Modal balancing of flexible rotors without test runs: An experimental investigation

In all methods of balancing flexible rotors currently in use (modal balancing and influence coefficient techniques) test masses and test runs are required for the calculation of correction masses. In the modal balancing procedure suggested by Gasch and Drechsler [1] a simple identification method is used to find the generalized unbalances without test runs. In this paper the Gasch and Drechsler balancing procedure is reported and extended to multibearing rotors with initial shaft bow. Systematic experiments done on two test rotors are described. The results show that flexible shafts mounted in ball bearings can be balanced with very good results. Even rotors in fluid film bearings, exceeding the scope of modal theory, were balanced with good results.