Sloppy wing root pins

[vetdrem]

I have a model 3 that I keep in a trailer as my hanger. I fold and unfold the wings every time I go out to fly. I have been noticing that the pins that attach the front spar to the carry-thru are not as tight as they used to be. Nothing terrible, but I am keeping an eye on them.

Does anyone know if there is a spec for the clearance, and if it the holes wear too much, how do you fix them?

I have been thinking about making a steel collar that would go on the outside of the spar with new holes that would tighten up the clearances

Louie

[n85ae]

My immediate thought would be to use a flange bushing top and bottom, and
use a bolt/nut rather than a clevis pin.

Regards,
Jeff Hays

[Dave S]

Louie,

I do not recall that there is a tolerance for this.

Have you measured the slop? A clever setup with a dial indicator, etc should yield some info. I would estimate that a few thousands would be rather noticable but not an issue. If it is banging around 1/4" - that would be obviously a bad thing that needs correction for sure.

The bottom line is it probably the responsibility of the builder to decide what tolerance is acceptable lacking any service tolerances provided with the kit manual....we know what the starting point is because of the build manual specs but that's not a service tolerance.

One point to consider - what has worn? If it is the holes on the spar - a flange bushing or spar collar would work to cut the slop. If it is the pin, new pins/bolts are pretty easy to do. If it is the hole in carry through fixture - probably don't want to mess with that. If it is all three, you'd probaby see a lot of slop even if the wear on any one of the three parts is minimal because it adds up.

I have seen it that bolts and pins do vary in their diameter by a couple thousands and it might be possible to select fit a fatter pin or bolt that reduces the slop.

Sincerely,

Dave S

[vetdrem]

We are talking in the .001-.002 play. Like I said, not bad, but worth watching. I did check to determine where the wear is occurring, and I am sure that it is the holes in the spar. The pin is as smooth as new, the carry-thru has 5/16"ID tube welded to it for the pin to go through and it is nice and snug. The only "excessive" clearance is in the holes in the spar.

Lacking a spec to compare it to, I'll just keep an eye on them and when I think it is time, I'll probably build a collar to around the end of the spar. I think that it will be a snap to build and install one.

Louie

[mr bill]

How will you attach the collar to the spar?

[vetdrem]

I haven't thought it through yet. I would think that a steel collar that fit snuggly around the spar, drilled the right size for the pins, and pop riveted to the spar should do the job.

I'm really early in the process, and will probably change my plan a dozen times before I actually start fabricating anything.

Louie

[PapuaPilot]

If play is only 1-2 thousandths that isn't very much. You might try new pins or a close tolerance NAS bolt, if there is a way to keep it in.

If it gets to be too much would the next bigger size pin work?

[Paul Z]

I would have to guess that is within tolerance for the pin. If I look at the Mil-Spec for Fasteners .005 to .006 is the Major diameter tolerance. However, like I said I would have to go look up the Mil Spec for the Pull Pins to determine the allowable tolerance.

[airlina]

I have a model 3 that I keep in a trailer as my hanger. I fold and unfold the wings every time I go out to fly. I have been noticing that the pins that attach the front spar to the carry-thru are not as tight as they used to be. Nothing terrible, but I am keeping an eye on them.

Does anyone know if there is a spec for the clearance, and if it the holes wear too much, how do you fix them?

I have been thinking about making a steel collar that would go on the outside of the spar with new holes that would tighten up the clearances

Louie

Louie, Back in the day circa 1999, when i was building My Series 5 there was a aftermarket Kitfox place that sold these SS spar inserts. I used them on my airplane and thought the photo might give you an idea on a fix for your problem. The photo shows one already inside the spar and what they looked like before installation. Bruce N199CL

[vetdrem]

Bruce, that is pretty much what I had in mind, but I will size it to fit the exterior of the spar. the reinforcing plates that are already in the spars will stay in place. I think that I can add the new ring without even disturbing the fabric.

My only real question was about if there was a published spec so that I could decide WHEN I needed to do it.

Louie