Study of Vibrations in a Motorcycle Chassis

The study of vibrations in the structures of vehicles are very important to ensure its quality and integrity; thus, the study of the dynamic behavior of a motorcycle chassis is highly significant for their improvement. For that study, the modal analysis allows us to obtain the dynamic properties of the structure, such as its inertia and stiffness. Likewise, the damping is also an important parameter, which could be obtained by the frequency response function (FRF) of an impact load. In a motorcycle the engine, producing a broad frequency range, is the main source of excitation. A harmonic analysis with a shaker producing a frequency sweep allows one to better understand the vibratory transfer function between the engine and all the parts of the motorcycle. The experimental modal analysis (EMA) was used to characterize the dynamic behavior of the chassis. For that, a software was developed to use in a commercial board for the acquisition and processing of the accelerometer’s signals to obtain the FRFs and the eigenvectors. In parallel a numerical model was adjusted and used to compute the transfer function of vibration between engine and chassis and to test the modifications proposed for the reduction of the vibration’s transmissibility. The methodology adopted in this study managed to reduce the displacement in the motorcycle by 88% at 60 Hz, 13% at 100 Hz, and 47% at 117 Hz.