Return-Path: Received: from fed1rmmtao07.cox.net ([68.230.241.32] verified) by logan.com (CommuniGate Pro SMTP 4.2b8) with ESMTP id 327833 for flyrotary@lancaironline.net; Tue, 20 Jul 2004 12:47:59 -0400 Received-SPF: error receiver=logan.com; client-ip=68.230.241.32; envelope-from=ALVentures@cox.net Received: from BigAl ([68.107.116.221]) by fed1rmmtao07.cox.net (InterMail vM.6.01.03.02.01 201-2131-111-104-103-20040709) with ESMTP id <20040720164728.BERN15588.fed1rmmtao07.cox.net@BigAl> for ; Tue, 20 Jul 2004 12:47:28 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Oil Delta T Date: Tue, 20 Jul 2004 09:47:31 -0700 Message-ID: <000001c46e79$3ffab670$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C46E3E.939BDE70" 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 V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C46E3E.939BDE70 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: [FlyRotary] Oil Delta T was: 11th test flight =20 Hi Al; Nope that's not a typo. It surprised me as well, but since oil has = far less heat carrying ability than water, that's what I attributed it to. = They were not calibrated sensors & the gauge didn't have fine resolution, so = that may account for some inaccuracy, but I did swap sensor positions. This = data was during cruise flight after temps had stabilized. =20 Todd; Yeah, the specific heat of oil, the amount of heat it can carry per = degree of temperature change, is about 60% that of water. So it works the = other way - it requires a larger delta T for a given heat load. Typical oil flow rate at 5000 rpm might be about 10-12 gpm. At a 30F delta T it would carry about 1525 BTU, which is roughly the heat load to the oil at 140-150 hp. So I'll stand by suggestion that something is amiss, = because 9F delta T would correspond to somewhere around 40-45hp. =20 Of course it's not a big deal. Your cooling is fine, and that's what matters. Maybe the issue is where you are (were) measuring your oil = sump temp. =20 Actually I've been so busy flying that I've not had much time for any reports or discussion, but there is a few things I've noticed. One is = that my oil temps used to lag behind my coolant temps, while now they are = very close to the same, since I've rebuilt the engine. I've been thinking = about this and one possible explanation that I've come up with is; I used to have my rotors ceramic coated to reduce heat absorption by = the rotor and in turn by the oil, however when I tore the engine down the ceramic coating was all but gone with only a few traces left. So I = assumed that it had been gone since soon after first start. However now I wonder = if the shock of detonation was enough to cause the coating to flake off ? = This would explain why now I'm seeing ~20F higher temps on the oil than = before the detonation & rebuild? Anybody have any thoughts on this? Hum-m-m. Could be. Actually, I'd be surprised if the ceramic coating = would make that big a difference, but that's just a wild guess on my part. Do = you know roughly how thick the coatings were? =20 Al ------=_NextPart_000_0001_01C46E3E.939BDE70 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Subject: [FlyRotary] Oil Delta T was: 11th test flight

Hi = Al;

Nope that's not a typo. It surprised me as well, but since = oil has far less heat carrying ability than water, that's what I attributed it = to. They were not calibrated sensors & the gauge didn't have fine resolution, = so that may account for some inaccuracy, but I did swap sensor positions. = This data was during cruise flight after temps had = stabilized.

Todd;

Yeah, the specific heat of oil, = the amount of heat it can carry per degree of temperature change, is about = 60% that of water. So it works the other way – it requires a larger = delta T for a given heat load. Typical

oil flow rate at 5000 rpm might = be about 10-12 gpm. At a 30F delta T it would carry about 1525 BTU, which = is roughly the heat load to the oil at 140-150 hp. So I’ll = stand by suggestion that something is amiss, because 9F delta T would correspond = to somewhere around 40-45hp.

Of course it’s not a big = deal. Your cooling is fine, and that’s what matters. Maybe the issue is = where you are (were) measuring your oil sump temp.

Actually I've been so busy flying that I've not had much time for any reports or discussion, but there is a few things I've noticed. One is that my oil = temps used to lag behind my coolant temps, while now they are very close to = the same, since I've rebuilt the engine. I've been thinking about this and one = possible explanation that I've come up with is;

I used to have my rotors ceramic coated to reduce heat = absorption by the rotor and in turn by the oil, however when I tore the engine down = the ceramic coating was all but gone with only a few traces left. So I = assumed that it had been gone since soon after first start. However now I wonder if = the shock of detonation was enough to cause the coating to flake off ? This = would explain why now I'm seeing ~20F higher temps on the oil than before the detonation & rebuild? Anybody have any thoughts on = this?

Hum-m-m. Could be. = Actually, I’d be surprised if the ceramic coating would make that big a = difference, but that’s just a wild guess on my part. Do you know roughly = how thick the coatings were?

Al

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