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A ride comfort analysis of two-wheeled veichles is discussed in this work. A series of experimental tests were performed in relation to roads having different surface roughness; employed vehicles, differing on motorization, suspensions and wheel sizes, were instrumented with two axes (longitudinally and vertically oriented) accelerometers, fixed at the human-vehicle interfaces. Moreover, two axes accelerometers were also fixed to the wheel hubs, in order to record road inputs at each wheel. The comfort analysis, which was conducted following the international ISO 2631, allowed the influence of the primary vehicle suspension system to be investigated. In addition, a multibody model of the scooter-pilot system was built using Adams© code, for one of the employed vehicles, with the main aim of assessing the effectiveness of a dynamic simulation of ride comfort.

A theoretical analysis of the cornering behaviour of vehicles with locked differential is presented in this paper. In particular, attention is focused on karts, which, being characterised by the lack of any differential and suspension system, show a peculiar dynamic behaviour. A linear model for cornering dynamics is obtained in the first part of the paper: the yaw equilibrium is affected by the absence of the differential, since the longitudinal forces acting on the rear tyres are no longer equal. The steady state behaviour and the handling stability are then investigated using the developed model and discussed in comparison with those of an ordinary vehicle. The understeer gradient is shown to be a function of a steering parameter, such as, for example, the longitudinal speed, in addition to the lateral acceleration; as a consequence, the handling diagram is dependent on the manoeuvres used to obtain it.