To simplify and also to improve the modeling method and calculation process described in earlier reports, (1) each of the counter-weights was idealized by an equivalent spring model, (2) the flywheel was idealized by FEM model, and (3) the oil-film of crank-journal bearings was idealized by a set of multi-points spring-support system, respectively. By the modification (1), both the number of joints in the modeling and the size of system dynamic stiffness matrix could be reduced significantly, and by (2) and (3), a significant improvement could be obtained for the calculations of the natural frequencies and their corresponding mode shapes as compared to the previous reports. Especially, by the FEM model of the flywheel in addition to the vibration behaviour of the flywheel, the coupling behaviour between the crankshaft and flywheel vibrations can also be estimated distinctly.
