Tail Spring Arch Template

[Steve Pierce]

From Andy Anderson:

The Tail Wheel Spring Template available here is one I used to obtain more correct caster to the tailwheel on my Piper PA-22/20. A good spring shop can accomplish the re-arching using this template. The template was drawn from a rearched spring leaf, the lower of the four leafs in the PA-20 spring set. The arch was traced along the upper surface of this leaf. The other three leafs of the spring were patterned after the the bottom leaf after it was re-arched. When the spring shop is re-arching the other leafs, it is important that he match the arch of the lower spring as they are positioned with reference to the fuselage mounting hole ( the fwd hole ).A ruler scale was annotated on the original tracing to assist in getting the correct size print out to use as a template. You will likely have to blow up the "jpg" file by some amount to get the ruler scale to line up with an acutal ruler. The other thing that could be done is measure the angle change between the fuselage mounting end of the tracing to the tail wheel mounting end. Make a template with a smooth curve such that the change in angle between the start and the end is similar to this sketch.The re-arching is done in a major size press. The spring leafs are placed in the press at various and evenly spaced locations along the leaf to get a smooth increase in the arc. The arc is changed gradually with each interation to produce a realatively smooth arch. The spring steel should not be heated as it will change the spring properties.3719
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[Larry2011]

Nice, thank you!

[Brian]

I have my tail wheel and spring off doing some routine maintenance as part of the annual on my 22/20, replacing some worn bolts and overall cleaning and re lubrication. So with the leaf spring off for the first time in a couple decades, the idea to have it re arched comes up. I have the 3 leaf PA-25 spring which agreed is different than what Steve used to trace the arch in the PDF. However to my surprise when I printed out this PDF and scaled it for the ruled dimension, the longer leaf in my 3 leaf set very accurately lays on top of this PDF print to great precision. So the question for the group is, am I good to go, or would a little more arch be desired ? The ABW spring is arched to a clearly greater degree than this and seems to be the cat's meow for those who have upgraded to it. I believe my castor angle is pretty level to the ground when the 22/20 is empty but would definitely have a negative castor heavy loaded. Advice greatly appreciated.

[Lownslow]

Brian, I would say that if you track good and you don't have shimmy, it's like "if it ain't broke, don't fix it". Shimmy is not only aggravating, but also wears out your tailwheel. So if you don't have it, you are likely OK.

Lou

[Steve Pierce]

I agree, "if it ain't broke don't fix it."

[Brian]

I agree, "if it ain't broke don't fix it."

Yes I'm basically in that school of thought myself. This topic has gone "shortwing" viral however and I've had more than one shortwing enthusiast tell me I should really consider getting my TW spring re arched while visually ramp checking my TW.:icon_lol:

[Gilbert Pierce]

If it does not shimmy, why bother. The only reason you would increase the arch is so it won't shimmy. It works, leave it alone.

[IDPacer]

Had shimmy problem on my 1953 PA-22/20-135 since I bought the plane 2 weeks ago. Took leaf springs off, re-arced using the above template. Actually went slightly more than the template to allow for some loading and settling back. Cleaned, re-lubed pivot point and axle with AeroShell 5, painted spring leafs and mounting brackets/clamp. Assembled and taxi tested, flown yesterday. Hurrah, no shimmy! Thank you Andy Anderson.

[sierrasplitter]

I had mine re- arched yesterday. Had to go out of town before I could install. Will the re-arch cause slack in the tail wheel chains ?

[andya]

I've changed a couple springs after re-arch and never could see a change in cable slack.
My present spring was a brand new Univair spring that I had re-arched before I installed it.
from Univair it did not match my pattern I made to get the right angle.

[IDPacer]

When I re-arched my springs last year, it made no noticeable change to the tail wheel chain tension. Went back together with same chains, same length and tension. Worked great afterward. No more shimmy!

[sierrasplitter]

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Re-arched How’s that look ?

[Steve Pierce]

Looks good. Here is one year old FX3 Carbon Cub. Comparing the new AK Bushwheel spring to the 152 hr Univair spring. These are the two bolt tail springs used on the 2 bolt tailwheel head. Less issue with the head getting loose on the spring since I went this route.
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[sierrasplitter]

Thank You Gilbert and Steve for the excellent template and instructions. Re-arched mine and No More Shimmy !