The International Cessna 170 Association

I mean seriously! $170 for a bushing? Really?

I'm replacing all the tail wheel leaf springs because, 1) they just look like they probably need it, 2) the tailwheel geometry is way out of wack and I have quite shimmy going on, so they definately need it, 3) every other part was, I thought, quite reasonably priced, at least by airplane standards. 4) Versus the true cost of neglect and letting actually break before I do something about it.

So, what's the consensus on the leaf spring bushing p/n 0510000-36. The one used to attach the leaf spring to the empennage. Is the old more than like trashed and I'll need a new one? Is there another one available that is less expensive?

Any advice is appreciated?

I'm thinking that bushing, which is steel, probably isn't trashed and in need of replacing. Don't know what your springs look like the rarely does any more than the main spring need to be replaces. But while your at it look at all the parts that are suppose to be back there on the springs. Many a 170 don't have all the parts like the shackle and guard #15 and #16 and make sure the u-bolt is installed as shown with the nuts up. Many are upside down.

If I needed a new bushing, I'd make it. But then I have the tools to do so.

No I agree, I could probably get away with just changeing the main spring. Ordinarily i'd be one of the first to pop off with "if ain't broke, do't fix it" but this appears to be the exception to that rule. That and they just aren't that expensive for the rest of the set, so, I'm going all out. Then maybe I won't have to screw around with it for a while. Plus, you haven't seen me try to land this thing yet. I could sell ticket for most of'em!

A new 15 and 16 are also a must. Looks like someone cut the old ones to fit and dogged them down with a jackhammer. I'm not even sure about their proper orientation. But I'll make sure the new ones are installed correctly. Thanks.

Thanks again.

More to follow. I'm sure!

Sense you are going all out with new springs don't forget to bevel #12 at the back edge where it chafs on #11.

John

Ok I'm unfamiliar with that problem and/or with the need to bevel the new springs. So with the bevelng, just approximate the wear pattern of the old springs where 12 chafes on 11?

WSHIII wrote:John

Ok I'm unfamiliar with that problem and/or with the need to bevel the new springs. So with the bevelng, just approximate the wear pattern of the old springs where 12 chafes on 11?

WSHIII... there is a phenomenon commonly known as "stress riser", which is the concentration of stresses at minor scratches and dings, on metal objects which are subject to vibration or other stress. The stress builds up at such points.
It's similar to the way a glazier will break glass..... first he uses a tool with a small, incorporated roller to roll or "scratch" the glass pane...then he quickly "snaps" the glass and it will break exactly at that scratch.

Same thing with your propeller (and why we look for dings, scratches, and damage from rocks, etc. during pre-flight..... And why your mechanic/A&P/IA will dress the damage out with a file and abrasive-paper.... to remove those scratches, etc.. to prevent the build-up of stress in concentration.

The main leaf spring to which your tailwheel assy actually bolts, receives contstant wear and damage from the leaf spring above it. The lower, trailing-edge of that spring above leaves a tell-tale "scratch" or wear-pattern on the main leafspring, and that is where the main leafspring usually snaps.

It's considered good form to remove the sharp, lower-trailing-edge from the leafspring just above the main leafspring, to lessen the impact and reduce the development of a stress-riser on the mainspring.

Here is a photo I posted some time ago in another discussion about this matter. The photo is of the main leafspring, in the area damaged by the spring just-above. This damage occured in only a couple hundred hours operation on a new spring.

The main leaf spring to which your tailwheel assy actually bolts, receives contstant wear and damage from the leaf spring above it. The lower, trailing-edge of that spring above leaves a tell-tale "scratch" or wear-pattern on the main leafspring, and that is where the main leafspring usually snaps.

It's considered good form to remove the sharp, lower-trailing-edge from the leafspring just above the main leafspring, to lessen the impact and reduce the development of a stress-riser on the mainspring.

Ok I am familiar with " stress risers" so, I can definitely see the need and benefit from these relief bevels. And your description of why and where to make them has been very helpful.

Thanks.

One more thing. I'm inclined to just leave the new set of springs "as is" ( of course I haven't see them yet either) and just touch up and seal the beveled areas with black paint. Or, should I go all the way and seal them with a flexible two part "epoxy" paint?

I would use a fine file and remove the sharp lower edge of the 3rd spring, and polish the new edge. Then I'd paint each spring individually with Imron polyurethane "Gull Grey"....the same color Cessna used.
I would not install or take any other actions.

(I once experimented with teflon tape in this area but it proved useless as the tape quickly "squeezed" out and deteriorated.)

George,
I am now into many hours sense last tail wheel spring replacement and all that time I have had Teflon tape between spring layers with no tendency to squeeze out. Maybe the glue has improved (hard to understand how it is possible to have glue stick to Teflon tape).

johneeb wrote:George,
I am now into many hours sense last tail wheel spring replacement and all that time I have had Teflon tape between spring layers with no tendency to squeeze out. Maybe the glue has improved (hard to understand how it is possible to have glue stick to Teflon tape).

This reminds me.......George, did you furnish your own tape, or did I sell you the cheap shyt??

wingnut wrote:

johneeb wrote:George,
I am now into many hours sense last tail wheel spring replacement and all that time I have had Teflon tape between spring layers with no tendency to squeeze out. Maybe the glue has improved (hard to understand how it is possible to have glue stick to Teflon tape).

This reminds me.......George, did you furnish your own tape, or did I sell you the cheap shyt??

LOL. Yeah, Del... I furnished that tape you installed. It was supplied by Aircraft Spruce and it fairly quickly was shredded beyond usefulness. I thought it deserved a "try" tho'.
(That same tape has held up very well at the cowl-door fitment areas, and there has been no fretting/smoking/thinning of the sheet metal.)

I have seen a thin sheet of teflon installed for protection.

John

Bringing this post back from the dead! Man $170 doesn't seem so bad anymore. I have a little pitting on the bushing, but no uneven wear. What would you professionals do?

Yeah, for me it seems the price of the replacement part in inversely proportional to the necessity of its replacement. My 0510000-36 bushing measures 0.372” ID X 0.619” OD X 1.353” long. This 3” steel or this 2” stainless bushing might be worth considering for an owner-produced part.

This L-19 bushing is p/n 0642135. Might be worth a call to Air Repair, Inc. to see what they are asking for it. This website lists the dimensions for the L-19 bushing. It's shorter than my bushing which makes me question whether I have the correct bushing. When I clamp all four (unpainted) springs together they measure 0.944”.

0.9063 inches minimum and 0.9375 inches maximum overall length, 0.6150 inches minimum and 0.6230 inches maximum body outside diameter, 0.3670 inches minimum and 0.3870 inches maximum body inside diameter, steel comp 4130 overall material.

I would reuse that part using plenty of grease / antiseize on the through bolt, but I sometimes tend to have Scottish tendencies.