Today's Message Index:
----------------------
1. 05:09 AM - Thinking of buying (N129JG)
2. 05:56 AM - Re: Thinking of buying (Charles Dewey)
3. 08:42 AM - Re: Thinking of buying (N129JG)
4. 02:37 PM - Re: Landing gear shimmy (Bill Strahan)
5. 03:18 PM - Re: Re: Landing gear shimmy (Mefford, Walt)
6. 03:32 PM - Re: Re: Landing gear shimmy (Mark Stauffer)
7. 03:46 PM - Re: Re: Landing gear shimmy (Jim Logajan)
8. 05:09 PM - Re: Re: Landing gear shimmy (Tex Mantell)
9. 05:29 PM - Re: Re: Landing gear shimmy (Nick Otterback)
10. 08:19 PM - Re: Re: Landing gear shimmy (GARY BARNETT)
11. 09:01 PM - Re: Landing gear shimmy (Bill Strahan)
Message 1
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| Subject: | Thinking of buying |
No.. not a Lightning. As much as I would love one it is just not in the
budget. But I have been looking at an Esqual. In fact I believe it may
have been the last of the Factory built Demo planes, N622EA. I know
Buzz has made many modifications to his Esqual and I have read it flies
like a cat with it's tail on fire. I am planning to go inspect and take a
demo flight this Friday. I have an A&P IA traveling with me. Anything
in particular we need to be looking for?
Thanks,
Gene
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372616#372616
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| Subject: | Re: Thinking of buying |
Gene- There is a Lightning for sale in Shelbyville for $64K. It is on barnstormers
now.
--- On Tue, 5/8/12, N129JG <prophotoga@gmail.com> wrote:
> From: N129JG <prophotoga@gmail.com>
> Subject: Lightning-List: Thinking of buying
> To: lightning-list@matronics.com
> Date: Tuesday, May 8, 2012, 8:09 AM
> --> Lightning-List message posted
> by: "N129JG" <prophotoga@gmail.com>
>
> No.. not a Lightning. As much as I would love one it
> is just not in the
> budget. But I have been looking at an Esqual. In
> fact I believe it may
> have been the last of the Factory built Demo planes,
> N622EA. I know
> Buzz has made many modifications to his Esqual and I have
> read it flies
> like a cat with it's tail on fire.I am
> planning to go inspect and take a
> demo flight this Friday. I have an A&P IA
> traveling with me. Anything
> in particular we need to be looking for?
>
> Thanks,
>
> Gene
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=372616#372616
>
>
>
>
>
>
>
> Email Forum -
> - MATRONICS WEB FORUMS -
> List Contribution Web Site -
> -Matt
> Dralle, List Admin.
>
>
>
>
Message 3
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| Subject: | Re: Thinking of buying |
Thanks for the tip. I saw the ad on Barnstormers and I do not believe it is LSA
qualified.
That is a key for me. I am limited to about $50K budget right now as we are also
building a house.
Gene
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372631#372631
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| Subject: | Re: Landing gear shimmy |
Okay, no egg on my face I suppose. Finally got a video camera to check things
out. It's clearly the main gear.
It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few minutes.
This clip makes it pretty visible starting at 0:28 on the landing roll. I don't
use the brakes much to try to discount that influence, and I let the nose drop
the moment I land so I can see if it's the nose or mains.
On taxiing back, I decided to accelerate and test it again, and the second shimmy
can be seen at 1:28.
It may not look like much on a video camera, but that's a serious bit of wiggling
in the cockpit.
I'm astounded that the stiffeners don't make an impact on it. I can't flex them
by hand at all in that direction.
This is a big deal for me because I fly into some pretty busy places and it occurs
right at the speed I'd be doing on a long runway to hurry up and make a turnoff.
That, and I don't like passengers looking a little freaked out and asking
what the heck that was. And it can't be good for the whole plane to violently
shake like that.
For the record, I've balanced tires, changed to 6 ply tires, balanced those, and
now the fiberglass stiffeners. No relief yet. Not sure what comes next.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372654#372654
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| Subject: | Re: Landing gear shimmy |
Bill,
I have been plagued with similar problems. I tried most of what you have done,
except for stiffeners, with little or no effect. I did notice an improvement
when I remove the landing gear fairings. I did a lot of research on the subject
at one time. There are number of papers on the subject on the NASA web site.
These papers go back to the 1940's up to the 80's and 90's. There are just
to many variables for a simple fix. Things like tire pressure, runway surface
material, the kind of rubber used on the tire, flexing of the airframe, shape
of the gear, weight on the tire, toe in and toe out and the list keeps going
on. Even modern transports have problems at times and I been on some where
the shimmy was very noticeable.
A FULL-SCALE INVESTIGATION OF THE EFFECT OF
SEVERAL FACTORS On THE SHIMMY OF CASTING WHEELS
April 1940, Langley Aeronautical Laboratory.
TECHNICAL NOTE 3632
CORRELATION, EVALUATION, AND EXTENSION OF LINEARIZED
THEORIES FOR TIRE MOTION AND WHEEL SHIMMY
Langley Aeronautical Laboratory, Langley Field, Va.
Washington
June 1956
TECHNICAL NOTE 4001
SOME CONSIDERATIONS OF HYSTERESIS EFFECTS
ON TIRE MOTION AND WHEEL SHIMMY
Langley Aeronautical Laboratory, Langley Field, Va.
Washington
June 1957
REPORT No. 686
STABILITY OF CASTERING WHEELS FOR AIRCRAFT LANDING GEARS
REPORT 1299
CORRELATION, EVALUATION, AND EXTENSION OF LINEARIZED THEORIES FOR TIRE
MOTION AND WHEEL SHIMMY
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL MEMORANDUM 1378
DETERMINATION QF THE ELASTICC CONSTANTS
OF AIRPLANE TIRES
Washington
November 1954
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL MEMORANDUM 1337
Analytical Study of Shimmy of Airplane Wheels
Washington
September 1952
NASA/TM- 1999-209143
ARL-TR- 1976
An Overview of Landing Gear Dynamics
Langley Research Center, Hampton, Virginia
May 1999
Shimmy of Aircraft
Main Landing Gears
September 2000
ISBN 90-9014104-9
Copyright 2000 by I.J.M. Besselink
-----Original Message-----
From: owner-lightning-list-server@matronics.com [mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bill Strahan
Sent: Tuesday, May 08, 2012 2:37 PM
Subject: Lightning-List: Re: Landing gear shimmy
Okay, no egg on my face I suppose. Finally got a video camera to check things
out. It's clearly the main gear.
It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few minutes.
This clip makes it pretty visible starting at 0:28 on the landing roll. I don't
use the brakes much to try to discount that influence, and I let the nose drop
the moment I land so I can see if it's the nose or mains.
On taxiing back, I decided to accelerate and test it again, and the second shimmy
can be seen at 1:28.
It may not look like much on a video camera, but that's a serious bit of wiggling
in the cockpit.
I'm astounded that the stiffeners don't make an impact on it. I can't flex them
by hand at all in that direction.
This is a big deal for me because I fly into some pretty busy places and it occurs
right at the speed I'd be doing on a long runway to hurry up and make a turnoff.
That, and I don't like passengers looking a little freaked out and asking
what the heck that was. And it can't be good for the whole plane to violently
shake like that.
For the record, I've balanced tires, changed to 6 ply tires, balanced those, and
now the fiberglass stiffeners. No relief yet. Not sure what comes next.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372654#372654
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Message 6
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| Subject: | Re: Landing gear shimmy |
Hi Bill,
I'm sure you've already looked at this but what is your tire pressure?
We've also just experienced a case where the gear shimmied with no pants on
and then the shimmy was almost next to nothing with the wheel pants back on.
Go figure.
Also, I don't remember what setting we used when we set the toe in for your
gear. Double check that as well.
Best regards,
Mark
-----Original Message-----
From: owner-lightning-list-server@matronics.com
[mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bill Strahan
Sent: Tuesday, May 08, 2012 4:37 PM
Subject: Lightning-List: Re: Landing gear shimmy
Okay, no egg on my face I suppose. Finally got a video camera to check
things out. It's clearly the main gear.
It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few
minutes.
This clip makes it pretty visible starting at 0:28 on the landing roll. I
don't use the brakes much to try to discount that influence, and I let the
nose drop the moment I land so I can see if it's the nose or mains.
On taxiing back, I decided to accelerate and test it again, and the second
shimmy can be seen at 1:28.
It may not look like much on a video camera, but that's a serious bit of
wiggling in the cockpit.
I'm astounded that the stiffeners don't make an impact on it. I can't flex
them by hand at all in that direction.
This is a big deal for me because I fly into some pretty busy places and it
occurs right at the speed I'd be doing on a long runway to hurry up and make
a turnoff. That, and I don't like passengers looking a little freaked out
and asking what the heck that was. And it can't be good for the whole plane
to violently shake like that.
For the record, I've balanced tires, changed to 6 ply tires, balanced those,
and now the fiberglass stiffeners. No relief yet. Not sure what comes
next.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372654#372654
Message 7
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| Subject: | Re: Landing gear shimmy |
On 5/8/2012 2:36 PM, Bill Strahan wrote:
> It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few minutes.
Looks like a bit of resonance kicking in. Not sure, but it looks like maybe each
leg alternates in vibration; that is as one vibrates forward the other is going
backward.
I'm not a mechanical engineer and don't play one on TV, but my uninformed guess
is that when one of the legs flexes, the leg geometry may be such that it can't
help but cause the wheel to change its toe-in or toe-out angle. In this case as
one of the legs starts to bend it may be causing a toe-out condition in the
wheel, which causes even more bending and more toe-out. This would likely cause
the plane to pull to one side, causing the other wheel to experience a relative
toe-out condition, setting up the same thing there. Energy starts swapping sides.
Swept-back gear legs _might_ have an inherent geometry problem due to how they
rotate the axis of the wheels when they flex due to loads. So the toe-angle
would also change with changes in how much you load the airplane.
Perhaps gear legs straight out (right angle to the average direction of motion)
would flex mostly only up or down, changing the camber angle of the wheels but
not the toe-angle.
But as I said, I am not an engineer and the above might not be valid observations.
Message 8
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| Subject: | Re: Landing gear shimmy |
Bill, great video, thank you for your effort. Tex
----- Original Message -----
From: "Bill Strahan" <bill@gdsx.com>
Sent: Tuesday, May 08, 2012 5:36 PM
Subject: Lightning-List: Re: Landing gear shimmy
>
> Okay, no egg on my face I suppose. Finally got a video camera to check
> things out. It's clearly the main gear.
>
> It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few
> minutes.
>
> This clip makes it pretty visible starting at 0:28 on the landing roll. I
> don't use the brakes much to try to discount that influence, and I let the
> nose drop the moment I land so I can see if it's the nose or mains.
>
> On taxiing back, I decided to accelerate and test it again, and the second
> shimmy can be seen at 1:28.
>
> It may not look like much on a video camera, but that's a serious bit of
> wiggling in the cockpit.
>
> I'm astounded that the stiffeners don't make an impact on it. I can't
> flex them by hand at all in that direction.
>
> This is a big deal for me because I fly into some pretty busy places and
> it occurs right at the speed I'd be doing on a long runway to hurry up and
> make a turnoff. That, and I don't like passengers looking a little
> freaked out and asking what the heck that was. And it can't be good for
> the whole plane to violently shake like that.
>
> For the record, I've balanced tires, changed to 6 ply tires, balanced
> those, and now the fiberglass stiffeners. No relief yet. Not sure what
> comes next.
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=372654#372654
>
>
>
Message 9
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| Subject: | Re: Landing gear shimmy |
What about a different materal for the leg all together?
We dont have the problem on the lsa gear that often if at all. But the overlay
angle or sweep of the gear is not as pronounced.
Have thought about the use of titanium gear legs. That material is said to be "dead"
material due to make up. It does flex but does not spring back with as much
pep. Sonex uses this for their main legs, it is a bit more expensive but may
be a solution. Let me look into it.
Nick
Sent from my pocket
On May 8, 2012, at 7:06 PM, "Tex Mantell" <wb2ssj@rochester.rr.com> wrote:
>
> Bill, great video, thank you for your effort. Tex
>
>
>
>
>
>
>
> ----- Original Message ----- From: "Bill Strahan" <bill@gdsx.com>
> To: <lightning-list@matronics.com>
> Sent: Tuesday, May 08, 2012 5:36 PM
> Subject: Lightning-List: Re: Landing gear shimmy
>
>
>>
>> Okay, no egg on my face I suppose. Finally got a video camera to check things
out. It's clearly the main gear.
>>
>> It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few minutes.
>>
>> This clip makes it pretty visible starting at 0:28 on the landing roll. I don't
use the brakes much to try to discount that influence, and I let the nose
drop the moment I land so I can see if it's the nose or mains.
>>
>> On taxiing back, I decided to accelerate and test it again, and the second shimmy
can be seen at 1:28.
>>
>> It may not look like much on a video camera, but that's a serious bit of wiggling
in the cockpit.
>>
>> I'm astounded that the stiffeners don't make an impact on it. I can't flex
them by hand at all in that direction.
>>
>> This is a big deal for me because I fly into some pretty busy places and it
occurs right at the speed I'd be doing on a long runway to hurry up and make a
turnoff. That, and I don't like passengers looking a little freaked out and
asking what the heck that was. And it can't be good for the whole plane to violently
shake like that.
>>
>> For the record, I've balanced tires, changed to 6 ply tires, balanced those,
and now the fiberglass stiffeners. No relief yet. Not sure what comes next.
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=372654#372654
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>
Message 10
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| Subject: | Re: Landing gear shimmy |
BillThere is a natural resonance in my landing gear around 8 to 10 miles pe
r hour. If you are slower or faster there is no vibration but when you hit
that speed the wheels bounce pretty good. By adding or subtracting weight
(Wheel pants etc.) you just change the resonant frequency. With a resonan
ce problem in your landing gear the wheels can be perfectly balanced but th
e slightest excitement from a bump in the runway or an out of balance tire
=2C at the right speed=2C will get it going Try this=2C jack a wheel off t
he ground and using an air gun with a lot of pressure=2C in the area of the
tread spin the wheel up to see if you have a balance problem or out of rou
nd tire. Make sure you warm up the tire first by a few landings and then b
efore it cools off jack it up and let it sit for an hour to stabilize (reac
h it's natural shape). Then test it. You may need to put a padded support
under the area of the fuselage so the gear can flex freely during the test
. If the tires are allowed to cool after a flight while the plane is sitti
ng on them they will develope a flat spot that will lead to wheel bounce no
matter what you do.
Gary Barnett N335AL Sn 133.> Subject: Lightning-List: Re: Landing gear shi
mmy
> From: bill@gdsx.com
> Date: Tue=2C 8 May 2012 14:36:50 -0700
> To: lightning-list@matronics.com
>
>
> Okay=2C no egg on my face I suppose. Finally got a video camera to check
things out. It's clearly the main gear.
>
> It should be on youtube here: http://youtu.be/rzb_eeyhLJU in a few minu
tes.
>
> This clip makes it pretty visible starting at 0:28 on the landing roll.
I don't use the brakes much to try to discount that influence=2C and I let
the nose drop the moment I land so I can see if it's the nose or mains.
>
> On taxiing back=2C I decided to accelerate and test it again=2C and the s
econd shimmy can be seen at 1:28.
>
> It may not look like much on a video camera=2C but that's a serious bit o
f wiggling in the cockpit.
>
> I'm astounded that the stiffeners don't make an impact on it. I can't fl
ex them by hand at all in that direction.
>
> This is a big deal for me because I fly into some pretty busy places and
it occurs right at the speed I'd be doing on a long runway to hurry up and
make a turnoff. That=2C and I don't like passengers looking a little freak
ed out and asking what the heck that was. And it can't be good for the who
le plane to violently shake like that.
>
> For the record=2C I've balanced tires=2C changed to 6 ply tires=2C balanc
ed those=2C and now the fiberglass stiffeners. No relief yet. Not sure wh
at comes next.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=372654#372654
>
>
>
>
>
>
>
===========
===========
===========
===========
>
>
>
Message 11
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| 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.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=372675#372675
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