Two approaches for optimum design of motorcycle engine mount systems

This article examines the dynamic response of a motorcycle engine mounting system used for vibration isolation. The engine is modelled as a rigid body connected to the frame by rubber mounts as well as tie-links. The suspension dynamics is included in the model through the attachment point with the motorcycle swing-arm. The forced excitations include shaking forces due to engine imbalance transmitted to the frame as well as loads caused by irregularity of the road profile. Two optimization-based procedures are implemented to design an engine mount system. The first procedure minimizes the load transmitted to the frame while constraining the engine displacement due to dynamic loads within a defined envelope. The second procedure changes the natural frequencies of the system (by altering mount parameters) so as to avoid certain predefined ranges of operating frequencies. Both optimization procedures use engine mount stiffness, location, and orientation as design variables. Three numerical examples are presented to illustrate the effectiveness of the proposed techniques in optimizing the performance of an engine mounting system.