That knock can be the drumming on the aly mount and the sides of the wooden mount below , Ive got a plane which drums or Knocks real bad , that Im actually making a rubber isolator mount today to see if it makes a difference , even with a good glow it bangs, its got a hollow foam wing covered with brown paper


5 noise sources

, Drumming ,( airframe )

Venturi ,

Exh ,


prop

Mechanical slop ( engine )

Vibes , some of mine vibe bigtime when they are burping , the cylinder blurrs, its the only way to fly .

And on rubber the engine will probably vibe a lot more