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Loose aileron pushrod fittings printer friendly version
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dannparks
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Posted Monday, October 13, 2014 @ 04:45 PM  

My aileron pushrod fittings are getting loose at this end (at the aileron) and causing some play in the control surface. The pin is tight in the steel fitting, but is loose on the aluminum tube. The other end is threaded into the other fitting. This looseness must be an issue for other Fourniers over time. What do you folks do about this?

I'm not crazy about these pins for a tight fit since the end fitting is already a smaller diameter than the inside of the tube. I'm thinking about replacing the whole thing with a steel tube and weld this end, but maybe there is another option.

Any suggestions appreciated. Thanks.

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Dann Parks • RF4D #4051 N2188 • now flying!
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Donald
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Posted Tuesday, October 14, 2014 @ 03:40 PM  

Hmm. An interesting problem Dann.

Clearly something is deteriorating since the problem is growing so I suppose it must be the softer aluminum tube rather than the steel fork end. Is that a roll pin I see connecting the two parts? And is there only one, or is there perhaps another 90° to the one visible? If it is a roll pin I'd be tempted to drive it out and have a look inside the tube to try to determine what's deteriorating before deciding how to proceed.

But as I see it you have several potential options:-
1. your steel tube and welded-in fork suggestion, but that wouldn't be my first choice.
2. if the aluminum tube shows internal wear then replacement with new, suitably sized tube.
3. if the aluminum tube is in good condition then swaging the end to a smaller diameter tight fit might be possible.
4. again assuming the tube is in good condition, might it be possible to reduce the internal diameter by the use of aluminum brazing then reaming to size. The snag with that idea is that generally the brazing is harder than the aluminum.
5. as 4. above but instead using a resin filler to close the internal diameter to a snug fit.

With all but the welded steel solution I would expect there to be some sort of mechanical connection, like the roll pin(s) already mentioned.

I should add a disclaimer that I have never done any of these things and I make these suggestions merely as food for thought. My first action, though, would be to have a look inside the tube.

dannparks
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Posted Wednesday, October 15, 2014 @ 01:57 AM  

Thanks Donald for the suggestions.

It is only a single roll pin. I would imagine that these must be loose on other 4's. This type of attachment requires the parts to be very close tolerance and can't exactly be "tightened" to remove slack. It's likely the aluminum has worn a bit over time - assuming it was tight originally. I like the idea of swaging the end down to make it snug again if it didn't damage the aluminum. But then again, a new welded steel tube would give me the most confidence that nothing would loosen again.

If you get a chance, see if yours is loose.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

Donald
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Posted Wednesday, October 15, 2014 @ 02:22 AM  

Dann, I presume the aileron push rod we're discussing is the one(s) that runs spanwise in the wing. The RF3 doesn't have them but instead has cables and the only rods are the short ones from the bellcranks to the ailerons.

I'll be interested to read what other 4 owners say about this. The use of a single roll pin is a little surprising but I'm not going to second-guess Sportavia and say that's wrong.

Markku
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Posted Wednesday, October 15, 2014 @ 04:52 AM  

The steel fork part is connected to aluminium rod ( Dia. 12/6mm) with a M8 thread, the pin is only for securing the joint not to rotate open. I had to replace one bended rod in my plane, and I secured the joint also by thread seal
dannparks
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Gender: Male
Location: Parkside Airpark, Battle Ground, WA
Registered: Oct 2006
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Posted Wednesday, October 15, 2014 @ 10:56 PM  

Interesting info Markku - thanks. And Donald, these are the short rods from the bellcrank to the aileron. If the fitting is threaded, then the threads are quite worn from the movement and I will likely replace both of them with steel. If others find them loose, I'd like to know.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

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