Today's Message Index:
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1. 05:37 PM - Gear leg shimmy experiments (N1BZRich@aol.com)
2. 06:32 PM - Re: Gear leg shimmy experiments (Colin J. Kennedy)
3. 07:58 PM - Re: Gear leg shimmy experiments (Jim Langley)
4. 08:34 PM - Re: Gear leg shimmy experiments (N1BZRich@AOL.COM)
5. 08:35 PM - Re: Gear leg shimmy experiments (N1BZRich@AOL.COM)
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Subject: | Gear leg shimmy experiments |
Hello all Lightning and Esqual listers,
Just before Christmas I send out what I called a "two year report for
N31BZ" which was some thoughts on the Jabiru 3300 and my highly modified Esqual
LS (meaning lots of Lightning Stuff) after flying for two years and some
400+ hours. One thing I mentioned was that I planned to do some experimenting
on the gear leg shimmy that we sometimes see (for me it is almost always when
landing or taxiing on a hard surface and occurs only when at about 22 mph).
Following is that paragraph about the shimmy and below that will be some
preliminary results of the shimmy experiments.
I have had no real airframe issues during the past two years. The only
thing I plan to change, when I get the time, will be to do some experiments on
the main gear legs to try to get rid of the sometime gear leg shimmy. I may go
the "broom stick" mod that the RV guys do, but before doing that I want to
try an easier fix by using a small "V" angle aluminum strip (say 1/8" thick by
1/2" on the angles, by what ever length the gear leg is) that will be
clamped to the trailing edge of the gear leg. All I need is the time. I already
have the parts. This shimmy occurs on landing roll out on hard surface as you
are slowing down through about 22 mph. It does not happen on grass. Tire
pressure definitely has an effect, with lower pressure being better. I
normally air my mains up to 25 PSI and then re-air them when they look low. That
low look seems to be about 15 to 18 PSI. I will let you all know the results
when I get the time to do the experiments.
As I mentioned above, I have now done some preliminary experiments to
find an easy fix to the main gear leg shimmy problem. Actually, I should say
that Joe and Linda Mathias and I have done some experiments since we used
their Lightning (N59JL) for the experiments. They had their gear leg fairings
off during the week after Christmas, so it just seemed like a good idea to try
my idea on their airplane. We actually tried two different size aluminum
stips clamped to the trailing edge of the gear legs. The first piece of
aluminum "V" angle was 1/16" thick by 1/2 wide and 13 inches long. We used three
hose clamps on each gear leg to hold these 1/16" V strips in place on each main
gear leg. We tried the thinner material first thinking that if it worked it
would weigh less. Results were not that noticeable on the taxi test -
maybe some improvement, but not near the reduction in shimmy that we wanted.
Next we put the 13" long strips of 1/8" thick by 3/4" wide and used the same
hose clamps to securely attach the strips to each gear leg trailing edge.
Results were very promising on the taxi test and one flight that Linda made that
day. Her exact words were "no gear leg shimmy on that landing".
Obviously more test flights will be made to confirm that this is a good
fix, but we did want to get the word out in case others want to add to our
efforts and try it out on your airplane. The aluminum V angle seems to be
available at all Lowes, Home Depot and Ace Hardware stores that I have visited,
and it is 1/8" thick by 3/4" wide and I think 42" inches long . Only one
piece of the aluminum strip is required (about $8.00) and you will cut the length
to fit each of your gear legs. We used two 13" pieces on N59JL. The hose
clamps are standard hose clamps like we all have laying around the hangar or
readily available at the hardware stores. The long term fix will probably be
to weld the aluminum V strips to the aluminum gear legs, but the clamps allow
you to get them on quickly for the testing. What this fix is doing is
adding stiffness to the gear legs, just like the RV guys do by fiber-glassing
a
grooved broom stick to the trailing edge of the gear legs. I think out fix is
less work.
Let us all know if you have any questions and if you try this and what
results you have. I should have had some photos to send out with this, but
alas, I did not think to take photos. I am sure Linda will let us know when
she has made a few more landings with this gear leg mod in place.
Blue Skies and Happy New Year,
Buz
**************Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
Message 2
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Subject: | Gear leg shimmy experiments |
Buz,
What about using epoxy to attach the aluminum angles?
Do you think there is a risk of failure and subsequent damage from
flying
metal?
While a good weld is very strong, could the heat be enough to change the
properties of the gear leg material?
Colin K.
OK
-----Original Message-----
From: owner-lightning-list-server@matronics.com
[mailto:owner-lightning-list-server@matronics.com] On Behalf Of
N1BZRich@aol.com
Sent: Thursday, January 03, 2008 7:37 PM
Subject: Lightning-List: Gear leg shimmy experiments
Hello all Lightning and Esqual listers,
Just before Christmas I send out what I called a "two year report
for
N31BZ" which was some thoughts on the Jabiru 3300 and my highly modified
Esqual LS (meaning lots of Lightning Stuff) after flying for two years
and
some 400+ hours. One thing I mentioned was that I planned to do some
experimenting on the gear leg shimmy that we sometimes see (for me it is
almost always when landing or taxiing on a hard surface and occurs only
when
at about 22 mph). Following is that paragraph about the shimmy and
below
that will be some preliminary results of the shimmy experiments.
I have had no real airframe issues during the past two years. The only
thing I plan to change, when I get the time, will be to do some
experiments
on the main gear legs to try to get rid of the sometime gear leg shimmy.
I
may go the "broom stick" mod that the RV guys do, but before doing that
I
want to try an easier fix by using a small "V" angle aluminum strip (say
1/8" thick by 1/2" on the angles, by what ever length the gear leg is)
that
will be clamped to the trailing edge of the gear leg. All I need is the
time. I already have the parts. This shimmy occurs on landing roll out
on
hard surface as you are slowing down through about 22 mph. It does not
happen on grass. Tire pressure definitely has an effect, with lower
pressure being better. I normally air my mains up to 25 PSI and then
re-air
them when they look low. That low look seems to be about 15 to 18 PSI.
I
will let you all know the results when I get the time to do the
experiments.
As I mentioned above, I have now done some preliminary experiments
to
find an easy fix to the main gear leg shimmy problem. Actually, I
should
say that Joe and Linda Mathias and I have done some experiments since we
used their Lightning (N59JL) for the experiments. They had their gear
leg
fairings off during the week after Christmas, so it just seemed like a
good
idea to try my idea on their airplane. We actually tried two different
size
aluminum stips clamped to the trailing edge of the gear legs. The first
piece of aluminum "V" angle was 1/16" thick by 1/2 wide and 13 inches
long.
We used three hose clamps on each gear leg to hold these 1/16" V strips
in
place on each main gear leg. We tried the thinner material first
thinking
that if it worked it would weigh less. Results were not that noticeable
on
the taxi test - maybe some improvement, but not near the reduction in
shimmy
that we wanted. Next we put the 13" long strips of 1/8" thick by 3/4"
wide
and used the same hose clamps to securely attach the strips to each gear
leg
trailing edge. Results were very promising on the taxi test and one
flight
that Linda made that day. Her exact words were "no gear leg shimmy on
that
landing".
Obviously more test flights will be made to confirm that this is a
good
fix, but we did want to get the word out in case others want to add to
our
efforts and try it out on your airplane. The aluminum V angle seems to
be
available at all Lowes, Home Depot and Ace Hardware stores that I have
visited, and it is 1/8" thick by 3/4" wide and I think 42" inches long .
Only one piece of the aluminum strip is required (about $8.00) and you
will
cut the length to fit each of your gear legs. We used two 13" pieces on
N59JL. The hose clamps are standard hose clamps like we all have laying
around the hangar or readily available at the hardware stores. The long
term fix will probably be to weld the aluminum V strips to the aluminum
gear
legs, but the clamps allow you to get them on quickly for the testing.
What
this fix is doing is adding stiffness to the gear legs, just like the RV
guys do by fiber-glassing a grooved broom stick to the trailing edge of
the
gear legs. I think out fix is less work.
Let us all know if you have any questions and if you try this and
what
results you have. I should have had some photos to send out with this,
but
alas, I did not think to take photos. I am sure Linda will let us know
when
she has made a few more landings with this gear leg mod in place.
Blue Skies and Happy New Year,
Buz
_____
Start the year off right. Easy ways to stay in shape
<http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489>
in
the new year.
Message 3
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Subject: | Gear leg shimmy experiments |
I wonder how the RV guys attach theirs?
_____
From: owner-lightning-list-server@matronics.com
[mailto:owner-lightning-list-server@matronics.com] On Behalf Of Colin J.
Kennedy
Sent: Thursday, January 03, 2008 9:31 PM
Subject: RE: Lightning-List: Gear leg shimmy experiments
Buz,
What about using epoxy to attach the aluminum angles?
Do you think there is a risk of failure and subsequent damage from flying
metal?
While a good weld is very strong, could the heat be enough to change the
properties of the gear leg material?
Colin K.
OK
Message 4
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Subject: | Re: Gear leg shimmy experiments |
In a message dated 1/3/2008 9:33:55 P.M. Eastern Standard Time,
cjk129@cox.net writes:
What about using epoxy to attach the aluminum angles?
Do you think there is a risk of failure and subsequent damage from flying
metal?
While a good weld is very strong, could the heat be enough to change the
properties of the gear leg material?
Hi Colin,
I guess we need to do some sort of study on the strength of epoxy when
used on aluminum. Probably the best way would be to epoxy it in place then
wrap it with one or two fibergass cloth wraps. That is what the RV guys do -
they fiberglass the wood to the gear leg. I really don't think that an epoxy
failure would be a major problem, but you certainly would get the shimmy
back. The un-epoxyed aluminum part should stay inside the gear leg fairing
(certainly with the fiberglass). Probably my only concern would be to immediately
check your brake line down that gear leg.
As to welding aluminum, I don't have the answer as to whether the heat
would alter the temper of the gear leg We need to ask Nick that. I seem to
remember seeing some aluminum welding rods at Oshkosh that had a working
temperature of around 700 dgrees and could be used with a propane flame. Other
than that method, I guess TIG would be the way to go. I only weld steel (4130)
with oxygen accelyne.
Blue Skies,
Buz
**************Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
Message 5
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Subject: | Re: Gear leg shimmy experiments |
In a message dated 1/3/2008 10:59:52 P.M. Eastern Standard Time,
pequeajim@gmail.com writes:
I wonder how the RV guys attach theirs?
They fiberglass the wood dowel to the gear leg.
Blue Skies,
Buz
**************Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
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