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Thread: Tailwheel Shimmy and Spring Arch

  1. #191

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    Default Re: Tailwheel Shimmy and Spring Arch

    Quote Originally Posted by Steve Pierce View Post
    I have the same experience with the hard rubber. I like the cushion and bouyancy of my Baby Bushwheel. It rides on top of the sand and gravel instead of acting like a plow disc. I want to beat the certified guys with their Catto props so I am pulling every legal trick I can think of this year. After the contest my BBW goes back on.
    This 80/38 sensinch I have spanks a Catto. Turns 2600 at 50mph on climb out. Sloooooow in cruise. 80mph was all I could get the whole way to osh


    Sent from my iPhone using Tapatalk

  2. #192

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    Apr 2008
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    Default Re: Tailwheel Shimmy and Spring Arch

    OK. I've gone through all this info on tailsprings but still am confused. Currently I have the PA-18 3 leaf spring on my Clipper purchased from AK Bushwheel and installed in 2011 due to a bad shimmy and lots of bent arms. Shimmy and bent arms GONE! the minute I put it on ... that is, until this summer 2020 (9 years later). Shimmy is back and is bad (but no bent arms). If you have this spring on your Clipper or Pacer I'd be curious to know how many years it has been good for. While there could be a number of other parts gone bad in my Scott 3200, I'm thinking the leaf spring would be a good place to start. If I replace it I am inclined to use the same thing which I believe I would purchase from Airframes AK. I've seen Univair's for the PA-16, but not liking it after what I have read here. I am also confused about the bolt clamp (adapter?). Mine is rectangular not U shaped. Thanks.

  3. #193
    Administrator Steve Pierce's Avatar
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    Default Re: Tailwheel Shimmy and Spring Arch

    The stock spring is 1 1/4" wide and the AK Bushwheel spring is 1 3/4" wide so they use a different clamp which is provided with the spring from Airframes Alaska. Geometry is key to solving tailwheel shimmy. Can be other issues but start with the geometry. Did you compare your geometry to the pictures in the link I sent you?

  4. #194

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    Default Re: Tailwheel Shimmy and Spring Arch

    I get the geometry part ... firm believer in the arch being correct. Truth be known ... your dad's article sits on my hangar desk -- has for years. It's pretty tattered. I refer to it often, but never have been able to figure out the measuring part on my Clipper. What can I say? But I do understand the concept. So you would be in favor of duplicating what I have had? I'm thinking if it worked for 9 years (assuming that is the problem) then why do anything different. Have also been thinking of a complete rebuild this winter on the entire tailwheel. Don't think we did it on rebuild in 2009.

  5. #195
    Administrator Steve Pierce's Avatar
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    Default Re: Tailwheel Shimmy and Spring Arch

    Which way does the split line of the tailwheel fork to head lay? Pointed up at the front, flat or pointed down. Sounds like you need someone else to look at it. I disassemble, clean, inspect and reassemble the tailwheel at annual.
    tws.jpg

  6. #196

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    Default Re: Tailwheel Shimmy and Spring Arch

    Not at my hangar. But that's the part I don't get. Anyway, disassembling this winter and on annual here after. Will probably hold off on springs until then.

  7. #197
    Gilbert Pierce's Avatar
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    Default Re: Tailwheel Shimmy and Spring Arch

    Since you can’t determine which way your steering axis pin is pointing have your mechanic overhaul the tailwheel and insure all the attachment hardware is secure and if you still have a problem, a hard landing probably bent the spring. Take the spring to a spring shop along with Andy’s drawing of the arch or mine and have them re-arch it.
    Last edited by Gilbert Pierce; 09-27-2020 at 06:04 PM.

  8. #198
    1950 PacerFlyer's Avatar
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    Default Re: Tailwheel Shimmy and Spring Arch

    I had a new AK Bushwheels spring. Worked great. Got 6 years out of it. Then lost its arch and got shimmy back.

  9. #199
    smcnutt's Avatar
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    Default Re: Tailwheel Shimmy and Spring Arch

    A shimmy can tear up the tailwheel pretty quick. When we were fighting ours we had to replace the thrustplate assy a couple of times when rebuilding. Got to the point I bought extras knowing the pins would be broken when I took it apart. Also seemed to wear the tire out pretty fast. Since we got the arch reset (using the template) and the shimmy taken care of all I've done is disassemble/relube/reassemble at each annual. The whole process is really pretty quick. We do replace the mounting bolts since they take a fair amount of abuse.
    “Seek advice but use your own common sense.”
    ― Yiddish Proverb

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