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TimRVator(at)comcast.net
Guest

Posted: Sat Aug 18, 2012 9:36 am Post subject: Shudder/shimmy on landing

Like many RV-10s (apparently), mine shudders during the landing 

rollout.  Mine starts when decelerating through 35-40 knots (or so) on 

landing.   The speed range at which the shudder occurs is only a small 

number of knots - less than 5 knot range I think, so the shudder phase 

stops pretty quickly during deceleration.  Hard braking may make the 

shudder more intense.



Based on the successful  experiences reported by Tim Olson and others, I 

bought the Marc Parnes DU42 wheel balancer 

(http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42), 

and used that to balance all my wheels.  The DU42 is very nice piece of 

equipment -- surprisingly sensitive.



http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42

https://dl.dropbox.com/u/93114308/ParnesOnStands.JPG



It took a significant amount of weight to balance the wheels (several 

1/4oz weights on each wheel).  From what I've read, others have had this 

same experience.

https://dl.dropbox.com/u/93114308/TireWts.JPG



I also installed the planearound.com Wheel Fairing Bracket Spacers to 

stiffen up the wheel fairing attachment to the main gear.  The 

planearound product is well made, fit fine, and really does stiffen up 

the wheel fairing bracket attachment.

https://dl.dropbox.com/u/93114308/PlaneAround1.JPG

https://dl.dropbox.com/u/93114308/PlaneAroundInstalled.JPG



Results:  No discernible change in landing roll out behavior.  I still 

get about the same shudder on roll out.  Perhaps the onset speed has 

been raised a small number of knots as a result of balancing and adding 

the brackets, but I'm not sure about that.



I'm not sure what else to try.



Tim



-- 

Tim Lewis -- HEF (Manassas, VA)

RV-6A N47TD -- 1104 hrs - sold

RV-10 N31TD -- 340 hrs

Strasnuts

Joined: 10 Feb 2009
Posts: 502
Location: Salt Lake City, UT

Posted: Sat Aug 18, 2012 10:06 am Post subject: Shudder/shimmy on landing

Tim,



I fiberglassed oak stiffeners on the back of my gear legs. They fit inside the fairing and are basically triangle shaped and milled to fit on the round tapered gear leg. They have really helped with the shimmy. Mine started around 30 kias. 

If I'm really light and by myself I feel a little shimmy but much less than ever before the stiffeners. If I have any passengers with me or cargo I have no shimmy at all with the stiffeners. Before it would shimmy in any configuration. 

You can try what I did an that was using strapping tape first to try then out. After it worked I prosealed the woo to the gear leg then glasses them in using a spiral technique with 3" glass tape. 



Good luck 

I might be delivering a CJ to Manassas at the end of the month. 



Sent from my iPhone



On Aug 18, 2012, at 11:35, Tim Lewis <TimRVator(at)comcast.net> wrote:



 	  Quote: 	
		   

 

 Like many RV-10s (apparently), mine shudders during the landing rollout.  Mine starts when decelerating through 35-40 knots (or so) on landing.   The speed range at which the shudder occurs is only a small number of knots - less than 5 knot range I think, so the shudder phase stops pretty quickly during deceleration.  Hard braking may make the shudder more intense.

 

 Based on the successful  experiences reported by Tim Olson and others, I bought the Marc Parnes DU42 wheel balancer (http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42), and used that to balance all my wheels.  The DU42 is very nice piece of equipment -- surprisingly sensitive.

 

 http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42

 https://dl.dropbox.com/u/93114308/ParnesOnStands.JPG

 

 It took a significant amount of weight to balance the wheels (several 1/4oz weights on each wheel).  From what I've read, others have had this same experience.

 https://dl.dropbox.com/u/93114308/TireWts.JPG

 

 I also installed the planearound.com Wheel Fairing Bracket Spacers to stiffen up the wheel fairing attachment to the main gear.  The planearound product is well made, fit fine, and really does stiffen up the wheel fairing bracket attachment.

 https://dl.dropbox.com/u/93114308/PlaneAround1.JPG

 https://dl.dropbox.com/u/93114308/PlaneAroundInstalled.JPG

 

 Results:  No discernible change in landing roll out behavior.  I still get about the same shudder on roll out.  Perhaps the onset speed has been raised a small number of knots as a result of balancing and adding the brackets, but I'm not sure about that.

 

 I'm not sure what else to try.

 

 Tim

 

 -- 

 Tim Lewis -- HEF (Manassas, VA)

 RV-6A N47TD -- 1104 hrs - sold

 RV-10 N31TD -- 340 hrs

_________________
40936
RV-10 SB N801VR Flying
780 Hours
SuperSTOL 60 hours

taildragon(at)msn.com
Guest

Posted: Sat Aug 18, 2012 4:00 pm Post subject: Shudder/shimmy on landing

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  I wonder if any of the after market guys are interested in making up some  stiffeners; either wooden or aluminum triangle shaped and milled to fit on the  round tapered gear leg? 

  

 Roger "mine shudders, too" Standley

  

 [quote]   ---

aircraftspecialty(at)gmai
Guest

Posted: Sat Aug 18, 2012 4:08 pm Post subject: Shudder/shimmy on landing

How many people would be interested in this?  I'm willing to do it if enough people would be interested.

To those that have done it....would aluminum or wood work better?  How long of a piece are we talking about?

Email me at steve(at)aircraftspecialty.com (steve(at)aircraftspecialty.com)



Sent from my iPhone



On Aug 18, 2012, at 16:58, "Roger Standley" <taildragon(at)msn.com (taildragon(at)msn.com)> wrote:



[quote]      <?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  I wonder if any of the after market guys are interested in making up some  stiffeners; either wooden or aluminum triangle shaped and milled to fit on the  round tapered gear leg? 

  

 Roger "mine shudders, too" Standley

  

 [quote]   ---

Jess
Guest

Posted: Sat Aug 18, 2012 6:02 pm Post subject: Shudder/shimmy on landing

Another way would be to fit an aluminum tube around the gear, form  it into a streamline shape inside the fairing and filling it with epoxy, we did  this to our 6 and it has worked miracles, we did this with weight off of the  gear.

Jess

  

  In a message dated 8/18/2012 5:00:32 P.M. Pacific Daylight Time,  taildragon(at)msn.com writes:

 [quote]      I wonder if any of the after market guys are interested in making up some    stiffeners; either wooden or aluminum triangle shaped and milled to fit on the    round tapered gear leg? 

    

   Roger "mine shudders, too" Standley

    

   [quote]     ---

bill.peyton

Joined: 19 Sep 2010
Posts: 198
Location: St. Louis, MO

Posted: Sun Aug 19, 2012 3:29 am Post subject: Re: Shudder/shimmy on landing

The truly right thing to do would be to have Vans address this issue with a newly designed strut!  Of course the chance of that happening is 0 to none!

_________________
Bill
WA0SYV
Aviation Partners, LLC

cgroote1(at)yahoo.com
Guest

Posted: Sun Aug 19, 2012 5:25 am Post subject: Shudder/shimmy on landing

I'm definitely interested in an aftermarket gear leg stiffener.

 "All shuddered out" Curt



 [quote][b]

amekler

Joined: 07 Oct 2010
Posts: 164

Posted: Sun Aug 19, 2012 5:43 am Post subject: Shudder/shimmy on landing

Hopefully Steve will make one available for us if there is enough demand.

Alan



Sent from my iPhone



On Aug 19, 2012, at 9:25 AM, curtis groote <cgroote1(at)yahoo.com (cgroote1(at)yahoo.com)> wrote:



[quote]I'm definitely interested in an aftermarket gear leg stiffener.

 "All shuddered out" Curt



  	  Quote: 	
		  

	


[b]

TimRVator(at)comcast.net
Guest

Posted: Sun Aug 19, 2012 6:53 am Post subject: Shudder/shimmy on landing

Sean,

Thanks for relating your experience.  It's encouraging to hear that worked.

I remember doing something similar on my RV-6A gear legs 15 years ago as 

part of the per-plans construction.  Although I gave the plans to the 

new owner when I sold the plane, I was able to find the relevant section 

in the preview plans.  For anybody who is interested, here's a link to 

that portion of the RV-6 plans:

https://dl.dropbox.com/u/93114308/Wood%20Shimmy%20Damper.pdf

Tim

-- 

Tim Lewis -- HEF (Manassas, VA)

RV-6A N47TD -- 1104 hrs - sold

RV-10 N31TD -- 340 hrs

Seano said the following on 8/18/2012 2:05 PM:

 	  Quote: 	

 Tim,

 I fiberglassed oak stiffeners on the back of my gear legs. They fit inside the fairing and are basically triangle shaped and milled to fit on the round tapered gear leg. They have really helped with the shimmy. Mine started around 30 kias.

 If I'm really light and by myself I feel a little shimmy but much less than ever before the stiffeners. If I have any passengers with me or cargo I have no shimmy at all with the stiffeners. Before it would shimmy in any configuration.

 You can try what I did an that was using strapping tape first to try then out. After it worked I prosealed the woo to the gear leg then glasses them in using a spiral technique with 3" glass tape.

 Good luck

 I might be delivering a CJ to Manassas at the end of the month.

 Sent from my iPhone

 On Aug 18, 2012, at 11:35, Tim Lewis <TimRVator(at)comcast.net> wrote:

> 

>

> Like many RV-10s (apparently), mine shudders during the landing rollout.  Mine starts when decelerating through 35-40 knots (or so) on landing.   The speed range at which the shudder occurs is only a small number of knots - less than 5 knot range I think, so the shudder phase stops pretty quickly during deceleration.  Hard braking may make the shudder more intense.

>

> Based on the successful  experiences reported by Tim Olson and others, I bought the Marc Parnes DU42 wheel balancer (http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42), and used that to balance all my wheels.  The DU42 is very nice piece of equipment -- surprisingly sensitive.

>

> http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42

> https://dl.dropbox.com/u/93114308/ParnesOnStands.JPG

>

> It took a significant amount of weight to balance the wheels (several 1/4oz weights on each wheel).  From what I've read, others have had this same experience.

> https://dl.dropbox.com/u/93114308/TireWts.JPG

>

> I also installed the planearound.com Wheel Fairing Bracket Spacers to stiffen up the wheel fairing attachment to the main gear.  The planearound product is well made, fit fine, and really does stiffen up the wheel fairing bracket attachment.

> https://dl.dropbox.com/u/93114308/PlaneAround1.JPG

> https://dl.dropbox.com/u/93114308/PlaneAroundInstalled.JPG

>

> Results:  No discernible change in landing roll out behavior.  I still get about the same shudder on roll out.  Perhaps the onset speed has been raised a small number of knots as a result of balancing and adding the brackets, but I'm not sure about that.

>

> I'm not sure what else to try.

>

> Tim

>

> -- 

> Tim Lewis -- HEF (Manassas, VA)

> RV-6A N47TD -- 1104 hrs - sold

> RV-10 N31TD -- 340 hrs

>

Wood_Shimmy_Damper.pdf

Description:

Download

Filename:

Wood_Shimmy_Damper.pdf

Filesize:

2.71 MB

Downloaded:

809 Time(s)

scottmschmidt(at)yahoo.co
Guest

Posted: Sun Aug 19, 2012 8:14 am Post subject: Shudder/shimmy on landing

Tim, I have done everything you have as well as realigned my gear to exactly 1.5 degrees of toe-in. I talked with Van and he recommended the wood on the gear. 

It is a design problem for sure. A round gear is not optimal but is cheap to manufacture. 



I think the real fix is a total redesign of the gear leg. What I would like to see is a titanium, composite or aluminum gear shaped in a rectangle like the Cirrus or RV-8 taildragger. 

I believe the Cirrus gear is composite. I think you could reduce the weight by 50% which would add around 50 lbs to the useful load and eliminate the shimmy. 



Sent from my iPad



On Aug 19, 2012, at 8:52 AM, Tim Lewis <TimRVator(at)comcast.net> wrote:



 	  Quote: 	
		   Sean,

 

 Thanks for relating your experience.  It's encouraging to hear that worked.

 

 I remember doing something similar on my RV-6A gear legs 15 years ago as part of the per-plans construction.  Although I gave the plans to the new owner when I sold the plane, I was able to find the relevant section in the preview plans.  For anybody who is interested, here's a link to that portion of the RV-6 plans:

 

 https://dl.dropbox.com/u/93114308/Wood%20Shimmy%20Damper.pdf

 

 Tim

 

 -- 

 Tim Lewis -- HEF (Manassas, VA)

 RV-6A N47TD -- 1104 hrs - sold

 RV-10 N31TD -- 340 hrs

 

 Seano said the following on 8/18/2012 2:05 PM:

> 

> 

> Tim,

> 

> I fiberglassed oak stiffeners on the back of my gear legs. They fit inside the fairing and are basically triangle shaped and milled to fit on the round tapered gear leg. They have really helped with the shimmy. Mine started around 30 kias.

> If I'm really light and by myself I feel a little shimmy but much less than ever before the stiffeners. If I have any passengers with me or cargo I have no shimmy at all with the stiffeners. Before it would shimmy in any configuration.

> You can try what I did an that was using strapping tape first to try then out. After it worked I prosealed the woo to the gear leg then glasses them in using a spiral technique with 3" glass tape.

> 

> Good luck

> I might be delivering a CJ to Manassas at the end of the month.

> 

> 

> 

> 

> 

> Sent from my iPhone

> 

> On Aug 18, 2012, at 11:35, Tim Lewis <TimRVator(at)comcast.net> wrote:

> 

>> 

>> 

>> Like many RV-10s (apparently), mine shudders during the landing rollout.  Mine starts when decelerating through 35-40 knots (or so) on landing.   The speed range at which the shudder occurs is only a small number of knots - less than 5 knot range I think, so the shudder phase stops pretty quickly during deceleration.  Hard braking may make the shudder more intense.

>> 

>> Based on the successful  experiences reported by Tim Olson and others, I bought the Marc Parnes DU42 wheel balancer (http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42), and used that to balance all my wheels.  The DU42 is very nice piece of equipment -- surprisingly sensitive.

>> 

>> http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42

>> https://dl.dropbox.com/u/93114308/ParnesOnStands.JPG

>> 

>> It took a significant amount of weight to balance the wheels (several 1/4oz weights on each wheel).  From what I've read, others have had this same experience.

>> https://dl.dropbox.com/u/93114308/TireWts.JPG

>> 

>> I also installed the planearound.com Wheel Fairing Bracket Spacers to stiffen up the wheel fairing attachment to the main gear.  The planearound product is well made, fit fine, and really does stiffen up the wheel fairing bracket attachment.

>> https://dl.dropbox.com/u/93114308/PlaneAround1.JPG

>> https://dl.dropbox.com/u/93114308/PlaneAroundInstalled.JPG

>> 

>> Results:  No discernible change in landing roll out behavior.  I still get about the same shudder on roll out.  Perhaps the onset speed has been raised a small number of knots as a result of balancing and adding the brackets, but I'm not sure about that.

>> 

>> I'm not sure what else to try.

>> 

>> Tim

>> 

>> -- 

>> Tim Lewis -- HEF (Manassas, VA)

>> RV-6A N47TD -- 1104 hrs - sold

>> RV-10 N31TD -- 340 hrs

>> 

>> 

>> 

>> 

>> 

> 

> 

> 

> 

> 

 

 <Wood Shimmy Damper.pdf>

dave.saylor.aircrafters(a
Guest

Posted: Sun Aug 19, 2012 8:44 am Post subject: Shudder/shimmy on landing

I asked Robby Grove about aluminum legs for the -10.  He said the

cross section where they fit into the socket just doesn't provide

enough area for aluminum.  So it would be a fairly complex task to

either modify the socket to accept a rectangular leg or create some

kind of adapter to make the changeover outside of the socket.  And

leaving the biggest part of the leg in steel with the rest in some

lighter material kind of defeats the purpose.



I agree though, it seems like there must be something better.  I'm

just not sure I'd want to be the guinea pig if means a broken gear

leg.



Dave Saylor

831-750-0284 CL

On Sun, Aug 19, 2012 at 9:13 AM, Scott Schmidt <scottmschmidt(at)yahoo.com> wrote:

 	  Quote: 	
		   



 Tim, I have done everything you have as well as realigned my gear to exactly 1.5 degrees of toe-in. I talked with Van and he recommended the wood on the gear.

 It is a design problem for sure. A round gear is not optimal but is cheap to manufacture.



 I think the real fix is a total redesign of the gear leg. What I would like to see is a titanium, composite or aluminum gear shaped in a rectangle like the Cirrus or RV-8 taildragger.

 I believe the Cirrus gear is composite. I think you could reduce the weight by 50% which would add around 50 lbs to the useful load and eliminate the shimmy.



 Sent from my iPad



 On Aug 19, 2012, at 8:52 AM, Tim Lewis <TimRVator(at)comcast.net> wrote:



> Sean,

>

> Thanks for relating your experience.  It's encouraging to hear that worked.

>

> I remember doing something similar on my RV-6A gear legs 15 years ago as part of the per-plans construction.  Although I gave the plans to the new owner when I sold the plane, I was able to find the relevant section in the preview plans.  For anybody who is interested, here's a link to that portion of the RV-6 plans:

>

> https://dl.dropbox.com/u/93114308/Wood%20Shimmy%20Damper.pdf

>

> Tim

>

> --

> Tim Lewis -- HEF (Manassas, VA)

> RV-6A N47TD -- 1104 hrs - sold

> RV-10 N31TD -- 340 hrs

>

> Seano said the following on 8/18/2012 2:05 PM:

>> 

>>

>> Tim,

>>

>> I fiberglassed oak stiffeners on the back of my gear legs. They fit inside the fairing and are basically triangle shaped and milled to fit on the round tapered gear leg. They have really helped with the shimmy. Mine started around 30 kias.

>> If I'm really light and by myself I feel a little shimmy but much less than ever before the stiffeners. If I have any passengers with me or cargo I have no shimmy at all with the stiffeners. Before it would shimmy in any configuration.

>> You can try what I did an that was using strapping tape first to try then out. After it worked I prosealed the woo to the gear leg then glasses them in using a spiral technique with 3" glass tape.

>>

>> Good luck

>> I might be delivering a CJ to Manassas at the end of the month.

>>

>>

>>

>>

>>

>> Sent from my iPhone

>>

>> On Aug 18, 2012, at 11:35, Tim Lewis <TimRVator(at)comcast.net> wrote:

>>

>>> 

>>>

>>> Like many RV-10s (apparently), mine shudders during the landing rollout.  Mine starts when decelerating through 35-40 knots (or so) on landing.   The speed range at which the shudder occurs is only a small number of knots - less than 5 knot range I think, so the shudder phase stops pretty quickly during deceleration.  Hard braking may make the shudder more intense.

>>>

>>> Based on the successful  experiences reported by Tim Olson and others, I bought the Marc Parnes DU42 wheel balancer (http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42), and used that to balance all my wheels.  The DU42 is very nice piece of equipment -- surprisingly sensitive.

>>>

>>> http://www.marcparnes.com/Ducati_Motorcycle_Wheel_Balancer.htm#DU42

>>> https://dl.dropbox.com/u/93114308/ParnesOnStands.JPG

>>>

>>> It took a significant amount of weight to balance the wheels (several 1/4oz weights on each wheel).  From what I've read, others have had this same experience.

>>> https://dl.dropbox.com/u/93114308/TireWts.JPG

>>>

>>> I also installed the planearound.com Wheel Fairing Bracket Spacers to stiffen up the wheel fairing attachment to the main gear.  The planearound product is well made, fit fine, and really does stiffen up the wheel fairing bracket attachment.

>>> https://dl.dropbox.com/u/93114308/PlaneAround1.JPG

>>> https://dl.dropbox.com/u/93114308/PlaneAroundInstalled.JPG

>>>

>>> Results:  No discernible change in landing roll out behavior.  I still get about the same shudder on roll out.  Perhaps the onset speed has been raised a small number of knots as a result of balancing and adding the brackets, but I'm not sure about that.

>>>

>>> I'm not sure what else to try.

>>>

>>> Tim

>>>

>>> --

>>> Tim Lewis -- HEF (Manassas, VA)

>>> RV-6A N47TD -- 1104 hrs - sold

>>> RV-10 N31TD -- 340 hrs

>>>

>>>

>>>

>>>

>>>

>>

>>

>>

>>

>>

>

> <Wood Shimmy Damper.pdf>

johngoodman

Joined: 18 Sep 2006
Posts: 530
Location: GA

Posted: Sun Aug 19, 2012 8:54 am Post subject: Re: Shudder/shimmy on landing

Going back to the original issue, I have experienced the 35-45k shimmy in another RV-10, but never in mine. I seriously doubt that stiffening the legs is a cure, only mitigates a symptom.

As far as why I don't have any shimmy, I haven't a clue. I can point out that I detest pants and have never put them on. I faired up everything without them and I'm content. It's tempting to suggest the pants, but I know that's not the issue. Obviously, wheel balancing didn't solve it, so it's something else. I have the better nose axle - as do most folks, so that's probably not it.



I have several thoughts that should be explored. The first is Tire Pressure. Incredibly, my tires have not lost a single pound of air pressure in the year+ that I've been flying it. 42 on the mains and 40 on the nose. They are stock Van's tires and tubes. The tires are showing no wear. The smoking gun to me is the outside wear so many have experienced. Could it be that the tires are "scrubbing" on their outside edges due to some sort of "pronation or supination"? If the main axle was "toed in or out" a little (I mean something very small), I could envision a "scrubbing" issue. At higher speeds, the tires would simply sand themselves on the runway, and at slow speeds the flexibility of the rubber would compensate for the scrub, and not be felt. If my theory holds any water at all, the transition between the sanding to the scrubbing is at 40 knots, or so.



IF, my theory is true (I'm no expert), then that would suggest the culprit is the bolt in the main mount. Without referring to the plans, I remember I needed a 7.9mm drill bit for that. I bought one and used it on mine. Van obviously wanted a close tolerance so the main couldn't move at all. If you used a 5/16" bit, you would have 0.0015" of slop. It sounds incredibly small but could it be enough?



Anyway, it's the only thing I've come up with so far.



John

_________________
#40572 Phase One complete in 2011

amekler

Joined: 07 Oct 2010
Posts: 164

Posted: Sun Aug 19, 2012 9:18 am Post subject: Shudder/shimmy on landing

I have the shimmy and  abnormal tire wear now apparent after 150 hrs. ( mostlty short flights-ie alot of landings)Shimmy seems a little worse now.

It appears to me that the shimmy has caused the abnormal tire wear and the abnormal tire wear makes the shimmy worse.

Alan



Sent from my iPhone



On Aug 19, 2012, at 12:54 PM, "johngoodman" <johngoodman(at)earthlink.net> wrote:



 	  Quote: 	
		   

 

 Going back to the original issue, I have experienced the 35-45k shimmy in another RV-10, but never in mine. I seriously doubt that stiffening the legs is a cure, only mitigates a symptom.

 As far as why I don't have any shimmy, I haven't a clue. I can point out that I detest pants and have never put them on. I faired up everything without them and I'm content. It's tempting to suggest the pants, but I know that's not the issue. Obviously, wheel balancing didn't solve it, so it's something else. I have the better nose axle - as do most folks, so that's probably not it.

 

 I have several thoughts that should be explored. The first is Tire Pressure. Incredibly, my tires have not lost a single pound of air pressure in the year+ that I've been flying it. 42 on the mains and 40 on the nose. They are stock Van's tires and tubes. The tires are showing no wear. The smoking gun to me is the outside wear so many have experienced. Could it be that the tires are "scrubbing" on their outside edges due to some sort of "pronation or supination"? If the main axle was "toed in or out" a little (I mean something very small), I could envision a "scrubbing" issue. At higher speeds, the tires would simply sand themselves on the runway, and at slow speeds the flexibility of the rubber would compensate for the scrub, and not be felt. If my theory holds any water at all, the transition between the sanding to the scrubbing is at 40 knots, or so.

 

 IF, my theory is true (I'm no expert), then that would suggest the culprit is the bolt in the main mount. Without referring to the plans, I remember I needed a 7.9mm drill bit for that. I bought one and used it on mine. Van obviously wanted a close tolerance so the main couldn't move at all. If you used a 5/16" bit, you would have 0.0015" of slop. It sounds incredibly small but could it be enough?

 

 Anyway, it's the only thing I've come up with so far.

 

 John

 

 --------

 #40572 Phase One complete and flying.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=381253#381253

arplnplt(at)gmail.com
Guest

Posted: Sun Aug 19, 2012 10:10 am Post subject: Shudder/shimmy on landing

Why no issue on take off, only landing?



Dave Leikam



On Aug 19, 2012, at 11:54 AM, johngoodman wrote:



 	  Quote: 	
		   

 

 Going back to the original issue, I have experienced the 35-45k shimmy in another RV-10, but never in mine. I seriously doubt that stiffening the legs is a cure, only mitigates a symptom.

 As far as why I don't have any shimmy, I haven't a clue. I can point out that I detest pants and have never put them on. I faired up everything without them and I'm content. It's tempting to suggest the pants, but I know that's not the issue. Obviously, wheel balancing didn't solve it, so it's something else. I have the better nose axle - as do most folks, so that's probably not it.

 

 I have several thoughts that should be explored. The first is Tire Pressure. Incredibly, my tires have not lost a single pound of air pressure in the year+ that I've been flying it. 42 on the mains and 40 on the nose. They are stock Van's tires and tubes. The tires are showing no wear. The smoking gun to me is the outside wear so many have experienced. Could it be that the tires are "scrubbing" on their outside edges due to some sort of "pronation or supination"? If the main axle was "toed in or out" a little (I mean something very small), I could envision a "scrubbing" issue. At higher speeds, the tires would simply sand themselves on the runway, and at slow speeds the flexibility of the rubber would compensate for the scrub, and not be felt. If my theory holds any water at all, the transition between the sanding to the scrubbing is at 40 knots, or so.

 

 IF, my theory is true (I'm no expert), then that would suggest the culprit is the bolt in the main mount. Without referring to the plans, I remember I needed a 7.9mm drill bit for that. I bought one and used it on mine. Van obviously wanted a close tolerance so the main couldn't move at all. If you used a 5/16" bit, you would have 0.0015" of slop. It sounds incredibly small but could it be enough?

 

 Anyway, it's the only thing I've come up with so far.

 

 John

 

 --------

 #40572 Phase One complete and flying.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=381253#381253

amekler

Joined: 07 Oct 2010
Posts: 164

Posted: Sun Aug 19, 2012 10:23 am Post subject: Shudder/shimmy on landing

I think on take off you pass through the shudder speed so quickly you don't notice it.

Alan



Sent from my iPhone



On Aug 19, 2012, at 2:09 PM, David Leikam <arplnplt(at)gmail.com> wrote:



 	  Quote: 	
		   

 

 Why no issue on take off, only landing?

 

 Dave Leikam

 

 On Aug 19, 2012, at 11:54 AM, johngoodman wrote:

 

> 

> 

> Going back to the original issue, I have experienced the 35-45k shimmy in another RV-10, but never in mine. I seriously doubt that stiffening the legs is a cure, only mitigates a symptom.

> As far as why I don't have any shimmy, I haven't a clue. I can point out that I detest pants and have never put them on. I faired up everything without them and I'm content. It's tempting to suggest the pants, but I know that's not the issue. Obviously, wheel balancing didn't solve it, so it's something else. I have the better nose axle - as do most folks, so that's probably not it.

> 

> I have several thoughts that should be explored. The first is Tire Pressure. Incredibly, my tires have not lost a single pound of air pressure in the year+ that I've been flying it. 42 on the mains and 40 on the nose. They are stock Van's tires and tubes. The tires are showing no wear. The smoking gun to me is the outside wear so many have experienced. Could it be that the tires are "scrubbing" on their outside edges due to some sort of "pronation or supination"? If the main axle was "toed in or out" a little (I mean something very small), I could envision a "scrubbing" issue. At higher speeds, the tires would simply sand themselves on the runway, and at slow speeds the flexibility of the rubber would compensate for the scrub, and not be felt. If my theory holds any water at all, the transition between the sanding to the scrubbing is at 40 knots, or so.

> 

> IF, my theory is true (I'm no expert), then that would suggest the culprit is the bolt in the main mount. Without referring to the plans, I remember I needed a 7.9mm drill bit for that. I bought one and used it on mine. Van obviously wanted a close tolerance so the main couldn't move at all. If you used a 5/16" bit, you would have 0.0015" of slop. It sounds incredibly small but could it be enough?

> 

> Anyway, it's the only thing I've come up with so far.

> 

> John

> 

> --------

> #40572 Phase One complete and flying.

> 

> 

> 

> 

> Read this topic online here:

> 

> http://forums.matronics.com/viewtopic.php?p=381253#381253

> 

> 

> 

> 

> 

> 

> 

> 

> 

>

Strasnuts

Joined: 10 Feb 2009
Posts: 502
Location: Salt Lake City, UT

Posted: Sun Aug 19, 2012 11:00 am Post subject: Shudder/shimmy on landing

I concur



Sent from my iPhone



On Aug 19, 2012, at 12:23, Alan Mekler MD <amekler(at)metrocast.net> wrote:



 	  Quote: 	
		   

 

 I think on take off you pass through the shudder speed so quickly you don't notice it.

 Alan

 

 Sent from my iPhone

 

 On Aug 19, 2012, at 2:09 PM, David Leikam <arplnplt(at)gmail.com> wrote:

 

> 

> 

> Why no issue on take off, only landing?

> 

> Dave Leikam

> 

> On Aug 19, 2012, at 11:54 AM, johngoodman wrote:

> 

>> 

>> 

>> Going back to the original issue, I have experienced the 35-45k shimmy in another RV-10, but never in mine. I seriously doubt that stiffening the legs is a cure, only mitigates a symptom.

>> As far as why I don't have any shimmy, I haven't a clue. I can point out that I detest pants and have never put them on. I faired up everything without them and I'm content. It's tempting to suggest the pants, but I know that's not the issue. Obviously, wheel balancing didn't solve it, so it's something else. I have the better nose axle - as do most folks, so that's probably not it.

>> 

>> I have several thoughts that should be explored. The first is Tire Pressure. Incredibly, my tires have not lost a single pound of air pressure in the year+ that I've been flying it. 42 on the mains and 40 on the nose. They are stock Van's tires and tubes. The tires are showing no wear. The smoking gun to me is the outside wear so many have experienced. Could it be that the tires are "scrubbing" on their outside edges due to some sort of "pronation or supination"? If the main axle was "toed in or out" a little (I mean something very small), I could envision a "scrubbing" issue. At higher speeds, the tires would simply sand themselves on the runway, and at slow speeds the flexibility of the rubber would compensate for the scrub, and not be felt. If my theory holds any water at all, the transition between the sanding to the scrubbing is at 40 knots, or so.

>> 

>> IF, my theory is true (I'm no expert), then that would suggest the culprit is the bolt in the main mount. Without referring to the plans, I remember I needed a 7.9mm drill bit for that. I bought one and used it on mine. Van obviously wanted a close tolerance so the main couldn't move at all. If you used a 5/16" bit, you would have 0.0015" of slop. It sounds incredibly small but could it be enough?

>> 

>> Anyway, it's the only thing I've come up with so far.

>> 

>> John

>> 

>> --------

>> #40572 Phase One complete and flying.

>> 

>> 

>> 

>> 

>> Read this topic online here:

>> 

>> http://forums.matronics.com/viewtopic.php?p=381253#381253

>> 

>> 

>> 

>> 

>> 

>> 

>> 

>> 

>> 

>> 

> 

> 

> 

> 

> 

>

_________________
40936
RV-10 SB N801VR Flying
780 Hours
SuperSTOL 60 hours

carl.froehlich(at)verizon
Guest

Posted: Sun Aug 19, 2012 11:06 am Post subject: Shudder/shimmy on landing

At 35 hours I again greased the nose fork and adjusted the tension.  As

someone suggested, I drilled another hole perhaps 30 degrees off the current

hole as the tension was either too tight or too loose using the existing

hole.  This significantly reduced the shudder.  I am also using the

replacement nose wheel bearing - and recommend it.  All tires have been

balanced.



On the 8A I noted a significant reduction in shudder after I replaced the

main gear tires.



Carl

38 hours.



--

toaster73(at)embarqmail.c
Guest

Posted: Sun Aug 19, 2012 1:51 pm Post subject: Shudder/shimmy on landing

And the RV-14 has main gear with rectangular cross section...they finally listened. 

-Chris

N919AR



--

bill.peyton

Joined: 19 Sep 2010
Posts: 198
Location: St. Louis, MO

Posted: Sun Aug 19, 2012 3:15 pm Post subject: Re: Shudder/shimmy on landing

Is the shimmy caused by only the main gear, or does the nose gear have the same issue?  I recall seeing a video of the nose gear, but not the mains..  I also recall Geoff Combs telling me that he did not have this shudder until he attached the wheel pants.

_________________
Bill
WA0SYV
Aviation Partners, LLC

aerosport1

Joined: 07 Nov 2007
Posts: 231

Posted: Sun Aug 19, 2012 3:59 pm Post subject: Shudder/shimmy on landing

Bill was correct about my gear shimmy. It showed up after wheel pants were installed. The wheel pants are really what cause it or should I say make it finally show up or make it worse. I video taped my gear and the wheel pants shake. I never had it until wheel pants were installed. I had over 60 hours on airplane before pants installed. 



Geoff



Sent from my iPhone



On Aug 19, 2012, at 7:15 PM, "bill.peyton" <peyton.b(at)sbcglobal.net> wrote:



 	  Quote: 	
		   

 

 Is the shimmy caused by only the main gear, or does the nose gear have the same issue?  I recall seeing a video of the nose gear, but not the mains..  I also recall Geoff Combs telling me that he did not have this shudder until he attached the wheel pants.

 

 --------

 Bill 

 WA0SYV

 Aviation Partners, LLC

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=381287#381287

_________________
Geoff Combs
RV-10 QB N829GW
Flying 500 hrs
40033

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