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New landing gear tracking?

RCharles

Registered User
Atlanta, Ga
How should the wheels be installed on a stock L21B with 800x6 tires so as to have the plane track straight with the tail wheel centered? Just installed new Univair stock gear and taxing everything feels fine but at landing speed touchdown the plane wants to feel as though it has gotten a gust of wind from the right requiring control inputs to stop the drift to the left . The nose is being held pointing straight down the runway but the plane still feels as though it is being blown by a wind from the right until it slows down with breaking...should the wheels be parallel,toed in ,toed out,or what? Or does the pilot just need some dual instruction? Help please.
 
Parallel. Take a simple tape meaure and check front center and back center. On your tires any toe in more than about 3/4" will give you trouble. Much better to have less than 1/2" difference, but zero is the desired.
 
Parallel. Take a simple tape meaure and check front center and back center. On your tires any toe in more than about 3/4" will give you trouble. Much better to have less than 1/2" difference, but zero is the desired.
Thanks Bob , I thought that would be the answer but now confirmed.
 
I found that 1/2" toe in on 31" Dessers was a bear. How did the plane react prior to the gear swap? When I repair fuselages we weld the gear fittings on with them parallel.
 
The issue with Cub style gear is there is no adjustment possible unless bending the axles is possible?? I have heard of folks putting a long pipe over the axle and adjusting the toe in by carefully bending the axle with the long pipe. Is this an accepted practice?
 
The issue with Cub style gear is there is no adjustment possible unless bending the axles is possible?? I have heard of folks putting a long pipe over the axle and adjusting the toe in by carefully bending the axle with the long pipe. Is this an accepted practice?

That's basically the practice--most use heat. But I don't think it is the axle you are bending. It's the tubes attached to the axle that actually bend a little.

Heating up the axle itself sounds like an opening to all sorts of troubles. My opinion only, based on making landing gear for my homebuilt.
 
What RV said! I have a similar issue that we looked at exactly as you described and came to the same conclusion as above. No predictable way to control the bending site!
 
tramcking

[Q
iIs there a way to shim the wheel angle at the attach point some way. to move it left or right.plane has double puck Cleveland breaks .?

UOTE=Kid Durango;803076]What RV said! I have a similar issue that we looked at exactly as you described and came to the same conclusion as above. No predictable way to control the bending site![/QUOTE]
 
Just installed new Univair stock gear and taxing everything feels fine but at landing speed touchdown the plane wants to feel as though it has gotten a gust of wind from the right requiring control inputs to stop the drift to the left .

How did the plane react prior to the gear swap? Was the gear the only thing changed?
 
How did the plane react prior to the gear swap? Was the gear the only thing changed?
[/QUOTE

that was all that was done.checked today and showed 1/4 inch toe in at front of tires with tape measure.Hit or miss. Question is ,what direction are the headed in...maybe both slightly left? Time for a laser I guess'
 
Snap a line down the center from the spinner tip to the tail post, clamp a straight edge to the brake discs and measure 40" forward of the axle center. .350 inch difference to the center line at 40 inches is .5 degrees toe in which I find is perfect. Heating the cluster is the only way to go, get it cherry red and let it cool slowly. PIA but well worth the effort, it will change the ground handling dramatically.


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I go 1/8" toe in 18" forward of the axle on the Taylorcrafts that I work on, they taxi perfect without squatting. I wound up using a piece of 5' well pipe to bend the gear into submission to get it there. Tim
 
Here is what I did today .The result was a bit hard to believe if I did this correctly. I shot a laser line down the center of fuselage and marked the laser dot on the hanger door. Then put a straight edge along side each wheel with small lasers attached to each and marked where they showed on the door. The plane was in level with the tail in what would be about a tail low wheel landing position.The LEFT main wheel laser dot measured 5 inches further from it to the center , than the right main wheel laser dot. The hanger door was 61/2 ft from the front of the wheels each the same....LEFT WHEEL WAY OUT THERE PULLING TO LEFT? Is this a valid way to get an idea what going on?
 
Seems to me it would be. I can’t see why it would be any different going forward rather than down, as long as everything was at the same ‘altitude’.
Tim: how did you control where the gear bent? Or can you tell where it bent?
 
Here is what I did today .The result was a bit hard to believe if I did this correctly. I shot a laser line down the center of fuselage and marked the laser dot on the hanger door. Then put a straight edge along side each wheel with small lasers attached to each and marked where they showed on the door. The plane was in level with the tail in what would be about a tail low wheel landing position.The LEFT main wheel laser dot measured 5 inches further from it to the center , than the right main wheel laser dot. The hanger door was 61/2 ft from the front of the wheels each the same....LEFT WHEEL WAY OUT THERE PULLING TO LEFT? Is this a valid way to get an idea what going on?

Just to be sure, I'd do it from the brake disks--or from rims without tires. From what you have observed there is a lot of misalignment. But it is good to take the tire variables out of the equation.

I did something similar on my homebuilt--measuring with a straight edge against the tires. The variation was quite noticeable when you turned the wheels 90 degrees and tried again.
 
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You are correct indeed ,the tires do not work well so shot the lines using the rotors and got better readings but still showing toe out on the left side .Seems like every time we measure we get some other reading.Checked the rotors with the laser and they are running true. So what the ...?
 
So just a thought. If you move the plane forward you have the actual ‘toe-in’. But if you push it in backwards the tires could put a little torque on things because of the geometry. It would be a small change, but I sure notice it.
 
This thread is confusing. You had a properly operating stock Cub on which for some reason you decided to install new landing gear. Why did you install new gear? Also since it apparently was functioning properly with the old gear, your new Univair gear appears to have an issue. What is Univair doing to fix their gear?

There appears to be some information missing in your request for help.
 
The answer is simple.The old gear was put on the cub in 1954 and the aircraft appeared to have been under water at one time because the fuselage hade to be replaced in 1994 but the gear was not. So I felt it was time to do so.
 
So just a thought. If you move the plane forward you have the actual ‘toe-in’. But if you push it in backwards the tires could put a little torque on things because of the geometry. It would be a small change, but I sure notice it.

Are you using greased plates under the wheels?
Double layer trash bags can be substituted.
 
...You had a properly operating stock Cub on which for some reason you decided to install new landing gear. Why did you install new gear? Also since it apparently was functioning properly with the old gear, your new Univair gear appears to have an issue. What is Univair doing to fix their gear?

Who's to say that the gear which was removed hadn't been tweaked to track straight sometime in the past?
The Univair gear might be right on the money, maybe the attach fittings or the fuselage are off.
 
last check done today .it seems a both wheels are pointed left . the left wheel is toed out5/16 inch and the right wheel is toed in by 9/16 0f an inch... both going to the left.So no wonder it wants to take of in that direction on landing?
 
When you roll the plane forward a toed in tire will ride up and narrow the track a toed out tire will do the opposite to a point. Roll it back and the opposite happens. You need to establish a proper track width and do your measurements at that width otherwise your numbers will change. If you’re confidant of your angles start with that left gear and bend it straight. It may be all you need
 
Truth be told - I don’t know! I’ve wondered and worried about it enough that I was afraid to try it on mine. I was concerned with changing the geometry as the gear swings, perhaps having something in a bind. Thanks though.
 
Leave good enough alone before you go twisting up a good set of gear. The toe difference is minimal and the fact that it's pointing both to the left isn't likely causing the plane to veer any such way. If 1/2" of toe and 7/16" left was causing cubs to veer off the left side of the runway there would be a whole lot more cubs off in the weeds. If you look at any cub out there close enough you'll find similar or worse measurements of the gear alignment. Cessnas are often even worse but they don't throw themselves off the runway on landing somehow.

I know this might be a touchy subject but is it possible that landing technique has something to do with your plane veering left? What's your landing speed? Can you just put in a bit more right rudder when flaring to keep the plane straight?
 
I have flown several taildraggers with 3/4" toe in, measured on 6" or 8" tires front to back. They are nowhere near as stable as a good set of zero toe in legs.

I have an orphan Cub gear leg that was removed from a ground loop Cub. I would love to have a simple measurement technique to see if it is tweaked without having to put it on an aircraft.
 
I have an orphan Cub gear leg that was removed from a ground loop Cub. I would love to have a simple measurement technique to see if it is tweaked without having to put it on an aircraft.
Try leaning it against a wall with the axle parallel to the floor. Measure the gear bolt bushings distance from the wall to see that they are the same. Then using a carpenters square see if the axle is perpendicular to the wall.
 
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