X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 06 Sep 2007 18:47:25 -0400 Message-ID: X-Original-Return-Path: Received: from bay0-omc2-s27.bay0.hotmail.com ([65.54.246.163] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2315727 for lml@lancaironline.net; Thu, 06 Sep 2007 14:44:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.54.246.163; envelope-from=joscales98@hotmail.com Received: from hotmail.com ([65.55.135.20]) by bay0-omc2-s27.bay0.hotmail.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 6 Sep 2007 11:43:41 -0700 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 6 Sep 2007 11:43:40 -0700 X-Original-Message-ID: Received: from 75.81.226.134 by BAY130-DAV10.phx.gbl with DAV; Thu, 06 Sep 2007 18:43:39 +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 List" Subject: ES shake (apparently not strut related) X-Original-Date: Thu, 6 Sep 2007 13:43:38 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0014_01C7F08B.EE1AE990" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.50.0039.1900 Seal-Send-Time: Thu, 6 Sep 2007 13:43:38 -0500 X-OriginalArrivalTime: 06 Sep 2007 18:43:40.0813 (UTC) FILETIME=[D811A3D0:01C7F0B5] X-Original-Return-Path: joscales98@hotmail.com This is a multi-part message in MIME format. ------=_NextPart_000_0014_01C7F08B.EE1AE990 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Well, I'm back. This time with some new information, though, so bear = with me. The last thread about my ES shake issues revolved around the = nose gear strut and its role in the problem. The latest tests do not = support that position. I have video taped the landing gear of my ES during slow speed taxi, = high speed taxi, light braking, heavy braking, normal take off and = normal landing. I taped the nose wheel, LH main wheel and RH main wheel = individually. I now have a pretty good idea of what the "shake" looks = like and where it is. Of course, this is not the same as knowing what = is causing it and how to fix it. =20 The nose wheel is rock solid with no shimmy, shake or shudder at any = speed. This surprised me. It also occurs to me that the "shake" that I = have felt through the years has not changed. That leads me to believe = that the nose strut has probably not been a part of the problem on my = airplane at all. The video shows the main gear wheel pants exhibiting a light shudder, = moderate shake or what appears to be a fairly violent shake at various = speeds, conditions and brake application. I did quite a number of tests and taped the following events (the left = main exhibited somewhat more severe shake than the right main, but the = events happened under the same conditions and speeds): -Slight but definitely noticeable shake at steady taxi speed of 12 = knots. One or two knots either side of that number and the taxi is = smooth. -High speed taxi tests were conducted by accelerating to 50-60 knots, = reducing power and braking as in a normal landing and rollout. In = every test the shake showed up at around 35 knots and went away at about = 30 knots when decelerating. The degree of the shake was directly = related to brake force. Harder braking, harder shake. Light braking, = light shake. No braking, very little or no shake. Shake lasts = somewhere in the 2-3 second range. It is felt in the seat somewhat but = is more notably felt in the stick as a rapid, short stroke, front to = rear movement.......think "rattle". The impression is also there that = the tail is jumping. Don't know if it is, but plan on taping the tail = during an event and see. -Interestingly, the video showed that the mains shake moderately for a = second or two during acceleration, somewhere around the 40-50 knot = range. I believe this has been present for quite some time and that I = usually dismissed it, when I noticed it, as runway related. The runway = at my home airport was just resurfaced so I am now convinced that this = shake is related to issues I am trying to address. If this were a car and exhibited these symptoms I would suspect any or = all of the following issues: -Out of round tire, flat spotted or faulty ply. -Severe out of balance tire/wheel assembly. -Warped or wavy brake disc. -Worn or defective suspension part. At the present time, the condition of the wheel/tire/brake assembly is: = brand new discs, no visual defects or deformity in the tires, balanced = on static fixture. I do realize that tire balance can be relative to speeds and that a = static balanced tire does not necessarily mean that the tire remains = balanced at all speeds and forces. The part of the puzzle that is most = difficult for me is the consistent speed relation to the shake. The = current tires are Goodyear Customs, as were the previous set.=20 Before that, I had McCreary. Before that was Michelin. I don't = remember what the original brand was that came with the kit. In all = instances the tires were statically balanced. In all instances, when = the shake occurred, it was at the about the same speeds. As I write this, though, I seem to = have the impression that when I installed new tires the shake would = diminish somewhat. The speeds would remain the same but the severity of = the shake seemed to be less. I don't really have any specific memories = to support this. The main gear has been aligned per factory specs. I checked the = alignment again during the recent annual inspection and found no = problem. I have run a variety of air pressures and can not really see any = difference in how the airplane acts. If there is an effect on the plane = it is certainly small. I currently run 60 in the mains and 45 in the = nose. The discs and wheels show about a .015" run out. This was the same = variance that I found with the old discs. Evidently the wheels are = slightly out of true. The wheels and discs are the Cleveland numbers = that were with the original kit. However, it would seem that if the = disc were the problem that the shake would occur at all speeds when = brakes were applied. I am trying to draw conclusions from this exercise and am having trouble = reaching the definitive answer. It would seem on the surface to be a = balance issue. That is, until I throw in the braking and the fact that = every set of tires has been balanced and every set has exhibited the = shaking to various degrees at about the same speeds and under the same = conditions as every other set. This makes me think it might be an = airframe related problem with harmonics and interaction of components, = etc. I wouldn't even begin to know how to chase that down. If I were not so closely connected to the issue and were analyzing = someone else's problem I would probably point to the tire assembly = balance as being the problem and suggest that the tires and tubes be = replaced and the assembly dynamically balanced rather than statically = balanced. I would suggest the wheels be replaced or rebuilt to true so = the run out as a possible contributor would be eliminated. I would = assume that when the tire has a tendency to shake due to imbalance or = tire deformity the application of brakes magnifies the problem and gets = the violent shake going. The person whose problem I was trying to solve = would probably point out that I was being too simplistic and that the = problem was much more complex than that. Just thinking out = loud............ I have been in touch with Lancair and they have been very interested in = helping solve the problem. They have asked some very specific questions = and offered some suggestions. I expect to continue that communication = as well as posting this on the LML site for any additional input. I = would appreciate any input. I apologize for the length of this post but = there was just too much information. If I can figure out how to upload the video I will do that, too. =20 Thanks in advance for your comments, questions, = solutions................. Jim Scales ------=_NextPart_000_0014_01C7F08B.EE1AE990 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Well, I'm back.  This time with some new information, though, = so bear=20 with me.  The last thread about my ES shake issues revolved around = the nose=20 gear strut and its role in the problem.  The latest tests do not = support=20 that position.
 
I have video taped the landing gear of my ES during slow speed = taxi, high=20 speed taxi, light braking, heavy braking, normal take off and normal=20 landing.  I taped the nose wheel, LH main wheel and RH main wheel=20 individually.  I now have a pretty good idea of what the "shake" = looks like=20 and where it is.  Of course, this is not the same as knowing what = is=20 causing it and how to fix it. 
 
The nose wheel is rock solid with no shimmy, shake or shudder at = any=20 speed.  This surprised me.  It also occurs to me that the = "shake"=20 that I have felt through the years has not changed.  That leads = me to=20 believe that the nose strut has probably not been a part of the problem = on my=20 airplane at all.
 
The video shows the main gear wheel pants exhibiting a light = shudder,=20 moderate shake or what appears to be a fairly violent shake at various = speeds,=20 conditions and brake application.
 
I did quite a number of tests and taped the following events = (the left=20 main exhibited somewhat more severe shake than the right main, but the = events=20 happened under the same conditions and speeds):
 
-Slight but definitely noticeable shake at steady taxi speed of 12=20 knots.  One or two knots either side of that number and the taxi is = smooth.
 
-High speed taxi tests were conducted by accelerating to 50-60 = knots,=20 reducing power and braking as in a normal landing and = rollout.   In=20 every test the shake showed up at around 35 knots and went away at about = 30=20 knots when decelerating.  The degree of the shake was directly = related to=20 brake force.  Harder braking, harder shake.  Light braking, = light=20 shake.  No braking, very little or no shake.  Shake lasts = somewhere in=20 the 2-3 second range.  It is felt in the seat somewhat but is more = notably=20 felt in the stick as a rapid, short stroke, front to rear = movement.......think=20 "rattle".  The impression is also there that the tail is = jumping. =20 Don't know if it is, but plan on taping the tail during an event and = see.
 
-Interestingly, the video showed that the mains shake moderately = for a=20 second or two during acceleration, somewhere around the 40-50 knot = range. =20 I believe this has been present for quite some time and that I usually = dismissed=20 it, when I noticed it, as runway related.  The runway at my home = airport=20 was just resurfaced so I am now convinced that this shake is related to = issues I=20 am trying to address.
 
If this were a car and exhibited these symptoms I would suspect any = or all=20 of the following issues:
-Out of round tire, flat spotted or faulty ply.
-Severe out of balance tire/wheel assembly.
-Warped or wavy brake disc.
-Worn or defective suspension part.
 
At the present time, the condition of the wheel/tire/brake assembly = is:  brand new discs, no visual defects or deformity in the tires, = balanced=20 on static fixture.
 
I do realize that tire balance can be relative to speeds and that a = static=20 balanced tire does not necessarily mean that the tire remains balanced = at all=20 speeds and forces.  The part of the puzzle that is most difficult = for me is=20 the consistent speed relation to the shake.  The current tires are = Goodyear=20 Customs, as were the previous set.
Before that, I had = McCreary.  Before=20 that was Michelin.  I don't remember what the original brand was = that came=20 with the kit. In all instances the tires were statically balanced.  = In all=20 instances, when the shake occurred,
it was at the about the same speeds.  As I write this, though, = I seem=20 to have the impression that when I installed new tires the shake would = diminish=20 somewhat.  The speeds would remain the same but the severity of the = shake=20 seemed to be less.  I don't really have any specific memories = to=20 support this.
 
The main gear has been aligned per factory specs.  I checked = the=20 alignment again during the recent annual inspection and found no = problem.
 
I have run a variety of air pressures and can not really see any = difference=20 in how the airplane acts.  If there is an effect on the plane it is = certainly small.  I currently run 60 in the mains and 45 in the = nose.
 
The discs and wheels show about a .015" run out.  This was the = same=20 variance that I found with the old discs.  Evidently the wheels are = slightly out of true.  The wheels and discs are the Cleveland = numbers that=20 were with the original kit.  However, it would  seem that = if the=20 disc were the problem that the shake would occur at all speeds when = brakes were=20 applied.
 
I am trying to draw conclusions from this exercise and am having = trouble=20 reaching the definitive answer.  It would seem on the surface to be = a=20 balance issue.  That is, until I throw in the braking and the fact = that=20 every set of tires has been balanced and every set has exhibited the = shaking to=20 various degrees at about the same speeds and under the same = conditions as=20 every other set.  This makes me think it might be an airframe = related=20 problem with harmonics and interaction of components, etc.  I = wouldn't even=20 begin to know how to chase that down.
 
If I were not so closely connected to the issue and were analyzing = someone=20 else's problem I would probably point to the tire assembly balance as = being the=20 problem and suggest that the tires and tubes be replaced and the = assembly=20 dynamically balanced rather than statically balanced.  I would = suggest the=20 wheels be replaced or rebuilt to true so the run out as a possible = contributor=20 would be eliminated.  I would assume that when the tire has a = tendency to=20 shake due to imbalance or tire deformity the application of brakes = magnifies the=20 problem and gets the violent shake going.  The person whose problem = I was=20 trying to solve would probably point out that I was being too simplistic = and=20 that the problem was much more complex than that.  Just thinking = out=20 loud............
 
I have been in touch with Lancair and they have been very = interested in=20 helping solve the problem.  They have asked some very specific = questions=20 and offered some suggestions.  I expect to continue that = communication as=20 well as posting this on the LML site for any additional input.  I = would=20 appreciate any input.  I apologize for the length of this post but = there=20 was just too much information.
 
If I can figure out how to upload the video I will do that, = too. =20
 
Thanks in advance for your comments, questions,=20 solutions.................
 
Jim Scales
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