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The paper analyses an undesired dynamic behaviour which occurs at the front suspension of a tilting motorcycle having two front wheels and a rear one. In particular, experimental data obtained on a first prototype of the vehicle have shown that the amplitude of the hop oscillation of the two front wheels becomes very high when the velocity of the three wheeler is about 85 km/h. In order to analyze the oscillations and to understand how to reduce them, a linear model of the front axle has been developed to estimate the eigenvectors and eigenvalues of the front suspension. Afterwards, two different ways to reduce the undesired oscillation are presented and evaluated. The obtained results show that, by the use of properly designed mass dampers, it is possible to greatly reduce the vibrations without affecting the handling behaviour of the vehicle. Finally, a multibody model allowed to analyze the effects of different sources of nonlinearities such as those due to the tire contact forces.

In this work a lumped-parameter model, able to simulate the dynamic behavior of different types of valve train systems, was developed. Among the various aspects, the rocker arm flexibility, the valve lash, the possibility that the mechanical elements lose contact with each other and the possible impact of the valve in its seat were taken into account. The model includes two different descriptions of the valve spring, which can be schematized either by an ideal elastic reaction or by a multi-mass scheme, including the possibility of contact among adjacent masses.