Leaf Springs

lawson · Post by **lawson** » Fri Jul 30, 2004 8:36 pm

I have a 51' Cessna 170A. I need to replace the leafsprings. The part that I received from Unavair Corporation(# UO542106) is a two-bend leaf spring. This doesn't work, because the 2nd bend makes the tailwheel hub assembly sit at an angle, which is incorrect.

Any advice on where to purchase correct leafspring? has anyone had this problem before?

Thank you. cameron

zero.one.victor · Post by **zero.one.victor** » Sat Jul 31, 2004 12:23 am

From your description, I'm not so sure you have the wrong part(s). The tailwheel kingpin (vertical axle) should be at a leading angle-- that is, the kingpin should be angled forward at the bottom. Then when there's a load on the spring,the tailwheel kingpin will be at a pretty much neutral angle. If the kingpin is at a trailing angle ( leaning top-forward), it will increase the tendency to shimmy. Especially when there's a load on the spring & the kingpin really goes into an exagerated trailing angle!

Eric

doug8082a · Post by **doug8082a** » Sat Jul 31, 2004 12:35 am

Ditto on Eric's comments. If the kingpin in neutral when sitting on the ground then it will "trail" when a load is applied (landing) and shimmy. The main spring is supposed to have two bends... one where it exits the tailcone and one just before the tailwheel assembly. The diagram in the IPC shows this as well. Univair p/n U0542106 is the correct one. I have the same one installed on my '52.

I had similar reservations when I first went to change my springs (and caused George a certain amount of grief from my constant disagreeing with him

). Basically, the main spring on mine was so old that the second bend (where it attaches to the tailwheel) had actually straightened out!

It sounds like this may the case with yours as well. Remove the main spring and have a look on the top of it where the next spring in the stack rests on the main spring. Do you see a groove being worn across the main spring there? Chances are you will. This is where the spring fails (breaks). If your spring has straightened out it's probably pretty old and you should count yourself lucky it hasn't broken yet.

lawson · Post by **lawson** » Sat Jul 31, 2004 12:52 am

Hi Eric & Doug-

Thank you so much for passing your info/experience along. I'll show this to my mechanic over at Yellowstone Jet Center. I'll let you know how it all turns out next Tuesday when I go to work on the plane again.

Thank you. Cameron