The structural design of front motorbike suspensions

The fundamental goal of this paper is to provide a methodology useful for the structural design and optimization of front motorbike suspensions. Two different types of shaft-hub couplings are normally used to assembly the whole suspension: (i) an interference-fit coupling (between the fork and the steering pin) and (ii) a clamped joint (between the fork and the leg and between the leg and the wheel pin). Firstly the Design of Experiment method has been applied in order to evaluate the static friction coefficient μll. Secondly a mathematical model, based on the thick-wall cylinder theory, has been developed in order to calculate the tensile state in the fork–pin couplings. Finally other mathematical models have been defined with the aim to calculate the maximum bending stress and the mean coupling pressure generated in the fork-leg and in the wheel-clamp couplings. The research results have been used to realize an innovative software (Leg Design©) that is useful to design and to verify the whole front motorbike suspensions with correct and effective results obtained for different geometries and material combinations.