X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost03.isp.att.net ([207.115.11.53] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2249998 for flyrotary@lancaironline.net; Wed, 08 Aug 2007 09:17:00 -0400 Received-SPF: none receiver=logan.com; client-ip=207.115.11.53; envelope-from=rusty@radrotary.com Received: from rad (adsl-065-006-194-009.sip.pns.bellsouth.net[65.6.194.9]) by bellsouth.net (frfwmhc03) with SMTP id <20070808131620H0300t5u6ie>; Wed, 8 Aug 2007 13:16:20 +0000 X-Originating-IP: [65.6.194.9] From: "Russell Duffy" To: "'Rotary motors in aircraft'" Subject: electric fans Date: Wed, 8 Aug 2007 08:16:20 -0500 Message-ID: <000001c7d9be$501e5fd0$a301a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7D994.674857D0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6822 Importance: Normal Thread-Index: AcfZvk4na4xkqwH/TtK01nxAvV0uCQ== X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7D994.674857D0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Greetings, =20 I've only been skimming through the cooling posts, but I haven't seen = much talk of electric fans. I was thinking about this during my drive time yesterday, and it seems to me that we have exactly the same need for an electric fan as a car does. =20 =20 - Packaging limits size and location of radiators. - Ducting optimized for normal cruise speed, fan compensates at low = speeds. =20 It would seem to me that the best situation would be to optimized your = inlet and ducting for normal cruise flight, then use a fan during climb. The drawbacks would be weight, drag, and perhaps bearing life on the fan, = but the positives could make up for these I think. =20 =20 From what I've read, it's common to use a switch to tie the motor leads together, which keeps the motor from completely freewheeling when = unpowered in cruise. It would seem that you can reduce the drag and bearing = problems that way. I would also think a clever guy could provide a switch mode = that allows you to generate alternate electricity from the freewheeling fan. = =20 Just something old to think about again.=20 =20 Rusty =20 ------=_NextPart_000_0001_01C7D994.674857D0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
Greetings,
 
I've only been = skimming=20 through the cooling posts, but I haven't seen much talk of electric = fans. =20 I was thinking about this during my drive time yesterday, and it seems = to me=20 that we have exactly the same need for an electric fan as a car = does. =20
 
- Packaging = limits size and=20 location of radiators.
- Ducting = optimized=20 for normal cruise speed, fan compensates at low=20 speeds.  
 
It = would seem to me=20 that the best situation would be to optimized your inlet and=20 ducting for normal cruise flight, then use a = fan during=20 climb.  The=20 drawbacks would be weight, drag, and perhaps bearing life on the fan, = but the=20 positives could make up for these I = think.  
 
From what I've = read, it's=20 common to use a switch to tie the motor leads together, which keeps = the=20 motor from completely freewheeling when unpowered=20 in cruise.   It would seem that you can reduce the drag = and=20 bearing problems that way.  I would also think a clever guy could = provide a=20 switch mode that allows you to generate alternate electricity from = the=20 freewheeling fan.  
 
Just = something old to=20 think about again. 
 
Rusty
  
------=_NextPart_000_0001_01C7D994.674857D0--