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Lightning Gear shimmy

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info(at)flylightning.net
Guest

Posted: Tue Jun 01, 2010 1:44 pm Post subject: Lightning Gear shimmy

This subject has been brought up several times here on the list. Yes I would agree that the Lightning main gear design will shimmy if the proper conditions occur, however this is not just the Lightning but pretty much any aircraft with a round rod gear leg. Yes we have had demonstrators do it. Our solution that worked best was, proper tire inflation, and gear toe. This did minimize the shimmy if not completely eliminating it all together. Those that still had it found better tires worked, because of that we switched to a 6ply aero-classic tire with the name “LSA” on it. These are much improved over the 4ply supplied earlier. Recently we have replaced a couple of sets here on the standard gear and found much better results.   

It is possible that the nose wheel will shimmy but unlikely. The pivot point for the swivel is swept forward not on a vertical axis. This is to put forward and downward pressure on the fork assembly and not allow it to be in free caster trail position. This is the case on aircraft like the Cirrus, RV, ect, those aircraft do have the swivel axis vertical to the direction of travel, and the fork can go back and forth easily hence the need for tension to keep it straight after takeoff and keep it there for landing. If you notice on the lightning if you move it left or right the nose will lower slightly this can not happen with the aircraft moving forward during landing or takeoff. This will keep the fork from shimmying. True the block should be tensioned so no slop is evident, as the blocks can wear if there is movement causing other issues. This was the reason for the move to the oilite bushing in the nylon blocks. You can not put tension on the oilite bushing but they will keep the pivot point true and free from wear.  

   

Nick Otterback  

        [quote][b]

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Bill Strahan

Joined: 20 Aug 2008
Posts: 145

Posted: Tue Jun 01, 2010 4:08 pm Post subject: Re: Lightning Gear shimmy

So it sounds safe to assume that any shimmy is coming from the main gear.  If that is the case, do you think it is an imbalance in the tires matching the natural frequency of the main gear?  If so, then balancing the tires should prevent it.



Have you noticed it manifesting differently, if at all, on the new style gear?

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selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Wed Jun 02, 2010 3:55 am Post subject: Re: Lightning Gear shimmy

[quote="info(at)flylightning.net"] This was the reason for the move to the oilite bushing in the nylon blocks. You can not put tension on the oilite bushing but they will keep the pivot point true and free from wear.  

   

Nick Otterback  

         	  Quote: 	
		  [b] 	




Um, which move to oilite bushings was that? I noticed the bushes in Buz's photos and wondered where they came from.  Its not in the build manual, no service bulletins, can't find it anywhere on the Arion site, can't remember reading it in the newsletter.  What's the status of the change, is it part of ongoing development or a recommended retrofit?

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_________________
Cheers, Selwyn
Kit 66 VH-ELZ

info(at)flylightning.net
Guest

Posted: Wed Jun 02, 2010 6:25 am Post subject: Lightning Gear shimmy

About the beginning of the year I noticed a slight vibration in flight on

one of our planes. It felt as if it was coming from the nose I could feel it

in the pedals. After pushing down on the tail in the hanger, I noticed that

the nose block had a small amount of slop in it and the fork assembly could

be moved around a bit, this was not due to a suspicion of shimmy. I took the

fork off and thought about trying a large bushing. Because the steel leg and

the nylon are different materials I figured that the small trash or bur

might wear the plastic quickly and I think that is what happened. So I found

a large oilite bushing (oil bronze bushing) to put in the block. This did

take care of the slop and the vibration/buffeting in the nose wheel and pant

in flight. We than put in the news letter that if anyone noticed this in

their Lightning that this bushing could be retrofitted as a fix. True the

blocks should be tight so not to develop slop in the system but beyond that

the tension is not to combat a nose wheel shimmy the design itself is, the

the bushing to combat wear. We can release recommendations and things we

have noticed in the design thru the newsletter or web site to help make

things better. It would not be right for a kit manufacturer to issue an AD

or SB as we are not the manufacturer of the Aircraft the builder is and we

do not control their construction. So with that in mind we set it out in the

newsletter as a bring to everyone's attention type thing and have now added

the bushing to the kits and machined the blocks to match. 



As a side note it is important to recognize the difference in the esqual

nose leg and the lightning. The esqual nose leg does have a vertical pivot

point, it is not swept forward. So the nose leg on an esqual with out the

blocks tightened can shimmy. Some later esqual's had lightning parts because

we got none from them. 



Nick Otterback

--

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FamilyGage(at)aol.com
Guest

Posted: Wed Jun 02, 2010 8:04 am Post subject: Lightning Gear shimmy

Nick:

 Thanks so much for the information. I will try Buz's fix first, and if  there is no improvement; are the newer bushings available?  I think  that the nose gear is Ligntning.  I recently purchased two new main  gear from you. Everyone appreciates your factory support.

 My Best,

 Ray Gage

  

  In a message dated 6/2/2010 10:25:38 A.M. Eastern Daylight Time,  info(at)flylightning.net writes:

  	  Quote: 	
		  -->    Lightning-List message posted by: "fly lightning"    <info(at)flylightning.net>



About the beginning of the year I noticed    a slight vibration in flight on

one of our planes. It felt as if it was    coming from the nose I could feel it

in the pedals. After pushing down on    the tail in the hanger, I noticed that

the nose block had a small amount of    slop in it and the fork assembly could

be moved around a bit, this was not    due to a suspicion of shimmy. I took the

fork off and thought about trying    a large bushing. Because the steel leg and

the nylon are different    materials I figured that the small trash or bur

might wear the plastic    quickly and I think that is what happened. So I found

a large oilite    bushing (oil bronze bushing) to put in the block. This did

take care of the    slop and the vibration/buffeting in the nose wheel and pant

in flight. We    than put in the news letter that if anyone noticed this in

their Lightning    that this bushing could be retrofitted as a fix. True the

blocks should be    tight so not to develop slop in the system but beyond that

the tension is    not to combat a nose wheel shimmy the design itself is, the bushing to combat    wear. We can release recommendations and things we

have noticed in the    design thru the newsletter or web site to help make

things better. It would    not be right for a kit manufacturer to issue an AD

or SB as we are not the    manufacturer of the Aircraft the builder is and we

do not control their    construction. So with that in mind we set it out in the

newsletter as a    bring to everyone's attention type thing and have now added

the bushing to    the kits and machined the blocks to match. 



As a side note it is    important to recognize the difference in the esqual

nose leg and the    lightning. The esqual nose leg does have a vertical pivot

point, it is not    swept forward. So the nose leg on an esqual with out the

blocks tightened    can shimmy. Some later esqual's had lightning parts because

we got none    from them. 



Nick Otterback

-----Original    Message-----

From:    owner-lightning-list-server(at)matronics.com

[mailto:owner-lightning-list-server(at)matronics.com]    On Behalf Of selwyn

Sent: Wednesday, June 02, 2010 6:55 AM

To:    lightning-list(at)matronics.com

Subject: Re: Lightning Gear    shimmy



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



[quote="info(at)flylightning.net"]    This was the reason for the move to the

oilite bushing in the nylon blocks.    You can not put tension on the oilite

bushing but they will keep the pivot    point true and free from wear.  

   

Nick Otterback     

        

 	  Quote: 	
		   [b]


	




Um, which move to    oilite bushings was that? I noticed the bushes in Buz's

photos and wondered    where they came from.  Its not in the build manual, no

service    bulletins, can't find it anywhere on the Arion site, can't remember

reading    it in the newsletter.  What's the status of the change, is it part

of    ongoing development or a recommended    retrofit?



--------

Cheers,  Selwyn

Kit    66





Read this topic online    here:



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  [quote][b]

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N1BZRich(at)AOL.COM
Guest

Posted: Wed Jun 02, 2010 12:59 pm Post subject: Lightning Gear shimmy

Hi Selwyn,

     Check the December 2009 issue of the Lightning  Newsletter for info on the new bushings.

 Buz 

  

  In a message dated 6/2/2010 7:56:15 A.M. Eastern Daylight Time,  selwyn(at)ellisworks.com.au writes:

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



[quote="info(at)flylightning.net"]    This was the reason for the move to the oilite bushing in the nylon blocks.    You can not put tension on the oilite bushing but they will keep the pivot    point true and free from wear.  

   

Nick Otterback     

        

 	  Quote: 	
		   [b]


	




Um, which move to    oilite bushings was that? I noticed the bushes in Buz's photos and wondered    where they came from.  Its not in the build manual, no service bulletins,    can't find it anywhere on the Arion site, can't remember reading it in the    newsletter.  What's the status of the change, is it part of ongoing    development or a recommended retrofit?



--------

Cheers,     Selwyn

Kit 66





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=299712#299712===============================================

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



	


  [quote][b]

- The Matronics Lightning-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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