Experiments and stability predictions of two sets of tilting pad bearings on an overhung rotor.
An overhung motor with critical speeds of 3000 and 6800 rpm was experimentally tested in two sets of five shoe tilting pad bearings with preload factors of 0.1 and 0.5 respectively. Mounted on the first set the rotor remained stable to over 11,000 rpm but on the second set went unstable due to whip at 10,400 rpm. Theoretical analysis indicates that the system is marginally stable and that small cross couplings generated by the disk shaft mountings destabilised the system. Predictions had given the 0.1 preload to provide most stability and also indicated that sybsynchronously (rather than synchronously) reduced bearing coefficients should be used in stability analyses.