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Landing gear shimmy
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Author Message

Bill Strahan

Joined: 20 Aug 2008
Posts: 145

Posted: Tue May 08, 2012 8:00 pm Post subject: Re: Landing gear shimmy

Yes!  Titanium for the win!



Okay, it just sounds cool.  I'd be interested.  To cover a few points first:

1) I know the wheels/tires are balanced.  I bought a balancer just for that purpose.  I'm satisfied they're spot on.



2)  I've tried everything from 22 to 38 PSI.  No detectable change.



3)  It's WORSE with wheelpants.  Much worse.



4)  I saw no difference with the heavier ply tires, so switched back.  The shape was different with the heavier ply and I didn't want to mess with any wheelpant mods to get them to fit.  Since they made no difference, I switched back.



5)  Braking during the onset of shimmy appears to shorten duration, but I don't know if it's a direct effect, or if it just causes a faster transition out of the resonant frequency.



I absolutely love flying 7RW...I just don't enjoy touch and goes or landings very much.



I have a 3000 mile trip planned for July, and I would sure like to get this off my list before I go.  I've been using the trip to get the last few things I want ironed out (like the ADS-B weather finally!) and this is the last one.  Trying to plug away at it.



Tomorrow I'll add 6 layers of fiberglass to the stiffeners.  If that doesn't do it then the stiffeners are not the solution.  And I'll await Nick's info on titanium.



I may fly up and see if Nick will try a few high speed runs to see what he thinks.

rick(at)trickair.com
Guest

Posted: Wed May 09, 2012 5:47 am Post subject: Landing gear shimmy

I had the gear leg shimmy on my Lightning 830LW.  I took pieces of maple2" x

3"  and shaped them to fit the gear leg . I routed out the front edge to fit

the gear leg then made the piece of wood the same width as the gear leg and

then tapered the trailing edge.  I bonded the wood on to the gear leg with

Plexus MA310. It is a methacrylate adhesive.  I then laminated over the gear

leg and the wood with 3 layers of 12 oz. carbon fiber and vinylester resin.

The results are so far so good. 

Rick Discher



--

craigsumner(at)comcast.ne
Guest

Posted: Wed May 09, 2012 5:46 pm Post subject: Landing gear shimmy

Outstanding video Bill!  Thanks for taking the time to mount a camera for

all to see.  I will share this with others and see what our NASA/DoD

engineers think could be the right fix.  I know the folks in Shelbyville

(who are outstanding folks) would like to see this issue resolved.

Best Regards,  

Craig Sumner

N155JM

Esqual 074



--

NowackLinden(at)gmx.de
Guest

Posted: Thu May 10, 2012 5:46 am Post subject: Landing gear shimmy

I think some time ago somebody mentioned that round gear legs are prone 

to shimmy.

IMHO the trouble results from the spring properties of the round gear 

legs and a certain toe in.

You can see on the video that the gear legs do a  fast fore and aft 

motion . If one looks at the gear geometry one sees that

a bending  aft will also mean a decrease in toe in ( or increase in toe 

out, whatever) This will momentarily increase the gear drag and result  

a circular motion of the wheel and the gear leg.

  The solution: make machined airfoil- shaped gear legs ( made from 

Aluminum, no expensive and difficult to machine Titan necessary!) that 

don`t bend fore and aft but still can do their bending outward for the 

necessary suspension.  They could  have a groove for the brake line on 

the inside, so we would`t even need leg fairings!

Just my 3 Euro-Cents!



Gerd  D-ELIY    No. 89





Am 10.05.2012 03:45, schrieb Craig Sumner:

[quote] 



 Outstanding video Bill!  Thanks for taking the time to mount a camera for

 all to see.  I will share this with others and see what our NASA/DoD

 engineers think could be the right fix.  I know the folks in Shelbyville

 (who are outstanding folks) would like to see this issue resolved.

 Best Regards,

 Craig Sumner

 N155JM

 Esqual 074



 --

nick(at)flylightning.net
Guest

Posted: Thu May 10, 2012 6:23 am Post subject: Landing gear shimmy

Gerd,



Its funny you mention the airfoil shape. I discussed it yesterday with our

machine shop and they are getting prices on both. 



Nick



--

elledien

Joined: 03 Feb 2010
Posts: 43

Posted: Thu May 10, 2012 6:26 am Post subject: Landing gear shimmy

Tha gear legs of Pioneer 200/300 are made exactly how described from Gerd.

More than one third of the leg, from the wheel axle, is "sliced" from both side. 

Probably the reason is the one anounced.

If I find a picture of this leg, I will provide to show one.

Regards

Luigi

Esqual I-9854

 

        Da: Gerd +  Uli Nowack <NowackLinden(at)gmx.de>

 A: lightning-list(at)matronics.com 

 Inviato: Giovedì 10 Maggio 2012 15:46

 Oggetto: Re: Lightning-List: Re: Landing gear shimmy

  

 

--> Lightning-List message posted by: Gerd + Uli Nowack <NowackLinden(at)gmx.de (NowackLinden(at)gmx.de)>



I think some time ago somebody mentioned that round gear legs are prone 

to shimmy.

IMHO the trouble results from the spring properties of the round gear 

legs and a certain toe in.

You can see on the video that the gear legs do a  fast fore and aft 

motion . If one looks at the gear geometry one sees that

a bending  aft will also mean a decrease in toe in ( or increase in toe 

out, whatever) This will momentarily  increase the gear drag and result  

a circular motion of the wheel and the gear leg.

  The solution: make machined airfoil- shaped gear legs ( made from 

Aluminum, no expensive and difficult to machine Titan necessary!) that 

don`t bend fore and aft but still can do their bending outward for the 

necessary suspension.  They could  have a groove for the brake line on 

the inside, so we would`t even need leg fairings!

Just my 3 Euro-Cents!



Gerd  D-ELIY    No. 89





Am 10.05.2012 03:45, schrieb Craig Sumner:

[quote] -->  Lightning-List message posted by: "Craig Sumner"<craigsumner(at)comcast.net (craigsumner(at)comcast.net)>



 Outstanding video Bill!  Thanks for taking the time to mount a camera for

 all to see.  I will share this with others and see what our NASA/DoD

  engineers think could be the right fix.  I know the folks in Shelbyville

 (who are outstanding folks) would like to see this issue resolved.

 Best Regards,

 Craig Sumner

 N155JM

 Esqual 074



 --

NowackLinden(at)gmx.de
Guest

Posted: Thu May 10, 2012 6:55 am Post subject: Landing gear shimmy

Nick,



If you ´ve got the price please tell us!

I think I might pick up a pair of short ones in October!



Gerd



Am 10.05.2012 16:22, schrieb Nick Otterback:

[quote] 



 Gerd,



 Its funny you mention the airfoil shape. I discussed it yesterday with our

 machine shop and they are getting prices on both.



 Nick



 --

jh(at)gulftel.com
Guest

Posted: Fri May 11, 2012 11:11 am Post subject: Landing gear shimmy

Good Afternoon,



I had some serious shimmy problems in my Vans RV3 which has similar gear/leg construction. 

 

Nearly all of my shimmy problem was solved by simply balancing the pant/wheel fairings. I also reduced tire press. to 22 pounds.



Bench testing revealed considerable aft weight prior to balancing.



Jim Henderson, Lightning in Gulf Shores, AL

checkpoint2(at)comcast.ne
Guest

Posted: Fri May 11, 2012 12:43 pm Post subject: Landing gear shimmy

How does one balance gear leg pants and wheel fairings?  Thank you 

for your contribution. Bob Haas.



--

n45bm(at)yahoo.com
Guest

Posted: Fri May 11, 2012 1:36 pm Post subject: Landing gear shimmy

Bob,

Both gear leg fairings need to be aligned with the fuselage center line (for lateral trim purposes), No balancing needed. The wheel pants need to be statically balanced fore and aft. First remove the wheel pants and build a jig that will freely support the fairing along the axle center line first. The rear of the pant should be considerably heavier. Then add weight to the very front of the fairing until it balances. You can add the weight to the outside, then when they balance, epoxy the weight inside to the front of the fairing. Lead shot and epoxy work great for this.

Bernardo

Lightning kit #110 in Houston, TX



--- On Fri, 5/11/12, Bob Haas <checkpoint2(at)comcast.net> wrote:

[quote]

From: Bob Haas  <checkpoint2(at)comcast.net>

Subject: Re: Re: Landing gear shimmy

To: lightning-list(at)matronics.com

Date: Friday, May 11, 2012, 3:42 PM



--> Lightning-List message posted by: "Bob Haas" <[url=/mc/compose?to=checkpoint2(at)comcast.net]checkpoint2(at)comcast.net[/url]>



       How does one balance gear leg pants and wheel fairings?  Thank you for your contribution. Bob Haas.



--

checkpoint2(at)comcast.ne
Guest

Posted: Sat May 12, 2012 6:58 am Post subject: Landing gear shimmy

OK  That makes sense, a  whole new aspect to contend with  Thanks!  Bob.

  From: Bernard Melendez, Jr. (n45bm(at)yahoo.com) 

 Sent: Friday, May 11, 2012 5:35 PM

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

 Subject: Re: Re: Landing gear  shimmy

             Bob,

Both gear leg fairings need to be aligned with the        fuselage center line (for lateral trim purposes), No balancing needed. The        wheel pants need to be statically balanced fore and aft. First remove the        wheel pants and build a jig that will freely support the fairing along the        axle center line first. The rear of the pant should be considerably        heavier. Then add weight to the very front of the fairing until it        balances. You can add the weight to the outside, then when they balance,        epoxy the weight inside to the front of the fairing. Lead shot and epoxy        work great for this.

Bernardo

Lightning kit #110 in Houston,        TX

--- On Fri, 5/11/12, Bob Haas        <checkpoint2(at)comcast.net> wrote:

       [quote]

From:          Bob Haas <checkpoint2(at)comcast.net>

Subject: Re: Lightning-List:          Re: Landing gear shimmy

To: lightning-list(at)matronics.com

Date:          Friday, May 11, 2012, 3:42 PM

         --> Lightning-List message posted by: "Bob Haas"          <wlmailhtml:/mc/compose?to=checkpoint2(at)comcast.net (checkpoint2(at)comcast.net)>

                How does one balance gear leg pants and wheel fairings?  Thank you          for your contribution. Bob Haas.

--

jeynon2

Joined: 25 Oct 2007
Posts: 24
Location: Southern Illinois

Posted: Mon May 28, 2012 6:40 am Post subject: Re: Landing gear shimmy

Has anyone considered torsion in the spar box as a possible culprit for the shimmy?  The video shows both legs vibrating forward and back, and it is the spar box that links the two.  This could also explain why stiffening the gear legs has little effect.  You might check to see if the holes through the fiberglass for the bolts that attach the spar box to the fuselage have elongated indicating some slippage which would allow the spar box to flex.  Perhaps just re-torquing the bolts would help.



John Eynon

n45bm(at)yahoo.com
Guest

Posted: Mon May 28, 2012 7:08 am Post subject: Landing gear shimmy

Correct .... sorta kinda. It appears to me that the problem lays in the wheel(s) alignment and the fact that the main gear is splayed back. Consider this: as the wheels come in contact with the runway, if they are not lined up with the line of travel, they catch slightly on one side and then they spring back past the alignment point and catch on the other side (front or rear of the wheel). There is a torque force on the entire length of the gear itself, which in turn causes the gear to flex fore and aft. That's my story, and I'm sticking to it (unless someone convinces me with a better explanation)

Bernardo Melendez

kit #110



--- On Mon, 5/28/12, jeynon2 <jeynon2(at)frontier.com> wrote:

 	  Quote: 	
		  

From: jeynon2  <jeynon2(at)frontier.com>

Subject: Re: Landing gear shimmy

To: lightning-list(at)matronics.com

Date: Monday, May 28, 2012, 9:40 AM



--> Lightning-List message posted by: "jeynon2" <[url=/mc/compose?to=jeynon2(at)frontier.com]jeynon2(at)frontier.com[/url]>



Has anyone considered torsion in the spar box as a possible culprit for the shimmy?  The video shows both legs vibrating forward and back, and it is the spar box that links the two.  This could also explain why stiffening the gear legs has little effect.  You might check to see if the holes through the fiberglass for the bolts that attach the spar box to the fuselage have elongated indicating some slippage which would allow the spar box to flex.  Perhaps just re-torquing the bolts would help.



John Eynon





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=374087#374087http://www.matronics.com/Nav========================http://forums.ma            - List Contribution Web Site;                     &nb; http:========================





	
 [quote][b]

nowacklinden(at)gmx.de
Guest

Posted: Tue May 29, 2012 5:31 am Post subject: Landing gear shimmy

John,



You`re practically sitting on the spar box!

Don`t you think  your tender behind would feel the vibration if thereÂ´d be any?

I can assist the voiced opinion that the unbalanced wheel pants play an important role in the shimmy drama: So far I have made high speed taxi tests with my D-ELIY up to 55kts on the runway, no wheel pants installed so far, and observed absolutely no shimmy, neither empty nor fully loaded with wife Uli and full tanks.

BTW I hope to get my german Permit To Fly in July. Or so.



Gerd kit no.89



-------- Original-Nachricht --------

 	  Quote: 	
		   Datum: Mon, 28 May 2012 07:40:51 -0700

 Von: "jeynon2" <jeynon2(at)frontier.com>

 An: lightning-list(at)matronics.com

 Betreff: Re: Landing gear shimmy


	


 	  Quote: 	
		   

 

 Has anyone considered torsion in the spar box as a possible culprit for

 the shimmy?  The video shows both legs vibrating forward and back, and it is

 the spar box that links the two.  This could also explain why stiffening

 the gear legs has little effect.  You might check to see if the holes through

 the fiberglass for the bolts that attach the spar box to the fuselage have

 elongated indicating some slippage which would allow the spar box to flex.

  Perhaps just re-torquing the bolts would help.

 

 John Eynon

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=374087#374087

EAFerguson(at)AOL.COM
Guest

Posted: Wed May 30, 2012 4:54 am Post subject: Landing gear shimmy

So how do you explain the shimmy in Lightnings like mine that have no wheel  pants? BTW, It was less noticeable when the aircraft was new.

  

 Earl Ferguson

 Kit # 5

  

  In a message dated 5/29/2012 9:31:58 A.M. Eastern Daylight Time,  nowacklinden(at)gmx.de writes:

  	  Quote: 	
		  I can    assist the voiced opinion that the unbalanced wheel pants play an important    role in the shimmy drama: 	


 [quote][b]

davemcc

Joined: 28 Feb 2007
Posts: 74

Posted: Thu May 31, 2012 3:59 am Post subject: Landing gear shimmy

Earl

 This is certainly not a new subject.  I built my Esqual in 05 and it  has 810 hrs on it.  Let me tell u what I have tried.

 1.  clamping "broom handles" to the legs-this worked the 

      best

 2.  epoxy aluminum rods to the legs

 3.  epoxy fiberglass rods to the legs

 4.  wrapping legs with fiberglass

 5.  balance wheel pants- still have weights inside pants

 6.  remachined new struts a couple thousands thicker

      this helped but did not cure it 

 7.  balanced my tires in water, with a shaft in wheel, buble  

      balancer, spinning tires on aircraft

 8.  had video taken in 05 found it to be in mains not nose 

      wheel after I built a springed nose gear, this  worked well 

      but did not fix problem

 9.   bought the best tires

 10. replace all rims and brakes

  

 I only am trying to save u guys a lot of work, the only thing that worked  for me was finding a spin balancer that would fit the small rims.  Now I  have no shimmy

 Flat spots on the tires cause it to shimmy also

  

 good luck

  

 Dave McCorquodale

 167DM

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

 [quote]   ---

n45bm(at)yahoo.com
Guest

Posted: Thu May 31, 2012 6:18 am Post subject: Landing gear shimmy

Group,

Question for you guys having shimmy problems:

On Lightnings, is this happening to the main landing gear on both the LSA and the old style gears, or only on one type?

Inquiring minds want to know. Thanks.

Bernardo Melendez, kit #110



--- On Thu, 5/31/12, Dave Mccorquodale <corky(at)hbci.com> wrote:

[quote]

From: Dave Mccorquodale <corky(at)hbci.com>

Subject: Re: Re: Landing gear shimmy

To: lightning-list(at)matronics.com

Date: Thursday, May 31, 2012, 6:58 AM



         Earl

 This is certainly not a new subject.  I built my Esqual in 05 and it  has 810 hrs on it.  Let me tell u what I have tried.

 1.  clamping "broom handles" to the legs-this worked the 

      best

 2.  epoxy aluminum rods to the legs

 3.  epoxy fiberglass rods to the legs

 4.  wrapping legs with fiberglass

 5.  balance wheel pants- still have weights inside pants

 6.  remachined new struts a couple thousands thicker

      this helped but did not cure it 

 7.  balanced my tires in water, with a shaft in wheel, buble  

      balancer, spinning tires on aircraft

 8.  had video taken in 05 found it to be in mains not nose 

      wheel after I built a springed nose gear, this  worked well 

      but did not fix problem

 9.   bought the best tires

 10. replace all rims and brakes

  

 I only am trying to save u guys a lot of work, the only thing that worked  for me was finding a spin balancer that would fit the small rims.  Now I  have no shimmy

 Flat spots on the tires cause it to shimmy also

  

 good luck

  

 Dave McCorquodale

 167DM

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

 [quote]   ---

barnett6088(at)msn.com
Guest

Posted: Thu May 31, 2012 8:18 am Post subject: Landing gear shimmy

Bernard

I see one resonance around 8 to 10 miles per hour, taxiing faster or slower gets away from it.  There is a second resonance around 40 knots on takeoff which I attribute to the wheels being out of balance.  I have not spin balanced my wheels yet but plan to as soon as I find a motorcycle shop with the required balancer.  Gary Barnett ELSA SN 133

 



Date: Thu, 31 May 2012 07:17:44 -0700

From: n45bm(at)yahoo.com

Subject: Re: Re: Landing gear shimmy

To: lightning-list(at)matronics.com



Group,

Question for you guys having shimmy problems:

On Lightnings, is this happening to the main landing gear on both the LSA and the old style gears, or only on one type?

Inquiring minds want to know. Thanks.

Bernardo Melendez, kit #110



--- On Thu, 5/31/12, Dave Mccorquodale <corky(at)hbci.com> wrote:

[quote]

From: Dave Mccorquodale <corky(at)hbci.com>

Subject: Re: Re: Landing gear shimmy

To: lightning-list(at)matronics.com

Date: Thursday, May 31, 2012, 6:58 AM



         Earl

 This is certainly not a new subject.  I built my Esqual in 05 and it  has 810 hrs on it.  Let me tell u what I have tried.

 1.  clamping "broom handles" to the legs-this worked the 

      best

 2.  epoxy aluminum rods to the legs

 3.  epoxy fiberglass rods to the legs

 4.  wrapping legs with fiberglass

 5.  balance wheel pants- still have weights inside pants

 6.  remachined new struts a couple thousands thicker

      this helped but did not cure it 

 7.  balanced my tires in water, with a shaft in wheel, buble  

      balancer, spinning tires on aircraft

 8.  had video taken in 05 found it to be in mains not nose 

      wheel after I built a springed nose gear, this  worked well 

      but did not fix problem

 9.   bought the best tires

 10. replace all rims and brakes

  

 I only am trying to save u guys a lot of work, the only thing that worked  for me was finding a spin balancer that would fit the small rims.  Now I  have no shimmy

 Flat spots on the tires cause it to shimmy also

  

 good luck

  

 Dave McCorquodale

 167DM

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

 [quote]   ---

n5pb(at)AOL.COM
Guest

Posted: Thu May 31, 2012 3:21 pm Post subject: Landing gear shimmy

Mine is an old style gear.

   

 

 

  

   --

nowacklinden(at)gmx.de
Guest

Posted: Fri Jun 01, 2012 12:31 am Post subject: Landing gear shimmy

Dave



One important, maybe crucial detail I find in your list missing: the toe in.

Former statements in this group have mentioned it, and IMHO it plays a major role, too.

I have adjusted my toe in to 1/2 deg, measured with a laser gun sight pointer from the brake disks back to a dedicate plank that I put under the tail and centered with a plumb. I made markings for 0deg toe in by measuring from center of fuse (plumb again) to the point of the brake disk where I later put the laser pointer. This mark is toe in 0, you can easily calculate the distance from 0 to 1 or 1/2 deg with a scientific calculator  or the internet( http://www.rapidtables.com/calc/math/Tan_Calculator.htm  or an old slide rule by multiplying the tangent of your desired toe in angle with the distance from brake disk to measuring plank. Then make another pencil mark there - outboard of the 0-mark, when you want toe in, of course. Which is where your laser pointer should point.

 This way you don`t have to make chalk lines all over the place and you can check unwanted airplane movement that would spoil your measurement by just leaving the plumb in place. And you can keep the plank for later measurements.

Coming to think of it : I made my adjustment without the wings on and of course no load , and should measure the toe in again with wings and fuel.



Please excuse if i sound teaching.I write all this because I hope we all might get some data basis. Then we can compare toe in of the shakers and the non-shakers and maybe get a hint.



Gerd   



 

 	  Quote: 	
		   Datum: Thu, 31 May 2012 06:58:21 -0500

 Von: "Dave Mccorquodale" <corky(at)hbci.com>

 An: lightning-list(at)matronics.com

 Betreff: Re: Re: Landing gear shimmy


	


[quote] Earl

 This is certainly not a new subject.  I built my Esqual in 05 and it has

 810 hrs on it.  Let me tell u what I have tried.

 1.  clamping "broom handles" to the legs-this worked the 

      best

 2.  epoxy aluminum rods to the legs

 3.  epoxy fiberglass rods to the legs

 4.  wrapping legs with fiberglass

 5.  balance wheel pants- still have weights inside pants

 6.  remachined new struts a couple thousands thicker

      this helped but did not cure it 

 7.  balanced my tires in water, with a shaft in wheel, buble 

      balancer, spinning tires on aircraft

 8.  had video taken in 05 found it to be in mains not nose 

      wheel after I built a springed nose gear, this worked well 

      but did not fix problem

 9.   bought the best tires

 10. replace all rims and brakes

 

 I only am trying to save u guys a lot of work, the only thing that worked

 for me was finding a spin balancer that would fit the small rims.  Now I

 have no shimmy

 Flat spots on the tires cause it to shimmy also

 

 good luck

 

 Dave McCorquodale

 167DM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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