Today's Message Index:
----------------------
1. 05:55 AM - Re: Main gear alignment Shimmy (MP)
2. 07:40 AM - Re: Main gear alignment Shimmy (Bernard Melendez, Jr.)
3. 03:07 PM - Re: Main gear alignment Shimmy (mozart1@ctemail.net.au)
Message 1
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| Subject: | Main gear alignment Shimmy |
Hi Bernardo,
I'm also very close to mount the wheels as I have already installed the Spar
Box, I was reading all the information about shimmy and also methods of
wheel alignment. One interesting part I discovered on my spar box was, as I
had fitted the box into the fuse I double, triple checked all measurements
and was certain the box is square to the firewall when I measured the
distance, firewall to the leg mounts as I found a difference of 3mm. One
tube is 3mm more to the front as the other. This will be not an issue during
operation as such I hope; if one wheel is a few mill further back as the
other, but if you use the method you displayed it could be. Because then you
could end up with one wheel toe in and the other toe out; worst case!
Therefor I did also some trig calcs and found that in my case with 5mm
difference on the wheel position I could end up with 0.25deg difference in
toe, which could be enough at a certain speed to create unequal pressure to
the wheels to create the shimmy as a few people experience. Maybe this is
nothing to be worry about, but thought I'll bring it up for others to
commend on it!
I suggest your method is good if everything is square, but I will definitely
use also a laser to align each wheel independent and check!
That's one more theory to the shimmy issue to confuse the minds!
Cheers
Michael
From: owner-lightning-list-server@matronics.com
[mailto:owner-lightning-list-server@matronics.com] On Behalf Of Bernard
Melendez, Jr.
Sent: Sunday, 30 September 2012 3:03 AM
Subject: Lightning-List: Main gear alignment
Hi guys,
Here's my method for aligning the main gear. Of course, it helps to have a
machinist buddy to make my drilling jig(s).
First, two 1/2" aluminum tubes are inserted in the axles so that they meet
in the middle. That tells me that the wheels are parallel with the fuselage
center line. Then using trigonometry to determine and rotate the gear to
match the short leg of the triangle, twist one gear leg to the desired
toe-in (I used 1 1/2 degrees toe-in). The gear socket is then drilled,
preferably using a drill jig. Once that's done, twist the other gear leg so
that the end of the aluminum rods again meet and drill the second leg. Easy
peachy, lemon squeezy.
Hope this helps.
Bernardo
Message 2
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| Subject: | Main gear alignment Shimmy |
Hi Michael,
You could nitpick yourself to death on little or non-existing issues and ne
ver finish or fly the plane. Believe me, very minor differences such as you
're very accurately measuring won't make any difference.
I'd be more concerned that the angle of incidence and squareness of the win
gs (and tail) to the center line of the fuselage are as close to each other
as you can make it. Then finish and fly the thing. Whether you use a laser
to align the main gear, or use the 1/2" diameter rod for alignment is your
choice. The fact that one wheel is 3 mm further back than the other won't
make a hill of beans. Keep building, don't worry, be happy.
Bernardo
--- On Wed, 10/10/12, MP <mozart1@ctemail.net.au> wrote:
From: MP <mozart1@ctemail.net.au>
Subject: RE: Lightning-List: Main gear alignment Shimmy
Hi Bernardo, =C2-I=99m also very close to mount the wheels as I hav
e already installed the Spar Box, I was reading all the information about s
himmy and also methods of wheel alignment. One interesting part I discovere
d on my spar box was, as I had fitted the box into the fuse I double, tripl
e checked all measurements and was certain the box is square to the firewal
l when I measured the distance, firewall to the leg mounts as I found a dif
ference of 3mm. One tube is 3mm more to the front as the other. This will b
e not an issue during operation as such I hope; if one wheel is a few mill
further back as the other, but if you use the method you displayed it could
be. Because then you could end up with one wheel toe in and the other toe
out; worst case! Therefor I did also some trig calcs and found that in my c
ase with 5mm difference on the wheel position I could end up with 0.25deg d
ifference in toe, which could be enough at a certain speed to create unequa
l
pressure to the wheels to create the shimmy as a few people experience. Ma
ybe this is nothing to be worry about, but thought I=99ll bring it up
for others to commend on it!I suggest your method is good if everything is
square, but I will definitely use also a laser to align each wheel indepen
dent and check!That=99s one more theory to the shimmy issue to confus
e the minds! =C2-CheersMichael =C2- =C2- =C2-From: owner-lightning-
list-server@matronics.com [mailto:owner-lightning-list-server@matronics.com
] On Behalf Of Bernard Melendez, Jr.
Sent: Sunday, 30 September 2012 3:03 AM
Subject: Lightning-List: Main gear alignment =C2-Hi guys,
Here's my method for aligning the main gear. Of course, it helps to have a
machinist buddy to make my drilling jig(s).
First, two 1/2" aluminum tubes are inserted in the axles so that they meet
in the middle. That tells me that the wheels are parallel with the fuselage
center line. Then using trigonometry to determine and rotate the gear to m
atch the short leg of the triangle, twist one gear leg to the desired toe-i
n (I used 1 1/2 degrees toe-in). The gear socket is then drilled, preferabl
y using a drill jig. Once that's done, twist the other gear leg so that the
end of the aluminum rods again meet and drill the second leg. Easy peachy,
lemon squeezy.
Hope this helps.
Bernardo =C2-
Message 3
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| Subject: | Main gear alignment Shimmy |
=C2- =0A=0ANo worries Bernardo,=0A=0AI'll try to not nitpick mys
elf to death Ha Ha, =0A=0Abut with all the communication about the sh
immy and people with toe=0Ain, toe out, different tires and pressure som
e get it some not,=0Atherefore I believe there is maybe just a minor dif
ference in the=0Aindividual setup which causes the shimmy. Beside if you
got on your=0Acar one wheel out of alignment you get very quickly oscil
lation,=0Athat=99s happen already on a short axle attach point, in
our case it=0Ais ~1m away! That=99s what I tried to get across as
just a thought for=0Aother people with this problem.=C2-=C2- =C2-
=0A=0A=C2- =0A=0A=9Cthe devil is in the detail=9D=0A
=0A=C2- =0A=0ARgds=0A=0AMichael=0A=0A----- Original Message -
----=0A From:lightning-list@matronics.com=0ATo:=0ACc:=0ASent:Wed, 10 Oct
2012 07:39:43 -0700 (PDT)=0ASubject:RE: Lightning-List: Main gear align
ment Shimmy=0A=0AHi Michael,=0AYou could nitpick yourself to death on li
ttle or non-existing issues=0Aand never finish or fly the plane. Believe
me, very minor differences=0Asuch as you're very accurately measuring w
on't make any difference.=0AI'd be more concerned that the angle of inci
dence and squareness of=0Athe wings (and tail) to the center line of the
fuselage are as close=0Ato each other as you can make it. Then finish a
nd fly the thing.=0AWhether you use a laser to align the main gear, or u
se the 1/2"=0Adiameter rod for alignment is your choice. The fact that o
ne wheel is=0A3 mm further back than the other won't make a hill of bean
s. Keep=0Abuilding, don't worry, be happy.=0ABernardo =0A=0A--- On WED,
10/10/12, MP __ wrote:=0A=0AFrom: MP =0ASubject: RE: Lightning-List: Ma
in gear alignment Shimmy=0ATo: lightning-list@matronics.com=0ADate: Wedn
esday, October 10, 2012, 7:54 AM=0A=0AHi Bernardo, =0A=0A=C2-
=0A=0AI=99m also very close to mount the wheels as I have alre
ady installed=0Athe Spar Box, I was reading all the information about sh
immy and also=0Amethods of wheel alignment. One interesting part I disco
vered on my=0Aspar box was, as I had fitted the box into the fuse I doub
le, triple=0Achecked all measurements and was certain the box is square
to the=0Afirewall when I measured the distance, firewall to the leg mou
nts as I=0Afound a difference of 3mm. One tube is 3mm more to the front
as the=0Aother. This will be not an issue during operation as such I ho
pe; if=0Aone wheel is a few mill further back as the other, but if you u
se the=0Amethod you displayed it could be. Because then you could end up
with=0Aone wheel toe in and the other toe out; worst case! =0A=0ATh
erefor I did also some trig calcs and found that in my case with=0A5mm d
ifference on the wheel position I could end up with 0.25deg=0Adifference
in toe, which could be enough at a certain speed to create=0Aunequal pr
essure to the wheels to create the shimmy as a few people=0Aexperience.
Maybe this is nothing to be worry about, but thought=0AI=99ll bri
ng it up for others to commend on it! =0A=0AI suggest your method is
good if everything is square, but I will=0Adefinitely use also a laser
to align each wheel independent and check!=0A=0A=0AThat=99s on
e more theory to the shimmy issue to confuse the minds! =0A=0A=C2-
=0A=0ACheers =0A=0AMichael =C2- =0A=0A=C2- =0A=0A=C2-
=0A=0AFROM: owner-lightning-list-server@matronics.com=0A[mailto:owne
r-lightning-list-server@matronics.com] ON BEHALF OF=0ABernard Melendez,
Jr.=0ASENT: Sunday, 30 September 2012 3:03 AM=0ATO: lightning-list@matr
onics.com=0ASUBJECT: Lightning-List: Main gear alignment =0A=0A=C2-
=0A=0AHi guys,=0AHere's my method for aligning the main gear. Of cou
rse, it helps to=0Ahave a machinist buddy to make my drilling jig(s).=0A
First, two 1/2" aluminum tubes are inserted in the axles so that they=0A
meet in the middle. That tells me that the wheels are parallel with=0Ath
e fuselage center line. Then using trigonometry to determine and=0Arotat
e the gear to match the short leg of the triangle, twist one gear=0Aleg
to the desired toe-in (I used 1 1/2 degrees toe-in). The gear=0Asocket
is then drilled, preferably using a drill jig. Once that's=0Adone, twis
t the other gear leg so that the end of the aluminum rods=0Aagain meet a
nd drill the second leg. Easy peachy, lemon squeezy.=0AHope this helps.
=0ABernardo=0A=0A=C2-=0A=0A
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