Effect of lateral installation deviation of arc-surface couplers on locomotive running safety during braking

Lateral installation deviation of arc-surface couplers (LID-ASC) can significantly affect locomotive dynamic responses and running safety during dynamic braking. Four LID-ASC layouts (Scenarios I–IV) are defined by the lateral offsets of front and rear couplers: front left–rear left, front right–rear right, front left–rear right, and front right–rear left. A validated multi-locomotive dynamic model, containing two16-axle locomotives, one idle unit, one dummy wagon, and four arc-surface coupler pairs, is adopted to evaluate the running performance of a 10,000-ton heavy-haul train. Results show that LID-ASC increases the maximum sum of Y forces and reduces the safety margin on straight track and five curves. On straight track, Scenarios III and IV exhibit larger coupler yaw angles and lower safety margins than Scenarios I and II, particularly for deviations over 15 mm. On curved tracks, Scenario IV oriented opposite to the track direction experiences the most critical conditions, and its sum of Y forces exceeds the safety limit at 10 mm deviation. Limiting LID-ASC, reducing the total dynamic braking force and restraining coupler yaw angles are three countermeasures to mitigate derailment risk. These findings offer practical guidance for installation quality control, braking strategy optimisation, and coupler design.