Investigation On Motorvehicle Structural Vibrations Caused By Engine Unbalances (1st Part-Handlebar)

Motor vehicle riding comfort is mainly affected by volumetric engine inertial unbalances. Those propagate till the rider passing via engine mounts, main frame and auxiliary sub systems physically in contact with driver. On-road traction vehicle's engines are mainly characterized by transient exercise. Thus, a width frequency range of excitation occurs: from 800rpm(=15Hz) for still standing up to 15000rpm(=250Hz) as cut off condition. Several structural resonances are forced by unbalances spectra exposing driver to amplified vibrations. Aim of the research is to reduce driver vibration exposure acting on modal response of structures physically in contact with driver, as handlebar, footpad and saddle. An experimental methodology able to identify local vibration modes has been developed. Application of methodology on reference vehicle allows to detect if/when/how above components' resonances are excited. Structural modifications have been studied through the use of numerical models. Handlebar innovative multi d.o.f. tuned mass damper has been optimised. In the paper "Investigation on motorvehicle's structural vibrations caused by engine unbalances (2nd part-Footplate)", footplate geometry has been modified in order to minimize nodal displacement of footrest beam binding. All structural modifications have been designed, realized and installed on vehicle. Modal investigations have been executed in order to predict modifications efficacy. ©2009 Society for Experimental Mechanics Inc