RE: metal to metal contact causing interference question
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.