Replacing Nylon pushrod with metal.
 

Hey all,

I was wondering if it was OK that I replaced the nylon pushrod from my rudder servo to my nose gear with a metal pushrod? I had read some things about metal pushrods possibly causing Rx interference, and didn't know if using a metal pushrod for the nose gear would cause such interference. All I know is that the metal pushrod will not kink at the servo horn like the nylon pushrod did, and if using metal will be OK than I would rather use metal.

Noah

RE: Replacing Nylon pushrod with metal.
 

It's ok as long as it's not a gasoline engine

RE: Replacing Nylon pushrod with metal.
 

Great! Thanks I was hoping to hear that!

Now, you raised my curiosity... Why not in a Gasser?

RE: Replacing Nylon pushrod with metal.
 

Spark plugs send out RF signals which can travel through the metal and into the radio compartment

RE: Replacing Nylon pushrod with metal.
 

Noah,

You might want to consider using a metal cable to the nosewheel. It may reduce the chance of transmitting a damaging mechanical shock to the rudder servo from the nosewheel. You can use soder to stiffen the ends that project out of the guide sheath.

Stan

RE: Replacing Nylon pushrod with metal.
 

I see. I thought that was the reason...

Interesting. It really didn't occur to a newb like my self that there could very well be a damaging shock to the servo. Makes perfect sense though. This is how my nylon pushrod was kinked. I was taxing around in my field and the nose gear struck a lump and kinked the pushrod at the clevis where it connects to the servo horn. So every time I went to make a left hand turn, the nose gear (without any resistance left) would turn completely perpendicular to the fuse, and it would come close to doing a face plant. I thought by replacing it with a metal pushrod, that it would eliminate the possibility of kinking and all would be good. I believe the metal pushrod would solve one problem but could possibly cause another.

Thanks for the advice Stan.

Oh! And I also though about increasing the size of my nose wheel too. I think that would help. But if I do that, should I increase the size of all three wheels?

Noah

RE: Replacing Nylon pushrod with metal.
 

Yes, you should - OR - you might be able to shorten the nose gear strut so the larger wheel doesn't change the stance.

RE: Replacing Nylon pushrod with metal.
 

You can increase just the nosewheel size if you want, however, the important thing is that the airplane sit close to level on it's wheels.

If the plane is strongly nose-up, it will be hard to land with out bouncing because the nosewheel will often touch down first, and it will have a tendancy to either take off before it should or "wheelbarrow" on takeoff. Wheelbarrowing is when the mains leave the ground, but the nosewheel is still in contact, often leading to a sudden sharp turn in an unpredictable direction.

If the plane is strongly nose-down, it will be easy to land, but hard to take off on a grass field. Nose down enough and the plane can accelerate to rather high speed with out lifting off until you touch the elevator, and the airplane suddenly leaps off the ground.

About the metal pushrod, you can do it, and many kits/arfs are designed that way, however it is possible to strip the gears of the rudder servo on a hard nose-first "arrival" (you know, not so much of a landing as a controlled crash into runway).
A metal gear servo will help with that, but then something else somewhere will break. However, if you work on landing smoothly, main wheels first, and work on keeping the nose "light" when taxiing and on takeoff, you won't have any issues. Basically, you want to hold up elevator when taxiing to take weight off the nosewheel. It also helps at the start of the take-off roll, but you have to get off the elevator before the plane jumps off the ground into a stall.

RE: Replacing Nylon pushrod with metal.
 

Cool. But i think I would be better off enlarging all three only because if I shortened the nose wheel strut, I would have a lawn mower and not an airplane.:)

Thanks MinnFlyer.


Noah

RE: Replacing Nylon pushrod with metal.
 

Ha ha! I like that... Wheel Barreling!! :D

Thanks for the advice Montague!


Noah

RE: Replacing Nylon pushrod with metal.
 

You wouldn't shorten the strut unless you used a bigger wheel on the nose only. Therefore there would be no change in height of the prop above the ground. Making all 3 wheels bigger would be better on grass or dirt also.

RE: Replacing Nylon pushrod with metal.
 

Yeah, it's pretty funny to watch as well, most planes are pretty darn unstable when going down the runway on just the nosewheel :D.

Minn was saying you can increase the size of the wheel and shorten the strut with the over all effect of leaving the crankshaft where it is in relation to the ground, so no change in prop clearance from what you have now.

Of course, mowing the lawn in narrow strips is amusing if nothing else. You can always tell when someone with too-short gear or too-long a prop has been at the field recently by all the funny lines in the grass. :) I did once have a student ask me what was causing all the funny lines in the grass....

Changing all 3 wheels is, of course, easy, and works best.

Depending on the plane, you might be able to bend the mains "down" a bit to raise the tail end of the plane to keep it level if you just enlarge the nosewheel.

(btw, the worst "nose high" trainers with bad take off handling I've seen were caused by repeated "pancake" landings that bent the mains outwards, lowering the tail. So keep an eye on the way the plane sits even after you've been flying it)

RE: Replacing Nylon pushrod with metal.
 

The correct term is "wheel barrowing". http://en.wikipedia.org/wiki/Wheel-barrowing

RE: Replacing Nylon pushrod with metal.
 

Heh heh...:eek: True enough! But you know, my grandfather made a Wheel Barrow out of a metal barrel the he lopped in half. He would use it to spring clean the lawn. Ironic!

And about changing the strut length, I overlooked that shortening the strut and adding a larger wheel only brings the nose back to its original position (DUH!:)), as long as I only shorten the strut the difference in distance from the center of both wheels to the outer edges.

RE: Replacing Nylon pushrod with metal.
 

Unfortunately, metal to metal contacts can cause interference whether you are running gasoline or glow. The problem is more prevalent on 72 MHz and lower than on 2.4GHz but can even exist there. This is caused by metal to metal vibration and, although a spark ignition can be more troublesome than just metal to metal, the problem is not isolated to spark ignition systems.