Investigations into the motional behaviour of bulk materials during centrifugal discharge have shown that the transition of a small finite mass particle from a state of rest into sliding motion can take place at two rotational angles of the bucket which differ from one another. Of these two angles the larger one is important for describing the motion of the mass particle. This physically based discovery refutes the empirical assumptions previously made on this subject. It was only possible to set up the theoretical motional model by using substantially simplified assumptions. However, a comparison of the paths of motion of a mass particle obtained in this way with the actual paths of motion of all the bulk material thrown from a bucket shows quite a good approximation. The motional model therefore provides the opportunity for designing bucket elevators for specific bulk materials.
