The International Cessna^® 170 Association

Speaking of tail spring life limit, '98C had 1260 hours when I bought her, and already had rudder damage from a dangling tailwheel.

Yikes, mine has a " lot" of hours on the frame and no idea when it was swapped.
I looked at the stack more closely the other day and they all seem bent, or at least the nearest three to the wheel.
Of course I didn't take a pic

...
Swixtt,
So here is a simple way to tell if you are in need of main spring replacement.......

... take a gander at your destroyed rudder and the repair bill!

IF your mainspring has 500 hours/landings on it... it needs replacement.

IF you have no idea when it was last changed.., unless you're willing to undergo a rudder repair job.... it needs replacement.

you bet, thanks for all the input on this topic. i'll be placing an order tomorrow!

I finally have my new springs ... holding them up against the original ones they are longer

also on the new one it has a slight increased bend right at the point it attaches to the tailwheel assembly. the original is straight as a board!! i should take a pic.

canav8 wrote:...
Swixtt,
So here is a simple way to tell if you are in need of main spring replacement.......

... take a gander at your destroyed rudder and the repair bill!

IF your mainspring has 500 hours/landings on it... it needs replacement.

IF you have no idea when it was last changed.., unless you're willing to undergo a rudder repair job.... it needs replacement.

Also, ask your self the same questions relative to the main landing gear legs. I have owned my plane some 30 plus years and had them completely re-worked by "The a Landing Gear Works" several years back to insure against a major bill if one of them broke. I believe the money was well spent

Thought i'd post a pic of the entire 'new' pack. hopefully the part numbers are readable. I purchased the pack and the 5th leaf came with it... probably won't be needing it though.
the pic below is the 5th, smallest leaf
the other pic of 4 are the rest of the pack.

If memory serves me, on the later 120/140's at least, the small spring goes on the top of the stack with the bent end facing up.... The 170's may be different though.

Just finished replacing mine, I'm happy with the results.

jrhoa2 wrote:If memory serves me, on the later 120/140's at least, the small spring goes on the top of the stack with the bent end facing up.... The 170's may be different though.

They all go one on top of the other shortest to longest all bends in the same direction whether a 140 or 170.

But the little guy is omitted on the fish mouth style tailwheel fitting 170A or B ?

c170b53 wrote:But the little guy is omitted on the fish mouth style tailwheel fitting 170A or B ?

Jim, is that a question or is it a Canadian statement? eh.

Since you fashioned that sentence as a question, at least here in the US, yes, you leave the shortest spring of the 5 spring set out on the later fish mouth type tail wheel bracket.

Soooo, after removing my old spring I found what looks to be a real backyard repair. the last two inches or so had been cut or broken off and the main bolt through the Scott tailwheel to spring was actually going through two leafs!!
you can actually see the rough edge of where the leaf had broken... they seemed to have just drilled another hole through both leafs and mounted the tailwheel!
so of course the new bolt I have is WAY too long
oh, very glad I went with replacing the entire pack after pulling it apart.

Wow, Looks like a temporary repair had been forgotten about. It will be nice to know everything is as it should be, after your done.

The repair you found is not so odd. Yes it looks bad when compared to new. I think you will find more 170s with this type modification than you would expect. I've seen a few and I've owned one that used two (full length) main springs.

First, I wouldn't be surprised if this repair was made 50 years ago. A different time. Folks made things, repaired things and where not afraid to improve a weak design. And lets face it, this is a weak design. Do you think these springs just started breaking or do you think they've been breaking with the same failure time since '48. Do you think a guy in '50, after a failure, specially one that destroyed his rudder and maybe an elevator, was going to be satisfied with changing a perfectly good spring out at 500 hrs. Hell no.

And they didn't have to look far for what to do. Piper products like the Cub they flew in the war have two main springs the tail wheel attaches two.

I've told this story before. My first 170 had 2 main springs. Took me a while back when I was just learning the 170, to realize I had 2 and wasn't suppose to. Going firmly against George's recommendation to remove that "dangerous" setup, I did not. I flew it that way for 10 years until the plane was wrecked in a micro burst on the ground. George felt that the 2 springs when bent would act like a shear and cut the AN-7 bolt holding the tail wheel on. I could see his point but the AN-7 never showed sign of shearing action.

Coincidentally I just removed the spring pack from my Cub yesterday. It had been a while and I need to rebush the Maule tail wheel and (every body take a breath) rearc the springs a bit. Low and behold the top spring of the 2 that hold the tail wheel on is slotted at the fuselage attach point. What this means is the 2 springs can bend independently for about a 1/4" and then impart a shearing action on the AN-5 bolt that holds it on. Interesting.

Back to our 170s. I do not recommend running 2 main springs. And while it is tempting I have not installed that configuration on my current 170. Of course legality is an issue but more than that is the failure rate of the bracket the spring pack attaches to is just to high. I wouldn't be surprised to find a 50% rate of 170s in a group with a crack somewhere in this bracket or the top plate for it.