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mozart1(at)ctemail.net.au
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 Posted: Wed Oct 10, 2012 4:55 am Post subject: Main gear alignment Shimmy |
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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(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Bernard Melendez, Jr.
Sent: Sunday, 30 September 2012 3:03 AM
To: lightning-list(at)matronics.com
Subject: 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
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n45bm(at)yahoo.com
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| Posted: Wed Oct 10, 2012 6:40 am Post subject: Main gear alignment Shimmy |
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Hi Michael,
You could nitpick yourself to death on little or non-existing issues and never 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 wings (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(at)ctemail.net.au> wrote:
| Quote: |
From: MP <mozart1(at)ctemail.net.au>
Subject: RE: Main gear alignment Shimmy
To: lightning-list(at)matronics.com
Date: Wednesday, October 10, 2012, 7:54 AM
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(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Bernard Melendez, Jr.
Sent: Sunday, 30 September 2012 3:03 AM
To: lightning-list(at)matronics.com
Subject: 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
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mozart1(at)ctemail.net.au
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| Posted: Wed Oct 10, 2012 2:07 pm Post subject: Main gear alignment Shimmy |
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No worries Bernardo,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
I'll try to not nitpick myself to death Ha Ha,
but with all the communication about the shimmy and people with toe in, toe out, different tires and pressure some get it some not, therefore I believe there is maybe just a minor difference in the individual setup which causes the shimmy. Beside if you got on your car one wheel out of alignment you get very quickly oscillation, that’s happen already on a short axle attach point, in our case it is ~1m away! That’s what I tried to get across as just a thought for other people with this problem.
“the devil is in the detail”
Rgds
Michael
[quote]---
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