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L-21B tail wheel shimmy

The Piper springs I have worked with require spread apart with a tool to get the chain on. I have seen the tear drop shape links safety wired. Really like the threaded chain links with safety hole that Bushwheel use to sell, made it easy to install and remove. I believe Maule still sells them. I really think if you replace the spring your issue will be solved, has worked in every single case of tail wheel shimmy in every kind of tail dragger I have dealt with over the years.


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Thanks for the reply--

I think that the shimmy problem happened because the tail wheel tire was flat (no air pressure in the tire--the gauge didn't even move when I checked it) I do like those quick links. I assume that I can't use the hardware store links since they don't have a safety wire hole? BTW could you please watch this video and tell me if it shows the CORRECT way to rig the spring and chains? https://www.youtube.com/watch?v=QtokU8mIDQk
 
Maule Parts: 229-985-2045 ask for Kasey She said she wouldn't hold it against me since my bird is not a Maule ;-)
 
I would think with some creative safety wiring an un-drilled quick link would suffice. Like full wrap wired from the raised portion of the threaded end over the barrel to the link's body just behind the turn barrel. If the barrel can't move away from the threaded portion's lip where's it going to go? I've used these for years in other applications and once well tightened with blue or red thread locker never had them release.

Gary
 
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Thanks for the reply--

I think that the shimmy problem happened because the tail wheel tire was flat (no air pressure in the tire--the gauge didn't even move when I checked it) I do like those quick links. I assume that I can't use the hardware store links since they don't have a safety wire hole? BTW could you please watch this video and tell me if it shows the CORRECT way to rig the spring and chains? https://www.youtube.com/watch?v=QtokU8mIDQk
Yes, that is actually a video done by Bushwheel that Wup has reposted.
 
I hitch the sash chain onto the spring with safety wire. I tried without and it just shakes its way off right when you need it to work. With the safety wire it can still slide as required, but it has enough friction to keep it on the hook.

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Yes, that is actually a video done by Bushwheel that Wup has reposted.


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Thanks---so I assume that the chain should have soon slack as shown. Some people seem to prefer a taut chain. Am I better to have some lack? ALSO, when I set up the chain as shown in the video I ended up having one side longer than the other by one link in the chain--is that a problem?
 
I prefer no slack but I am also running the long pawl so the steering brakes sooner. Turn and make sure the chain is not so tight that it bends the steering arms when turned all the way to either side before the tailwheel steering brakes. That was an issue Aviat was having years ago.
 
I hitch the sash chain onto the spring with safety wire. I tried without and it just shakes its way off right when you need it to work. With the safety wire it can still slide as required, but it has enough friction to keep it on the hook.

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Great idea! I will use that as well.
 
I have finished the tail wheel repair and adjustment. However, I am not as pleased as I would like. Seems that the chain is either too tight or too loose. If I could eliminate one half of a link it would be great!

So right now I went for the too loose.

Any ideas?
 

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What kind of problem happens when the tail wheel air pressure is too low?

I realize that it is not good for tire wear but would it cause a shimmy?
 
With the chain too loose the tail wheel will unlock just fine. With the chain too tight I need to push real hard to get it to unlock.
 
With the chain too loose the tail wheel will unlock just fine. With the chain too tight I need to push real hard to get it to unlock.

So it binds and tries to bend the steering arms before it unlocks? I would find a different pitch chain. I set mine up tight but they unlock fine.
 
So it binds and tries to bend the steering arms before it unlocks? I would find a different pitch chain. I set mine up tight but they unlock fine.

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No not that bad---If I adjust the chain so it is tight then when the rudder is all the way to the left or right and I move the tail wheel in the same direction, I can feel the resistance of the chain and large spring as I move the wheel past the unlock point. The wheel will go past the unlock point but there is some resistance. Those steering arms are pretty shout--I don't see how they would bend.
 
.... Seems that the chain is either too tight or too loose. If I could eliminate one half of a link it would be great!....

That's just sash chain.
My local hardware store has about three different pitch sizes of that.
Try a finer or coarser pitch to see if you can get the length you need.
or
Set it up on the too-tight side with the chain you have,
then squash each link a tiny bit which has the effect of lengthening them.
 
Soooooo, tailwheel shimmy has little to do with tight or loose sash chain! If you took them off as some do, it should not shimmy!!!!! I have had everything from way too tight and way to loose and it never cause a shimmy issue!! It just was not working as a tailwheel should. The pics you have shown are way too loose for me and I would adjust as Steve as advised (Consider squeezing each link flat to add length as needed). With the chain that loose I would say you have an issue the pics do not show. IE put weight in the plane and see what the spring is doing, check all parts of the tailwheel, bearings, tire, axle, bolts, ect, make sure everything is correct!! Then take a close look at that covered tail section!!! I mean close! you could have a busted tube under the fabric. Simple check is jack up the tail by he handle, grab the tailwheel and have a buddy watch the fabric as you try to rip the tail off. I had friends over and may have had a bit of white whine but, it it is not the springs/chain.
DENNY
 
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No not that bad---If I adjust the chain so it is tight then when the rudder is all the way to the left or right and I move the tail wheel in the same direction, I can feel the resistance of the chain and large spring as I move the wheel past the unlock point. The wheel will go past the unlock point but there is some resistance. Those steering arms are pretty shout--I don't see how they would bend.
Just so that it doesn't bind. How dos it steer on the ground? Wen I push the rudder pedal I want the tailwheel to move right then not after the slack comes out.
 
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