Comprehensive Durability Assessment of Planet Carrier in Heavy-Duty Tipper Gearboxes Using RLDA Torque Data

In heavy-duty tippers, where challenging conditions demand high torque, planet carriers play a crucial role by enabling efficient load distribution and torque transmission while supporting gear ratio and speed variation in space-constrained systems such as automatic transmissions, hybrid drivetrains, and electric vehicles. This paper focuses on the comprehensive durability performance assessment of planet carriers using duty cycles derived from RLDA measurements for a heavy-duty tipper gearbox development program. The existing Design Validation Plan (DVP) for the planet carrier considers first gear utilization of 10-15% at 40% vehicle overload, in line with historical data. However, recent trends in mining applications revealed vehicle overloads of 55-65%, leading to an increase in first gear utilization (25-35%). This shift presents challenges for OEMs to enhance design durability while incorporating additional safety margins to meet the demands of a competitive, cost-driven market. To address this discrepancy, Road Load Data Acquisition (RLDA) was conducted on a heavy-duty tipper with 65% abusive overloads. Torque telemetry on the propeller shaft captured RLDA data, which was processed to generate a torque profile for the planet carrier. This profile was then used to define the duty cycle via torque rainflow matrices across various gear conditions. The data revealed a 35% first gear utilization, prompting a revision of the existing DVP using this field-reflective data. Using revised DVP, a comprehensive durability assessment of the planet carrier was conducted, considering the torque rainflow matrices for all gear operating conditions. The fatigue assessment included the effect of induction hardening using a boundary layer approach in the commercial fatigue solver FEMFAT. Critical locations in the planet carrier were identified and addressed through suitable design modifications to meet the fatigue damage targets of the revised DVP. The final prototype design was validated through physical testing, showing no failures and aligning well with simulation predictions.