X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 25 Aug 2007 17:35:37 -0400 Message-ID: X-Original-Return-Path: Received: from bay0-omc1-s36.bay0.hotmail.com ([65.54.246.108] verified) by logan.com (CommuniGate Pro SMTP 5.1.11) with ESMTP id 2284237 for lml@lancaironline.net; Sat, 25 Aug 2007 12:14:38 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.54.246.108; envelope-from=joscales98@hotmail.com Received: from hotmail.com ([65.55.135.13]) by bay0-omc1-s36.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.2668); Sat, 25 Aug 2007 09:14:00 -0700 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Sat, 25 Aug 2007 09:14:00 -0700 X-Original-Message-ID: Received: from 75.81.226.134 by BAY130-DAV3.phx.gbl with DAV; Sat, 25 Aug 2007 16:13:56 +0000 X-Originating-IP: [75.81.226.134] X-Originating-Email: [joscales98@hotmail.com] X-Sender: joscales98@hotmail.com From: "Jim Scales" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: ES Strut issues - Columbia Legs X-Original-Date: Sat, 25 Aug 2007 11:14:02 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0052_01C7E709.0A91D5C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.50.0039.1900 Seal-Send-Time: Sat, 25 Aug 2007 11:14:02 -0500 X-OriginalArrivalTime: 25 Aug 2007 16:14:00.0324 (UTC) FILETIME=[F252C440:01C7E732] X-Original-Return-Path: joscales98@hotmail.com This is a multi-part message in MIME format. ------=_NextPart_000_0052_01C7E709.0A91D5C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks for the advice on the camera. I will consider that and, = whichever way I go, will share my findings with the community. Jim ----- Original Message -----=20 From: rtitsworth=20 To: lml@lancaironline.net=20 Sent: Saturday, August 25, 2007 9:07 AM Subject: [LML] Re: ES Strut issues - Columbia Legs Jim, etal =20 I'm presuming that you suspect that the nose gear shimmy might = (perhaps) be induced by the behavior of the main gear. I believe others = have hypothesized this before also. =20 I do know that the gear legs on my high-wing C172 can/do rapidly = oscillate for-aft much more than one would normally imagine during = landing/braking (sometimes as much as 4-6 inches, or more) and the gear = legs are solidly mounted to the fuselage. =20 A video of an ES main gear (during breaking/shimmy) would be very = interesting. Perhaps you might be able to just try a small/portable usb = PC/Laptop camera taped to the ES step (and wired to a laptop in the = cabin). They are pretty small and relatively in-expensive. Duct tape = and a long USB cable would probably do the trick. Recording audio from = inside the cabin and calling-out deceleration speeds/events would help = correlate the two. You could also re-aim it and video the front pant = from the step on subsequent landings. =20 Has anyone with relatively high ES hours/landings also closely checked = the main gear receptacles for signs of fatigue/fracture in the for/aft = direction? It seems/appears the design is very stiff/strong in that = orientation and thus I don't suspect much would happen to it - except to = transfer the energy to the spar bulkheads and fuselage. Ideally most of = it would get damped by the composite fuselage - but perhaps not. If the = energy/excitation were resonant with the nose pant's Fn it wouldn't take = much to get the nose pant/wheel going. Then, if the front strut's = damping where degraded in any way (heat, seals, etc), hold on. =20 FYI, I believe the Columbia main gear is quite different than an ES. = The Columbia gear mounts to the fuselage "behind" the wing, since the = Columbia wing is one continuous piece (tip-2-tip) and is mated to the = fuselage from the bottom (versus two ES wing halves mated into the = sides). I have never seen a Columbia gear without the leg fairings. I = also don't know if the Columbia brakes are the same/similar (I assume = so)? =20 Also note that the factory ES (407L) has an earlier/preliminary gear = leg design. It's gear sits much lower than all of ours. Tim, would = know if it's legs are made from a metal bar/plate (versus tapered tubes) = and/or all composite (like my Corvette suspension springs). =20 Rick =20 ------=_NextPart_000_0052_01C7E709.0A91D5C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks for the advice on the camera.  I will consider that = and,=20 whichever way I go, will share my findings with the community.
 
Jim
----- Original Message -----
From: rtitsworth
Sent: Saturday, August 25, 2007 = 9:07=20 AM
Subject: [LML] Re: ES Strut = issues -=20 Columbia Legs

Jim,=20 etal

 

I=92m = presuming that=20 you suspect that the nose gear shimmy might (perhaps) be induced by = the=20 behavior of the main gear.  I believe others have hypothesized = this=20 before also.

 

I do know = that the=20 gear legs on my high-wing C172 can/do rapidly oscillate for-aft much = more than=20 one would normally imagine during landing/braking (sometimes as much = as 4-6=20 inches, or more) and the gear legs are solidly mounted to the=20 fuselage.

 

A video of = an ES main=20 gear (during breaking/shimmy) would be very interesting.  Perhaps = you=20 might be able to just try a small/portable usb PC/Laptop camera taped = to the=20 ES step (and wired to a laptop in the cabin).  They are pretty = small and=20 relatively in-expensive.  Duct tape and a long USB cable would = probably=20 do the trick.  Recording audio from inside the cabin and = calling-out=20 deceleration speeds/events would help correlate the two.  You = could also=20 re-aim it and video the front pant from the step on subsequent=20 landings.

 

Has anyone = with=20 relatively high ES hours/landings also closely checked the main gear=20 receptacles for signs of fatigue/fracture in the for/aft = direction?  It=20 seems/appears the design is very stiff/strong in that orientation and = thus I=20 don=92t suspect much would happen to it =96 except to transfer the = energy to the=20 spar bulkheads and fuselage.  Ideally most of it would get damped = by the=20 composite fuselage =96 but perhaps not.  If the energy/excitation = were=20 resonant with the nose pant=92s Fn it wouldn=92t take much to get the = nose=20 pant/wheel going.  Then, if the front strut=92s damping where = degraded in=20 any way (heat, seals, etc), hold on.

 

FYI, I = believe the=20 Columbia main=20 gear is quite different than an ES.  The Columbia gear mounts to = the=20 fuselage =93behind=94 the wing, since the Columbia wing is one = continuous piece=20 (tip-2-tip) and is mated to the fuselage from the bottom (versus two = ES wing=20 halves mated into the sides).  I have never seen a Columbia gear = without the=20 leg fairings.  I also don=92t know if the Columbia brakes are the = same/similar (I=20 assume so)?

 

Also note = that the=20 factory ES (407L) has an earlier/preliminary gear leg design.  = It=92s gear=20 sits much lower than all of ours.  Tim, would know if it=92s legs = are made=20 from a metal bar/plate (versus tapered tubes) and/or all composite = (like my=20 Corvette suspension springs).

 

Rick

 

 
------=_NextPart_000_0052_01C7E709.0A91D5C0--