Return-Path: <13brv3@bellsouth.net> Received: from imf19aec.mail.bellsouth.net ([205.152.59.67] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 572713 for flyrotary@lancaironline.net; Sat, 18 Dec 2004 21:08:43 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.67; envelope-from=13brv3@bellsouth.net Received: from rd ([65.6.194.9]) by imf19aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20041219020811.FUSV2049.imf19aec.mail.bellsouth.net@rd> for ; Sat, 18 Dec 2004 21:08:11 -0500 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: cooler thoughts Date: Sat, 18 Dec 2004 20:08:31 -0600 Message-ID: <000501c4e56f$a33b7590$6101a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01C4E53D.58A10590" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_0006_01C4E53D.58A10590 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable The problem might simply be that the pulses are hitting high pressures = and fatiguing the reasonably flimsy evap cores. There's also the = possibility that the pulses hit a resonant vibration at some point, which causes the failure. =20 It would be interesting to see a trace of these pulses, and they may be important; but I am skeptical about them being the primary cause unless = your cooler is near the engine outlet, and you have rigid (solid metal) = lines. =20 =20 Hi Al, =20 If I thought a standard pressure sensor could catch the pulses, I'd be tempted to put a scope on it. I just don't think it would be a = conclusive test though. Leon has told me some interesting stories that lead me to believe in the pressure pulse theory. I also can't think of a better explanation. I don't quite buy the cycling pressure theory, because I'm only running about 80 psi at the cooler. I think the evap core probably sees close to an 80 psi cycle between static, and operating pressure. = Also, I believe the leak started after a good 20 minutes of flight, not on = initial pressure at startup, which wouldn't indicate that it failed on the = pressure cycle. =20 =20 Fortunately, I think the only point we need to prove is that evap cores = are a bad idea for oil coolers. =20 Cheers, Rusty =20 ------=_NextPart_000_0006_01C4E53D.58A10590 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
The problem = might simply be=20 that the pulses are hitting high pressures and fatiguing the reasonably = flimsy=20 evap cores.  There's also the possibility that the pulses hit = a=20 resonant vibration at some point, which causes the failure.

 

It would be = interesting to see a trace of these pulses, and they may be important; = but I am=20 skeptical about them being the primary cause unless your cooler is near = the=20 engine outlet, and you have rigid (solid metal) lines.   

 

Hi=20 Al,

 

If I=20 thought a standard pressure sensor could catch the pulses, I'd be = tempted=20 to put a scope on it. I just don't think it would be a conclusive test=20 though.  Leon has told me some interesting stories that lead = me to=20 believe in the pressure pulse theory.  I also can't think of a = better=20 explanation.  I don't quite buy the cycling pressure theory, = because=20 I'm only running about 80 psi at the cooler.  I think the evap core = probably sees close to an 80 psi cycle between static, and=20 operating pressure.  Also, I believe the leak started = after a=20 good 20 minutes of flight, not on initial pressure at startup, which = wouldn't=20 indicate that it failed on the pressure=20 cycle.  

 

Fortunately, I=20 think the only point we need to prove is that evap cores are a bad = idea for=20 oil coolers.

 

Cheers,

Rusty

 

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