Tailwheel spring corrosion

[gfeher]

The leaf spring “Shackle” (170B p/n 0542108) has the tit and is the same part as L-19 p/n 0642108. You can get it from Air Repair using either the 170B or L-19 part number. That's the only source I know of, other than an eBay find (like the one above).

I spray a light coat of LPS-3 on my tail spring stack to help prevent corrosion, and re-apply it about every year. It forms a waxy film and does not affect the finish. When re-applying it, first wipe off the old film using a mild solvent or something like WD-40, Corrosion X or LPS-2. Some may not like the appearance of the spring stack after applying the LPS-3 as the stack is no longer a nice shiny painted surface, but has a dull, waxy finish. But for me, it's a functional thing.

[DaveF]

If the stud thingy is missing, you can fit a short socket head cap screw head down, threaded end up through the hole in the shackle. 10-32, I think.

[c170b53]

I’ll take another take which differs a bit from or adds a qualifier to what Bruce posted. Looking at Reese’s tail spring pic, two things are obvious. There’s a few parts which are not OEM and the springs are not in a healthy state. I’ll conclude that there’s been mx action here before and hence it’s unlikely these are original springs but maybe they are.
What’s clear is there’s been major fretting occurring to the spring surfaces, so if I was to recommend following Bruce’s suggestions I would look very carefully at the condition of the springs looking for any deformation or wear into the surfaces. I would reject any that show localized wear such as (posted many times in the forums) the third spring end edge contacting the main spring forming a wear area line across the main spring, often the failure point. Obviously, the main spring being the longest to act as a lever is most likely to fail should it’s strength be compromised and being a single load path, never a good thing. Failure of the other springs are unlikely but wear (just my speculation) may allow more relative movement of the main spring, likely to hasten its service life.
I’d replace the main spring at a minimum, replace the spring and tailwheel attach bolts (You’ll likely find yours deformed).
LPs 3 is a great recommendation as does it does cling to surfaces, as mentioned just ensure the surfaces are cleaned prior to reapplication as most lubricants will also capture grit which can work against the end goal.

[mit]

Reece, I can not recommend you buy a whole new set. Due to time loss of manufacturing specs have gotten muddy as well as material availability has lead to considerable thickness variances of the springs you will receive today. Unfortunately I would give your chances of receiving a new spring pack that will actually fit as being ZERO. Univair is the only manufacture fo these springs. If you buy them elsewhere, unless they are new old stock from Cessna, the came from Univair. Univair knows there is a problem with thickness of their springs. Last I talked to Steve Dyer, President of Univair about it they are doing the best they can with the known knowledge they have within the limits of material availability to support our 170 spring needs. BTW it is not just Univair, I have in my possession, a "kit" of NOS Cessna springs bought from Air Repair that will not fit in the NOS bracket it came with.

At the most I would buy the bottom main spring only. I'd clean and paint your other springs and reuse them. It is not rocket science. Clean them and paint them with a good primer and paint. I like the Professional Grade Rust-Oleum Professional grade enamels. https://www.amazon.com/Rust-Oleum-23910 ... B0010P63NC. The darker gray is nearly the same color Cessna used at the factory.

Paint and give it a few days to fully cure.

Just got a stack, fit was fine, looked good.

[c170b53]

Any chance you can take and post a pic of the old spring, just so we can over analyze it Mit ?

[Bruce Fenstermacher]

[
Just got a stack, fit was fine, looked good.

This is good news Tim and I'm glad to hear it. Maybe should raise my odds a bit but I'm still pessimistic.

[mit]

Any chance you can take and post a pic of the old spring, just so we can over analyze it Mit ?

I tried to post a pic I have to figure out how to resize it to fit... I forgot how

[n2582d]

What does everyone recommend for spraying on this to prevent future corrosion? My aircraft lives outdoors. I usually rub a light coat of engine oil on exposed steel, but maybe there's a better solution? Preferably something I can get from the local hardware store

Reece,
Looks to me like you've been maintaining your tail springs "by the book". Take a look at Cessna's guidance for the L-19 in paragraph 4-358 of the Service Manual:

Given how oil will attract dirt and the advances in corrosion prevention products since Cessna published the L-19 manual, I'd agree with others here that there are better ways to maintain the leaf springs.

[GAHorn]

I’m fairly certain that only applies to L-19s using “Royal Lubricants” oil in Olive-Drab cans.

[c170b53]

I tried to post a pic I have to figure out how to resize it to fit... I forgot how

might happen to us all if we eat and drink right.
Easiest is to take a pic with your cell phone, log into the site with your phone, go to the thread and reply, then select the upload attachment tab, which asks you to choose a file from where-ever you store your pics. When you select the pic, you will have a choice of the file size, choose large and it will likely fit.

[mit]

I tried to post a pic I have to figure out how to resize it to fit... I forgot how

might happen to us all if we eat and drink right.
Easiest is to take a pic with your cell phone, log into the site with your phone, go to the thread and reply, then select the upload attachment tab, which asks you to choose a file from where-ever you store your pics. When you select the pic, you will have a choice of the file size, choose large and it will likely fit.

My phone is still attached to a cord in the wall! I'm well behind the technology......

[reecewallace]

Reece, I can not recommend you buy a whole new set. Due to time loss of manufacturing specs have gotten muddy as well as material availability has lead to considerable thickness variances of the springs you will receive today. Unfortunately I would give your chances of receiving a new spring pack that will actually fit as being ZERO. Univair is the only manufacture fo these springs. If you buy them elsewhere, unless they are new old stock from Cessna, the came from Univair. Univair knows there is a problem with thickness of their springs. Last I talked to Steve Dyer, President of Univair about it they are doing the best they can with the known knowledge they have within the limits of material availability to support our 170 spring needs. BTW it is not just Univair, I have in my possession, a "kit" of NOS Cessna springs bought from Air Repair that will not fit in the NOS bracket it came with.

At the most I would buy the bottom main spring only. I'd clean and paint your other springs and reuse them. It is not rocket science. Clean them and paint them with a good primer and paint. I like the Professional Grade Rust-Oleum Professional grade enamels. https://www.amazon.com/Rust-Oleum-23910 ... B0010P63NC. The darker gray is nearly the same color Cessna used at the factory.

Paint and give it a few days to fully cure.

I ordered a full spring kit from ACS a couple weeks ago. I guess I'll take my chances with the ACS full spring kit fitting. If not, I'll return it. I'll call Univair tomorrow and get their thoughts. Thanks

[Blue4]

It's well known that the typical failure point on our spring packs is the bottom-most or "main" leaf spring. But, why? The spring right above the main leaf tends to have a rather sharp right angle to it. This angle generally marks or scores the main leaf spring at the point where they meet. This scoring leads to corrosion (a rust line) and if left long enough, cracking and failure.

I find it advisable to chamfer the rear lower edge on the spring just above the main spring. This would be the 3rd or 4th spring from the top depending on installation (I've seen both, although I'm sure one method is likely wrong). Basically, just smooth out that edge a tiny bit and your main spring should last longer. I've used a scotchbrite wheel before with good results.

I like the club recommendation of 5 years / 500 hours for main leaf replacement. In airplane dollars, it really is cheap preventative maintenance. Its likely cheaper than a new set of spark plugs.

In answer to the corrosion preventative spray, I like LPS-3. Its aviation grade stuff and can usually be found at most Ace hardware affiliates. LPS-2 is a great all-around airplane lubricant, too.