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The computational method and the CAE technique have been developed to evaluate durability performance of a motorcycle body. The computational method in this study consists of three parts of simulation. The first is the mode analysis of the body parts. The second is the multi body dynamics simulation, which calculates forces loaded into the frame of a motorcycle body equivalent to actual durability tests. The third is the static structure analysis, which calculates stress distribution using the forces calculated by the multi body dynamics simulation as boundary conditions. Also, two kinds of durability tests, that are the chassis durability test and the falling durability test, are simulated in this study.

In order to optimize the balance between aerodynamics and air-cooling performances for a motorcycle, a simulation method of external flow around a vehicle has been developed. In this paper, steady-state flow calculations were performed using two types of turbulence models, the realizable k-ε and the SST k-ω, and two levels of mesh sizes of computational models and their results were compared. To validate the computational results, wind tunnel tests were conducted and CD, CL and mean velocity of flow passing through heat exchangers were measured. The computational results on drag coefficient and mean velocity show good agreements with the experimental ones.

The Mechanical CVT is mainly used for small size motorcycle called “scooter”, which has a 250 cc or less engine capacity. The speed characteristics of the Mechanical CVT are decided by engine speed and load-torque on driven pulley. In few papers, these characteristics are studied under full-load or no-load condition [1]-[2]. However, the characteristics at part-load condition are not well known. To develop a motorcycle with low fuel consumption, it is important that the characteristics at part-load condition are considered in driving cycle. Driving cycle simulation is needed to estimate CVT ratio at design stage. This research proposes equations representing the speed characteristics of the Mechanical CVT at part-load condition. Driving cycle simulation is also developed for estimation of the fuel consumption at optional driving cycles and the dynamic behavior of the CVT system. It could be a CVT design tool to makes sure whether its performance is achieved for design targets.

Traditionally, a Boundary Element Method (BEM) is often used for a radiation noise analysis. In recent years, to define an infinite region, a Finite Element Method (FEM) that can use an infinite boundary condition has been developed. However, studies on the radiation noise analysis by the FEM are few. Recently a number of an electric scooter has been increased. One of development issues is a radiation noise by a vibration of a wall surface of a swing-arm. In this paper, the vibration of the wall surface of the swing-arm is calculated, and a sound pressure level (SPL) of the radiation noise is calculated using a result of the frequency response analysis. And compare results of an experimental and an analytical sound pressure, its results were matched to within 5% error. Furthermore we used the method of this paper, proposed the model to reduce the radiation noise 10dB. Then we compare with the FEM and the BEM to verify the computation time and the mesh size.