Dynamic characteristics and comfort of rack vehicles under different slopes for empty and fully loaded conditions

Rack vehicles, specialized for large-slope routes, are increasingly vital to transportation systems in mountainous and complex terrains. A dynamic model of a rack vehicle–track (rack) system with variable slopes was established based on vehicle–track coupled dynamics theory. This model accounts for vehicle load, track slope, wheel–rail contact, gear-rack meshing, and track irregularity. The dynamic characteristics and comfort of rack vehicles under empty and fully loaded conditions across varying slopes were evaluated. Key metrics include acceleration, contact forces, meshing forces, derailment coefficient, and stability index. Results show that steeper slopes lead to increased longitudinal acceleration, meshing force, derailment coefficient (max: 0.43), and stability index (max: 2.96) for an empty vehicle, with reduced vertical acceleration and contact forces. For a fully loaded vehicle, higher values were observed: wheelset acceleration (3.3 m/s2), contact forces (119.9 kN vertical, 30.7 kN lateral), meshing forces (348 kN longitudinal, 220 kN lateral), and derailment coefficient (0.57), indicating elevated derailment risk. However, its stability index (2.72) is lower than that of the empty vehicle, reflecting enhanced smoothness due to greater mass and rigidity. These results provide a theoretical foundation for optimizing rack vehicle design and operation on complex slopes, improving safety and comfort.