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What's this part?

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Posted

And where do you get them?  20200130_194718.thumb.jpg.8fafc20624c718The pic is of the flap actuation portion of the flaperon mixer. The parts in question look basically like a bolt without a head, just threaded on each end, maybe 1/8" diameter. Ive looked through my manual but I just see a lot of part numbers that don't mean anything to me. So if someone could tell me where to find some more of these I'd be grateful.

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Posted

Those parts are in a Kitfox, and they connect the flap handle to the flaperon mixer, and are 3/16" or 1/4".  Wonder if they didn't use long bolts, cut the heads off, and thread that end then as well.  I don't think they are left hand thread on one end like a turnbuckle would be.  On some of the Avid parts, they used a piece of tubing with a bolt welded into each end for this part.  I'm going from memory, and am a long ways from where I could actually go look, so take it with a grain of salt on sizes.  Sure it's not 1/8" though.  :-)  Are you just wanting to change out these parts to new ones?   JImChuk

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Posted

20200130_223628.thumb.jpg.d10e5950357d3bAs you can see it's unthreaded in the middle with threads on either end. So it's not a chopped off bolt. 

Ive designed a new flaperon mixer system. It's a hybrid of the system on the models 1-3 and the -4 system with some other design elements as well.  It has the advantages of adding differential to the aileron movement and being much more compact than the current system.  I'll now have room behind the seat for a little cargo. It also allowed me to move the flap handle to the left side of the cockpit. 

The main disadvantage is that I'll have to disconnect the pushrods to fold the wings.

I need different lengths of the threaded rod in question for the new system.  It's pretty close to 3/16 but looks a tad under to me. Maybe it's a 8-32?

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Posted (edited)

An AN bolt would have only about 1/2" of thread on the one end, and the rest of the shank is unthreaded.  Maybe they just got some rod of the size they wanted, and threaded both ends.  I doubt that it's a off the shelf part, but I've certainly been wrong before.  JImChuk

 

 

PS  Just did some googling, and there are commercially available 3/16" studs in different lengths.  Maybe that's what Kitfox and Avid used.  Bolt Drilled Head An3h-16 By Aircraft Spruce

Edited by 1avidflyer

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Posted

Well that begs the question of just how likely it is to devolope a fatigue crack? All I think I know is that aviation fasteners should have rolled threads (I think) as opposed to cut threads? Honestly don't know how threads are rolled. I do know that the valley in the threads is rounded to not create stress risers and eventual cracks. So if these are not AN hardware were they manufactured to aviation standards, and if not how likely are they to fail? I know cars go an awful long time without large numbers of bolts failing, though it does happen from time to time. 

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Posted

Looks like standard 3/16 rod ends top and bottom. Most likely kitfox made them or made by their supplier. Properly installed and it normal use, breakage is highly unlikely.

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Posted (edited)

The thread on the Avid is a 10-32 and it was the F7a that used the 1/4" tube with a socket head screw welded in both ends supplied by some.  My welder did not like that idea so the ones that I supplied were constructed differently but at any rate I do believe that the original parts for both Avid and KF were a speciality part.  I looked at grade eight all thread but found some long grade 8 set screws to do the job but not sure if they make any long enough to use in the standard application.  I would be comfortable using the grade 8 all thread but that is just me.

https://www.mcmaster.com/all-thread-rods

Edited by wypaul

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Posted

Cut the threaded rod and weld it into a tube at the length you want.  Easiest way to accomplish what your trying to do.

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Posted

I ordered a complete set with ball joints from KF a while back, got them too

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Posted



There really  nothing more than a regular threaded  stud. Any Fastenal store should be able to get them for you.

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Posted

Ok thanks guys,  all thread or the threaded studs sound like the right idea. My rod end bearings will be roughly 2 3/8" center to center. The female mm-3 is about 1 1/16" from center to the end so there will be a little less than 1/4" between the 2 bearings. That might make it impossible to have a jamb nut though. 

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Posted (edited)

So, interesting conversation about using all-thread above.

So there I was yesterday at a friend's grass strip practicing slow short landings just above stall. I had just completed a landing, had turned around and was blasting off for another when the stick started moving around in my hand in a way that is hard to describe, but immediately disturbing. The strip is a bit rough so I thought maybe just that. It was getting worse as I accelerated so I aborted just before liftoff. I turned around and accelerated back to the starting point and it did it again. A very creepy and kind of violent but not really movement in the stick like something was broken. When stopped at the top again I moved the stick back and forth and it seemed firmly connected to the flapperons. When I moved it for and aft it felt like the elevator was firmly attached without excess slop. When I got out of the plane I found this: (photo) The strip is remote but I was able duct tape and bailing wire the trim tab in place to fly it home. The original builder used all thread for the connection and had a slight bend in it for clearance. I never thought a thing of it because I would never expect the forces to be great enough to bend or break the all thread. What I did not take into account was the infinite number of small flexes happening to that slightly bent piece of all thread led to catastrophic failure. 

I think it could have turned out to be a much bigger problem if it had failed mid flight. I think what happened is best described as a form of flutter.

Lessons learned for me: 1) The control arm should have been straight, not the gradual bend the original builder had in it and 2) I I will probably use all thread for this again even though I am not a fan, but it will be straight and I will sleeve it.

IMG_1640.JPG

Edited by ChrisBolkan
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Posted

 Chris, another thing you might wanna check is the rivets that hold the flap and attachment arm to the trim tab  to the elevator, I  Fly a seaplane in brackish/saltwater environment and corrosion ate the rivets up and The trim tab departed!!!!

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Posted


The only down side I see to using all thread is you will need a left hand Heim joint for one of the ends.

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Posted


The only down side I see to using all thread is you will need a left hand Heim joint for one of the ends.

If all thread is used then you would need 2 right hand heim joints. No left hand heim joints would be needed. Just won't be able to adjust it like a turnbuckle and will have to take a rod end loose to adjust.

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