No metal to metal contact - a furphy?

From the total of his posts I've read, I believe he may just be a troll. He has not said anything that is on the mark. I won't respond to his future posts - he's not worth out time.

Don

| From the total of his posts I've read, I believe he may just be a troll. He | has not said anything that is on the mark.

He has said things that are `on the mark'. In fact, most of what he's said has been relatively accurate.

But he has been _very_ wrong in a few cases ...

The reason I asked is because the plane (ARF) it had a metal throttle rod connected to the metal throttle lever on the OS61 when I built it 2 years ago. It was checked over by experienced club guys and passed all tests, including the range test, without any problems. Also flew well without glitches etc.

The issue came up with a new plane I built recently, and while of course I followed the advice the cluey guys gave me and changed to a non metal pushrod, I like to understand the why and how of things, rather than ONLY follow blindly

David

Doug McLaren wrote:

Thanks I will give it a try

David - who likes to understand the why and how of th> quietguy wrote:

The reason I made my original post is that the plane in question (Hitec Rx with JR Xmitter) does NOT demonstrate any problems despite the metal to metal contact - it has been checked over by the clubs good guys, and flys without glitches - that is why I asked the question

David

PS even good radios can be affected by > Donny boy:

David

| The reason I asked is because the plane (ARF) it had a metal | throttle rod connected to the metal throttle lever on the OS61 when | I built it 2 years ago. It was checked over by experienced club | guys and passed all tests, including the range test, without any | problems. Also flew well without glitches etc.

As long as there is a good electrical connection between the two pieces of metal, there is no problem. And if there is no connection between two pieces of metal, there is no problem.

It's only if there's a poor or intermittent connection that there's a problem. And the longer the pieces of metal are, the bigger the problem, because they're acting as antennas.

A range test doesn't always show the problem, because without the engine running at full throttle, you don't have the vibrations that may cause the problem. Or it could be caused by moving the sticks, or by the plane actually flying.

| The issue came up with a new plane I built recently, and while of | course I followed the advice the cluey guys gave me and changed to a | non metal pushrod, I like to understand the why and how of things, | rather than ONLY follow blindly

Well, in this case there's no need to follow blindly, because it's very easy to reproduce the problem and convince yourself that it's real. I mentioned one way of doing so in my previous post.

| Doug McLaren wrote: | | > Rather than convincing yourself that it can't happen, show yourself | > that it does.

Well, you _did_ seem quite busy explaining why you thought it was an old wives tale :)

Very good idea. We should do this more often, say in politics........... :) mk

From Doug M.:

Correct! It's the _intermittency_ of contact that causes the problem.

Correct again. They act as receiving antennas, and they also re-radiate. Picture having one piece of metal (say a pushrod) undergoing a make-break, make-break connection with another piece of metal (say an engine block). Both are acting as RF receptor/re-radiator elements. Now introduce a 3rd element- the receiver antenna. What the receiver is likely to 'hear' is a mishmash of static superimposed on the desired signal. The strength of this 'noise' in relation to the signal (signal-noise ratio) and the receiver's ability to reject the noise, largely determines whether you'll get glitching or not. And there's another potential noise source in the mix if both elements are electrically 'floating', i.e., not connected electrically to anything else: ambient electrical potential of the air itself. Both elements acquire a miniscule static electric charge, a literal voltage, in referance to earth.. AND there can be a voltage difference between the two elements. If they're in intermittent contact, this alone can generate spurious RF hash that can be heard on an adjacent receiver. So the strategy is to simply avoid any metal-metal intermittency, period.

Bill(oc)

Forgive me if this is a repeated post. Didn't see my original show up. I have a stranded brass cable running inside a Nyrod sleeve terminated in a Z-bend at the carb throttle lever. It doesn't seem to be a problem. Also, I tried scraping a screwdriver tip across a file near the receiver antenna with only the receiver powered up. It didn't get even the slightest response from a servo. I am using an old (circa 1990) Airtronics Vanguard radio system.

I certainly agree with the above. I can't explain how it happens , but I know it does. I've had it happen to me a few times until I learned how to avoid it. I had a 1/4 Midget go in at full throttle because I didn't check the clearance between my aileron servo linkage in the center of the wing and my elevator servo in the fuse. After the crash we could clearly see where the rods rubbed each other.We tested it and reproduced the glitch. Also had the same thing happen on throttle linkage , of course it didn't cause a crash. Like I said , this was in the late 80's , early 90's before I knew better. Haven't done it since then.

Ken Day

I may be wrong (its not totally unheard of) but he reminds me of that troll that goes by the title of C O Jones. Seems to be similarities in intelligence levels. I binned both of them a while back.

Reg

Same old troll, different name. Bragged today in the Duraplane post about money not being a concern. I forget what comes next. Was it advising the president, or was there something in between?

VERY true. I have actually SEEN the electric sparks generated by metal to metal contact when running up an engine after sundown.