X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao08.cox.net ([68.230.241.31] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1036132 for flyrotary@lancaironline.net; Thu, 16 Mar 2006 10:48:38 -0500 Received-SPF: none receiver=logan.com; client-ip=68.230.241.31; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao08.cox.net (InterMail vM.6.01.05.02 201-2131-123-102-20050715) with ESMTP id <20060316154432.WKBC26964.fed1rmmtao08.cox.net@BigAl> for ; Thu, 16 Mar 2006 10:44:32 -0500 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Motor teardown results Date: Thu, 16 Mar 2006 07:48:02 -0800 Message-ID: <000001c64911$028c2b10$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C648CD.F468EB10" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C648CD.F468EB10 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Degree of Lubrication could certainly play a role, but I personally = doubt=20 that it is the root cause - could be wrong about that, of course. I = believe it may have to do with the amount of play in the rotor housing apex seal = slots. I suspect that if the seals were pressing against the rotor = housing=20 wall in the manner they were designed to - the rounded top tangential to = the surface of the housing - there is minimal drag and friction. As the = slots=20 wear the seals become able to "flop" from one side to the other of the=20 housing as its chamber undergoes the 4 cycles =20 Ed; =20 I'd agree that what's happening is a vibration of the seal in the groove (wobble, or combination wobble-bounce), but I don't think that is the = root cause. The spacing of the marks suggests a frequency of something more = like a "squeak", not related to the cycles of the engine. The driving force = for the vibration must be the friction on the housing wall. Even with a = small clearance to start, it will get larger.=20 =20 Based on the spacing of the marks, I estimate a squeak frequency = somewhere between 6000 and 10,000 hz at 6000 rpm. =20 Since others use similar lubrication with better results, that MAY not = be the problem; although there are a number of variables there. The seal material (density, rigidity, friction coefficient; etc, would be = critical. =20 This opinion may only be worth what it cost you. =20 Al ------=_NextPart_000_0001_01C648CD.F468EB10 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Degree of Lubrication could certainly play a role, but I personally doubt =

that it is the root cause - could be wrong about that, of course.  I = believe

it may have to do with the amount of play in the rotor housing apex seal =

slots.  I suspect that if the seals were pressing against the rotor housing =

wall in the manner they were designed to - the rounded top tangential to the =

surface of the housing - there is minimal drag and friction.  As the slots =

wear the seals become able to "flop" from one side to the other of = the

housing as its chamber undergoes the 4 cycles

 

Ed;

 <= /font>

I’d = agree that what’s happening is a vibration of the seal in the groove (wobble, = or combination wobble-bounce), but I don’t think that is the root cause.  = The spacing of the marks suggests a frequency of something more like a = “squeak”, not related to the cycles of the engine.  The driving force for the vibration must be the friction on the housing wall. Even with a small = clearance to start, it will get larger.

 <= /font>

Based on the = spacing of the marks, I estimate a squeak frequency somewhere between 6000 and = 10,000 hz at 6000 rpm.

 <= /font>

Since others = use similar lubrication with better results, that MAY not be the problem; = although there are a number of variables there.  The seal material (density, rigidity, friction coefficient; etc, would be = critical.

 <= /font>

This opinion = may only be worth what it cost you.

 <= /font>

Al

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