This study determined the equivalent moment of inertia of the upper rotating body of an excavator, for the inertial endurance test of an excavator slewing system. The input speed and torque of the slewing reducer were measured by an excavator slewing test, and the equivalent moment of inertia of the upper rotating body of the excavator was calculated using iterative calculation. We developed a dynamic simulation model of the excavator slewing system, and validated the model by comparing it with the slewing test results. Using the validated model, we further developed a simulation model for the inertial endurance test, that considers the moment of inertia of the upper rotating body of an excavator. We concluded that the new dynamic model for the inertial endurance test of an excavator slewing system well exemplified the actual slewing test results.

The planetary geartrain can be reduced in size and weight, and has excellent durability since the input torque is divided by the number of planet gears when the power is transmitted. In order to improve its durability, the load sharing among planet gears must be even. However, of the various manufacturing errors possible, the carrier pinhole position error has the greatest influence on load sharing. This study compared and analyzed the load sharing and the gear safety of planetary gears, according to the phase of the carrier pinhole position error. We confirmed that load sharing among the planet gears varied, depending on the phase of the carrier pinhole position error. The mesh load factor is inversely related to the gear safety factor for bending and contact, and affects the durability of the planetary geartrain. Also, in the design of the planetary geartrain, the load sharing among planet gears is directly affected by the carrier pinhole position error and its phase. Therefore, the geometric tolerance must be managed efficiently, which needs to be reflected in the production drawings.