I am working on a project of developing a Flywheel energy storage (powered by electric motor) for a vehicle. The natural frequency of the system has to be calculated. Simple project description: The flywheel is held by two bearings inside a housing. The electric motor is fixed to the housing bottom and holds the clutch plate. The other end of the clutch is held by flywheel. When the clutch is engaged the electric motor drives the flywheel. All components as a whole is considered as a single assembly to be mounted on the vehicle. please refer the diagram attached here. I have less experience with FEM/Multi body simulation. However, started the analysis with simpack. All 4 bearings can be assumed to be spring models. Also, the shaft, flywheel and motor's shaft tolerance have to be considered for the analysis (means both the shaft to be considered as elastic bodies when working in simpack). The torque transfer from motor to flywheel during the assumed driving cycle also has to be taken into consideration for determining the natural frequency. But currently I am uncertain of the correctness of my decision. I would like to know whether FEM or MBS best suits for the analysis in determining the natural frequency of the complete system?