Theoretical investigation of the dynamic loading of a lifting mechanism

Abstract

A dynamic model of a lifting rope-drum mechanism, replaced by an equivalent two-mass system is created. Differential equations of rotation of the rotor under the action of constant torque and the movement of the load in the process of acceleration when starting the motor are formulated. Theoretical dependencies for studying the influence of the times in transitional processes on the dynamic load of the elements of lifting device and supporting metal structure are derived. Dependencies for establishment of the influence of the start / stop time ratio and the characteristic oscillations of the load after the completion of the transitional processes on the minimum and maximum amplitude values for the acceleration and the dynamic force are determined. It has been proven that during the process of moving downwards, the maximum dynamic load occurs after the acceleration process, which means that depending of the length of the rope or the period of damping, both - very high and very low values of the maximum dynamic load may be obtained for a given lifting mechanism and load. In the processes of starting and stopping during lifting and lowering of the load, the maximum overloads of the elements of the lifting mechanism and of the bearing elements of the metal structure are found, using the coefficient of dynamism, which is defined as the ratio of the maximum force in the flexible element to the summarized weight of the load and load handling device.