Replacing Tailwheel Leafsprings

[GAHorn]

The T3 tailwheel is an answer to a badly maintained tailwheel. So is good maintenance …(for a lot less expense)…. IMO.

[counsellj]

George. The T3 prevents broken springs and damaged rudders. Especially for those of us that operate off airport. The are pages and pages in these forums of problems with old and new tailwheel springs alike.

[dstates]

George. The T3 prevents broken springs and damaged rudders. Especially for those of us that operate off airport. The are pages and pages in these forums of problems with old and new tailwheel springs alike.

Can you put a T3 on an original style steel tailwheel bracket, or does it have to be the "fish-mouth" aluminum one?

[n2582d]

Dan Dufault, the developer of the T3, answered that question for me:

The STC does cover all 170s but they must have the later B type fish mouth brackets.

[DillanMcL]

So here’s what’s holding my tailspring to the bracket. Gary I think I’d like to buy your retainers please pm me a price.

[GAHorn]

George. The T3 prevents broken springs and damaged rudders. Especially for those of us that operate off airport. The are pages and pages in these forums of problems with old and new tailwheel springs alike.

Jon, I truly am not seeking to criticize any owner who believes it’s the best product for their purposes and wishes to spend the money on a T-3….
… But ANY design, including the more complex T-3… will require diligent maintenance to remain intact and not cause additional damage. The T-3 uses springs and bolts and brackets too…. All of which are subject to wear-and-tear.

I believe the main reason we haven’t seen them fail and damage rudders, etc ….Yet….is because they are All NEW.
If the 75-year old original, less-complex tailwheel gear, springs, and bolts were AS new… They would enjoy an Equal amount of success… for Less Money and trouble. Just sayin’…. Good Maintenance is the Key.

[sflynn30362]

George, I battled a tailwheel shimmy earlier this summer, it was resolved with a new tailwheel assembly as a previous owner made an egregious attempt to rebuild it, damaging it in the process. I have noticed that the camber on the pivot is nearly vertical, not cambered as it should. I was debating between the T3 and replacing the springs through univair. Is it worth just replacing the main spring or should the whole stack be replaced?

[Bruce Fenstermacher]

The change in caster is not because the entire spring pack relaxes, but the main spring fatigues and bends just aft of the trailing edge of the second spring. It will eventually break off and this point.

Replacing only the main spring is necessary to remedy the problem for years for most operators.

This is just one of many wear/maintenance issues we have to deal with owning a 170 or any mechanical thing. I don't think a claim of the T3 is that is is maintenance free.

[DillanMcL]

Hey folks any opinion on this tailwheel spring replacement job? I’ve had my IA replace the mainspring and the “non standard” bracket(with an L19 bracket) and other hardware but the caster angle is still slightly negative. There’s also a little air between the mainspring and the other older springs, but I assume this is no big deal.

I haven’t tried any landings yet but it seems to turn slightly better on the ground.

[n2582d]

A couple of things I notice that are non-standard include:
1.) The nut securing the leaf spring to the fork assembly is a AN310 castellated nut. While this is not what the IPC calls for, my greater concern is that it is installed without a cotter pin. Use table 7-1 in AC 43.13-1B for required torque value.
2.) The spring shackle is missing the guard, p/n 0442125. It's an 020" piece of aluminum -- easy enough to fabricate. See fig. 20-86 in the C-170 IPC.
3.) The shackle is installed with the wrong diameter bolt. Using a larger diameter bolt will help reduce that air gap slightly. Adding a thin walled tube over the bolt inside the shackle would serve to eliminate that air gap above the main spring.
4.) The forward attachment of the tailwheel steering chains is non-standard. The standard setup is for the springs to attach directly to the tabs on the rudder bellcrank, (p/n 0433132). Scott call for an eyebolt as seen the instructions Bruce posted here. Alternatively, Bruce suggests using a shackle here. While using a link is non-standard I don't know that I would call it unairworthy. However, the link attachment to the rudder bellcrack looks like it could rotate on the bolt. If so, it should be attached with a bolt and castellated nut.

[Bruce Fenstermacher]

All of what Gary said.

Here are my thoughts. You have the original style bracket. 5 springs are suppose to be used with this bracket. I believe your missing the shortest top spring though it looks like there is some type of spacer there. The 5th top spring was dropped with the later "fish mouth" style bracket.

Why wouldn't the spring be there. Cause the main spring your have is thicker than the original new springs are all thicker. Maybe what I'm seeing is a thinner spacer at the top instead of the spring to make room for the thicker main spring. I doubt it makes a difference not having that top spring except for paperwork. (Edit- I had a brain fart. The 5th spring was dropped at the start of 170A production according to the IPC)

What's more concerning to me is the main spring seems to be sprung or bent already. I've never seen a gap between it and the rest of the springs. Comparing the lines in my crude drawing the top spring is what we see normally, yours seems to be bent like the bottom spring. If it is that would explain why you still have some negative caster.

Untitled-1.jpg

Was the new main spring bowed like that when you got it?

[dstates]

All of what Gary said.

Here are my thoughts. You have the original style bracket. 5 springs are suppose to be used with this bracket. I believe your missing the shortest top spring though it looks like there is some type of spacer there. The 5th top spring was dropped with the later "fish mouth" style bracket.

Why wouldn't the spring be there. Cause the main spring your have is thicker than the original new springs are all thicker. Maybe what I'm seeing is a thinner spacer at the top instead of the spring to make room for the thicker main spring. I doubt it makes a difference not having that top spring except for paperwork.

What's more concerning to me is the main spring seems to be sprung or bent already. I've never seen a gap between it and the rest of the springs. Comparing the lines in my crude drawing the top spring is what we see normally, yours seems to be bent like the bottom spring. If it is that would explain why you still have some negative caster.
Untitled-1.jpg

Was the new main spring bowed like that when you got it?

Bruce,
5 springs is only for the 170, not the 170A with the original bracket. You keep mis-remembering that fact.

Dillan,
I looked back and now see that when you say you replaced the bracket you were not talking about the fishmouth bracket at the end of the fuselage, but the clamp at the end of the tail of your fuselage. That is a good improvement.
Please also take another look back at this post. viewtopic.php?p=154685&hilit=tailwheel#p154685
It has some other links to check out as well.

I also agree that the castle nut on the main bolt to tailwheel should be something more secure. I'd recommend a metal locking nut. I've seen that nut come loose on my plane before and it causes a heck of a shimmy and if that continued a likely loss of tailwheel.

You are still missing one piece (see below) and I agree with Bruce that your new main spring looks "pre-bent" with an arch in the wrong direction. If you click on the first link in the post I reference above it shows the brand new stack of springs I bought in the past and the bottom spring is straight. That is what you want.

Here is the piece you are missing. It is a simple "U" shaped aluminum part just to keep spring chains from catching on anything.

tailwheel1.jpg

Doug

[cessnut]

Let's get this straight. The airplane in question is a 48 170, so what spring stack does he need with that bracket?
If you look at his original pictures it appears that perhaps the whole stack is bent. It seems like further investigation is warranted to determine why that new main spring is bent the way it is.

[n2582d]

Cessnut,
I partly to blame for this confusion as I referenced the C-170A IPC in my earlier post about the shackle guard. My apologies. I've edited that to reflect the same part number in the C-170 IPC. Bruce has a screenshot of fig. 20 of the C-170 IPC on the first page of this thread.

I wonder if the mainspring here appears to be flexed the wrong way because the weight of the aircraft is causing this spring to "pivot" on the back end of spring #4 (fig. 20-75, p/n 0542105). It's fulcrum is there because the shackle is not securing the spring set tight together. This is because the shackle is an L-19 shackle, p/n 0642108, which is designed to include a thicker mainspring. I'd be interested in seeing a profile picture of the tailspring assembly with the weight off the tailwheel. If I'm correct, the solution is to use the correct larger diameter bolt with that L-19 shackle and to shim it so that the springs stack tight against each other. My suggestion is to use a bushing around the correct diameter bolt. Alternatively, replace the L-19 shackle with the correct C-170 shackle, p/n 0542108. The problem with leaving it as is (in addition to poor steering and/or shimmy) is that the end of spring #4 will cause a stress riser on the top of the mainspring as it pivots there. (There are other threads here which recommend filing or grinding the sharp end of spring #4 so this will not occur).

[DillanMcL]

All of what Gary said.

Here are my thoughts. You have the original style bracket. 5 springs are suppose to be used with this bracket. I believe your missing the shortest top spring though it looks like there is some type of spacer there. The 5th top spring was dropped with the later "fish mouth" style bracket.

Why wouldn't the spring be there. Cause the main spring your have is thicker than the original new springs are all thicker. Maybe what I'm seeing is a thinner spacer at the top instead of the spring to make room for the thicker main spring. I doubt it makes a difference not having that top spring except for paperwork. (Edit- I had a brain fart. The 5th spring was dropped at the start of 170A production according to the IPC)

What's more concerning to me is the main spring seems to be sprung or bent already. I've never seen a gap between it and the rest of the springs. Comparing the lines in my crude drawing the top spring is what we see normally, yours seems to be bent like the bottom spring. If it is that would explain why you still have some negative caster.
Untitled-1.jpg

Was the new main spring bowed like that when you got it?

Thanks for the reply Bruce. Yes the new spring looked perfect. Same thickness etc as the old one. I had them keep the rest of the stack intact and swapped in that one, but I did replace the old homebrew spring shackle with an L19 shackle and told them to use a larger dash 5 bolt with a metal sleeve which I believe they did not(because it “wasn’t in the drawings”). I’m pretty sure the resulting looseness is what’s causing the sag. They delivered the plane before I had a chance to complain so I’ll have to wait till next annual to fix this, but it seems fine for now, obviously sticking to wheel landings as much as possible