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Gil Pierce & Wup Winn on Tailwheel Shimmy

Anne

Anne

Registered User
SE Michigan
In the Hands On column in Sport Aviation, Jan 2014, Gil Pierce ("whose son operates Pierce Aero in Graham, Texas") and Wup Winn ("of Alaskan Bushwheel") discuss tailwheel shimmy. It's a very good, informative article on what causes shimmy and how to mitigate it. Thanks, Gil & Wup!

Anne.
 
Bud Davidson did a great job as usual writing that article. Some of the comments written in responce to the article by EAA members are very interesting. http://www.eaa.org/news/2014/releases/2014-01-23_Tail-Wheel-Shimmy-letters.pdf Having used this technique to solve shimmy on everything from Cubs, Citabrias, Huskys, Super Cub, Maules etc. I don't really care what others theories are. It works and that is what matters to me. Because of this article my Dad wrote is posted on my website I get emails from people who want to argue with me about it. I just tell them their theory is interesting but this works.
 
It was all clear till I started reading those comments. :-? I think I'll stick with the original article and the one on Steve's page.

Phil
 
Gilbert's Method works -- we have re-arched springs now on two planes with great results. The 1970 graduate from Purdue is all wet but I'm sure no one would ever convince him.
 
The 1970 graduate from Purdue is all wet but I'm sure no one would ever convince him.
Click to expand...
He sure is! I
think there's a lot more going on with that shimmy effect than any of the posters alluded to. It's just like flutter, with a myriad of factors influencing the dynamics.
 
Gil & Wup are the shimmy kings. This has been a problem they were dealing with since the roaring 20's.

 
Gordon Misch said:
He sure is! I
think there's a lot more going on with that shimmy effect than any of the posters alluded to. It's just like flutter, with a myriad of factors influencing the dynamics.
Click to expand...
My thought exactly. I suspect in a shimmy there's a resonant oscillation going on, very similar to control flutter.
 
Very simple practical test to prove out the theories, which we did a few years ago at one of our EAA meetings. Large R/C tailwheel assembly including spring and a table top belt sander to simulate rolling it across the ground. Tilt the spring up and down with some loading on the spring to see what happens. The results are as outlined in the article.

-CubBuilder

TW Shimmy.jpg
Tailwheel shimmy simulator.
 

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Can someone offer help with method of rearching 1-1/4 pa18 tailspring? Link above does not seem to be working.
 
I rearch mine with press and 6 inch pipe. Do bottom first and arch others to match. One thing I really notice on my 3 spring is how much easy it is to steer when it is properly arched.
DENNY
 
So I checked today and the head of my bolt is aft of vertical like it's supposed to be and I still get shimmy. What next?

its a Alaska bush wheels spring with 85 hours on it. One year old.
 
Vertical is good but tilted back (positive castor) is even better. When the spring is compressed like when you are loaded heavy or when the spring flexes as the tail touches down the bolt will tilt forward of vertical and you will get shimmy. Also condition of the thrust washer stack, number of shimmy dampening springs, and steering chain setup have a lot to do with it.
 
Piper J5.5: did you check it fully loaded to gross weight? And perhaps a g load as the tail wheel goes on firmly?
 
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