X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 07 Jun 2011 14:18:26 -0400 Message-ID: X-Original-Return-Path: Received: from imr-ma01.mx.aol.com ([64.12.206.39] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5011197 for lml@lancaironline.net; Mon, 06 Jun 2011 13:38:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.39; envelope-from=VTAILJEFF@aol.com Received: from imo-ma04.mx.aol.com (imo-ma04.mx.aol.com [64.12.78.139]) by imr-ma01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p56Hbore028696 for ; Mon, 6 Jun 2011 13:37:50 -0400 Received: from VTAILJEFF@aol.com by imo-ma04.mx.aol.com (mail_out_v42.9.) id q.10c3.44d3b9a (45482) for ; Mon, 6 Jun 2011 13:37:47 -0400 (EDT) Received: from smtprly-dc03.mx.aol.com (smtprly-dc03.mx.aol.com [205.188.170.3]) by cia-mc07.mx.aol.com (v129.10) with ESMTP id MAILCIAMC071-d3bc4ded106912e; Mon, 06 Jun 2011 13:37:47 -0400 Received: from webmail-d049 (webmail-d049.sim.aol.com [205.188.167.91]) by smtprly-dc03.mx.aol.com (v129.10) with ESMTP id MAILSMTPRLYDC036-d3bc4ded106912e; Mon, 06 Jun 2011 13:37:45 -0400 References: X-Original-To: lml@lancaironline.net Subject: Re: [LML] Re: L-IV Choice of Engine X-Original-Date: Mon, 06 Jun 2011 13:37:45 -0400 X-AOL-IP: 76.215.111.99 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: vtailjeff@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CDF287944881EC_2760_5255D_webmail-d049.sysops.aol.com" X-Mailer: AOL Webmail 33790-STANDARD Received: from 76.215.111.99 by webmail-d049.sysops.aol.com (205.188.167.91) with HTTP (WebMailUI); Mon, 06 Jun 2011 13:37:45 -0400 X-Original-Message-Id: <8CDF28794415DC6-2760-28671@webmail-d049.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: VTAILJEFF@aol.com ----------MB_8CDF287944881EC_2760_5255D_webmail-d049.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Ted, A lot of testing goes into propeller selection for engines.=20 Jeff Edwards -----Original Message----- From: Ted Noel To: lml@lancaironline.net Sent: Mon, Jun 6, 2011 11:50 am Subject: [LML] Re: L-IV Choice of Engine Robert, That's a most interesting comment. Essentially what you are saying is that= a prop of 1. non-metallic construction 2. relatively prime number of blades compared to cylinders would lessen the effects of harmonic vibration since (1) would damp the vi= bration modes and (2) would limit the possibility of them feeding back to= damage the engine. I guess that means I'm in good shape, since I have an AeroComposites 3 bla= de prop rated for 800HP which satisfies both criteria. It is made of a foa= m core with carbon fiber over the foam for strength and fiberglass for fin= al shape. The only metal is the nickel leading edge and mating structure= in the hub. On top of that, I have a question for the physicists in the discussion. Ho= w important is blade weight? I can make an argument that a heavy blade (ty= pical aluminum, about 11#) would damp vibration better due to mass effect.= I can also argue that a light blade (AC, about 7#) would incite less vibr= ation. We might even suggest that the vibration frequency of the light bla= de would be higher, and might be less damaging? But the foam core would mo= re easily damp higher frequencies? Which is the case? Help me out here. Ted Noel On 6/4/2011 9:52 AM, Lancair wrote:=20 I have read some discussion on the effects of different props, reducing ha= rmonic vibration by changing the number of blades (4 blades on a 6-cylinde= r engine for example, vs. 2 or 3 blades which have lower harmonics) and th= is might be beneficial. That thought process might lead one to a 3 blade= or 5 blade on an 8-cylinder engine. =20 Another concept which might be considered is the prop material itself, wi= th composite props like the MT damping out the combustion shock more than= an aluminium prop. =20 Guess that=E2=80=99s what makes these planes =E2=80=9Cexperimental=E2=80= =9D. =20 Robert M. Simon ES-P N301ES ----------MB_8CDF287944881EC_2760_5255D_webmail-d049.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Ted,
 
A lot of testing goes into propeller selection for engines.
 
Jeff Edwards



-----Original Message-----
From: Ted Noel <tednoel@cfl.rr.com>
To: lml@lancaironline.net
Sent: Mon, Jun 6, 2011 11:50 am
Subject: [LML] Re: L-IV Choice of Engine

Robert,

That's a most interesting comment. Essentially what you are saying is that= a prop of
1. non-metallic construction
2. relatively prime number of blades compared to cylinders
would lessen the effects of harmonic vibration since (1) would damp the vi= bration modes and (2) would limit the possibility of them feeding back to= damage the engine.

I guess that means I'm in good shape, since I have an AeroComposites 3 bla= de prop rated for 800HP which satisfies both criteria. It is made of a foa= m core with carbon fiber over the foam for strength and fiberglass for fin= al shape. The only metal is the nickel leading edge and mating structure= in the hub.

On top of that, I have a question for the physicists in the discussion. Ho= w important is blade weight? I can make an argument that a heavy blade (ty= pical aluminum, about 11#) would damp vibration better due to mass effect.= I can also argue that a light blade (AC, about 7#) would incite less vibr= ation. We might even suggest that the vibration frequency of the light bla= de would be higher, and might be less damaging? But the foam core would mo= re easily damp higher frequencies? Which is the case? Help me out here.
Ted Noel

On 6/4/2011 9:52 AM, Lancair wrote:=20
I ha= ve read some discussion on the effects of different props, reducing harmon= ic vibration by changing the number of blades (4 blades on a 6-cylinder en= gine for example, vs. 2 or 3 blades which have lower harmonics) and this= might be beneficial.  That thought process might lead one to a 3 bla= de or 5 blade on an 8-cylinder engine.
&nbs= p;
Anot= her  concept which might be considered is the prop material itself,= with composite props like the MT damping out the combustion shock more th= an an aluminium prop.
&nbs= p;
Gues= s that=E2=80=99s what makes these planes =E2=80=9Cexperimental=E2=80=9D.
&nbs= p;
Robe= rt M. Simon
ES-P= N301ES
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