Assembling Uncertainty Effects on the Dynamic Response of Nominally Identical Motorbike Components

The chassis and swingarm are the main components of the motorbike frame. The dynamic response of these components strongly influences the frame flexibility and consequently the motorbike dynamics. However, there may be variability in nominally identical manufactured components. The uncertainty may arise from many sources including geometric tolerances, material properties, and variability in the manufacturing and assembling process, for example, adhesive bonding of hollow parts. The presence of uncertainties can significantly alter motorbike component dynamic response and modal properties, and thus their overall performance during a racing competition. Therefore, competitive riders test several components during the racing weekend to find the specific motorbike frame with which they are more comfortable. In this chapter, experimental modal analyses have been carried out on the flexible components of a motorbike frame. The experimental campaign results have demonstrated significative differences in frequency response functions, natural frequencies and damping of motorbike components. Modal assurance criterion and other indexes have been used to compare mode shapes of the seemingly identical components and to assess possible crossing and veering phenomena, due to uncertainty.