Return-Path: Received: from imf22aec.mail.bellsouth.net ([205.152.59.70] verified) by logan.com (CommuniGate Pro SMTP 4.2.5) with ESMTP id 572047 for flyrotary@lancaironline.net; Sat, 18 Dec 2004 09:31:32 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.70; envelope-from=bobperk@bellsouth.net Received: from HpPavilion310n ([65.1.127.8]) by imf22aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20041218143100.OLSB2051.imf22aec.mail.bellsouth.net@HpPavilion310n> for ; Sat, 18 Dec 2004 09:31:00 -0500 From: "Bob Perkinson" To: "Rotary motors in aircraft" Subject: RE: [FlyRotary] Great to hear: was [FlyRotary] I'm better now Date: Sat, 18 Dec 2004 08:30:58 -0600 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00A2_01C4E4DB.E6697C20" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_00A2_01C4E4DB.E6697C20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit I would lean more towards the pulsation set up by the positive displacement pump. I don’t know what the frequency of the pressure waves would be, but it could be calculated. These pressure waves would transmit to all surfaces of the oil system. The vibration would cause stress fatigue on the evaporator core even though it was insulated from the other engine components. I have witnessed metal fatigue in the discharge piping of a positive displacement vacuum pump used in an industrial setting; the remedy was to replace the piping with heavier gauge material. The stock Mazda oil cooler appears to be made of significantly thicker material. Bob Perkinson Hendersonville, TN. RV9A If Nothing Changes Nothing Changes! -----Original Message----- Rusty, glad to hear you have reconsidered, especially given the amount of effort and how close (I think) to working out all the bugs. Having experienced several similar heart thumping, cushion gripping events myself, I understand what you are going though. After all we are putting ourselves at some degree of risk. However, I personally consider the most dangerous part of each flight the 10 mile drive to the airpatch on a narrow two lane road with everything from very senior citizens to huge dump trucks passing me at a closure rate of 90 mph two feet or so away. Think about it! Regarding the core. I think there are some significant difference between the pressures and impulses encounter in the coolant system and the oil system. For one the oil pump is a positive displacement pump meaning that it is going to put out 156 psi (dropping to 80 psi by oil controller activates) in rapid pulsation - regardless of what resistance it encounters. The coolant pump on the other hand is a centrifugal type pump, it does not have the high peak pulsation of the lobed oil pump (smoother flow), plus if it encounters flow resistance, it simply slows down the flow (head pressure increases) or it causes the pump to cavitate. Also we have a difference in stress between a 80-100 psi pulsating operating pressure and a 5-15 psi operating pressure in the cores. I suspect the difference in viscosity is also a factor as the cross channels are something on the order of 1/8-3/16 sq inches each. I would imagine that cold 40-50 weigh oil encounters considerable resistance to flow in these channels. Got to cause more stress on the cores than water at least on startup before the oil has warmed up.. Now I am not a pump expert (nor any other kind - even on TV) but I believe there are these significant differences between the stresses encounter in the two different core applications. Besides, the core has been used by numerous folks for coolant without problems and if mounted correctly and with consideration of stresses on fittings I believe you will do just fine in that application. However, if your confidence about using cores is somewhat understandably shakened, then by all means have custom radiators built - worth it for you peace of mind and still a small cost compared to your total investment in the project. Whatever you do don't sell it, but if you do sell it - don't sell it to Ken Powers, he has more than enough unfinished projects {:>) Ed Anderson ------=_NextPart_000_00A2_01C4E4DB.E6697C20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message

I = would lean more towards the pulsation set up by the positive displacement = pump.  I don’t know what the = frequency of the pressure waves would be, but it could be calculated.  These pressure waves would transmit to all surfaces = of the oil system.  The vibration = would cause stress fatigue on the evaporator core even though it was insulated = from the other engine components.  = I have witnessed metal fatigue in the discharge piping of a positive = displacement vacuum pump used in an industrial setting; the remedy was to replace the = piping with heavier gauge material.  = The stock Mazda oil cooler appears to be made of significantly thicker = material.

 

Bob Perkinson

Hendersonville, TN.

RV9A

If = Nothing Changes

Nothing Changes!

 <= /p>

-----Original Message-----

Rusty, glad to hear you have reconsidered, especially given the amount of = effort and how close (I think) to working out all the bugs.<= /p>

 <= /p>

Having experienced several similar   heart thumping, cushion = gripping events myself, I understand what you are going though.  After all = we are putting ourselves at some degree of risk.  However, I personally = consider the most dangerous part of each flight the 10 mile drive to the airpatch = on a narrow two lane road with everything from very senior citizens to huge = dump trucks passing me at a closure rate of 90 mph two feet or so away.  = Think about it!

 <= /p>

Regarding the core.  I think there are some significant difference between = the pressures and impulses encounter in the coolant system and the oil system.  For one the oil pump is a positive displacement pump = meaning that it is going to put out 156 psi (dropping to 80 psi by oil controller = activates) in rapid pulsation - regardless of what resistance it encounters.    The coolant pump on the other hand is a centrifugal type pump, it does not have the high peak pulsation of the = lobed oil pump (smoother flow), plus if it encounters flow resistance, it = simply slows down the flow (head pressure increases)  or it causes the = pump to cavitate.  Also we have a difference in stress between a 80-100 psi pulsating operating pressure and a 5-15 psi operating pressure in the = cores. I suspect the difference in viscosity is also a factor as the cross = channels are something on the order of 1/8-3/16 sq inches each.  I would imagine = that cold 40-50 weigh oil encounters considerable resistance to flow in these channels.  Got to cause more stress on the cores than = water at least on startup before the oil has warmed up..<= /p>

 <= /p>

Now  I am not a pump expert (nor any other kind - even on TV) but I believe = there are these significant differences between the stresses encounter in the two different core applications. Besides, the core = has been used by numerous folks for coolant without problems and if mounted = correctly and with consideration of stresses on fittings I believe you will do = just fine in that application.

 <= /p>

However, if your confidence about using cores is somewhat understandably = shakened, then by all means have custom radiators built - worth it for you peace of = mind and still a small cost compared to your total investment in the = project.  <= /p>

 <= /p>

Whatever you do don't sell it, but if you do sell it - don't sell it to Ken = Powers, he has more than enough unfinished projects {:>)<= /p>

 <= /p>

Ed Anderson

 

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