Estimationof Loads and Frame Deformation on Motorcycle Handling

Motorcycle frames have been designed based on static stiffness, which are frame characteristics related to stability and maneuverability. With this approach, lightweight frames have been designed, while achieving stability and maneuverability have been an ongoing trial-and-error process. To further improve them, studies on dynamic frame deformation in motion have already been reported. However, the mechanism that can explain the relationship between frame deformation and motorcycle dynamics has not been clarified yet. It is necessary to clarify the relationship between frame deformation and the change in load acting on the vehicle due to frame deformation. In this study we focus on the relationship between time history deformation of the frame and the combined loads that cause such deformation. Focusing on the transient response during turns related to motorcycle handling, the dominant frame deformation and load relationships are identified. For this objective, we propose a method to accurately reconstruct frame deformations during running and a method to analyze the dominant frame deformations during turning. In addition, the relationship between the combined loads acting on the frame during turning and frame deformation is explained based on a mathematical model of the motorcycle. Furthermore, differences in deformation response to load are analyzed using actual motorcycles with different transient responses in sensory evaluations. As a result, it was found that local deformation of the frame delays the response of the deformation relative to the load and affects the motorcycle handling.