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Thread: Tail wheel shimmy

  1. #11
    Senior Member Centmont's Avatar
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    Default Re: Tail wheel shimmy

    Scott: In my conversations with Wup, when they owned ABW, he would tell you; Baby Bush Wheels will frequently wobble on hard surfaces. They were not apologetic about it letting everyone know that is simply not what they were designed to do. There are some things you can do to decrease the Wobble (shimmy), angle being the most important, but as they said "BBW's can shimmy". If I absolutely have to land pavement...I keep as much weight off the tail as possible until the last minute. I love my BBW, but if I landed pavement, it would go down the road. Ralph
    Ralph Rogers
    Owner: TheCubWorks
    www.TheCubWorks.com
    CCSS #142 N123MR
    I have always felt the supercub is one thing mankind got right the first time but that there were better materials and methods to build them. CubCrafters products are proof I was right.

  2. #12
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    Default Re: Tail wheel shimmy

    Thanks Ralph. Dont normally but between seasons. Spring bolt was loose. Havnt been able to test it, blizzard.

  3. #13
    Senior Member Centmont's Avatar
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    Default Re: Tail wheel shimmy

    Scott: Battleford? You are a neighbor by Montana/Sask standards. Make it down for the front end of "Bushwheel Awareness Week"....aka Breaks Flyin in Winifred, MT (9s7) mid June. Best of luck. R
    Ralph Rogers
    Owner: TheCubWorks
    www.TheCubWorks.com
    CCSS #142 N123MR
    I have always felt the supercub is one thing mankind got right the first time but that there were better materials and methods to build them. CubCrafters products are proof I was right.

  4. #14
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    Default Re: Tail wheel shimmy

    I did not realize there was such a thing! Always up for something new.

  5. #15
    Senior Member randylervold's Avatar
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    Default Re: Tail wheel shimmy

    All of the above advice regarding angles and tightness is good, but we have found that the 3200B (baby bushwheel) will shimmy when the standard 3200 tailwheel will not on the same aircraft and tail spring. We haven't taken it on as an engineering project to understand why (we aren't the manufacturer), just drawn that conclusion from observing quite a few aircraft.

    Personally, I think the regular 3200 will work fine in most of the environments out there, though admittedly it doesn't look as macho. Given the proclivity to shimmy and the extra weight I don't see much of a need for the 3200B myself so you might consider changing if you can't resolve it any other way.
    Randy Lervold

  6. #16
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    Default Re: Tail wheel shimmy

    It is the nature of the beast to some extent as I have experienced some shimmy on my SC as well. the only time it is an issue for me is on cross country trips when pavement landings are necessary. The shimmy on the CC was due to loose spring bolt which has been rectified.

  7. #17
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    Default Re: Tail wheel shimmy

    Quote Originally Posted by Scott c View Post
    It is the nature of the beast to some extent as I have experienced some shimmy on my SC as well. the only time it is an issue for me is on cross country trips when pavement landings are necessary. The shimmy on the CC was due to loose spring bolt which has been rectified.

    Had a tail shimmy one time on my CCEX. It also was on pavement. Did something Mitch suggested at the time. Just don't remember what it was. Anyway, I haven't had any more problems since then.

    Richard

  8. #18
    Junior Member JohnC's Avatar
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    Default Re: Tail wheel shimmy

    I had a problem with my tail wheel that caused a severe ground loop. I had the 3200 tail wheel with the Pawnee leaf spring. Because the leaf spring is wider than normal, I did not have the 1 1/2" spacer installed. I did install the bushing in the leaf spring 1/2' bolt hole for the AN7 bolt. At the time, I did not realize the bushing was very slightly too long without spacer. This caused the tailwheel head to not seat flush against the leaf spring. With the bolt tightened to specs, this condition was not noticeable. This condition allowed the tailwheel head to rock very slightly left and right on landing. Not noticeable on grass or when the aircraft was lightly loaded. More noticeable on a hard surface and when the plane was heavy. This action slowly stretched the bolt and loosen the tailwheel head allowing the tailwheel to slightly tilt on landing. While making a heavy weight landing on a hard surface, the tailwheel canted and knife edged on the tire. This caused a quick, hard turn. After this, the tailwheel head noticeably loose and the AN7 bolt was stretched. I reassembled the tailwheel with new hardware and noticed the same potential problem, the bushing is very slightly too long. I shorten the bushing and now the leaf springs fit flush in the tailwheel head. I've had no further problems. Also, I found the 4 leaf springs to be too stiff and not at a good tailwheel geometry. I installed a 3 leaf tail spring from Cubcrafters and the aircraft ground handling is much improved. Hope this helps.

  9. #19
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    Default Re: Tail wheel shimmy

    Quote Originally Posted by JohnC View Post
    I had a problem with my tail wheel that caused a severe ground loop. I had the 3200 tail wheel with the Pawnee leaf spring. Because the leaf spring is wider than normal, I did not have the 1 1/2" spacer installed. I did install the bushing in the leaf spring 1/2' bolt hole for the AN7 bolt. At the time, I did not realize the bushing was very slightly too long without spacer. This caused the tailwheel head to not seat flush against the leaf spring. With the bolt tightened to specs, this condition was not noticeable. This condition allowed the tailwheel head to rock very slightly left and right on landing. Not noticeable on grass or when the aircraft was lightly loaded. More noticeable on a hard surface and when the plane was heavy. This action slowly stretched the bolt and loosen the tailwheel head allowing the tailwheel to slightly tilt on landing. While making a heavy weight landing on a hard surface, the tailwheel canted and knife edged on the tire. This caused a quick, hard turn. After this, the tailwheel head noticeably loose and the AN7 bolt was stretched. I reassembled the tailwheel with new hardware and noticed the same potential problem, the bushing is very slightly too long. I shorten the bushing and now the leaf springs fit flush in the tailwheel head. I've had no further problems. Also, I found the 4 leaf springs to be too stiff and not at a good tailwheel geometry. I installed a 3 leaf tail spring from Cubcrafters and the aircraft ground handling is much improved. Hope this helps.
    Very interesting. Do you have any pics? I am not sure if I need the spacer or to modify the bushings on mine.

  10. #20
    Junior Member JohnC's Avatar
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    Default Re: Tail wheel shimmy

    As for the tailwheel spacer, the width of the leaf springs will determine the need. If your springs are 1 1/4" wide, the "cup shaped" spacer is used. The tailwheel head can receive leaf springs as wide as 1 1/2". The bolt bushing fits inside the tailwheel head and must not be so long as to keep the springs from seating flush against the tailwheel head. My bushing needed to be shortened. With a load on the tailwheel, the springs rocked very slightly and stretched the bolt. Here's a picture showing the wear in the tailwheel head that was made by the rocking leaf springs. Also, a picture of the leaf springs not flush against the tailwheel head (before I shortened the bushing). A picture of the bushing along with the bolt,nut, and washer. Sorry, not great pictures. Call me if you have questions. John 817-480-3080.

    IMG_1020.jpgIMG_1014.jpgIMG_1019.JPG

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