X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.103] (HELO ms-smtp-04-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 975184 for flyrotary@lancaironline.net; Wed, 08 Feb 2006 18:20:16 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.103; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-04-eri0.southeast.rr.com (8.13.4/8.13.4) with SMTP id k18NJTp9010556 for ; Wed, 8 Feb 2006 18:19:30 -0500 (EST) Message-ID: <000c01c62d06$20930ec0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Six port bolt-on manfold progress (was: RX-8) Date: Wed, 8 Feb 2006 18:19:36 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01C62CDC.376BD980" 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-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0009_01C62CDC.376BD980 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable >=20 > Bill, I think Ed was saying that if you pitch the prop to absorb 243HP = > at 3157, then it will be producing ?160HP? at ?2000RPM?. You're = engine=20 > will be turning 5700 with the prop at that RPM. The question is, = "Will=20 > 5700 engine RPM produce 160HP or greater?" If you don't get >160HP at = > 5700 RPM, you'll never be able to get TO the 243HP that is sitting = there=20 > waiting for you. A CSprop would let you feather it past the lower = RPMs=20 > and bring you into the sweet nirvana where you manifolds tuning works = at=20 > its maximum. With a fixed pitch prop, it may be questionable until = you=20 > build one and try to run it. >=20 > How'd I do, Ed? >=20 >=20 Better job of explaining it than I did, Earnest. Thanks Yes, it doesn't matter what HP you produce at 6000, 7000,8000 or 9000 = rpm if the load of the prop at some point before those points is more = than the engine can produce. The load on the prop goes up as the rpm^3 = (following found on the internet)=20 Taking these three points, the power in watts required to drive a prop = would be: Watts =3D Const * rpm^3.0 * diameter ^4 * pitch =20 Therefore, a small increase in rpm raises the amount of power needed = considerably to meet the load. Of course, as you point out so well, = Ernest, a variable pitch prop permits you to change the pitch factor in = the equation reducing the power needed at any specific rpm.=20 If your pitch is small enough (load low enough) there is no doubt you = can reach your manifold airflow design limit, but for a useful pitch = then the engine must overcome the prop load at every lower rpm point to = keep revving into that golden zone. So there are really only two factors I can think of that will cause a = engine from continuing to accelerate to higher rpms under load. =20 1. The load is too great for the power being produced at an rpm 2. The induction system (intake/exhaust) has choked at that rpm (see = 1.) At least that's the way appears to me. So if Bill's beautiful design = can produce the HP to over come a realistic prop load (72x88?) up into = the 6500 rpm range (where apparently all the valves in the auto manifold = are open) then I think he will have a good chance of making his goal of = 9000.=20 If I wanted to absolutely ensure that my engine could reach that golden = rpm range of 240HP, then I believe a variable pitch prop is the only way = to ensure that (or a gear box {:>)). Certainly, if you have a fixed = pitch prop whose diameter and pitch producing a sufficiently small load = factor (which might be too small to be useful) to can also reach it. I believe the question Bill will need to answer if his manifold is = going to become a product is "What is the maximum prop load that can be = place on an engine with his manifold and still permit the engine to = climb into the golden RPM range". I think he will further have to = determine this in terms of prop diam and pitch (and perhaps # blades) so = that the requirement can be translated into "airplane speak" {:>) I am rooting for his success - naturally I would only run 8000 rpm with = his intake on my older 13B, but I would be happy with that {:>) Ed. Ed ------=_NextPart_000_0009_01C62CDC.376BD980 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 

>
> Bill, I think Ed was saying = that if you=20 pitch the prop to absorb 243HP
> at 3157, then it will be = producing=20 ?160HP? at ?2000RPM?.  You're engine
> will be turning 5700 = with the=20 prop at that RPM.  The question is, "Will
> 5700 engine RPM = produce=20 160HP or greater?"  If you don't get >160HP at
> 5700 = RPM, you'll=20 never be able to get TO the 243HP that is sitting there
> waiting = for=20 you.  A CSprop would let you feather it  past the lower RPMs =
>=20 and bring you into the sweet nirvana where you manifolds tuning works at =
> its maximum.  With a fixed pitch prop, it may be = questionable=20 until you
> build one and try to run it.
>
> How'd I = do,=20 Ed?
>
>
Better job of explaining it than I did, = Earnest. =20 Thanks
 
Yes, it doesn't matter what HP you produce at = 6000,=20 7000,8000 or 9000 rpm if the load of the prop at some point before those = points=20 is more than the engine can produce.  The load on the prop goes up = as the=20 rpm^3  (following found on the internet)

Taking these three points, the power in watts required = to drive a=20 prop would be:

Watts =3D Const * rpm^3.0 * diameter = ^4  *=20 pitch

 

 
Therefore, a small increase in rpm raises the = amount of=20 power needed considerably to meet the load.  Of course, as you = point out so=20 well, Ernest, a variable pitch prop permits you to change the pitch = factor in=20 the equation reducing the power needed at any specific = rpm. 
 
If your pitch is small enough (load low enough)=20  there is no doubt you can reach your manifold airflow design = limit, but=20 for a useful pitch then the engine must overcome the prop load at every = lower=20 rpm point to keep revving into that golden zone.
 
So there are really only two factors I can think = of that=20 will cause a engine from continuing to accelerate to higher rpms under=20 load.  
 
1.  The load is too great for the power = being=20 produced at an rpm
2.  The induction system (intake/exhaust) = has choked=20 at that rpm (see 1.)
 
At least that's the way appears to me.  So = if Bill's=20 beautiful design can produce the HP to over come a realistic prop load = (72x88?)=20 up into the 6500 rpm range (where apparently all the valves in the auto = manifold=20 are open) then I think he will have a good chance of making  his = goal of=20 9000. 
 
If  I wanted to absolutely ensure = that my=20 engine could reach that golden rpm range of 240HP, then I believe a = variable=20 pitch prop is the only way to ensure that (or a gear box {:>)).  = Certainly, if you have a fixed pitch prop whose diameter and pitch = producing a=20 sufficiently small load factor (which might be too small to be useful) = to can=20 also reach it.
 
 
 I believe the question Bill will need to = answer if=20 his manifold is going to become a product  is "What is the = maximum=20 prop load that can be place on an engine with his manifold and still = permit the=20 engine to climb into the golden RPM range".   I think he will = further=20 have to determine this in terms of prop diam and pitch (and perhaps # = blades) so=20 that the requirement can be translated into "airplane speak"=20 {:>)
 
I am rooting for his success - naturally I would = only run=20 8000 rpm with his intake on my older 13B, but I would be happy with that = {:>)
 
Ed.
 
 
 
 
Ed
 
 
 
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