Methodology to design a vibration absorption footplate for motorcycle application: From phenomena investigation to prototype performance evaluation

The aim of this research is to reduce driver vibration exposure by acting on the modal response of key contact structures.The footplate is one of the components with which the driver comes into contact while riding. For this reason, footplate geometry and structural properties were investigated with a view to re-designing this component in order to reduce driver exposure.Due to the massive chassis area on which the footplate is constrained, vibrations induced by engine unbalances easily propagate in quasi-steady conditions on all surrounding components, inducing a width frequency band of load excitation. Even though the footplate geometry allows for fairly high natural frequencies, these could occur in the excitation range. Therefore, the first step of the methodology proposed entails the use of a numerical and experimental (modal analysis) procedure to identify the local vibration modes of the original components to detect if/when/how the resonances of the above mentioned components are excited.Due to an awareness of the weakness of the original solution, structural modifications, using numerical models, were studied. The footplate geometry was modified to minimize nodal displacement of the footrest beam binding. All structural modifications were designed, developed and installed on the vehicle.Finally, in order to predict modification efficiency, both the new footplate and the original one were experimentally compared. The comparison was made by means of modal investigations and by positioning the reference vehicle on a suitable roller test bench in order to simulate real working conditions.

► The aim of this research is to reduce driver vibration exposure by acting on the modal response of key contact structures.
► An innovative footplate was designed to avoid resonance amplifications.
► A good improvement of riding comfort is obtained for the whole operating R.P.M. range of the engine.