Tailwheel Springs

[canav8]

Bruce/George, you have advised replacing a nylon type locknut with a steel one and there is some question regarding replacement of the bolt itself.

1) Did the L-19 bolt we purchased have a steel nut or a nylon locknut?
2) Any advise on when or if the L-19 bolt should be replaced?

The 0642105 eyebolt (L-19) was not furnished with a nut. The all-steel locknut is recommended.
The nut and bolt should both be replaced when the mainspring is replaced at 500 hours, or whenever the tailwheel assy is overhauled.

Doug, I don't agree that tail mainsprings only break when there is movement of that bolt/nut. The mainspring receives considerable stress where it contacts the trailing edge of the #3 spring, as that is where the loads are transferred to airframe. That #3 spring trailing edge abuses the mainspring whether or not it is radiused... but the mainspring durability is doubtless increased when the #3 spring lower, trailing edge is radiused/smoothed as that reduces wear and abrasion of the mainspring at that point (which is exactly where the mainsprings eventually fail if left in-service too long.)

George, your so literal.It is symantics. Okay the stress riser from the #3 spring trailing edge only causes failure when it looks at the main spring. How is that! lol

[Roesbery]

Back in the 1970's a number of 170's around Fairbanks had two main leaf springs installed. The problem that I saw was that there was not enough ( spring ) in the spring and the tail cone would break just forward of the attach bracket. Of course these were planes working off river gravel airstrips. Some of the rocks would be as big as your foot. I bent several new main springs within a few landings on such a strip. If you are working such strips, and a lot of Alaskans do, My best solution so far has been to use the L-19 main leaf and a bush wheel with a larger softer tire that does not hang up on the rocks as bad as the small hard tire. If you are only using blacktop or smooth grass fields, and light weights, then a standard spring should do ok.

[Bruce Fenstermacher]

The L-19 bolt as far as I know is only available from Air Repair who sells L-19 parts. I don't have the part number.

George what I meant by treat the L-19 bolt like any other bolt I meant it is just an AN bolt with a ring on top. Nothing more special about it. So treat it as you would a unmodified AN bolt holding your tail wheel on.

You are right, like the main spring, any bolt in this location should probably be replaced with the main spring as good preventative practice.

[GAHorn]

Thanks George,
The mainspring is 0542106
The steel lock nut is AN363-720

What is the part number for the L-19 eyebolt and do most people install it eye up (easier to tie-down) or down?

Thanks again!

As posted previously, the L-19 eyebolt PN is 0642105. The L-19 installation was eye down, but most civilian operators place it eye up, presumeably for easier access to the ring. Eye down actually accesses most airport permanent tie-downs better.

[...George, your so literal.It is symantics. Okay the stress riser from the #3 spring trailing edge only causes failure when it looks at the main spring. How is that! lol

I probably irritate some folks be appearing "picky" or "literal" but my actual intent is to be "specific". So many times the written word is a reflection of the spoken word....but without the inflection,....and it offers so many opportunities for errors when discussing technical matters. Since so much of the forums is about maintenance particulars, I usually strive for specifics. (Many times my specificity is interpreted as critical or argumentive when in-fact, I'm merely trying to be helpful. It's sometimes really difficult to walk that fine-line and I'm almost always surprised when I see an angry response.)
Anyway, we all see the importance of replacing that mainspring regularly, even tho' we don't all agree as to the propriety of installing a double set.

[akclimber]

Well, I replaced the tailwheel spring (ended up doing the whole stack) and the shimmy is as bad as before...
The only other thing I can think of is the steering chains are too tight. But when I add one more link, both springs are slack and there doesn't seem to be enough throw on the tailwheel to give sufficient steering.
I am now thinking of rearching the brand new univair spring to give it more positive caster angle.
Is there anything else I may be missing?

[Bruce Fenstermacher]

It is not a slack or to tight chain. Send me a picture to my email listed under my signature showing the caster angle and I'll tell if that is your problem.

[GAHorn]

I can virtually promise you that re-arching a new spring is not the answer. All that will serve is to kill the airworthiness of that spring, IMO.

[tweiss]

This thread has encouraged me to replace my main spring sooner than later. I received it last week from Univair, and am now waiting for the rest of the hardware from Spruce, mainly because Univair didn't have the undrilled bolt required for the assembly.
I cleaned up the three shorter springs and then painted all four to match the plane.
My question is, do you coat each spring with grease or something when putting it back together, or just assemble/stack em dry?
Thanks in advance.
Tom

[canav8]

This thread has encouraged me to replace my main spring sooner than later. I received it last week from Univair, and am now waiting for the rest of the hardware from Spruce, mainly because Univair didn't have the undrilled bolt required for the assembly.
I cleaned up the three shorter springs and then painted all four to match the plane.
My question is, do you coat each spring with grease or something when putting it back together, or just assemble/stack em dry?
Thanks in advance.
Tom

Tom the important part is to make sure each spring edge is smooth when the lay on top of each other. The end of the spring on the side closest to the tail wheel. Each leaf is generally made using a shear. When the shear cuts the metal it usually has a burr on the end from manufacturing. That must be removed. Also grease is not necessary. I hope the paint is a good quality paint because it will rub off between the springs and also can cause stress risers between the spring layers. D

[bagarre]

This is what mine looked like once together.
It shows how I rounded the sharp edge of the springs. Less than an minute with a hand file.
My old main spring did have an obvious wear mark from the chafe.
I didn't bother with any grease between the springs and I've never seen anything that called for it.
I hit mine with some LPS2 a few times a year (along with a lot of other parts) but I keep her tied outside all year long.

tw1.JPG

[akclimber]

Where did you get that eye bolt?
I've searched everywhere online and got one quote of $989!!!
I figured I'll pass....

[DaveF]

Where did you get that eye bolt?
I've searched everywhere online and got one quote of $989!!!
I figured I'll pass....

Per George's recommendation a few years ago, I bought mine from Air Repair in Mississippi. A search of the forums will probably turn up more info.