 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
nick(at)flylightning.net
Guest
|
 Posted: Wed Sep 12, 2012 6:09 am Post subject: Landing Gear and shimmy |
 |
|
The original esqual gear was a flat plate steel type which bolted to the fuselage thru the 6 bolts holding the spar box in. the overturn angle of the gear (how much it angled from the fuselage) was very steep. This transfers more load to the attach points and surrounding structure because it wont flex as much. The EXP tube gear has greater angle and less load transfer but is more subject to shimmy being a round rod. The Lightning EXP gear is 7075T6, plenty sturdy for the intended application. The Equal round gear is a different type alloy, although I do not remember what, experience in the field says it’s something lighter in alloy than the 7075T6.
A spring steel gear is not necessarily stronger than aluminum. The RV are spring steel an too subject to shimmy, I have experienced in a few of the RV models I have flown. IT is just a matter of a round tube subject to it. The Steel has a higher frequency and may not exhibit a shimmy at the same speed and aircraft weight of the aluminum. I have even experienced in a Rans S7S with round tube gear, just at a lower speed around 12-15mph on roll out.
What we have found works here, covered multiple times. Is about 1 degree toe out on the EXP gear. This coupled with air-pressure in the 22-25psi range with keep drag on the gear and minimize it from moving around . Higher air-pressure just causes the tire to skip and shimmy better. Also it seems that the Better tires help, I believe from the squared off tire tread they have instead of the round tread.
If all of this does not help we have almost completely eliminated it on aircraft when bonding hardwood to the gear leg. Simply clamping the hard wood to the Leg will not help. I have used wood like Oak. A piece of hard wood that it fitted to within ” of the bottom of the fuselage to the lower socket. Mill out one side round to fit the gear leg. The wood should be at least the 1” wide that the gear is, by about 2” aft of it. Mill the trailing edge to fit under the leg fairing. Lightly sand the aft side of the gear leg. Bond the gear leg to the back of the gear leg with 24hr epoxy and flox, clamp in place to cure. After cure wrap the wood and leg with 10oz glass. The glass should be cut in sections the same length as the hard wood by about 7” wide to completely wrap the gear. Also it is critical to cut these sections out of the glass cloth on a 45 degree bias to the weave. IF you simply use the glass in the direction of the weave it will not resist the fore and aft movement of the gear. I have use about 4 layers of glass. I suppose if you wished 2 layers of carbon cut a laminated the same way should work.
The wood does stiffen the gear, but keeps the spring it needs, What the wood does is change the frequency that the gear shimmy’s at and helps dampen out any that may occur. Lighter or softer materials will not work. Simply adding glass to the gear will not help.
As for the LSA wide track landing gear. We set the gear at 0 toe, straight ahead, with the wings off the aircraft. Actually we set this with the spar box out of the aircraft during the build process. With a little weight on the gear it may toe out slightly. We very rarely run into shimmy with the big gear, if we do it usually goes back to over inflated tires, flat spots, or infrequent flying that flat spots the tires and creates a skip. The overturn angle of the LSA gear is much greater than the EXP gear. The LSA gear is 2.125” at the top and 1.25” at the bottom VS 1.375” and 1” on the EXP gear just for FYI.
Nick Otterback
Arion Aircraft LLC
R&D Technical Support
931-680-1781
nick(at)flylightning.net (nick(at)flylightning.net)
[quote][b]
| | - The Matronics Lightning-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Lightning-List |
|
|
|
| Back to top |
|
 |
dwwilt
Joined: 06 Dec 2010
Posts: 192
|
| Posted: Wed Sep 12, 2012 6:19 am Post subject: Landing Gear and shimmy |
|
|
My EA-B version of the LSA has the LSA gear just because they are supposed to be a bit more sturdy. My only complaint with the lightning gear is that it is not very forgiving on landing. It is pretty stiff, so if you happen to land a little hard, you will bounce and that means a go around for me. Some of you may be better at saving such a landing, but I choose to go around and do it again, hopefully without the bounce.
I set my toe to 0 degrees without weight on the wheels and keep my air pressure around 25 psi. I have never had the shimmy.
Have a wonderful day,
Dennis
N616DW (Arion LightningS/N 132)
--
| | - The Matronics Lightning-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Lightning-List |
|
_________________
Dennis |
|
| Back to top |
|
|
nick(at)flylightning.net
Guest
|
| Posted: Wed Sep 12, 2012 8:04 am Post subject: Landing Gear and shimmy |
|
|
I think you might mean springy not stiff. During drop test at gross weight, we have nearly 6” deflection of the landing gear system. The little tube in a tube is an easy way to check deflection, set against the ground before the drop and see how far it gets displaced. Usually the bounce comes from the nose gear return and the aircraft going back into a flight attitude with sufficient speed to fly.
Attached some pics for fun. The drop test were the funnest testing we did, along with destructive testing of the wing.
Nick
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Dennis W. Wilt
Sent: Wednesday, September 12, 2012 9:18 AM
To: lightning-list(at)matronics.com
Subject: Re: Landing Gear and shimmy
My EA-B version of the LSA has the LSA gear just because they are supposed to be a bit more sturdy. My only complaint with the lightning gear is that it is not very forgiving on landing. It is pretty stiff, so if you happen to land a little hard, you will bounce and that means a go around for me. Some of you may be better at saving such a landing, but I choose to go around and do it again, hopefully without the bounce.
I set my toe to 0 degrees without weight on the wheels and keep my air pressure around 25 psi. I have never had the shimmy.
Have a wonderful day,
Dennis
N616DW (Arion Lightning S/N 132)
--
| | - The Matronics Lightning-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Lightning-List |
|
|
|
| Back to top |
|
|
dwwilt
Joined: 06 Dec 2010
Posts: 192
|
| Posted: Wed Sep 12, 2012 9:31 am Post subject: Landing Gear and shimmy |
|
|
Nick, could be, but I know of at least 2 that was a bounce off the mains. Cool pictures, I would like to see video.
Have a wonderful day,
Dennis
N616DW (Arion LightningS/N 132)
--
| | - The Matronics Lightning-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Lightning-List |
|
_________________
Dennis |
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
