Experimental investigation for the dynamic mechanical properties of a vertical anisotropically supported rotor

•A vertical Jeffcott rotor test rig with adjustably anisotropic supports is erected, whose stiffness anisotropy is measured.•For the first time, the positive correlation between backward whirl regions and support stiffness anisotropy is validated by experiments.•The number of peaks and the amplitude of transient unbalance response tested depend on the mounting inclination of sensors.•Alternations of whirl modes passing critical speeds are confirmed and explained by the beat vibration theory.