Shock absorbent landing gear  
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All Forums >> RC Airplanes >> S.P.A.D. Aircraft - Coroplast design >> Shock absorbent landing gear
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Shock absorbent landing gear - 2/29/2008 8:32:32 PM   
BillBabe


 

Posts: 61
Joined: 11/1/2003
From: Baltimore, MD, USA
Status: offline 		I don't like the idea of inserting skewers into the flutes on the bottom of a plane for protection against crushing. Has anybody tried installing a foam rubber pad between the bottom of the plane and the landing gear mounting block? it would seem that this should provide some shock absorbancy as well as protect the bottom of the plane. Has anyone tried this or have any other ideas?
       Post #: 1

RE: Shock absorbent landing gear - 2/29/2008 10:15:43 PM   
Villa



Posts: 873
Joined: 8/12/2003
From: Wilson, NC,
Status: offline 		Hi BillBabe
There are all types of foam rubber. The type I'm used to would crush solid by the time you tighten the gear mounting bolts and the shock absorbing capability would be gone. I use bamboo skewers in the flutes all the time. What problem do you have with them? I have a 4 year old SPAD Flying Lawnmower that can land hard enough to make a Navy Carrier pilot wince. It has bamboo skeweres under all of the mounting surfaces. I must confess I have no idea if there is a problem since i don't take it apart for inspection. It flyes well and lands great.

(in reply to BillBabe)
       Post #: 2

RE: Shock absorbent landing gear - 3/1/2008 3:36:46 AM   
OzMo



Posts: 1436
Joined: 9/2/2002
From: OZark, MO, USA
Status: offline 		Padding the LG would cause to much flex. The tried and true methods such as a little yard stick in side the fuse work well.
Skewers for anti crush is a great idea....not sure who had it first.... I stole it from someone who stole it from..........

_____________________________

Yes dear, I did glue my hand to the airplane to keep from dropping it.

(in reply to Villa)
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RE: Shock absorbent landing gear - 3/2/2008 12:00:08 AM   
BillBabe


 

Posts: 61
Joined: 11/1/2003
From: Baltimore, MD, USA
Status: offline 		The skewers remain my fall back method. Every time I build another plane, I try to find a different way of constructing. As some of these ideas pop into my head, I'm curious if they've been tried. Thats why I post. It still seems that the foam rubber would absorb a lot of the force that would normally be applied to the bottom of the plane from the landing gear. However, I can understand that there may be a vibration issue.

(in reply to OzMo)
       Post #: 4

RE: Shock absorbent landing gear - 3/2/2008 6:59:10 AM   
OzMo



Posts: 1436
Joined: 9/2/2002
From: OZark, MO, USA
Status: offline 		BillBabe,
Shock absorbing landing gear is a fine idea and has shown up on many a model and full scale plane, The Piper Cub's bungee set up is a good example. Most landing gear absorb shock or flex under load of landing. Foam wheels also help in this situation. Foam rubber would be a little to soft to be applicable IMHO. But that would depend on just how it was used so one never knows ...you may be on to something because there are a lot of different densities in "foam rubber". EPP for examlpe is much denser than the common cushion foam rubber and could possibly be used in this way.
A sleeve of EPP around the inside the fuse part of a music wire gear then hard fiberglass it to the fuse would add some shock absorption. hmmm

_____________________________

Yes dear, I did glue my hand to the airplane to keep from dropping it.

(in reply to BillBabe)
       Post #: 5

RE: Shock absorbent landing gear - 3/2/2008 2:28:45 PM   
Villa



Posts: 873
Joined: 8/12/2003
From: Wilson, NC,
Status: offline 		Hi BillBabe
I have been using torsion bar landing gear for many years. My planes can land hard enough to make a Navy Carrier pilot wince. Just yesterday I made a very hard landing with that plane when landing in wind gusts to 25MPH when I hit a downdraft. No damage. See http://www.rcuniverse.com/forum/m_7019698/anchors_7019698/mpage_1/key_twin%252Ctail%252Cspad/anchor/tm.htm#7019698
I have the same gear on my Flying Lawnmower. That plane hits hard occasionally because I love "touch and goes". That plane, without "wings", occasionally causes me to lose reference with the ground and I hit sooner than expected. Never a problem with the main gear. Are you familiar with torsion bars?

(in reply to OzMo)
       Post #: 6

RE: Shock absorbent landing gear - 3/2/2008 10:45:43 PM   
DLSmith2



Posts: 526
Joined: 8/25/2002
From: Nacogdoches, TX, USA
Status: offline
quote:

ORIGINAL: Villa

Are you familiar with torsion bars?


Yeah, it's a chain of saloons in the Raleigh-Durham area that caters to R/C pilots...


(in reply to Villa)
       Post #: 7

RE: Shock absorbent landing gear - 3/2/2008 11:22:36 PM   
BillBabe


 

Posts: 61
Joined: 11/1/2003
From: Baltimore, MD, USA
Status: offline 		Hi Villa:

I've heard of Joe's bar and Ed's bar, but I've never heard of Torsion's bar. Ugh!!

I think you hit it on the head. I think I understand from your pictures how it works. It seems that the force of the landing trying to push the vertical landing gear member backwards is absorbed by causing the horizontal member of the landing gear to twist. The result being that the net force on the landing gear seems to be directed toward the rear of the plane rather than upward into the plane trying to crush the coro. I have a 9 pound plane so I'm going to try this starting with 3/16 in wire.

Is this analysis close?

Clarence

< Message edited by BillBabe -- 3/2/2008 11:25:15 PM >

(in reply to Villa)
       Post #: 8

RE: Shock absorbent landing gear - 3/2/2008 11:45:21 PM   
Villa



Posts: 873
Joined: 8/12/2003
From: Wilson, NC,
Status: offline 		Hi BillBabe
Good choice for the wire diameter. I assume you are going to use music wire and bend it cold. Note the direction of the bend to make the axel shaft. I used to bend them in the opposite direction. I settled on the direction shown in my photos in order to maintain tire-toe in as the gear changes geometry from frequent usage. Bending it in the other direction gives toe-out with wear which is bad for good tracking on the ground. I try to make a complete pair of gear from the same rod. I have found that when I used to make one side from one rod and the other side from a different rod, that the gear bent out of shape differntly in hard landings. When you bend the wire use something that gives an inside bend radius not less than the wire diameter. You may find that others may completely dissagree with what I have stated. Be informed, open minded and read a few opinions. Good luck.

(in reply to BillBabe)
       Post #: 9

RE: Shock absorbent landing gear - 3/3/2008 1:01:49 AM   
BillBabe


 

Posts: 61
Joined: 11/1/2003
From: Baltimore, MD, USA
Status: offline 		Villa:

That bend direction for toe-in is very clever. I'll use it. Thanks again.

Clarence

(in reply to Villa)
       Post #: 10

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