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Thread: Tail wheel steering issue

  1. #1

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    Tail wheel steering issue

    Greetings, Forum! Happy 4th! I'm giving instruction to my daughter in our Super Cub, 150HP. Several landings on pavement recently. On last flight, we experienced some heavy tail wheel shimmy on one of the landings (made a few more after with no such shimmy). While taxiing in, we realized we could not steer the tailwheel to the right with the right rudder pedal. It worked fine on taxi out, and rudder pedal worked fine in flight for yaw movements. On taxi in, we moved right rudder all the way and only got a very small movement to the right. Winds were calm and no hard landings during the flight. I did recently service (grease) the tail wheel assembly. Any thoughts on what/how to trouble shoot? Thank you.

  2. #2
    behindpropellers's Avatar
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    Probably two problems:

    The arch is lacking in your spring and the pawl may be a bit worn inside of the tailwheel assy. Adding grease probably will not cure your problems. You can search both on here and find a bit more detail.

    Tim
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  3. #3

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    I had a similar issue a while back and replacing a worn paul solved it.


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    I agree with the above advice but it may just need to be disassembled, cleaned and lubed (light coat) that is the first thing I would try. Did you try double kick of the rudder full left/right/left. When the wheel unlocks in a turn, as you straighten out the fork has to be trailing and the steering arm assembly centered for it to relock. If you did a right turn before the problem started I think that is your issue. One thing you should never do is try to grind the pawl edge to make it work better. Polish with a buffing wheel will make it work smoother but the tolerance is very close and grinding/filing will cause problems down the road. You can always call bushwheels they are very helpful.
    DENNY

  5. #5
    www.SkupTech.com mike mcs repair's Avatar
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    Tail wheel steering issue

    You have a broken(or collapsed) flat spring for the right side problem. You may need to replace tire for shimmy, they get a pattern worn into them... in addition to the suggestions already mentioned


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  6. #6

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    With Mike on this. Unless you see something obvious, it is probably that internal flat spring.

    When you get it fixed, make sure the kingpin is vertical under load.
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    Thanks, Denny. We did turn right off of the runway and then the problem started. I cleaned it while still on (without disassembly) and tried again today to taxi but no luck. Turns left just fine, but full right pedal provides no to very little steering to the right. Can you elaborate on the double rudder kick? Do you just start a taxi and while rolling slowly, kick full rudder left, then right, then left and that may recenter/lock it?
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    Thanks, Mike. If other options don't work, to disassemble and replace the flat spring seems easy enough, except, I've heard the Scott Tail Wheels are temperamental and problematic to reassemble. Got any thoughts on that? Thanks again.

  9. #9
    www.SkupTech.com mike mcs repair's Avatar
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    Tail wheel steering issue

    Quote Originally Posted by Spad View Post
    Thanks, Mike. If other options don't work, to disassemble and replace the flat spring seems easy enough, except, I've heard the Scott Tail Wheels are temperamental and problematic to reassemble. Got any thoughts on that? Thanks again.
    Simple. Steve pierce posted a great video on rebuilding them. You just choose which side of flat spring to put the shims on. Ancient technology. Someone got a link to his video?


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  10. #10
    Wag2+2's Avatar
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    One of these might have the answer
    http://www.supercub.org/forum/showth...ld-a-tailwheel
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  11. #11

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    Absolutely nothing difficult about taking apart and inspecting, unless you press the center piece out to remove the the locking spring. Then you have to figure out proper shim replacement, but even that isn’t that difficult.

    https://m.youtube.com/watch?v=8MGri0D50hg

    this video doesn’t cover spring and shims, but how to do a normal take down and inspection.

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    Yes the double kick is just as you described. Airframes has the parts diagram on the website. As I said before I would just take it apart, clean, and put back together with a LIGHT coat of grease before you change any parts in the tailwheel. It sounds like it worked fine before you pumped grease into it. I have had the same issue when I used too much grease.
    DENNY

  13. #13

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    Double kick didn't fix it. Took it apart (see picture). Looks over-greased. Will clean and replace. Thanks, Denny. BTW, is what folks are calling the "flat spring", part #18 in this diagram?Tail wheel assembly.jpgIMG_2727.jpg

  14. #14
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    Check the fit of part #8 (what I call a horseshoe-shaped spring) into part #8 (steering arm).
    The notches in the steering arm can get worn, when the corners of the notch isn't sharp engagement goes to hell.
    Also check that part #9 (pawl) will properly kick the spring out of engagement with the steering arm.
    I've dressed worn notches in the steering arm, but it's a temporary fix.
    I think maybe wear on those notches is caused by the burrs on the end(s) of the spring (part # 8 )
    If you end up having to replace the steering arm, get the heavier-duty one with the turned-up ends (p/n 3214T).
    Last edited by hotrod180; 07-04-2018 at 12:10 PM.
    Cessna Skywagon-- accept no substitute!
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  15. #15

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    Thanks, Hotrod180 and to all. Attached is a picture of parts after cleaning. They look good to me, so I plan to clean, light lube and replace. Is there a particular lube that's recommended for Scott Tailwheels?IMG_2732.jpg

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  17. #17
    Stew's Avatar
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    The two copper rings (#7 on the diagram) have notches on the inner face.

    It is not clear in your image but it looks like the corresponding little peg on the fork has worn flush with the face allowing the copper ring to rotate independently.

    Might want to just check that now you have it all stripped down.

    Kind regards

    Stew
    Last edited by Stew; 07-04-2018 at 05:38 AM.

  18. #18

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    Quote Originally Posted by Stew View Post
    The two copper rings (#7 on the diagram) have notches on the inner face.

    It is not clear in your image but it looks like the corresponding little peg on the yoke has worn flush with the face allowing the two copper rings to rotate independently.

    Might want to just check that now you have it all stripped down.

    Kind regards

    Stew
    Thanks, Stew. I’ll look it over.



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  19. #19

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    IMG_2735.JPG
    The pin is flush (worn). Is there any fix besides a new tail wheel assembly?


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  20. #20
    Eddie Foy's Avatar
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    I think the pin is replaceable. It is a common problem.

  21. #21
    Stew's Avatar
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    Have taken three Scott 3200 units apart and rebuilt them thanks to Steve's video. All of them had this pin worn flush so the lower ring was not captured as designed.

    We carefully drilled a pilot hole directly underneath and punched it out. Pretty starightforward to get a new pin turned up and you are good to go.

    There are probably better ways to extract it but that is what we did.
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  22. #22
    Eddie Foy's Avatar
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    It's your can, Pierce! Pricey stuff.




    Quote Originally Posted by Eddie Foy View Post

  23. #23

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    I have punched the pin out from the bottom as described above and just flipped it over. If you need a new one airframes has them.
    DENNY
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  24. #24
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    I have also drilled a hole in the pin and used an easy out to remove. Then drill a small hole big enough for a punch to knock it out from the back side in case you have to replace it again. Take a picture of your steering arm on your fork. That tells a lot about the notches in the steering arm and the lock spring. also check the looseness of the steering arm to fork. Sometimes the fork gets worn and allows too much slop.
    20160309_174855.jpg

    Look at these notches.
    00002IMG_00002_BURST20180702181024_COVER.jpg

    Should be a slight amount of play between the lock spring and the notches in the arm. If there isn't it will bind and not unlock. If the notch is worn it will not lock. Have seen a lot of them filed on to make work. My Dad is a tight ass and did this and it worked ok for many years until it didn't. He sent me a picture of the steering arm on the fork and I sent him a new arm. He still talks about how nice it works now. You can see that the pawl pushes the locking spring and kicks it out of the notch in the steering arm unlocking the tailwheel.
    IMG_20180702_180829.jpg
    Steve Pierce

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  25. #25
    Steve Pierce's Avatar
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    Video of slop between the fork and the steering arm that causes lose of steering ability.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  26. #26
    Steve Pierce's Avatar
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    The brass washer on bottom should fit nicely over the pin on the fork.
    IMG_20180702_181957.jpg

    Then the washer looks like this.
    IMG_20180702_182122.jpg
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  27. #27
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Spad View Post
    IMG_2735.JPG
    The pin is flush (worn). Is there any fix besides a new tail wheel assembly?


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    Replace pin. Or flip it over

    Might be fun to get out.

    Maybe drill hole bellow it and tap it out.

    Maybe tig tack weld to pin to heat area and expand hole.




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  28. #28
    Steve Pierce's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Replace pin. Or flip it over

    Might be fun to get out.

    Maybe drill hole bellow it and tap it out.

    Maybe tig tack weld to pin to heat area and expand hole.




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    I drill a hole and use an easy out to pull it out.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  29. #29

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    Helpful as always, Steve. Thanks!


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  30. #30

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    Quote Originally Posted by Steve Pierce View Post
    I drill a hole and use an easy out to pull it out.
    And then there was all the fun we had on my Baby Bushwheel assembly, where someone had replaced the pin with a hardened rod. Thanks to the ingenuity of Steve Pierce and Tim Cochran, a piece tack-welded on, and some special "aviation maintenance vocabulary," it only took two hours for what should have been a half-hour job. I learned a lot though.

    Thanks. cubscout
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  31. #31
    Steve Pierce's Avatar
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    Quote Originally Posted by cubscout View Post
    And then there was all the fun we had on my Baby Bushwheel assembly, where someone had replaced the pin with a hardened rod. Thanks to the ingenuity of Steve Pierce and Tim Cochran, a piece tack-welded on, and some special "aviation maintenance vocabulary," it only took two hours for what should have been a half-hour job. I learned a lot though.

    Thanks. cubscout
    There are always those special ones that make you say "if it was easy everyone would do it". ��
    Steve Pierce

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  32. #32
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    Quote Originally Posted by Steve Pierce View Post
    I like to pry the spring out on the ends and make sure they're a nice snug fit into the notches.
    Also like to dress the ends of that spring so it doesn't erode the notches in the steering arm.
    There are a pair of shims where the spring pins into the fork,
    you can place those behind of ahead of the spring to adjust spring engagement into the fork.
    Cessna Skywagon-- accept no substitute!

  33. #33
    Steve Pierce's Avatar
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    Quote Originally Posted by hotrod180 View Post
    I like to pry the spring out on the ends and make sure they're a nice snug fit into the notches.
    Also like to dress the ends of that spring so it doesn't erode the notches in the steering arm.
    There are a pair of shims where the spring pins into the fork,
    you can place those behind of ahead of the spring to adjust spring engagement into the fork.
    If you take all the play out between the spring and the notches it will not unlock. Most of the steering arms have HT stamped on them designating that they are heat treated which should help with the notch wear. I have dressed those springs with a small flat file as well.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  34. #34

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    Regarding installing the new pin. Any trick to it, or will it simply slide in and then is held in place by compression of the other parts of the assembly?

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    Stew's Avatar
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    You won't have any problem there, it will just push in and should be flush with the top of the lower copper ring when fitted and yes, it is held in place by the other components above.

    If you haven't drilled up from below to get the old one out, do as Steve suggests when you get the pin out and drill down through the bottom of the pin hole so when it comes time to replace it again you can simply punch it out...simples.

  36. #36
    Eddie Foy's Avatar
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    It is what's called an "interference fit."

    Quote Originally Posted by Spad View Post
    Regarding installing the new pin. Any trick to it, or will it simply slide in and then is held in place by compression of the other parts of the assembly?

  37. #37
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    There is a certain satisfaction to repairing a well-used part and seeing it return to service. There is also a certain frustration involved in repeatedly trying to force a worn out part to behave like a new part.

    If it were me in your situation, I would bite the bullet, buy a new ABI tailwheel and get back to flying. Save the tailwheel rebuild project for a lazy weekend when you can afford to walk away. If and when you rebuild it, then you've got a spare. If you don't want a spare, someone will buy it. 3200s always sell for good money, and fast.

    Honestly, looking at the pictures, I think you're going to need major surgery on that to get it working to spec. It looks like it's got some really heavy wear. I think you're going to end up with a new tailwheel whether you buy it whole up front, or replace all of it one part at a time. I've done it the hard way, and I don't think I came out ahead financially.

    Give me your address and I'll send you a gob of SHC 100. I probably have enough to lubricate every tailwheel on earth into the next century.

    IMG_2735a.JPG
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  38. #38

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    Fancypants. Thanks for the sound advice. I've got the part in (pin) and so will put it together and see how it works...if it doesn't, I'll bite the bullet on a new assembly.

  39. #39

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    Tailwheel pin Replacement

    Anyone know the correct procedure for replacing the pin on the Scott 3200 tailwheel? Does it just fit in, and is held in place when the other parts are assembled with it? Thanks!

  40. #40
    Steve Pierce's Avatar
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    It is held in with friction.
    Steve Pierce

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    Will Rogers

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