Univair tail spring

How to keep the Cessna 170 flying and airworthy.

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c170b53
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Re: Univair tail spring

Post by c170b53 »

I’m on spring three, last two from Univair. One of the past springs had that lateral deviation as well but still seemed to do its job. Last spring installed last spring I had no issues with.
I’ve mentioned this once before but I’m not certain why I’ve seen a L-19 fish mouth that was a bit different from what’s on a later 170B. Maybe there’s more than one type of fish mouth for the L-19 and hence different springs for it as well ?
As for mistakes in the illustrated parts catalogues well this won’t help either, there’s often mistakes in the AMM’s , of course those would be approved mistakes. :)
Be careful in whatever you do, I guess.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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Bruce Fenstermacher
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Re: Univair tail spring

Post by Bruce Fenstermacher »

It's hell getting old and not remembering your memory isn't as good as it once was. And I hate putting out bad info, and then George goes along not questioning. Good thing Johneeb has a picture to refer to and not rely on his memory. :cry:

The '48 with the early steel bracket came with 5 spring leafs.

The '49 170A and on used the same steel tail wheel bracket but only used 4 springs, the same 4 lower springs but not the shortest top spring found on the '48. This carried through to the B model with the steel and then the "fish mouth" mount.

My mistake was I referenced only the B model IPC as I knew it had both brackets pictured. I saw the early steel bracket with 4 springs, not remembering only the '48 had 5, subtracted 1 from 4 or one spring less and incorrectly advise only 3 springs are used in the "fish mouth" bracket. Which of course I was being told fit nicely confirming my mistake. I'm sorry, I must be much more careful.

So in short, '48 with steel bracket, 5 springs, all other years no matter the bracket type, or a '48 with "fish mouth" bracket 4 springs.

As to why 3 springs might fit nicely I can't say. I've seen springs of various thickness, perhaps 3 thicker springs might fill the space, but there should be 4.
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Bruce Fenstermacher, Past President, TIC170A
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c170b53
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Re: Univair tail spring

Post by c170b53 »

Post Edit pn's added plus, Hopefully the poster with the three springs installed had the same thought process. The one variable here which should be considered, a new top plate comes un-drilled (p/n 0510000-31 official called channel spring retainer). These plates often have the end tab break off and are replaced. Possibly the replacement wasn’t positioned in the right spot causing grief on a revisit. Also I don't know if a new fish mouth has the holes drilled to size to fit the bolts retaining the spring block ( p/n 0510000-35). If the assembly has incorrect gap in terms of the spring build up or it's missing the spacer, the gap will eventually show up at the retainer plate. The bolt holding the springs in, at the forward end will either pull through the plate or deform the hole and bolt. A pic might help us do a more thorough guess.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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DaveF
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Re: Univair tail spring

Post by DaveF »

Here are some L-19 tailsprings I saw at OSH a few years ago. On all except the last picture, the spring brackets don't look like 170B. What's the purpose of the U-bolt on these?

IMG_2110 resize.jpg
rsz_img_2122.jpg
IMG_2113 resize.jpg
rsz_img_2111.jpg
Looks like 170B bracket
Looks like 170B bracket
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c170b53
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Re: Univair tail spring

Post by c170b53 »

Thks Dave, I knew I had seen a difference last time I got close to a L-19.
Bruce, I know what you mean. Just last week I think I,went from one end to the other through a team and put the puck top shelf just like I could whenI was 18.
It's hell getting old and not remembering your memory
It’s believing my memory now, that a problem :D
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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GAHorn
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Re: Univair tail spring

Post by GAHorn »

Re: what Bruce wrote: It's not that I don't question... It's that I can't count!
My own 170B has four springs... And I know/knew that.... Yet was so focused on the O1/L19 situation my typing fingers were traveling faster than I could Count! :oops:
Bruce has the numbers right.... 5 on the 48 and four subsequently...
The situation where only three will fit was on my mind when I brought up the Birddog springs.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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Bruce Fenstermacher
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Re: Univair tail spring

Post by Bruce Fenstermacher »

Dave, the clamp no doubt helps stop the springs from ripping out the end of the top retainer. The L-19 bracket evolution with the end tab being removed is pretty good evidence that depending on how nice they break off a 170, there is no need to replace the top retainer. Just install the longer U-bracket as they did on the L-19 which can be seen easily on the red bracket.
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johneeb
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Re: Univair tail spring

Post by johneeb »

So I braved polar vortex Jayden to take this photo. These are two of the types of tail-wheel spring mounting brackets that Air-repair sells, I bought them several years ago in a fit of I better buy them while they are available. I also purchased, at the same time, the main leaf springs shown in an earlier photo in this thread. I am pretty sure that while the thinner spring has an O1/L-19 part number that is what you get when you order a 170 spring from Air-repair.
IMG_0969.jpg
John E. Barrett
aka. Johneb

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Buckeyejim
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Re: Univair tail spring

Post by Buckeyejim »

John, nice pictures of those tail spring mounting brackets. The one on the right looks like the one on my B.
Looking at the pictures, I get the impression that the one on the left would have more room for spring
leaves than the one on the right.

If I can manage it I hope to take a picture of my set up tomorrow.

Taking a leaf from Bruce's book, I called Univair and talked to Jim Dyer about the "how many leaves" problem.
He couldn't shed any light, but when I suggested that they consider rounding the lower ends of the springs
so the sharp edge doesn't gouge a groove in the lower spring when they flex he seemed amenable to that idea.
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MoonlightVFR
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Re: Univair tail spring

Post by MoonlightVFR »

I like all the in put for the various differences in actual pictures of the parts.

Discrepancy about a Manual or Catalog is certainly pertinent. Keeps the grey matter sharpened.

Some one posted a picture of the UNIVAIR machine that was clipping out the springs.

Somewhere I was informed that the Spring Steel was a common temper 7**** don't remember. Same steel as big radius Lawn equipment. Dixie Chopper? maybe.

These springs are still breaking on a rather regular basis. Less that 500 Hrs? Mfg needs Repeat business to stay in business.
Two (2) reports on this forum have cited owner going to Airport to find "broken main spring " while aircraft idly tied down Outside. I do not accept this as NORMAL. Something is amiss. What is it? John Collins early club president had tailwheel spring break; Gas Service station near airport - taxied over - impromtu welded - flew home.

What do we Really need?
gradyb, '54 B N2890C
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GAHorn
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Re: Univair tail spring

Post by GAHorn »

If those who find their tailsprings broken kept better records …(in fact, if didn't we all...) :? … we'd be better able to predict this problem. But some of us operate in the boonies...some on dirt strips...some on pavement... some are good at touching down gently...some only do wheel landings...some bang it in on the tail... There is no control group so all we have is an anecdotal "poll" taken a dozen years ago in which we received about two dozen credible reports that they break around 700 hrs.
So we decided to recommend that 500 hrs might be a great time to replace that spring as a preventive measure. That, of course, is no guarantee that any spring will make it that far on your airplane.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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ghostflyer
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Re: Univair tail spring

Post by ghostflyer »

When I was putting together my aircraft the tail wheel area was already assembled , and looked correctly assembled but after many hours of my flying I had red dust forming between the leaves. So one wet weekend I pulled apart the spring pak . To my horror the top spring had a large gouge in it where the edge of the smaller spring had made its mark. New large spring sourced from spruce and all springs were walnut bead blasted clean . All the contact faces of springs were sprayed with dry moly coat and reassembled . The ends of the springs were all rounded on the linisher . It wasn’t easy reassembling the spring pak as clamps had to be used. Then every thing was sprayed with silver epoxy enamel paint. Then ACL-50 was sprayed on the tail wheel area. This was done about 5 years ago and during my SIDS check last year it still looked good.
Buckeyejim
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Re: Univair tail spring

Post by Buckeyejim »

In my original post I claimed that 3 leaves were a perfect fit, but as you can see from the attached very close up picuture
of my setup, there's a gap. About a fourth the thickness of a spring leaf - definitely not enough room for that 4th leaf.
I plan to insert an aluminum shim to close the gap.
Attachments
Tailspring fit.JPG
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johneeb
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Re: Univair tail spring

Post by johneeb »

Buck, Your spring pack appears to be made up of springs of three different thicknesses.
John E. Barrett
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Buckeyejim
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Re: Univair tail spring

Post by Buckeyejim »

Yes, the leaves appear to be 3 different thicknesses, but I think that's due to how I held the camera. Mr. Dyer told me the tailsprings
he sells are the same thickness as the original Cessna parts. I'm guessing it's 6 gauge steel.
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