Tailwheel Assy ATTACH bolts/nuts

[GAHorn]

How many washers beneath the nut is depicted in the IPC? (Shouldn't make much difference, however.)

[wingnut]

My next question is: Is the 450-500 inch pounds based on one washer, two washers, or no washers?

The amount of washers doesn't have anything to do with torque, UNLESS the nut is 'bottoming out' on the shank of the bolt (in other words, if the nut is running out of threads on the bolt because it begins to contact the unthreaded portion of the bolt shank, you could/would achieve the torque value you're shooting for, but not actually getting the required tension/torque between the parts you're fastening together.)
So you need to make certain that the grip length of the bolt (the measured distance of the unthreaded shank, from the bottom of bolt head, and the first full thread) is slightly less than the grip length of the bolt hole (all parts to be assembled including any washers).
Cessna parts catalogs are notoriously bad about not indicating the use of washers in many applications. Therefore, it become the mechanics job to insure that the olt length called out in the parts manual is of sufficient length (or not) to use a washer(s). I like to use washers, and have found in many cases, I need to use the grip length bolt to do so.

One other bit of info; not always, but most of the time when torqueing, you should first use the torque wrench to figure out how much resistance (torque) is required just to turn the lock nut. That amount should be added to the specified torque. With that said, if you torque in the middle of the specified torque range, you'll still be within the overall limit.

[DaveF]

Another one! Checked my tailwheel attach nut torque and found it about 200 in-lb. It's an Air Repair eyebolt and nylock nut that was new when installed.

[GAHorn]

I'm coming back to this thread because I noticed my METAL lock nut allowed the tie down ring to twist ...(meaning the bolt was not torqued.) I measured the grip length and see that the L-19 eyebolt... is probably sized for theL-19 mainspring... which is thicker than the 170 mainspring.

I had to add another plain washer to insure that the nut was not bottoming out.... and now it appears to be holding proper torque.

so... WARNING: If you have the l-19 tiedown eyebolt on your tailwheel... BEWARE... you might need more washers after-all to be certain the nut properly torques instead of bottoming out. (This may actually have been the problem with the nylon locknuts all along.)

[wingnut]

George, I will accept full credit for that improper grip measurement. I think I'm the one that last reinstalled that eyebolt when we painted all your springs Gull Gray, and added the telflon chaff tape. Sincere apologies and embarrassment from me to you. If I can make it up to you some how let me know. Glad you noticed it before a failure.
I seem to recall we chose the steel lock nut, AND used a split lock washer in attempt to prevent this problem. Obviously I did not check grip length as closely as I should should have. Lesson learned

[wingnut]

Something I would like to mention, but need to investigate further; we rolled an L19 into the hangar last week and noticed the eyebolt was very loose. I'll take a look at installation hardware and report back

[GAHorn]

It's not entirely your fault, Del. I meddled sufficiently in the task to distract you.

[wingnut]

One solution would be a dowel alignment pin/hole fore or aft of the bolt hole (this would be a major alteration.
A "C" channel shim to remove all radial play from the tail wheel fitting to spring union would also work and be easy.
The issue is, no matter how tight that single bolt is or the type nut/washer etc, there is enough radial play to eventually loosen and/or wear the bearing surfaces, decreasing the thickness. A couple thousandths of an inch would wear will make a big change in torque value. That one #7 bolt pivots every time the aircraft is steered

[bagarre]

I've noticed the bolt rotate a little over the course of a year's flying.
Only reason I notice is because the eye isn't straight by 10 degrees or so.
But the steel nut has never been lose when I check it.

I also don't 3 point very often (at all) so the plane is quite slow by the time the tail comes down.

[wingnut]

I have 3 short videos I just took with my phone. I don't know how to post video, but if someone wants to volunteer I can text them to be posted here

[wingnut]

Thank you for posting those videos Arash!
In the videos, you can see a "U" channel shim between the spring and casting. If this shim was either fabricated from a thicker material, or an additional shim added to eliminate the radial play, this would serve to greatly reduce the recurrence of the loosening of the bolt/nut, and bearing surface wear. Credit to Fred Hampton for his help on this.

[bagarre]

The shim under mine is pretty snug so even with the bolt lose there isn't much play.
You can see a little fretting in the finish from over the years.

tw2.jpg

This might also contribute to why mine stays snug.

[bagarre]

In that photo, it didn't.
That was from when I rebuilt the tailwheel and replaced the mainspring a year or so ago.

[wingnut]

Is it possible that aftermarket springs may be slightly narrower in width? Just spitballing here, but out of 3 in the hangar, all have the same issue. Maybe new parts would correct the issue.

[bagarre]

I got my spring from Spruce last year. Width was the same but thickness was slightly larger, which has been discussed here before.