Loctite on pushrod end bearings

[lostpilot28]

Just a quick question about this subject...I've been reading the other posts on how to prevent the aileron pushrods from unthreading and falling off. I know that they should have over half the threads engaged on each end of the pushrod, but I think mine are maybe 1 thread more than half. Not much!

Obviously, if the pushrod vibrated and twisted it's way to unthread one end, I'd be in trouble. Although, with a single jam-nut on each end, I should have 4 or 5 threads engaged at the least because it will prevent the pushrod from backing all the way out.

So my question is this - why not just use a healthy dose of blue locktite on the threads? Wouldn't this prevent the pushrod from rotating at all? I could go with 2 jam-nuts on each end, but I thought the loctite may be a worthy solution.

[KayS]

would like to dig out this old question that has never been answered. didn't find a general consensus on the use of Loctite on pushrods. i'm about to use the blue (less permanent) Loctite on the final rigged aileron pushrods etc., so the same question came up...

[Walt]

Certainly can't hurt, I usually do just the jam nuts myself.

[pulsar]

I agree with Walt... give it a go. Keep in mind that Loctite can loose its effectiveness over time (over years), so using a second form of locking is a good idea.

[PilotjohnS]

I recommend it be applied very carefully to avoid wicking into the actual bearing. Had this problem a lot on large scale RC aircraft.

[rongawer]

Originally Posted by pulsar

I agree with Walt... give it a go. Keep in mind that Loctite can loose its effectiveness over time (over years), so using a second form of locking is a good idea.

Ok, so I agree, a jam nut is the way to go (installed properly - as in snug with a hand wrench) and that blue loctite won't hurt (although I would not use it, simply because it's not needed and something else to annoy me if adjustment was needed).

However, your statement that Loctite loses (you said "loose", but I think mean "lose" - although contextually, both words could apply) it's effectiveness over time gave me pause. This statement isn't supported by either the manufacturer or by my own experience. As a matter of fact, the use of red Loctite is considered a permanent thread locking solution - as in forever, and requires the use of about 500ºF to remove it. And while blue loctite is removable with hand tools, it will retain it's thread locking tension indefinitely.

What is your basis for saying Loctite will lose its effectiveness?

[pulsar]

The effectiveness loss just comes from my experience with it. No white paper or other specific data on the topic. I?ve spent a bunch of years working as an engineer in the R&D world. There have been a number of times when the loctite we installed has lost a sizable percentage of its initial breakaway torque. It could have been contaminated joints or other unrelated failures.... we were never sure. A little contamination can go a long way to messing things up. Grease, oil, gremlin spit, they can all do bad things to thread lock. These joints were assembled by knowledgeable folks (pros with wrenches) and we still found the occasional loss of breakaway torque. This happened over years on in-service equipment that was living out in the sun. The lesson for me was sometimes even what you think is a properly assembled joint, things can can still go bad and it?s worth the occasional look. I probably should have been more clear on that. Loctite is great stuff and I use it when the application is right.


Loose... lose... ya you are right, I should reread what I type so early in the morning.

[Wunderon]

For anyone under construction I would suggest not using loctite until after flying and rigged to satisfaction. The jam nuts require a specific torque, which would be checked each year during condition inspection presumably.

[rdamazio]

Originally Posted by Wunderon

For anyone under construction I would suggest not using loctite until after flying and rigged to satisfaction. The jam nuts require a specific torque, which would be checked each year during condition inspection presumably.

Now I'm curious - what is the required torque, and (dumber question) how do you measure if if you can't put a socket on it?

[wirejock]

Originally Posted by rdamazio

Now I'm curious - what is the required torque, and (dumber question) how do you measure if if you can't put a socket on it?

Torque from the table. Varies with size.
Use a crowsfoot and adjust torque for the additiinal length of the crowsfoot.