Synchronous Whirl of a Vertical Shaft Having Clearance in One Bearing

Abstract

If a vertical undamped shaft has one clearance bearing, the other bearings having zero clearance and all being in line, then there are two possible regimes of synchronous whirl which can hold, namely: that in which the shaft does not touch the clearance bearing, that in which the shaft touches the clearance bearing continuously, the point of contact running round the bearing at the shaft speed. It is shown that in some speed ranges regime (1) holds and in others (2). There are also speed ranges in which either regime is possible. When damping is allowed for, these results are not greatly modified. The whirling behaviour of the shaft differs however from that of a shaft with zero bearing clearance in several ways. In particular the critical speeds are lower, and also there is a more abrupt drop in the whirl amplitude curve above the critical speeds. The behaviour of the shaft when it is accelerated through a critical can differ from that when it is decelerated.