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Bill Strahan

Joined: 20 Aug 2008
Posts: 145

Posted: Wed Jan 19, 2011 11:12 am Post subject: Wheel shimmy - solutions?

I've reached the point that the thing bugging me most on 7RW is the wheel shimmy after landing.  I've been putting it off while addressing other things, but it's now at the top of the list.



So, can I get some feedback from people who have solved theirs and exactly how they did it?  I've read about wood stiffeners on the landing gear, and replacing the tires with higher-priced and quality tires.



I'd like to hear all the solutions before I decide what to do next.



Bill

lbmathias(at)verizon.net
Guest

Posted: Wed Jan 19, 2011 1:25 pm Post subject: Wheel shimmy - solutions?

Bill,



        I tried lots of things and some made it a little better; however, I 

think the combination of 3 things created the greatest improvement.   I 

noticed a little shimmy on a flight about two weeks ago but it was the first 

time in over 6 months I have felt it.



The 3 items are:

1)  bought 3 new high-end quality 6-ply tires

2)  balanced the wheels with the new tires

3)  run the pressure at 28 psi



The wooden stiffeners didn't help me at all.



Good luck, Linda



---

n5pb(at)AOL.COM
Guest

Posted: Wed Jan 19, 2011 2:47 pm Post subject: Wheel shimmy - solutions?

Bill,

    

   Like Linda Ive tried several things. if you remember my blog from last year, I put new tires on, new brakes pads, new wheels, balanced the tires, checked to make sure i had no looseness in the nose wheel; and although these things helped me, I still have it.   My only thought now is to check the alignment of the mains.

    

   Bear

 

 

   

 

 

   --

n45bm(at)yahoo.com
Guest

Posted: Wed Jan 19, 2011 4:56 pm Post subject: Wheel shimmy - solutions?

Has anybody taken a look at the RV-6A nose gear? If I remember right, there is one, maybe two curved washers that make the wheel a little hard to turn by hand, but not when mounted on the plane. I believe that Vans' had a similar shimmy problem, but once they re-designed the swivel with the resistance washers, the shimmy problems went away.

I think my RV-6A hangar mate has an extra nose gear at the hangar. If I can find it, I'll study it and see what can be done to the Lightning nose gear to help solve that problem. Or then again, maybe the whole thing needs to be re-designed. It's too nice a plane to be having those issues.

Bernardo Melendez, Kit #110



--- On Wed, 1/19/11, n5pb(at)AOL.COM <n5pb(at)AOL.COM> wrote:

[quote]

From: n5pb(at)AOL.COM  <n5pb(at)AOL.COM>

Subject: Re: Wheel shimmy - solutions?

To: lightning-list(at)matronics.com

Date: Wednesday, January 19, 2011, 4:44 PM



 Bill,

    

   Like Linda Ive tried several things. if you remember my blog from last year, I put new tires on, new brakes pads, new wheels, balanced the tires, checked to make sure i had no looseness in the nose wheel; and although these things helped me, I still have it.   My only thought now is to check the alignment of the mains.

    

   Bear

 

 

   

 

 

   --

Kayberg(at)AOL.COM
Guest

Posted: Wed Jan 19, 2011 5:44 pm Post subject: Wheel shimmy - solutions?

In a message dated 1/19/2011 7:57:20 P.M. Eastern Standard Time,  n45bm(at)yahoo.com writes:

  	  Quote: 	
		                      Has anybody taken a look at the RV-6A nose gear? If I          remember right, there is one, maybe two curved washers that make the          wheel a little hard to turn by hand, but not when mounted on the plane.          I believe that Vans' had a similar shimmy problem, but once they          re-designed the swivel with the resistance washers, the shimmy problems          went away.

I think my RV-6A hangar mate has an extra nose gear at the          hangar. If I can find it, I'll study it and see what can be done to the          Lightning nose gear to help solve that problem. Or then again, maybe the          whole thing needs to be re-designed. It's too nice a plane to be having          those issues.

Bernardo Melendez, Kit    #110



	


 

 Bernardo,

  

 Dont bother.  The shimmy has never come from the nose  gear.   I have an RV-6A and am building a Witman Buttercup with the RV  trigear.   They are not remotely the same nose gear.

  

 And the design of the Lightning nose gear is superior to Vans in many  ways.  No redesign needed.   Lightning nose gear doesn't tuck  under and flip the plane like the Vans.

  

 Doug Koenigsberg

  [quote][b]

malannx(at)bigpond.com
Guest

Posted: Thu Jan 20, 2011 2:08 am Post subject: Wheel shimmy - solutions?

You might like to email Dennis Borchardt (the Australian Lightning Dealer). 

None of his builds have had a shimmy problem, likewise his builders if they 

followed his advice. It's an alignment issue. Wooden broom sticks are for 

witches and rv builders.

As for nose wheel shimmy check out the following:

http://www.periheliondesign.com/downloads/nosewheelshimmy.pdf



Malcolm Ferguson

WBrowns

Joined: 02 Apr 2008
Posts: 4
Location: Fishers, IN

Posted: Thu Jan 20, 2011 9:15 am Post subject: Re: Wheel shimmy - solutions?

Bill,



When I first built my Lightening I flew the plane for maybe 60 hours before putting on the wheel pants.  During that initial 60 hours I never had any shimmy.  Almost the first time I taxied the plane after the wheel pants were installed I felt the a shimmy.  I was really surprised.  Since then I have installed new 6 ply tires which were balanced and the brakes have been redone.  Better, but still more shimmy that I would like.



Thinking back to the initial 60 hours I got to wondering why I started feeling the shimmy after the wheels pants were installed.  Got to wondering if they were "magnifying" some harmonics that occurred from from the gear leg.  So I got to looking at the way the wheel pants are mounted.  The inside mounts are fixed but the outside mount "floats" inside the axle.  I'll admit that "floats" may be a little strong but it is certainly not tight.  I went to the Farm and Fleet Aviation department (LOL) and got some 4/5 inch long expansion springs and some large washers.  Removed the outside wheel pant bracket and installed a washer, a spring, and another washer at the other end.  Pushed the bracket back in place and re-installed the cotter pin to hold everything in place.  Now I have a "stiff" mounting point which seems to have helped reduce shimmy - not perfect but better.



I think it helped reduce the shimmy.  It is a simple fix if you want to give it a try.



Bill Browns

Clive J

Joined: 03 Nov 2007
Posts: 340
Location: UK

Posted: Thu Jan 20, 2011 11:25 am Post subject: Wheel shimmy - solutions?

I'm sure it has been mentioned before however, I saw the 'balancing' of

a wheel pant (spat) being done with lead shot set in epoxy.

This was to make the pant the same mass about the axle (I suppose) and

hence stop it from setting up a shimmy.



Was that a Lightning thing or somewhere else (Vans?).



Regards, Clive



--

N1BZRich(at)AOL.COM
Guest

Posted: Fri Jan 21, 2011 10:35 am Post subject: Wheel shimmy - solutions?

Hi Bill,

     Your question on what others have done to  solve wheel shimmy really points out two areas of improvement that I  think we need for the Lightning community.  Obviously the first is the  wheel shimmy itself, and I'll mention a few things below on that, but the second  issue is one that I think would greatly benefit the entire Lightning  community when seeking info on any issue or concern.  And that would be  some sort of a searchable index for the past Lightning newsletters.  If you  had that capability available to you now, all you would have had to do would be  to type in wheel shimmy and all past references to wheel shimmy that had ever  been published in our newsletter would help you research what the possible  causes are and what others have done to work the issue.  And there have  been lots written about wheel shimmy in numerous past issues.  Yes, we do  have an index, but not being searchable, you can spend a lot of time looking  over the entire index to find all the issues that have mentioned it.  So,  here is yet another request for help for the newsletter.  Surely someone  out there has the computer programing knowledge to develop a searchable index  for our newsletter.  I'm sure the Lightning factory and the new Newsletter  editor, John Jenkins, would be happy to have that capability and it would  benefit the entire Lightning community.  

     OK, now to say a few things about wheel shimmy  based on my memory of things I have done and things I remember putting in past  newsletters that other Lighting builders and flyers have sent in.  To  start, we are only talking about main gear wheel shimmy.  The Lightning  does not have any issues with nose wheel shimmy.  If there has been one or  two instances of a nose wheel shimmy, it is a rare occurrence based on that  particular airplane's specific problem.  But main wheel shimmy has been  noticed by a lot of the Lightnings out there, but the shimmy is not  limited to Lightnings.  It has also been seen on RVs and any airplane  that has the round rod gear legs, and the tapered gear legs seem to  be worse than the non tapered gear legs.  And speaking of  gear legs, another variable is the toe in or toe out setting of the gear axle  set up alignment.  Malcolm mentioned this and I feel certain that it  is one of the biggest factors in not having shimmy -  when setting up your  alignment, set it straight - zero toe in or out.  I am pretty sure that is  now how the factory guys set the gear legs.  

     Another thing to note is that the shimmy only  occurs if you routinely fly off of paved runways.  There is no wheel  shimmy on grass or dirt runways that I have heard of and I have never  experienced shimmy when I have landed on grass.  So one of the factors is  the runway surface.  I even noticed a difference when landing on black top  verses a paved runway.  The black top asphalt runway would always tend to  be worse for shimmy, at least that is my experience.   

     Tire pressure is another big thing.  After  extensive experimenting - 28 psi seems to be the best that I have found.   For all weights - airplane at gross, or airplane very light when landing - the  28 psi is the best for me.  

     The stiffer side wall tires also seem to help, so  use the 6 ply tires.  And wheel balancing helps.  It is sometimes hard  to balance the small aircraft wheels, but we have found two solutions.  The  go kart racking industry has wheel balancing equipment that works great for  aircraft wheels and tires.  That is what I use.  Another possibility  is taking your wheels and tires to a cycle shop.  Some of them have the  ability to balance them.  Linda used that approach.  

     As to wheel pant balancing, Dick Clevenger had an  article on that some time ago.  The idea here is that if the gear leg has  even a minor shimmy, then it will get worse if you add weight to the front  or rear of the axle.  Since most wheel pants are heavier in the aft part,  adding weight to the nose of the pant to balance the overall pant as it will be  installed, will help that issue.  Bill Browns message about using an  expansion spring to stiffen up the outside wheel pant bracket certainly sounds  like a great trick.  Bill, how about some photos and short write up for a  future newsletter.  I'm sure JJ would appreciate that for the  newsletter.  

     So to kind of sum it up, wheel or gear leg shimmy  seems to have many factors - Type of gear leg, gear leg/axle alignment,  tire pressure, tire type, airplane weight, runway surface, wheel pants, and most  probably, black magic.  

     Discussions on all of these things have been in  past newsletters, so someone, please come up with a way for us to search the  Lightning past issues for this type of info.  Of course, this list is  another great source of info.  Here is where you communicate with the folks  flying, experiencing, and solving the issues that we face.  Keep up the  great work.

 Blue Skies,

 Buz



  

  In a message dated 1/19/2011 2:17:07 P.M. Eastern Standard Time,  bill(at)gdsx.com writes:

  	  Quote: 	
		  -->    Lightning-List message posted by: "Bill Strahan"    <bill(at)gdsx.com>



I've reached the point that the thing bugging me    most on 7RW is the wheel shimmy after landing.  I've been putting it off    while addressing other things, but it's now at the top of the list.



So,    can I get some feedback from people who have solved theirs and exactly how    they did it?  I've read about wood stiffeners on the landing gear, and    replacing the tires with higher-priced and quality tires.



I'd like to    hear all the solutions before I decide what to do    next.



Bill





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=327595#327595===============================================

_-=    Use the  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


  [quote][b]

Bill Strahan

Joined: 20 Aug 2008
Posts: 145

Posted: Sat Jan 22, 2011 11:36 am Post subject: Re: Wheel shimmy - solutions?

Buz:



It's not a perfect solution, but bird in hand...



Anyway, try this:



Go to google.com and do a search that looks like this.



shimmy site:flylightning.net



You can replace the "flylightning.net" with any site that is hosting the newsletters.



You'll get a list of pages, almost all of which will be PDF files from the newsletters, that have the word "shimmy" in them.



You can hold down the shift key while clicking on the "quick view" link for the search results and it will open the PDF.  You may then have to put the search term in the PDF viewer as well, but this will at least take you to newsletters with the words you're looking for.



Trying "tire pressure site:flylightning.net" brought up a list of newsletters that talk about tire pressure.  You get the idea.



Again, not perfect, but it's pretty useful.



Now, back to shimmy.  I had already searched all the newsletters and I had also searched the Matronics list before I made my post.  The info is all over the map, and most of it is a) stiffen gear legs, b) 6 ply tires, c) set toe in, or out, or neutral, and d) balance the wheel/tire assembly.



I had already balanced my tires using a motorcycle wheel balancer.  It could tell a difference in how smooth it rolled when it wasn't shimmying, but it didn't help the shimmy.  So my real intention was to find out what was really working...I guess the best thing would be to take a poll.



Poll one would be for people who never had shimmy.  What is their setup, notably the tires and the toe in/out?



Poll two would be to find out what you did to fix shimmy if you had it.  What finally worked.



Since I've balanced my tires I'm leaning towards getting 6-ply tires and balancing again and installing.  It's the least work and least modification to the airframe.  If that doesn't do it, I think I'll make some wooden stiffening pieces to glue to the front and back of the gear.



The goal would be to get as much bending moment away from the center of the rod to raise the stiffness and perhaps get the resonant frequency above what is generated at the speed I see on the ground.



I had also mentioned to Nick that it might be worthwhile to find someone who could machine some bar stock into a landing gear.  Take a piece of aluminum the length of the current gear leg, as thick as the current gear, but about twice as wide.  Machine the ends into the rod shape needed to fit in the spar box and in the axle weldment.  Then machine the rest of the bar into a teardrop shape.



Drill the teardrop part for the brake line, and now you don't need any type of landing gear leg fairing.  The teardrop shape would start just outside the fuselage and would end just before the axle weldment, so simple fairings like I already have to fair that shape into the fuse and the wheelpants would be all you'd need.



The leg would have almost the same flexibiltiy in landing, but would be much stiffer fore and aft due to the added material further away from the neutral line.



I have no idea the cost of that process, perhaps Grove would give an estimate.  But If the additional cost wasn't more than about $500 I think it would be slam-dunk considering you would save the cost and installation time of the gear leg fairings.



And I'd be happy to beta test them for free!



I will document my progress in addressing this issue for 7RW.

Bill Strahan

Joined: 20 Aug 2008
Posts: 145

Posted: Sat Jan 22, 2011 11:50 am Post subject: Re: Wheel shimmy - solutions?

Okay, another quick question, hopefully someone is reading to the bottom of this thread.



If I order Aero Classic 5.00 X 5 tires do I need to get matching tubes or can I reuse my old tubes?

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Sun Jan 23, 2011 1:48 am Post subject: Re: Wheel shimmy - solutions?

Hi Bill,



I'd have to agree, there are proponents of just about every combination.



I have about 2 inches of toe out, measured as per build manual, standard tires, 28lb pressure and occasionally get a brief shimmy on roll out slowing through around 28 kt, a quick tap on the brakes stops it.  It has never been a problem.  I'm just in the process of fitting spats so that may be interesting in the light of earlier comments.



My question to the group would be: does anyone with toe out set have significant shimmy problems?

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

n45bm(at)yahoo.com
Guest

Posted: Sun Jan 23, 2011 7:27 am Post subject: Wheel shimmy - solutions?

Hi Selwyn,

Most people would consider toe IN, rather than toe out, if any, to be beneficial. Not there yet on my project, so I'm interested in following this thread and see what results others are getting.

Bernardo Melendez, Kit #`110, Corby Starlet n45bm



--- On Sun, 1/23/11, selwyn <selwyn(at)ellisworks.com.au> wrote:

[quote]

From: selwyn <selwyn(at)ellisworks.com.au>

Subject: Re: Wheel shimmy - solutions?

To: lightning-list(at)matronics.com

Date: Sunday, January 23, 2011, 3:48 AM



--> Lightning-List message posted by: "selwyn" <[url=/mc/compose?to=selwyn(at)ellisworks.com.au]selwyn(at)ellisworks.com.au[/url]>



Hi  Bill,



I'd have to agree, there are proponents of just about every combination.



I have about 2 inches of toe out, measured as per build manual, standard tires, 28lb pressure and occasionally get a brief shimmy on roll out slowing through around 28 kt, a quick tap on the brakes stops it.  It has never been a problem.  I'm just in the process of fitting spats so that may be interesting in the light of earlier comments.



My question to the group would be: does anyone with toe out set have significant shimmy problems?



--------

Cheers,  Selwyn

Kit 66





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=327981#327981



http://www.matronics                     &nbs;-->  [quote][b]

voroninmax(at)gmail.com
Guest

Posted: Sun Jan 23, 2011 7:55 am Post subject: Wheel shimmy - solutions?

1 degree toe out is the standard these days.

 I would either do that, or set them at 0. 

Max 

 	  Quote: 	
		  On Jan 23, 2011 10:29 AM, "Bernard Melendez, Jr." <n45bm(at)yahoo.com (n45bm(at)yahoo.com)> wrote:



 Hi Selwyn,

Most people would consider toe IN, rather than toe out, if any, to be beneficial. Not there yet on my project, so I'm interested in following this thread and see what results others are getting.

Bernardo Melendez, Kit #`110, Corby Starlet n45bm

 

--- On Sun, 1/23/11, selwyn <selwyn(at)ellisworks.com.au (selwyn(at)ellisworks.com.au)> wrote:

 	  Quote: 	
		   

From: selwyn <selwyn(at)ellisworks.com.au (selwyn(at)ellisworks.com.au)>

Subject: Re: Wheel shimmy - solutions?

To: lightning-list(at)matronics.com (lightning-list(at)matronics.com)

 Date: Sunday, January 23, 2011, 3:48 AM

 	  Quote: 	
		   --> Lightning-List message posted by: "selwyn" <selwyn(at)ellisworks.com.au (selwyn(at)ellisworks.com.au)>

 >
	


 	  Quote: 	
		   Hi Bill,



 I'd hav...http://www.matronics                     &nbs;--> 

 
	


	


	
  [quote][b]

n45bm(at)yahoo.com
Guest

Posted: Sun Jan 23, 2011 9:38 am Post subject: Wheel shimmy - solutions?

Okee dokee. 0 degrees sound ok to me, but I'm still not convinced. Besides, doesn't the toe out increase as the landing gear is splayed out, when the plane is loaded, and especially at landing? I've always heard that putting 1 or 2 degrees toe IN makes an aircraft track more true, or straight. Food for thought.

Bernardo



--- On Sun, 1/23/11, Maxim Voronin <voroninmax(at)gmail.com> wrote:

 	  Quote: 	
		  

From: Maxim Voronin <voroninmax(at)gmail.com>

Subject: Re: Re: Wheel shimmy - solutions?

To: lightning-list(at)matronics.com

Date: Sunday, January 23, 2011, 9:53 AM

1 degree toe out is the standard these days.

 I would either do that, or set them at 0. 

Max 

 	  Quote: 	
		  On Jan 23, 2011 10:29 AM, "Bernard Melendez, Jr." <[url=/mc/compose?to=n45bm(at)yahoo.com]n45bm(at)yahoo.com[/url]> wrote:



 Hi Selwyn,

Most people would consider toe IN, rather than toe out, if any, to be beneficial. Not there yet on my project, so I'm interested in following this thread and see what results others are getting.

Bernardo Melendez, Kit #`110, Corby Starlet n45bm

 

--- On Sun, 1/23/11, selwyn <[url=/mc/compose?to=selwyn(at)ellisworks.com.au]selwyn(at)ellisworks.com.au[/url]> wrote:

 	  Quote: 	
		   

From: selwyn <[url=/mc/compose?to=selwyn(at)ellisworks.com.au]selwyn(at)ellisworks.com.au[/url]>

Subject: Re: Wheel shimmy - solutions?

To: [url=/mc/compose?to=lightning-list(at)matronics.com]lightning-list(at)matronics.com[/url]

 Date: Sunday, January 23, 2011, 3:48 AM

 	  Quote: 	
		   --> Lightning-List message posted by: "selwyn" <[url=/mc/compose?to=selwyn(at)ellisworks.com.au]selwyn(at)ellisworks.com.au[/url]>

 >
	


 	  Quote: 	
		   Hi Bill,



 I'd hav...http://www.matronics                     &nbs;--> 

 
	


	


http://www.matronics.comofollow" target="_blank"

el="nofollow" target="_blank" href="http://www.matronics.com/contribu=== 	


	
 [quote][b]

N1BZRich(at)AOL.COM
Guest

Posted: Sun Jan 23, 2011 7:26 pm Post subject: Wheel shimmy - solutions?

Hey Bill,

     Right on, a bird in hand.  I was not aware of  that google feature, but as you said it does allow a type of search  feature.  Certainly better than nothing.  I'll suggest the new  newsletter editor, John Jenkins, put a note about it in an upcoming issue.   

     After you switch to the 6 ply tires and balance  them again, I think you will notice a big improvement.  If you do decide to  try the wood stiffeners, I might suggest buying an ax handle at Lowes or Home  Depot.  With some work on a band saw, then a table saw, and then  a router, you can come up with some parts that fit pretty well.  However,  before you go to all that work, you might want to try an aluminum angle - again  from Lowes or Home Depot.  I think what I used was about 1/2 inch on each  side of the angle and the length was cut to fit the gear leg.  Just be sure  the thickness of the angle is enough to provide some stiffness to the gear  legs.  I held them in place on the gear leg with two or three hose  clamps.  Done carefully, it will still fit under the fiberglass gear leg  fairings.  

 Buz

  

  

  

  

  In a message dated 1/22/2011 2:39:59 P.M. Eastern Standard Time,  bill(at)gdsx.com writes:

  	  Quote: 	
		  -->    Lightning-List message posted by: "Bill Strahan"    <bill(at)gdsx.com>



Buz:



It's not a perfect solution, but bird    in hand...



Anyway, try this:



Go to google.com and do a search    that looks like this.



shimmy site:flylightning.net



You can    replace the "flylightning.net" with any site that is hosting the    newsletters.



You'll get a list of pages, almost all of which will be    PDF files from the newsletters, that have the word "shimmy" in    them.



You can hold down the shift key while clicking on the "quick    view" link for the search results and it will open the PDF.  You may then    have to put the search term in the PDF viewer as well, but this will at least    take you to newsletters with the words you're looking for.



Trying "tire    pressure site:flylightning.net" brought up a list of newsletters that talk    about tire pressure.  You get the idea.



Again, not perfect, but    it's pretty useful.



Now, back to shimmy.  I had already searched    all the newsletters and I had also searched the Matronics list before I made    my post.  The info is all over the map, and most of it is a) stiffen gear    legs, b) 6 ply tires, c) set toe in, or out, or neutral, and d) balance the    wheel/tire assembly.



I had already balanced my tires using a motorcycle    wheel balancer.  It could tell a difference in how smooth it rolled when    it wasn't shimmying, but it didn't help the shimmy.  So my real intention    was to find out what was really working...I guess the best thing would be to    take a poll.



Poll one would be for people who never had shimmy.     What is their setup, notably the tires and the toe in/out?



Poll two    would be to find out what you did to fix shimmy if you had it.  What    finally worked.



Since I've balanced my tires I'm leaning towards    getting 6-ply tires and balancing again and installing.  It's the least    work and least modification to the airframe.  If that doesn't do it, I    think I'll make some wooden stiffening pieces to glue to the front and back of    the gear.



The goal would be to get as much bending moment away from the    center of the rod to raise the stiffness and perhaps get the resonant    frequency above what is generated at the speed I see on the ground.



I    had also mentioned to Nick that it might be worthwhile to find someone who    could machine some bar stock into a landing gear.  Take a piece of    aluminum the length of the current gear leg, as thick as the current gear, but    about twice as wide.  Machine the ends into the rod shape needed to fit    in the spar box and in the axle weldment.  Then machine the rest of the    bar into a teardrop shape.



Drill the teardrop part for the brake line,    and now you don't need any type of landing gear leg fairing.  The    teardrop shape would start just outside the fuselage and would end just before    the axle weldment, so simple fairings like I already have to fair that shape    into the fuse and the wheelpants would be all you'd need.



The leg would    have almost the same flexibiltiy in landing, but would be much stiffer fore    and aft due to the added material further away from the neutral line.



I    have no idea the cost of that process, perhaps Grove would give an    estimate.  But If the additional cost wasn't more than about $500 I think    it would be slam-dunk considering you would save the cost and installation    time of the gear leg fairings.



And I'd be happy to beta test them for    free!



I will document my progress in addressing this issue for    7RW.





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=327915#327915===============================================

_-=    Use the  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


  [quote][b]

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Sun Jan 23, 2011 10:58 pm Post subject: Re: Wheel shimmy - solutions?

Hi Guys,



I didn't want to get into a debate about the merits of one or the other, that's been done to death already.  I simply want to gather some data.



Is there anyone who has had significant shimmy problems with definite toe out set?

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

Clive J

Joined: 03 Nov 2007
Posts: 340
Location: UK

Posted: Sun Jan 23, 2011 11:35 pm Post subject: Wheel shimmy - solutions?

Hi Selwyn, I haven't had any shimmy on the Esqual since I reset it and

before nothing that would worry me it was more as I thought the tyres

would wear.

However, I did wrestle with alignment on the Esqual after my Jabiru,

which was very carefully set as required, wore it's tyres out in 150

hrs.

I reset the toe after 5 years (3 sets of tyres) with the plane fully

fuelled but empty.



Initially when rolling the Esqual over a painted hangar floor it

squeaked.

I rolled it over some newspaper and the twist showed it was toed out. I

believe the recommended set was 2 degrees in? I obviously got it wrong

or...

Staring at the thing it looks to me like the aircraft would toe out the

heavier it got. This from the angle of the legs (same as the Jab).

I'd set the toe before it had the wings + engine on and was loaded.

So I did it again full of fuel and with barrels or water in the seats to

simulate 1 pilot.

I set it as straight as I could get it, not in or out.

Now it doesn't squeak.



My thoughts on the shimmy. 

If it's out of toe when rolling surely the wheels will try and get

further apart (toed out), further together (toed in).

When the wheel rotates the rubber will flex and then release,  flex then

release, as it tries to steer the leg away from it opposite side leg (or

towards it-toed in). Ideal to set up a shimmy?



So my vote goes for parallel at middle weight which is why I did what I

did.



This at the risk of doing the subject to death a little more....sorry.



My question is? How are people repeatedly changing the tracking? Surely

you only get one shot and then you drill the holes, after they are

drilled how do you make adjustments?



Regards, Clive



--

n45bm(at)yahoo.com
Guest

Posted: Mon Jan 24, 2011 7:25 am Post subject: Wheel shimmy - solutions?

Hi Selwyn and Clive,

Not trying to throw gasoline on the fire, but from my experience in tail wheel aircraft, and from general consensus and information I've read on the subject, toe in is preferred. The reason is, is that toe out tends to make the plane wander from the center line. And from looking at the geometry of the Lightning landing gear, that is, trailing back (like the RV's), not straight out to the sides, it would appear to me, and it makes sense that as the aircraft is loaded (as in landing and on roll out), the little bit of toe in built onto the airframe when empty would cause the wheels to toe out, hopefully parallel to the airplane center line, or thereabouts.

The REAL question in my mind, is how much toe in to build in when the wingless (light weight) fuselage is in your shop so that the desired  results are achieved when the plane is finished and loaded. I'm planning to build in 1 or 2 degrees of toe IN on my plane when I get to that stage in my build.

On my Corby Starlet, the wheels are set at 1degree toe in, and it tracks straight. But the landing gear is vertical to the ground when the plane is in a landing, or take off position, with the tail wheel off the ground. That way, when my plane is loaded, the gear splays out, but the tracking does not change. Matter of fact, most tail wheel planes have a little toe in built in.

The geometry of the landing gear when the rubber hits the road is what is important. I believe that wheel shimmy is caused by the wheels trying to go in a different direction than the plane is going, and their propensity to grab, and then let go of the contact surface.

As stated, I'm not trying to confound the issue, and everyone is free to choose their poison, but I'm  pretty clear on how I will do mine.

Regards,

Bernardo Melendez, Kit # 110



--- On Mon, 1/24/11, James, Clive R <clive.james(at)uk.bp.com> wrote:

[quote]

From: James, Clive R <clive.james(at)uk.bp.com>

Subject: RE: Re: Wheel shimmy - solutions?

To: lightning-list(at)matronics.com

Date: Monday, January 24, 2011, 1:26 AM



--> Lightning-List message posted by: "James, Clive R" <[url=/mc/compose?to=clive.james(at)uk.bp.com]clive.james(at)uk.bp.com[/url]>



Hi Selwyn, I haven't had any shimmy on the Esqual since I reset it and

before nothing that would worry me it was more as I thought the tyres

would wear.

However, I did wrestle with alignment on the Esqual after my Jabiru,

which was very carefully set as required, wore  it's tyres out in 150

hrs.

I reset the toe after 5 years (3 sets of tyres) with the plane fully

fuelled but empty.



Initially when rolling the Esqual over a painted hangar floor it

squeaked.

I rolled it over some newspaper and the twist showed it was toed out. I

believe the recommended set was 2 degrees in? I obviously got it wrong

or...

Staring at the thing it looks to me like the aircraft would toe out the

heavier it got. This from the angle of the legs (same as the Jab).

I'd set the toe before it had the wings + engine on and was loaded.

So I did it again full of fuel and with barrels or water in the seats to

simulate 1 pilot.

I set it as straight as I could get it, not in or out.

Now it doesn't squeak.



My thoughts on the shimmy. 

If it's out of toe when rolling surely the wheels will try and get

further apart (toed out), further together (toed in).

When the wheel rotates the rubber will  flex and then release,  flex then

release, as it tries to steer the leg away from it opposite side leg (or

towards it-toed in). Ideal to set up a shimmy?



So my vote goes for parallel at middle weight which is why I did what I

did.



This at the risk of doing the subject to death a little more....sorry.



My question is? How are people repeatedly changing the tracking? Surely

you only get one shot and then you drill the holes, after they are

drilled how do you make adjustments?



Regards, Clive



--

selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Tue Jan 25, 2011 6:40 pm Post subject: Re: Wheel shimmy - solutions?

Hi Clive,



My solution for altering the alignment was to drill a bigger hole, I now have AN5 bolts through the legs.  If I was doing it again I would start with AN3 bolts, do some testing, adjust and redrill to AN4 if necessary.  If my first setting was OK I would still replace the AN3 bolts with AN4 early in the test program.

_________________
Cheers, Selwyn
Kit 66 VH-ELZ

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