by changing pulley sizes,

but at the risk of the cooling at idle and taxiing.

Looking at = the relationship between speed, flow and power dissipation, I come to a different = conclusion. The pump output curve goes up relatively linearly with speed and bends = over toward flat as the back pressure builds. The power dissipation = required (with a prop) goes up roughly as the cube of the speed (parabolically), = so it goes up slowly at first and then heads up pretty steep as you get past 3-4000 = rpm. At some point out there the curves for flow produced and the flow required = cross, and beyond that you have a cooing problem. So the greatest excess = flow with the belt driven pump is probably somewhere in there around 3000 +- = (where you probably don’t care if you are wasting a couple of horses), = and at the power output at 6000-6500 needs all the flow you get; and then some = if you have marginal cooling capacity.

The electric pump allows demand-based flow, using only =

as much energy as necessary to provide adequate cooling at =

that moment.

Not using the controller, leaves three basic options:

(A) wire direct, pumping full flow all the time and using

a thermostat to maintain minimum heat.

(B) wire direct, with no thermostat, and run cold during

decents and other low-load conditions.

(C) Put in a manual speed control.

Rusty's concern - inadequate "minimum" flow speed - can =

be dealt with fairly easily.

I’d go with the controller. Probably at = cruise the EWP can save a bit of pumping power.

<= /font>

Al

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