The aperiodic behaviour of a rigid shaft in short journal bearings

A study is presented of the symmetrical steady‐state motion of a rigid shaft supported by two ‘short’ (Ocvirk) journal bearings. The equations of motion for a balanced or unbalanced shaft were solved using numerical ‘initial value problem’ techniques. Frequency analysis, which was used to determine the components of the steady‐state motion, confirmed that, for most conditions, the motion was asymptotically periodic comprising a small number of components—principally at synchronous and half synchronous frequency. However, a region of the operating space was found, in which the motion was complex and did not settle to a limit cycle. An estimate of the extent of this region is given and the suspected cause investigated.