This study investigates the stresses and deflections of a floating ring gear with external splines working in a large planetary wheel motor of a mining truck. Such calculations carried out with conventional engineering approaches described in popular standards and textbooks are not comprehensive because of the complexity of the problem. These approaches can give us good stress numbers for non-floating gears and some guidance about the rim thickness factor but they lack the capabilities to effectively calculate the deflections and their influences on the stresses, especially for floating gears. Moreover they cannot calculate an entire gearing system and the interdependent influences of the different components. The model studied consists of a floating ring gear driving a torque tube. The ring gear is driven through internal gear meshing by three planets and it transmits the torque to the torque tube through its external splines. The torque tube transmits the motion to the hub and the truck tires. A nonlinear static analysis of the ring gear and torque tube was conducted in ABAQUS. Linear 8-node hex elements and linear tetra elements were used to model the ring gear and torque tube. External torque was resolved into corresponding tangential force, which was then applied directly onto three of the ring gear's internal teeth. Contact pairs were used to capture the load transfer between the ring gear and torque tube through the splines. The results show that the deflections in the ring gear were so excessive that about one-tenth of the spline teeth were actually transmitting torque against the common engineering understanding that only half of the spline teeth are typically engaged. The crowning of the spline teeth had also effect on the stresses though quite small compared to the deflections. Conclusions and recommendations were made about the effectiveness of the design.
展开▼
