Modal Balancing of Flexible Shafts without Trial Weights

Most balancing procedures for flexible shafts involve the use of trial weights. The few techniques purporting to predict the shaft unbalance mathematically rely on modelling the system from measured characteristics. The bearings are difficult to model and the technique presented in the present paper evades the necessity for doing this. A technique is presented whereby the unbalance on a rotating shaft can be directly calculated from running vibration; no explicit representation of the bearing characteristics is required.