Stick Rigging question - Model 3

[wildirishtime]

After a recent bout with flutter/shudder, I'm inspecting my aileron rod ends and found something I'm not certain is correct - see my photo...

The Model3 build instructions I have show a seperate U shaped swivel (not currently installed on my plane), instead mine is swiveling using only the threads of rod ends, which strikes me as a dangerous wear potential since the jam nut remains loose and youre relying on only those threads for your pivot - I never realized just how much play I DO have there.

Is this correct? Or was the wrong rod end used in this implimentation? The bellcrank doesn't look like the one in the Model3 build instructions I have (it shows a thru hole for the above mentioned swivel, not welded tabs like mine does) so something is a little 'different' here but since I have no documentation on this, can someone send me some photos of how it SHOULD be, or explain to me how this method is OK????

Thanks!

[Av8r_Sed]

Hi Wild,

Here's a pic of my unmodified Model III linkage with the swivel (SN910). The project is nearing completion, but I still need to add a few touches like the missing cotter pins. I hope this helps.

-- Paul S

[wildirishtime]

Thanks - yea that is what I'd expect to see, but mine has tabs welded
on the bellcrank, looks factory - do i have a model 4 bellcrank? Anyone
have a picture of the model 4 configuration?

[Mnflyer]

HI Wild, my model III has the U swivel and it is needed to allow free movement as the stick is rotated for & aft, if it binds the threaded part of the rod end assy will eventually break causing loss of aileron control . This happened to me on takeoff luckily I was only 3/5' in the air when I discovered no control and landed with no problem. What happened in my case is the I tightened the swivel bolt too much and it would not swivel under certain stick positions bending the rod end threaded part. Now before every takeoff IO reach down and check that the swivel is free.

[wildirishtime]

I think I saw photos of yours (or a similar) incident on Matronics I think.

But the question is, why does mine not have the swivel bolt and the bellcrank seems to have welded tabs from the factory which appear to be designed to use rod ends ?

Anyone have a photo of a model 4?

[t j]

Here are a couple pictures of the Classic 4 control stick to aileron bellcrank rod ends. Look close and note that they have a very narrow body around the ball. This allows them to rotate as the sitck moves fore and aft.

Compare them to the third rod end that is on the tube that connects the two sticks. It has a thick body around the ball.

At all positions of the stick there is a slight amount of rotation still available. You should be able to wiggle the rod ends a slight amount no matter where the stick is positioned.

This makes two early Kitfoxes now that I know of that have had the male rod ends break. My opinion is someone modified it to the Model 4 style but used the wrong (Thick body) rod ends.

They are 3/16 X 1/4 - 28 M Rod end Kitfox part number 93001 and 3/16 X 14 -28 F Rod end Kitfox part number 93002.

[wildirishtime]

thanks for the photos, they are incredibly helpful! I see now you are exactly right, the builder/prev owner used the wrong rod ends. I'll try and locate them from Aircraft Spruce if possible.... you don't have aircraft spruce part numbers on those do you?

[t j]

I don't know what the spruce number is. The ones on my kitfox are Aurora bearings but no other markings on them.

[924549]

I have attached 2 pictures (I think) to show my current rigging and a picture of my assembly drwing. I check my set up out and it does not put pressure on the threaded rod.
Hope this helps

Pieter
1406

1407

[924549]

Here is the picture.

Pieter

1409

[wildirishtime]

Thank you all for the time and help - yes indeed the wrong rod ends were used - funny thing tho is that after digging through my box of build materials provided to me from the prev owner, THERE THEY WERE - still in their original bags with the correct part #'s on them.

They are now installed and I have WAY less slop, hopefully this prevents that flutter I felt last week for good......

[egp8111]

After reading this discussion I went and checked my model III (sr. 1166), the correct rod end was used but it was installed backwards. The manual reflects the old style set up but the parts list page list the newer rod end and the plane has the KFIV style aileron belcrank Obviously the manual was not keeping up with some design changes going on that time. The older set up has the rod end reversed. I'm not sure how significant it is but I changed it per the newer manual(thanks for posting the pages). Might be worth a look for anyone with this vintage KF.

[wildirishtime]

Yes I have a copy of a 1991 I believe service bulletin explaining to reverse those, but it specifically was referencing the OLD style Ushaped swivel.

I test few my bird today with the new rod ends, all seems pretty good but it was 15kt winds so I didn't learn much

[Dorsal]

Wild, glad you are back in the air.