The International Cessna^® 170 Association

BrianW wrote:I have a 55B, and purchased a new main spring U0542106 from univair. My mechanic also said it's too thick to put in with the rest of the stack. If I go ahead and buy the whole pack, will that fit correctly or fit by installing only 3 of the springs?

-Brian

You should not install a different number of springs than called for in the IPC. Does your installation comply with the IPC illustration? Are you certain the new spring is correct in thickness? Univair suffered a few mfr’g issues but I thought they’d corrected that.

What we don't know is what springs you have. Are they all original 1955, or has one, two or more been replaced. And if any where replaced, were they thicker than what was installed in 1955. We also don't know what thickness of springs Univair would be selling yours and how they would compare to yours.

I think there is a good chance, other than the main spring, that yours are original. If that is the case no other spring you get will be thinner.

You can't, without some form of approval, remove a spring and run only 3.

I suppose a call to Univair to ask them if they have any main springs in stock that are thinner than the one you got is in order and while they are looking maybe they could tell you the thickness of the rest of the pack they might sell you would be.

It is a shame replacing this spring has gotten so hard to replace.

I misunderstood what my A&P told me on the phone.. The replacement spring is actually thinner than the spring that is in there now.

The old spring measures .375 and the new spring is .312

Should I order the L19 0642101 part?

Brian,
The difference in thickness between the old spring and the new spring is 0.063". It's interesting to me that that number matches what Larry found here for the thickness of the shim or spacer on the tail cone assembly. Any chance someone removed that shim, p/n 0512000-76? Depending on what you find, I think your A&P should consider replacing or adding an additional 0.063" shim there and use your new spring.

Brian, you are in luck then. Your spring will fit. No, I would not order the L-19 spring myself. I certainly wouldn't order it without knowing the thickness of it and that it matches what you had and you know it would fit.

And before I did anything I'd look at the thread Gary linked to to see the IPC drawing of the box and the shim (circled in red) that he is talking about.

If you find a shim on yours. then I'd install your spring pack with your new spring and see how it fits. If loose, then you might want to shim it up.

Brian, could you please post another picture of your tailwheel spring bracket that includes just a little more of the spring bracket. It appears that you have a doubbler that takes in the last two spring bracket bolts, I have not seen this done before.

When installing the new spring don't forget to chamfer the edge of the first spring above the new spring, that will help prevent creating a stress riser in your new spring. There are stings somewhere on here that address this issue.

After reading this thread yesterday when I got home I realized something was missing on my New2Me 170B tailwheel assy. My tail fork assy had been replaced in the 90's with the "improved" set up but the "U" Bolt was never installed as far as I can tell. No evidence of wear on the sides or bottom of the saddle or retainer plate... simply amazing and lucky I guess as there is bo evidence of damage or adverse wear. Now for the question, where do I get a new Ubolt & retainer plate? I see some other posts indicating these are hard to come by...

Air Repair, Inc, Cleveland MS. (662) 846-0228

Tell them you’re a 170 Assoc’n Member for our traditional discount.

Ask for one of the tailwheel tiedown “EYEBOLTS” while you’re at it.

Thank you !