Twisted Tail Wheel Spring

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Twisted Tail Wheel Spring

Postby Tralika » Tue May 13, 2014 10:01 pm

I just mounted my tailwheel for the first time. It looks like my tailwheel leaf spring has a slight twist to it. The tailwheel is canted off to one side. I put the spring on a level work bench top and I can see the two ends are not even. Anybody else have this problem?
John Nealon
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Re: Twisted Tail Wheel Spring

Postby User GDS » Tue May 13, 2014 10:59 pm

Never had that problem but mine yield over time and need to be bent back to the correct angle. I take the trailer hitch out of the receiver on my truck and put the pin back in. Then stick the spring into the receiver under the pin and use a steel fence post pole on the end for a cheater bar. I drew a template for the perfect bend on a piece of wood for reference. You could use the same system and a BF crescent wrench with a cheater bar to remove a twist. I'm not an engineer, but I understand using heat will wreck the spring, they need to be cold-set.

I'm now using two springs, a JA supplied spring, supplemented with a secondary spring from my friend's Aeronca Chief, it's the perfect fit.
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Re: Twisted Tail Wheel Spring

Postby messenger » Wed May 14, 2014 4:01 pm

I also use a double tailwheel spring, Boise spring works in Boise, Idaho made mine. It takes a lot of the bounce out of the tailwheel on a hard landing. R L Messenger
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Re: Twisted Tail Wheel Spring

Postby User GDS » Thu May 15, 2014 10:49 am

I'll be up there in June, I'll order one from them. My local spring shop couldn't find the 1 1/2" stock to make it, probably need a shop in a more agricultural area.
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Re: Twisted Tail Wheel Spring

Postby Tralika » Thu May 15, 2014 11:39 am

I may be interested in ordering one from them as well. In the attached photo you can see that my tail wheel assembly is pitched up. The pivot point should be level. This is with my main landing gear axles sitting on a couple of 2x4s on the floor. When I mount the wheels the tail wheel will be pitched up even more. I've had problems with tail wheel shimmy caused by the tail wheel pitched down after the leaf spring wore out. I'm not sure if shimmy can occur from the tail wheel being pitched up but I don't really want to find out.
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Re: Twisted Tail Wheel Spring

Postby danerazz » Thu May 15, 2014 11:45 am

My understanding is the tailwheel pivot SHOULD be pitched up a little as on yours. Somewhere on here there is a link to a post on supercub.org (I think) about this exact question, and it is explained that a little "trail" of the tailwheel helps prevent shimmy. Do a little research, I would hate to see you make a trouble where there wasn't any.


Edit: it is on backcountry.org, here: http://www.backcountrypilot.org/forum/interesting-article-on-tailwheel-shimmy-687
Dane

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Re: Twisted Tail Wheel Spring

Postby Gil T » Thu May 15, 2014 3:13 pm

IMG_2695 (1024x768).jpg
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I thought I would put my two cents worth in since I have had a couple of interesting tail wheel affairs. My first tail wheel was a Maule and it had a severe case of "Grocery Store Shopping Cart Syndrome". It shimmied from the first flight till the time I changed it. The first time it shook so bad that I tried to use a little forward stick to lightened the tail and when that didn't work I figured well maybe a little more back stick will help. Big mistake, I left the tail wheel a hundred feet or so behind be. When I got the plane glued back together I gave the Maule to a friend of mine (former). He overhauled it and it worked the same with him except it was cleaner. Having accumulated a volume of info on tail wheel shimmy by this time I got an Iron Design one and have been satisfied ever since. It would seem that the angle you have is the correct one but as you load the plane it will change to a more vertical one so maybe it's a matter of seeing how it works and if it needs to be changed any. As you can see by my pictures I have a bracket at the bottom of the tail post. Where the spring fit in the channel there seemed to be a bit of wiggle and that was put there to make sure the spring didn't jump of the channel. That could have contributed to my spring breaking since that is where all of the stress of the flexing is. That was the same spring from the first event. It just seems that two springs would be better but I'm not an engineer. Maybe I should make sure that I'm not trying to land the Super STOL way.

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Re: Twisted Tail Wheel Spring

Postby Tralika » Fri May 16, 2014 11:42 am

Gil T, It was fortunate that your tail wheel failure occurred where you could get to the plane with a trailer. Years ago I helped a guy with a cub lash an ax handle to his tail wheel spring after he knocked the tail wheel off on a beaver dam when taking off of a gravel bar. He landed on a little strip but had to go back to town so we did the McGiver thing using wire, para cord and of course duct tape. It worked well enough so he could get home.

I've flown several planes with tail wheel shimmy. I flew a 185 for several years that shimmied on just about every landing on pavement. At one point the mechanics got so frustrated they tightened up the tail wheel so much it wouldn't steer. They were pretty proud of themselves but it didn't make the pilots happy. You had to land and keep the tail off the runway for as long as possible. Not easy when loaded heavy. I got sick of trying to explain to the passengers that the violent shimmy was normal for that airplane. I'm surprised the plane didn't fall apart but as far as I know it's still out there doing its shimmy. I'm partial to locking tail wheels. I know this has been discussed on this forum in the past but I doubt I'll put one on my Highlander.

My airframe does not have the bracket I see in your photos. One bolt connects the front of the spring in a channel. Maybe this was an improvement by the factory.
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Re: Twisted Tail Wheel Spring

Postby FlyerChief » Fri May 16, 2014 12:45 pm

Hi Gil,

It appears in your photos like the tailwheel issue also created a rudder issue when it collapsed. Did it actually crush the bottom of the rudder? I assume that's why clipping the back of the rudder seems to be one of the mods that guys are doing.

I'm just wondering if it would be possible to make a retainer bracket that also would act as a standoff in the event of a tailwheel departure event... maybe just a bent post or steel ring welded 90 degrees to the to the bracket would work?

What do you think?
Maybe Steve Henry would be a good guy to provide feedback too. I know he's lost tailwheels also.

Dan

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When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. ~Henry Ford
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Re: Twisted Tail Wheel Spring

Postby Gil T » Fri May 16, 2014 1:22 pm

I see a lot of guys are going for a non steering tail wheel which I guess is okay if you don't have to taxi on a lot of hard surface but I can see a lot of wear on the brakes. I spent a lot of time in interior Alaska in 180's and 185's and had my share of shimmying tail wheels. The only thing that was consistent was that everyone you talked to had a different version of what was wrong and how to fix it. The first thing I can say is that I am not a mechanic. I kind of told our maintenance people that we worked as a team. I break um you fix um. The first locking tail wheel I flew was a new 185 with 300hp. After you remembered to lock the tail wheel on take off it made a lot of difference in the feel of it. So if we're having a vote on it I'm for a locking TW.

When my tail wheel came off it was dangling by one steering spring and when it came off was when I landed at home. I can remember the rock that I hit that did the damage but I did't know about it until my touch down at home and the noise coming from the tail and then looking straight into the mid-day sun. That steering spring saved me about $650. Yes there was damage to the bottom of the rudder. I probably should have changed the bottom tube and had it welded to the next one up as I see several have done but not being a welder and wanting to get in the air soon I just straightened the tube and put it back as originally done. I know some kind of save device could be made but maybe that would encourage me to be braver than I should be.

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Re: Twisted Tail Wheel Spring

Postby messenger » Fri May 16, 2014 4:22 pm

I think I have talked about this tailwheel shimmy problem before. Steve Pierce and and his dad Gilbert have worked out the solution to the shimmy problem and have posted on supercub.org and shortwingpipers.org extensively. Do some searching on those two sites and you will find all the info you will ever need about tailwheels. It does not matter what your tailwheel is on, there is a certain geometry that it needs to adhere to or you will have problems. steerable, non-steerable, locking, whatever, follow the guidelines they explain in detail and you will be on your way to a happy tailwheel experience. R L Messenger
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