Modal analysis of overhung rotor systems, including the gyroscopic moment and rotary inertia effect, is presented and the parametric study is carried out in order to identify the forward and backward modes. In order to experimentally verify the analytical results, an overhung rotor system in the laboratory is excited by two pairs of electro magnets mounted at right angles around the overhung disk. The magnets are driven such that they can generate the force moving forward or backward at a rotating speed as desired. The experimental results clearly show that the forward and backward modes are well separated in modal frequencies and directions as the rotation speed increases, confirming the analytical results.
