X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 30 [X] Return-Path: Received: from mail01.syd.optusnet.com.au ([211.29.132.182] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTPS id 2061961 for flyrotary@lancaironline.net; Tue, 22 May 2007 18:02:53 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.182; envelope-from=lendich@optusnet.com.au Received: from george (d211-31-197-148.dsl.nsw.optusnet.com.au [211.31.197.148]) by mail01.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l4MM29Lp015558 for ; Wed, 23 May 2007 08:02:11 +1000 Message-ID: <008401c79cbc$dba18990$94c51fd3@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Gear box oil temps Date: Wed, 23 May 2007 08:02:13 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0081_01C79D10.AC477430" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Antivirus: avast! (VPS 0657-0, 12/12/2006), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0081_01C79D10.AC477430 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, Your 249F is convincing me to run a separate oil and cooler. George ( down under) Figures I found on the web indicates 3% is a fairly standard figure = used for a planetary gearbox efficiency. So if that figure is close and you are producing in cruise - say 160 = HP- then the gear box will produce heat with about 3% of the input = power. So 3% of 160 HP =3D 4.8 HP which is mostly converted to heat. I assume the oil is already cooled by the oil cooler before it is = fed to the PSRU. So the temp of the oil going into the gear box might = be around 180F. I am not certain how many GPM of oil Tracy's PSRU flows = but the old Ross flowed around 1 to 1 1/2 pint/minute, but that was = apparently rather marginal. So assume Tracy's flows 8 times that or 8 = pints/minute =3D 1 gal a min. Probably not that high but lower flow = just means the temperature calculation will be higher than in this = example. The Cp of oil is around 0.4 and its mass is approx 7.3 lbs/gallon. 4.8Hp converts to 203 BTU/Min, so we need to find out what temperature = rise that might cause in the oil. Delta T =3D Heat/(Mass flow *Cp) or if we start out with 180F oil = (Ti) then we need to find the final temperature (Tf) . So Tf =3D Ti + = (Heat/(mass flow *cp) Tf =3D 180F + (203/((7.3 *.5) *0.4) =3D 180F + 69F =3D 249F So using this example and assuming I haven't screwed up, I would = expect the oil temps coming out of the gear box to be around 249F. =20 Less efficiency would mean higher temps. More oil flow would lower = the temp and less would increase it. Less power being produced would = also decrease the temperatures. There may be some heat lost through air = flow around the gearbox, but probably offset by heat from the engine = through the spacers and plate. In my case, I would likely producing around 80 HP at cruise based on = fuel burn numbers (8 gph). My oil temp at that power is around 170F. So Tf =3D 170F + (102/(7.3*0.4) =3D 170F + 35F =3D 205 F. =20 So don't know if that tracks or not with what you guys are seeing, but = that's my 0.02 on it. Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.dmack.net/mazda/index.html ------=_NextPart_000_0081_01C79D10.AC477430 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Ed,

Your 249F is convincing me to run a = separate oil=20 and cooler.

George ( down under)

Figures I found on the web indicates 3% is a = fairly=20 standard figure used for a planetary gearbox efficiency.

So if that figure is close and you are = producing in=20 cruise - say 160 HP- then the gear box will produce heat with = about 3%=20 of the input power.   So 3% of 160 HP =3D 4.8 = HP =20 which is mostly converted to heat.

I assume the oil is already cooled = by the=20 oil cooler before it is fed to the PSRU. So the temp of = the oil=20 going into the gear box might be around 180F. I am not certain = how many=20 GPM of oil Tracy's PSRU flows but the old Ross flowed around 1 to 1 = 1/2=20 pint/minute, but that was apparently rather marginal. So = assume=20 Tracy's flows 8 times that or 8 pints/minute = =3D 1  gal=20 a min. Probably not that high but lower flow just means the = temperature=20 calculation will be higher than in this example.

The Cp of oil is around 0.4 and its mass is = approx 7.3=20 lbs/gallon.

4.8Hp converts to 203 BTU/Min, so we need to = find out=20 what temperature rise that might cause in the oil.

Delta T =3D Heat/(Mass flow *Cp) or if = we start out=20 with 180F oil (Ti) then we need to find the final temperature (Tf)=20 .   So Tf =3D Ti + (Heat/(mass flow *cp)

Tf =3D 180F + (203/((7.3 *.5) *0.4) =3D = 180F=20 + 69F       =3D 249F

So using this example and assuming I haven't = screwed up,=20 I would expect the oil temps coming out of the gear box to be = around=20 249F.

Less efficiency would mean higher temps. = More oil=20 flow would lower the temp and less would increase it. Less power = being=20 produced would also decrease the temperatures. There may be some = heat=20 lost through air flow around the gearbox, but probably offset by heat = from the=20 engine through the spacers and plate.

In my case, I would likely producing = around 80 HP=20 at cruise based on fuel burn numbers (8 gph). My oil temp at = that power=20 is around 170F.

So Tf =3D 170F + (102/(7.3*0.4) =3D 170F + 35F = =3D 205=20 F.

So don't know if that tracks or not with what = you guys=20 are seeing, but that's my 0.02 on it.

Ed

Ed Anderson
Rv-6A N494BW Rotary = Powered
Matthews,=20 NC
eanderson@carolina.rr.comhttp:/= /members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda= /index.html

------=_NextPart_000_0081_01C79D10.AC477430--