If metal to metal contact friction causes radio interference then why do all RC things with a internal combustion engines not have problems with interference as the biggest metal on metal friction is the piston,cylinder and crank?

It's not the friction that causes the problem it's the metal to metal vibration that causes the problems such as metal pushrods on a metal carb link arm. Also, problems can be created with metal pushrods that run parallel to the antenna within the fuselage behind the servo's.

In every fuel/air engine there is a very very thin film of oil between all items in the engine. The only real time you get metal to metal is running it lean. If there was no film of oil, your engine would not last long.

In the gas engine (not nitro) part of this hobby, it's more important to keep everything connected to the receiver as far away as possbile from the engine and electronic ignition if it has one.

Glow engines are self supporting so they need no outside ignition source so the distance between it and the receiver does not need to be as far as gas.

Pull-Pull cables can be really bad for this also. Especially when they cross over each other and are not coated or at least one of them is not in a tube

It's not the friction, and it's not the contact, that causes interference. It's the making and breaking of the contact.

Dr.1

i have a metal control horn that i had to drill out the nylon part, and i have the metal pushrod going through because i am using and L bend, will this be a problem?

Dang,

Learn something new every day thanks Dr.1 [sm=thumbup.gif]

We are talking about metal to metal contact, you are describing using a metal to metal contact, so I would say yes, this can be a problem once it starts to work loose and it will start to work loose from normal vibrations. It may be on a small plane but why would you risk it.

The problem is created by sparking from intermittent metal-to-metal contact, particularly intermittent contact of dissimilar metals (brass & steel, for example). The engine vibration will make loose-fitting parts like clevises vibrate, causing sparking -- & producing weak broad-band radio interference. It is real & it is unpredictable, but under particular circumstances it can kill your model. It is most dangerous if the vibrating parts are in proximity to the antenna.

Engine components are normally tight fitting and insulated by a lubricant film -- no sparking. However, a muffler that is vibrating loose can also cause the same problem, although the muffler is not normally located near the antenna.

The problem with vibration generated RF is that you will never know what resonant frequency it is generated at and, of course, what the harmonics are unless you know the frequency.. thus back to the beginning of this sentence.

So, if you do have inteference, and the fundamental is around 72 MHz (for those that are using 72 MHz RC radios), that frequency could generate an inteference level high enough to cause garbled reception in the receiver (from the transmitter) which causes the receiver to glitch. Even harmonics, if high enough in level, can cause a problem.

So, it's best to avoid metal to metal, and easy enough to do.

DS.

Thanks guys. Helped me out 100%