Hi,

Hope someone can help with this quick question im buliding a ARFT kit but its come with plastic nylon clevises, ive been advized to use metal ones.....

Is it ok to use metal ones on all the connections ie: ailerons, rudder and elevator ?

Are these alot stronger than plastic ?

And do i need to use threadlock on them once thier in place ?

Thx in advance for your time

Quick reply.

metal ones will be fine in any place you have plastic ones. But, they are possibly not necessary. There is no urgency to replace the nylon with metal. Metal ones will be more durable, but do you need bullet-proof clevises when the control surface is balsa?

As for threadlock, NO, NO, and NO!

If clevises move slightly on the threads, it is not a problem. Due to the nature of push-rods, it would be most unusual for a clevis to rotate even 1/8th of a turn when attached. Further, the pushrods are threaded for a reason, clevises have a purpose, they are meant to be adjusted.

The trim of your plane changes over time, and unless you want to constantly have off-center trim adjustments on your TX, then you have to adjust the trim by adjusting the clevises on your pushrods.

gus

..............as Gus stated, there's no need to change them out, however, if you do - make sure that the ARF pushrod wires are not metric. Many ARF are, and if you replace with standard metal clevises, they will screw on OK, but can work loose and come off.

Dragon I concur with Gus for most trainer/sport models nylon clevis' are fine. There are poor quality ones of both types. Additionally Metal Clevis' have just as many failure modes as the nylon types, just differant. One of which is some brands of metal clevis are effected by vibration and the threads can eventually strip (not good). Some are stramped and rolled with a seam running the length of the threads. This seam can expand allowing the clevis to start sliding on the threads too.

One major warning though: Never use a metal clevis on a metal throttle arm. If it is a metal arm use a plastic clevis. Vibration at this point can and will cause radio glitching problems (not good).

Some of my favorites are plastic with metal pins (of course not on a metal throttle though).

John

Hate to dissagree, but I have had plastic clevises strip from vibration and come off. The only plane I use them on is gliders and my magic because all the pushrods were strange sizes and I didn't feel like changing them. If the metal clevises screw on and are the same thread, switch them. If not, keep an eye on them.

When the one stripped on me, it was on a landing approach, with just a bit of up elevator. You never know when they will come out. Use metal unless you can't because of rod size.

Use what came in the kit. Thread them on as far as they go, leaving a few turns available for adjustments if necessary. Good luck!

What ever you do, don't use the metal clevises on the throttle, if any. The vibration from the engine will create an aluminum to aluminum friction which will result in you needing to replace the throttle after time. It will also prodcue a black liquid type of stuff that can stain monocote. I had that happen to me. To remove the stain I used 409 with orange. BIG no no. Now I cannot glue monocote on the area I wiped. It just comes right off. Also make sure that your engine bolts are as tight as possible to reduce the possiblity of an aluminum to aluminum friction.

The real danger in metal to metal at the throttle arm is not cosmetics or a worn arm, it is RF noise generated at that point which can and will disable any Rx. It has been the cause of many lost airplanes.

John

Metal Z-Bends at the throttle linkk will cause radio glitching or just metal clevises??? I have made this linkage on my newest plane and now I got concerned....

Eagle

any metal to metal at the throttle arm will do it and worse if the hole is sloppy such as a 'Z' bend. The type of metal does not make any differance. Use a plastic clevis if the arm is metal.

John

Thanks a lot, tomorrow first thing to do in the morning will be putting nylon clevis on the throttle arm ......

JohnBucker,

I didn't know that it could disable your RX. Metal to Metal is worse than I thought. You learn somethin every day.

I use nylon clevises on all my combat planes. They go plenty fast, and the nylon handles it just fine. Nylon won't strip if put on properly (watch that metric vs english thing). Properly installed metal clevises are a bit stronger, but as others have said, they can fail as well.

If you use metal, your best bet is to use a jam nut on there. You DO NOT want the clevis rotating in flight, any movement will result in wear that will lead to it stripping out eventually. So locktite would be ok, but you'd loose the adjustability, which is why people use jamb nuts instead. You also don't want any movement on the nylon either.

IMPORTANT: When putting any clevis on there, make sure at least 2 turns of threads are sticking out between the clevis arms. Threading the clevis only part way on the rod is asking for failure, no matter what material. At the very least, be flush. Sure, you get get away with less, but you aren't getting the full strength of the clevis and are risking failure.

btw, control systems are one of those religious things that you will find people swearing up down and sideways that their way is the only one true way and all the rest are doomed. I'm a bit agnostic.

Instead, I suggest you find what you are comfortable with and stick with it. I always use the same brand nylon clevises on the same metal rods, done the same way. I know from lots of experience that they are a good fit together and won't fail me. You won't find me buying another brand rod or clevis, not because they aren't as good, but because I won't know until I get it that it will work just right. It doesn't take much in the way of under- or over-sizeing to make stuff not quite fit right and lead to problems. (notice I didn't mention what brands I use? It's because they aren't any better or worse than the others, just what I'm used to).

DH, Whichever you decide to use, cut a small section of fuel line and slide it over the rod before you screw the clevice on.
After you connect the clevice to the horn, slide the fuel line over the clevice to secure it from unsnapping in flight.