X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from zproxy.gmail.com ([64.233.162.198] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 984250 for flyrotary@lancaironline.net; Sat, 04 Jun 2005 00:42:49 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.233.162.198; envelope-from=wdleonard@gmail.com Received: by zproxy.gmail.com with SMTP id 34so688258nzf for ; Fri, 03 Jun 2005 21:42:05 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:reply-to:to:subject:in-reply-to:mime-version:content-type:references; b=cWlpPeSH+BaY/altv07pSJ649RN50tW7YwPsrj+0Cn+SEROM6Hwy4NU7nfdx5kH9sdP74LFG8PSTQl/gCzJqC5X9eSjo50Ni4E5y9AW41oZU6TCFTzk4rzuQ/Rh08GJfqGUDkroCd45/jpw7LsxXvstU/V0RWvB8Xe99vyAjL0A= Received: by 10.36.178.2 with SMTP id a2mr1602079nzf; Fri, 03 Jun 2005 21:42:05 -0700 (PDT) Received: by 10.36.9.4 with HTTP; Fri, 3 Jun 2005 21:42:05 -0700 (PDT) Message-ID: <1c23473f05060321422e2cd5ec@mail.gmail.com> Date: Fri, 3 Jun 2005 21:42:05 -0700 From: David Leonard Reply-To: David Leonard To: Rotary motors in aircraft Subject: Re: [FlyRotary] Apples and Oranges (was: COZY: Rotary risks) In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_9346_21084043.1117860125033" References: ------=_Part_9346_21084043.1117860125033 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On 6/3/05, Bill Dube wrote:=20 >=20 >=20 > >http://www.maddyhome.com/canardpages/pages/alwick/risk.html >=20 > This is an interesting read, but a flawed analysis. >=20 > It looks like a mathematician's approach, rather than an > engineer's approach. >=20 > He compares failure rates for auto engine components operating in > an automobile with aircraft components operating in an aircraft. He then > assumes that the auto component will have the same mean time between > failures when installed on an airplane. >=20 > The speed and load profile for a car component and an airplane > component are completely different. >=20 > This would explain how he "doesn't get it" about the inherent MTBF > advantages of a rotary engine. It is quite likely that he doesn't > understand the drastic effect fatigue failure has on the MTBF as you > increase the continuous load. >=20 > As a rule of thumb, if you double the reversing load, you decrease > the the cycle life by a factor of 100. For a car engine connecting rod in > an airplane, you are not only (at least) doubling the load (torque) you= =20 > are > also doubling the RPM, so the connecting rod will have a MTBF 200 times > shorter in the airplane than in the car. >=20 > The rotary has very few moving parts subject to fatigue failure > (unlike piston engines.) >=20 > Bill Dube' Bill, I agree. This method is neither scientific, professional, objective= =20 or even sophisticated. First year medical students would do a better job of= =20 seeing fallacy (in the research sense) and applying statistical methods. Al is right that it is important to examine these issues and his system ca= n=20 help clarify which issues are more important. But I sure wouldn't pay $150= =20 to go to any seminars. The point system he uses has no reference validation= ,=20 no statistical power analysis, and therefore very little meaning. While he is right about the CAS being an issue, he seems very uninformed o= n=20 other issues yet comes across as someone who feels that he is well informed= .=20 He even went so far as to presume to know the way Tracy thinks and=20 approaches problems. Anyway, don't put too much faith in his professional "risk analysis." He= =20 may very well have a great deal to share, but his system is as armature as= =20 my rotary installation. --=20 Dave Leonard Turbo Rotary RV-6 N4VY http://members.aol.com/_ht_a/rotaryroster/index.html http://members.aol.com/vp4skydoc/index.html ------=_Part_9346_21084043.1117860125033 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline

On 6/3/05, B= ill Dube <bdube@al.noaa.gov= > wrote:

>http://www.maddyhome.com/ca= nardpages/pages/alwick/risk.html

        This is an inte= resting read, but a flawed analysis.

     &= nbsp;  It looks like a mathematician's approach, rather than anengineer's approach.

       &nb= sp;He compares failure rates for auto engine components operating in
an automobile with aircraft components operating in an aircraft. He the= n
assumes that the auto component will have the same mean time betweenfailures when installed on an airplane.

    &n= bsp;   The speed and load profile for a car component and an= airplane
component are completely different.

    &nbs= p;   This would explain how he "doesn't get it" ab= out the inherent MTBF
advantages of a rotary engine. It is quite likely = that he doesn't
understand the drastic effect fatigue failure has on the= MTBF as you
increase the continuous load.

     &nbs= p;  As a rule of thumb, if you double the reversing load, you dec= rease
the the cycle life by a factor of 100. For a car engine connecting= rod in
an airplane, you are not only (at least) doubling the load (torq= ue) you are
also doubling the RPM, so the connecting rod will have a MTBF 200 times=
shorter in the airplane than in the car.

    = ;    The rotary has very few moving parts subject to fa= tigue failure
(unlike piston engines.)

        Bill Dube'
 
Bill, I agree.  This method is neither scientific, professional, = objective or even sophisticated.  First year medical students would do= a better job of seeing fallacy (in the research sense) and applying statis= tical methods.
 
Al is right that it is important to examine these issues and his syste= m can help clarify which issues are more important.  But I sure wouldn= 't pay $150 to go to any seminars.  The point system he uses has no re= ference validation, no statistical power analysis, and therefore very littl= e meaning.
 
While he is right about the CAS being an issue, he seems very uninform= ed on other issues yet comes across as someone who feels that he is well in= formed.  He even went so far as to presume to know the way Tracy think= s and approaches problems.
 
Anyway, don't put too much faith in his professional "risk analys= is."  He may very well have a great deal to share, but his system= is as armature as my rotary installation.

--
Dave Leonard
Tu= rbo Rotary RV-6 N4VY
http:/= /members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/vp4skydoc/index.h= tml
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