The International Cessna^® 170 Association

Shortly after I bought my airplane in Jan '01 my talwheel leaf spring broke. Fortunately, no other damage- the airplane was parked, unattended, when I heard a loud BANG ! - the tail dropped and sat on the remaining springs.

The spring broke just forward of the bracket casting, where it was in contact with the forward edge of a STEEL spacer. To further complicate this story, I had asked a mechanic to slightly bend the lower leaf spring to make the talwheel pivot angle vertical. He heated the sprng to bend it- a big mistake as that can change the temper of the spring. A few days later, the spring broke.
I just re-installed the old steel spacer because the aluminum spacer was wearing and the bolt was loosening. BTW, there was and is also a thin shim inside the steel spacer to make a snug fit around the leaf spring.

But maybe there's a good reason to use an aluminum spacer- Can the forward edge of the steel spacer cut into the spring, causing a stress concentration just forward of the casting, where my spring broke ? Did the previous heating of the spring contribute to or cause the breaking ?
Would it be advisable to grind off and round out the sharp corner on the leading edge of the steel spacer ?
I may take the old broken spring to a metallurgical lab for analysis.
If I do, I'll report the findngs.
Would apprecate your comments, thoughts and suggestions-
Rudy

If it was me, I'd deburr the leading edge of that spacer AND the tailwheel casting. But that isn't to say that a sharp edge caused the spring failure. This is a natural place for that main leaf to fail-- when it flexes, the flexing stops where the leaf is backed up by the t/w casting. Eventually, this can & will cause the metal to fatigue. Think about it. I've seen several broken main leafs, and this seems to be where they break at. Or else at the trailing end of the #2 leaf-- again, where the flexing is concenrated.
Not a hell of a lot you can do about it except replace the leaf periodically. Someone here mentioned 500-1000 hours as a replacement interval, which seems a bit low to me-- but better safe than sorry. Main leafs are cheap compared to rudder repairs-- or worse!

Eric

Eric, that makes good sense- (can always count on you for an insightful analysis of a problem)
Rudy