Rail hunting refers to the tendency for a train to assume a correlated side-to-side (sinusoidal) movement as the locomotive and wagon wheels alternately make and break contact with the inside of the rail track. In extreme cases, this sinusoidal movement can become excessive and lead to track damage and/or derailment. Rail hunting is speed dependent for a given train and track combination, and is one factor in determining the maximum rated travel speed of the train.
The project involved instrumenting a section of working track with an array of six laser proximity sensors mounted inside the track, and aligned to measure the distance between the inside of a passing wheel and the track itself. The laser sensors were simultaneously sampled at 2,000 samples/sec to provide a profile of wheel distance from the track for each individual train wheel over the instrumented track section. The system ran unmonitored 24/7 for extended time periods during normal rail operations. It automatically detected an approaching train and switched logging on or off as required.
The data was analysed to provide profiles of average separation of locomotive/wagon wheel vs speed, which formed part of a proposal to review the maximum rated speed for empty trains returning to their load point.
National Instruments CompactRIO PAC Chassis, Controller and I/O Modules, Sick Laser Proximity sensors