X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTP id 5323120 for flyrotary@lancaironline.net; Thu, 22 Dec 2011 08:42:46 -0500 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Return-Path: X-Authority-Analysis: v=2.0 cv=ePqRfQV1 c=1 sm=0 a=SC71y0a/4S6V9vjVxUojGA==:17 a=0_CYS9iNVnsA:10 a=pedpZTtsAAAA:8 a=Ia-xEzejAAAA:8 a=7g1VtSJxAAAA:8 a=q0Tpqmcm70uu01oJuCgA:9 a=8Ns1NABaoX7XXaEQi6UA:7 a=wPNLvfGTeEIA:10 a=Qa1je4BO31QA:10 a=eJojReuL3h0A:10 a=EzXvWhQp4_cA:10 a=eRLigfuSAAAA:8 a=JBCyGP61Q8sZK71UycgA:9 a=0mUG_N1OotGp5xcIxp8A:7 a=tXsnliwV7b4A:10 a=SC71y0a/4S6V9vjVxUojGA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 174.110.175.135 Received: from [174.110.175.135] ([174.110.175.135:55138] helo=EdPC) by cdptpa-oedge01.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id B8/31-17351-2B333FE4; Thu, 22 Dec 2011 13:42:10 +0000 Message-ID: <71C15E9641CA49FABD060DB76B8EB7D7@EdPC> From: "Ed Anderson" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: off topic, propeller carving and paint Date: Thu, 22 Dec 2011 08:41:58 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0039_01CCC085.90FC02C0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 This is a multi-part message in MIME format. ------=_NextPart_000_0039_01CCC085.90FC02C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Not quite that simple, Andrew. While more rpm (air mass flow) + more fuel =3D more power is basically = correct, there is more to matching prop load and engine than that.=20 I know of an indivdual who was a very smart individual when it came to = electronics (converted auto CPUs for aircraft usage), but did not = understand the relationship between rpm, prop pitch and thrust. He = tuned his adjustable pitch prop to get maximum rpm - He took off and = discovered (sadly too late) that he had very little thrust. He had = sufficient thrust to get airborne but could not fly out of ground = effect - contacted a catus off the end of the runway and died. Maximum = rpm is not the answer. The answer is maximum thrust (at least for take = off). The key is balance -- if you have too little prop load (too = little pitch for example) , you get great rpm - but little thrust. If = you have too much prop load (too much pitch or diameter or chord), you = reduce the rpm the engine can obtain, therefore your power and thrust. = So the key is balance. =20 I run an older 13B with the 2.85 and an 74x88x5.25 prop - I get = 6000-6100 rpm static at WOT. However, if I take the prop off (no load), = my engine will turn 5000 rpm at the idle setting. So rpm is not the = sole criteria. Ed From: Andrew Martin=20 Sent: Thursday, December 22, 2011 5:39 AM To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: off topic, propeller carving and paint whats with assuming max rpm is 6000, I intend to use a CS prop with = Tracy's 2.85 drive so I can rev the renesis out to 7500rpm when needed = and dial it down when not, correct me if I'm wrong but doesn't more rpm = + more fuel =3D more power. Ernest's drive should be able to withstand = 8500-9000 rpm. Way to go! up there in Lynn's league.=20 Andrew On Thu, Dec 22, 2011 at 4:08 AM, Bill Bradburry = wrote: That is true, but if I was going to go with something else, I would = try to find something that will turn my prop close to the 2700 that most = props are designed for. That means that I would look for something in the = 2.2-2.4 ratio range, not 3.17. That ratio will mean your prop will never get = more than 2000 rpm with the rotary. Bill B -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Ernest Christley Sent: Wednesday, December 21, 2011 2:26 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: off topic, propeller carving and paint Bill Bradburry wrote: > Tracy's PSRU ratio is either 2.17 turning backwards (A,B) or 2.85 > turning forward (C) I think?? > > And it is a good product; but, it's not the only PSRU in the world. -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0039_01CCC085.90FC02C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Not quite that simple, Andrew.
 
While more rpm (air mass flow) + more fuel =3D = more power is=20 basically correct,   there is more to matching prop load and = engine=20 than that. 
 
 I know of an indivdual who was a very = smart=20 individual when it came to electronics (converted auto CPUs for aircraft = usage),=20 but did not understand the relationship between rpm, prop pitch and=20 thrust.  He tuned his adjustable pitch prop to get maximum rpm - He = took=20 off and discovered (sadly too late) that he had very little = thrust.  He had=20 sufficient thrust to get airborne but could not fly out  of ground = effect -=20 contacted a catus off the end of the runway and died.  Maximum rpm = is not=20 the answer.  The answer is maximum thrust (at least for take = off). =20 The key is balance -- if you have too little prop load = (too little=20 pitch for example) , you get great rpm - but little thrust.  If you = have=20 too much prop load (too much pitch or diameter or chord), you reduce the = rpm the=20 engine can obtain, therefore your power and thrust.  So the key is=20 balance. 
 
I run an older 13B with the 2.85 and an = 74x88x5.25 prop -=20 I get 6000-6100 rpm static at WOT.  However, if I take the prop off = (no=20 load), my engine will turn 5000 rpm at the idle setting.  So rpm is = not the=20 sole criteria.
 
Ed
 
 
 
From: Andrew Martin
Sent: Thursday, December 22, 2011 5:39 AM
To: Rotary motors in = aircraft
Subject: [FlyRotary] Re: off topic, propeller carving and=20 paint

whats with assuming max rpm is 6000, I intend to use a CS = prop=20 with Tracy's 2.85 drive so I can rev the renesis out to 7500rpm when = needed and=20 dial it down when not, correct me if I'm wrong but doesn't more rpm + = more fuel=20 =3D more power. Ernest's drive should be able to withstand 8500-9000 = rpm. Way to=20 go! up there in Lynn's league.=20


Andrew

On Thu, Dec 22, 2011 at 4:08 AM, Bill Bradburry = <bbradburry@bellsouth.net>= =20 wrote:
That is true, but if I was going to go with = something else,=20 I would try to
find something that will turn my prop close to the = 2700 that=20 most props are
designed for.  That means that I would look for = something in the 2.2-2.4
ratio range, not 3.17.  That ratio = will mean=20 your prop will never get more
than 2000 rpm with the = rotary.

Bill=20 B

-----Original Message-----
From: Rotary motors = in=20 aircraft [mailto:flyrotary@lancaironline.net]=20 On
Behalf Of Ernest Christley
Sent: Wednesday, = December 21, 2011=20 2:26 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: off topic, propeller carving = and=20 paint

Bill Bradburry wrote:
> Tracy's PSRU ratio is = either 2.17=20 turning backwards (A,B) or 2.85
> turning forward (C) I=20 think??
>
>

And it is a good product; but, = it's not=20 the only PSRU in the world.


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