flyingagin

I have a general question regarding Radio interference and metal to metal contact, in particular on 72 MHZ. I have all all ways avoided any kind of metal to metal contact on moving parts.
I have always used a plastic sleeve on torque rods. I have seen examples were the torque rod rides in a brass sleeve and have been tempted to do that also. Is there any possible concern that, interference could be generated. i.e. RF noise?
I am not intending to start any controversy at all, just want to know if using torque rod ride in a brass sleeve is acceptable and safe practice. In particular since I am still using 72MHZ.

Gray Beard

My Feedback: (-1)

A general answer is it's not a good idea to ever have metal to metal that can vibrate and make RF noise if you can avoid it. If for some reason you can't avoid it then do it and see what happens. There are general rules to aircraft set up but rules are made to be broken. I have done things that everyone knows will create a problem and gotten away with it on gas and glow planes. Then tried to get away with the same thing and it didn't work. Not all noise is picked up by the RX and a PCM RX doesn't pick up noise as much as a standard FM RX.

flyingagin

Thanks Gray Beard
To take the question a little deeper if I may, Is there a way to mitigate RF noise if a builder chose to go metal to metal.
Would soldering a piece of multi strand wire (maybe with a flexible loop in in it) to each piece of metal significantly reduce interference? i.e. as a ground strap and if so should that then be tied to the battery ground wire?
I have so far avoided metal to metal at all cost, but I can envision instances were it would make building much simpler. For instance a steal aileron torque rod in brass torque/sleeve rod in a brass sleeve. Like the one in the picture from another thread on this site.
My current project (way to far along to make any major changes now) has flaps and ailerons. I put my airleron servos outboard with a center flap servo, but it sure would have been easier to do this.

Rodney

If you soldered a flexible conductor to both the torque rod and bearing (keeps them in solid electrical contact when the torque rod moves) you will not create any electrical noise. Your example of the aileron torque rods also will not cause a problem because there is always some part of the two components in contact. You need a make and break action to create the rf interference like vibration can cause if two metal object are just touching.

scale only 4 me

My Feedback: (158)

Well a running engine is metal to metal contact isn't it?

Seams to me way back in the dark ages (70's) metal torque tube bushings were the norm, I had several planes with them and never experienced any problem,, If I remember right those early EZ ARFs had metal (brass w/metal pin) hinges and those all worked just fine.

Plastic is just lighter and cheaper,, lighter and cheaper beats heavy and expensive any day. I wouldn't hesitate to use brass tube as a bushing,, but hey, I'm old school

Gray Beard

My Feedback: (-1)

I usually don't use torque rods but it's one of those things that is sometimes required. If you look at the torque rods that are pre made that come in kits they are metal on metal. I haven't had any problems with RF from them. If in doubt and you are making your own up you can use a plastic sleeve on the inside.

ARUP

I've never had any problem with it (just lucky???). Since you've already got it set up then put some heavy oil in the bushing.

Edwin

My Feedback: (2)

I've done brass tube with torque rods before and didnt have any problems. Just my opinion, but with a tight fit like the rod in tube you dont have enough vibration to cause a problem. Another option is a plastic tube if you can find one the right size. Best yet, use two aileron servos.
Edwin

flyingagin

Thanks guy

TFF

The secret is the brass tube. Brass will not make RF noise. if it was a steel on steel tube/wire, it is possible, but the brass is like a dead metal, RF wise.

flyingagin

Now that I did know know
So would it be safe to say brass on brass would not make noise? In the picture there are basically 2 torque rods, a steal one and then it's sleeve is also a torque rod and that one rides inside of a brass sleeve. So you get a steal to brass contact and then a brass to brass contact.

pimmnz

I've been flying a Curare and Sicroly with the exact same set up for 'plenty' of years, no RF interference. You need the vibration to actually be 'tapping' one thing against another to create a wee spark, and the rod in tube idea does not allow that to happen.
Evan, WB #12.

LesUyeda

"So would it be safe to say brass on brass"

It may not make noise, but it is not wise to use similar metals in contact with each other, they tend to gall way too easy. Steel on brass is probably the best choice.

And in the picture, it would be virtually impossible to "make and break". Some part of the rod will always be in contact with the sleeve.

Les

flyingagin

I Started flying control line back in the 60's, then built my first radio (a heath kit 8 channel single stick). Back then it was all A.M. I think that is were the concern came from. A.M. is really prone to static. I stuck with the practice (of NO metal to metal contact) even with today's good equipment.
This has certainly been interesting and informative. Thanks for all the input guys