Originally Posted by Gerry__
Harmonic resonance is something that affects EDF. The advice is to avoid the power settings that bring it on. Also, I think he said he balanced the props. If he's balanced the props, stiffened the mounts and avoids the affected power settings, then he's done all he can do.
I had this problem and it turned out to be that one prop was not tracking right. The two blades were not drawing the samw arc as each other,. I finally fitted two APCs and it went all away. [But still needed more power]
So then I fitted two brushless motors (used the MPI TS II upgrade kit) and the vibration problem came back. This time it was the mounts that needed tightening up. Gorilla glue to the rescue!
And then 3 years later it came back at high rpm. This time it was a bad bearing in one motor. Buzzed a high rpm.
The TS II has some flex in the foam around the wing pod mounts. I think that mine may be getting "foam-fatigue!". If all is tight and balanced it works -- if not fit EDFs :-)
It's always something.....