Alignment or What??

[vetdrem]

I have a problem that I hope someone can help me with.

I have a model III with a bungee gear and FOXKING tires that I "hanger" in an enclosed trailer.

I placed blocks in the ground to help position the mains while the tailwheel is put in a track centered in the trailer. I put the mains on the blocks, tailwheel in the track and winch the plane into the trailer.

It seems that the plane tends to move to the right as it enters the trailer. When I winch the plane back out, it moves to the right even more. It will move 10-12 inches. Picture 1 shows how I position it before winching it into the trailer, picture 2 shows how far to the right it moves when winching it in and back out.

I did a quick check of the alignment and I think that it is toed-in a little, but both seem to be about equal. The distance from the main axel to the tailwheel is equal for both wheels. We just changed the bungees and there seems to be quite a bit of camber with it sitting empty but I think that is to be expected.

I just don't understand why it acts like the mains are turning to the left when winching it into the trailer, and like the mains are turning (a lot) to the right when winching it out of the trailer.

ANY IDEAS?????

Louie

[jrevens]

Louie,
The wheels may be aligned perfectly with each other but are not aligned with the center-line of the aircraft, or the gear is not aligned with the center-line. They should be aligned with reference to the center-line of the fuselage, as well as with each other. The only other thing I can think of right now is some possible excess friction (i.e. - a dragging brake) on one of the wheels.

[KFfan]

Here is a good tutorial on alignment

http://www.teamkitfox.com/Forums/showthread.php?t=2802&highlight=align

[t j]

That is strange. Does the main gear spread when rolled backwards and close back in when rolled forward...due to the toe in? Maybe that has something to do with it but I can't figure out why it doesn't come back to the same spot.

[PapuaPilot]

That is correct. If you have toe in the wheels will tend to come when going forward and spread if you back the plane up.

BTW I am going to add a couple more suggestions to the thread on wheel alignment.

[beeryboats]

Does it have a tendency to try and ground loop? My dad had a Baby Great Lakes that was a little touchy on landing. He found it had excessive toe-in.

[vetdrem]

It's not a problem on grass, and I usually try to avoid pavement like the plague. I tried it today and landed twice at two different paved runways, and was even able to fly it back to my home airport.

I think that the toe-in condition that I think exists is most likely the cause. I'll work at correcting the alignment, then let everyone know how it came out.

Loue

[PapuaPilot]

What you describe is normal for a plane with poor wheel alignment. On the grass the wheels can slip and the plane keeps going the way the inertia is going. When you land in pavement the plane will go wherever the wheels are pointed.

When you get your wheels aligned your plane should be really sweet on pavement too. Make sure you read my tips that I added to the thread on wheel alignment.

[t j]

Papua, updates to the alignment thread don't show up for me. Is it my computer not updating?

[KFfan]

I didn't see any changes yesterday or today

[Paul Z]

Here is a good tutorial on alignment

http://www.teamkitfox.com/Forums/showthread.php?t=2802&highlight=align

Excellent Posting on how to do the alignments. Even if you know what you are doing this is a great refresher.

[KFfan]

This is from a posting relevant to automobiles but is applicable to the situation at hand. IMHO


"Caster is the tilting of the uppermost point of the steering axis either forward or backward (when viewed from the side of the vehicle). A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear. Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster. When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster. With too little positive caster. If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster."


The picture in my brain indicates the mains moving one direction, moving backwards, and the opposite direction, moving forward.


My wife would probably have said, "You're wrong". :eek:

[mr bill]

You are making my head hurt.

[KFfan]

Caster(oil) may help :eek:

[PapuaPilot]

That's strange. :confused: I posted to the original thread the other night.

Anyways, I just did it again at:

http://www.teamkitfox.com/Forums/showthread.php?t=2802&highlight=align

[vetdrem]

OK, I am convinced that I need to do a good check of the alignment. I am sure that it is out, and needs "adjusting".

My access to equipment is very limited, and I am not even sure I can do the alignment check properly.

I am not anxious to put a 6' cheater on the axle and bending (hopefully) the axle. I can envision terrible things happening if it bends the wrong component. But I am equally reluctant to put the axle in a vice (if I had one that was stout enough to withstand the rigors of this task) and beat on it with a sledge hammer. I worry about figuring out where to bend it, how much to bend it and in what direction.

I have searched this site and youtube looking for videos on how to do it, but can't find any (where is Dave when you need him).

I have been thinking about making a lever that I can attach to the gear leg to take the torque being applied by the cheater on the axle. Hopefully, the axle will bend before something else distorts.

Does anyone have a good photos, videos or other ideas??

Louie

[beeryboats]

Hi Louie,
As I posted earlier my Dad's Baby Great Lakes had a pretty good toe in problem. It's been a while, but as I recall here's how he did it. He propped the tail up level. Then using a plumb bob marked the center line of the aircraft nose and tail. He marked the hangar floor then he connected the dots out the front far past the tires. Then he took a long strait edge and placed it horizontally across each tire on the outside. Marking the floor again he connected those dots. He then had an idea of how far off center each tire was pointing. As I remember the gear looked like a cut down Aeronca Champ gear. My older brother in law is an ex-olympic discus thrower. Not small by any means. My dad had him put a long steel rod into the hollow axle and "gently" pry the axle aft to twist out the toe-in. Using the plumb bob and the strait edge against the tire, he could see how far he needed to twist the gear. It sure did tame that tiger. If you happened to land too hard on one side, it would really toss you the other way. That airplane was a real trip to land as it had zero forward visibility on landing. It did have a locking tail wheel which did help a bunch. The best method was to come across the numbers at 70mph with the tail wheel locked, throttle at idle, and stare at the gas cap in front of you. When you saw the runway lights out the corners of you eyes, slowly pull the stick back and grease it on tail wheel first. And you sure as heck had to be fast with your feet!!! Talk about short coupled.

[cgruby]

Louie, From your description, it appears the gear is twisting to arrive at one spot going backward and another going forward.
Loose axle?
Broken gear strut?
Excessive wheel friction causing gear to twist?

Jack it up and check for any twisting movement.

And BTW, having been there and done that, I prefer to align the gear straight ahead, i. e., no toe in or out.

Good luck,

[vetdrem]

I looked everything over pretty good, and found no broken or bent components.

I then leveled the plane, snapped the chalk lines, did the measuring and came to the following conclusion.

The right main is almost at zero toe-in (maybe 1/16th of an inch, but close enough for me). the left main is toed-in about 3/4 inch. We verified it by measuring the distance between the brake mounting plates at the front of the wheels and again at the back of the wheels. We had about 3/8" difference in the two measurements, showing a toe- in condition.

I am going to leave the right gear alone and see what I can do with the left one.

I'll let you know how it goes. Does anyone have a spare left gear leg if I turn mine into DO-DO.