X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 30 [X] Return-Path: Received: from mail24.syd.optusnet.com.au ([211.29.133.165] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTPS id 2062096 for flyrotary@lancaironline.net; Tue, 22 May 2007 20:21:13 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.133.165; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-139-91.dsl.nsw.optusnet.com.au [58.105.139.91]) by mail24.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l4N0KRro015988 for ; Wed, 23 May 2007 10:20:29 +1000 Message-ID: <003901c79cd0$2d5d2c40$5b8b693a@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Gear box oil temps Date: Wed, 23 May 2007 10:20:31 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0036_01C79D23.FDE3F620" 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_0036_01C79D23.FDE3F620 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, I hadn't worked through the maths, but have kept it for future = reference. Now that I worked through it - I understand what you mean. = 180+139=3D319, I wonder what happens to the oil at that temp, perhaps = turns to water. George ( down under) Other's have done so, George, so it certainly works. In fact, I = believe George Graham did so on his E racer. By the way the numbers of my example are correct, but a 0.5 crept into = the denominator of the equations (7.3 *0.5)*0.4) . The temperature is = correct for 1 gallon/min flow so the 0.5 should be removed - I had stuck = it in there when trying to get a handle on 1/2 gal/min flow but decided = that would lead to a 139F increase which did not seem even in the ball = park. Ed ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Tuesday, May 22, 2007 6:02 PM Subject: [FlyRotary] Re: Gear box oil temps 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_0036_01C79D23.FDE3F620 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
I hadn't worked through the maths, but = have kept it=20 for future reference. Now that I worked through it - I understand what = you mean.=20 180+139=3D319, I wonder what happens to the oil at that temp, perhaps = turns to=20 water.
George ( down under)
Other's have done so, George, so it certainly=20 works.  In fact, I believe George Graham did so on his E=20 racer.
 
By the way the numbers of my example are = correct, but a=20 0.5 crept into the denominator of the equations (7.3 = *0.5)*0.4) . =20 The temperature is correct for 1 gallon/min flow so the 0.5 should be = removed=20 - I had stuck it in there when trying to get a handle on 1/2 gal/min = flow but=20 decided that would lead to a 139F increase which did not seem even in = the ball=20 park.
 
Ed
----- Original Message -----
From:=20 George Lendich
To: Rotary motors in = aircraft=20
Sent: Tuesday, May 22, 2007 = 6:02=20 PM
Subject: [FlyRotary] Re: Gear = box oil=20 temps

Ed,
Your 249F is convincing me to run a = separate=20 oil 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=20 3% of the input  power.    So 3% of 160 HP =3D = 4.8=20 HP  which is mostly converted to heat.
 
I assume the  oil is  already = cooled by=20 the oil cooler before  it is fed to the PSRU.  So the = temp of=20 the oil going into the gear box might be around 180F.  I am = not=20 certain how many GPM of oil Tracy's PSRU flows but the old Ross = flowed=20 around 1 to 1 1/2  pint/minute, but that was apparently = rather=20 marginal.  So assume Tracy's flows 8 times that or=20 8 pints/minute =3D 1  gal a min.  = Probably not that=20 high but lower flow just means the temperature calculation will be = higher=20 than  in this example.
 
The Cp of oil is around 0.4 and its mass = is approx=20 7.3 lbs/gallon.
 
4.8Hp converts to 203 BTU/Min, so we need = to find=20 out what temperature rise that might cause in the = oil.
 
Delta T =3D Heat/(Mass flow *Cp)  or = if we start=20 out 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=20 up,  I would expect the oil temps coming out of the gear box = to be=20 around 249F. 
 
Less efficiency would mean higher = temps.  More=20 oil flow would lower the temp and less would increase it.  = Less power=20 being produced would also decrease the temperatures.  There = may be=20 some heat lost through air flow around the gearbox, but probably = offset by=20 heat from the engine through the spacers and plate.
 
  In my case, I would likely = producing around=20 80 HP at cruise based on fuel burn numbers (8 gph).  My oil = temp at=20 that power 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=20 guys are seeing, but that's my 0.02 on it.
 
Ed
 
Ed Anderson
Rv-6A N494BW Rotary=20 Powered
Matthews, NC
eanderson@carolina.rr.comhttp:/= /members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda= /index.html
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