“Balancing A Three Mass Rotor With Shaft Bow,”
W. Foiles & E. J. Gunter, 1982.


Figure 1 represents a schematic diagram of the vertical three-mass rotor-bearing_ system developed in the Rotor Dynamics Laboratory. The system is an adaptation of one of the Bently rotor models. The shaft diameter is O. 375 inches and the total shaft length is approximately 27 inches long. In this particular rotor, three discs of 812 grams each were mounted symmetrically on the rotor shaft. The rotor is mounted on a vertical test stand as shown in Figure 2.

Figure 3 represents a schematic diagram of the instrumentation for the vertical rotor-bearing system and the horizontal Centritech rotor which is mounted on the same horizontal concrete slab. A control panel was constructed so that the vibration signals from any of the three rotor configurations can be connected into an a-channel FM tape recorder. The Bently Digital Vector Filters can analyze the vibration signals either directly, or after passing through the FM recorder.

Figure 4 represents a cross section of the vertical rotor-bearing system showing the setup of the horizontal and vertical probes at a typical shaft location. There are three mounting brackets with horizontal and vertical Bently displacement type probes monitoring the rotor motion at three axial planes. The location of these monitoring stations may be changed, as the holes for the mounting brackets are located on one inch centers. The horizontal and vertical probes to monitor the shaft motion are slightly offset so as not to induce cross-coupling signals due to their close proximity.