Automated Gauge Inspection

Several incidents had occurred on the Louisville & Nashville (L&N) Railroad where a dynamic gauge-widening tendency was believed to exist. To investigate this possibility, rail proximity sensors were mounted on a locomotive truck to measure track gauge under dynamic load. In association with the electronic system for gauge measurement, a paint spray system was installed which sprayed the track with a clearly visible line whenever gauge exceeds a predetermined threshold value. Using this equipment, track was inspected automatically at high speed and priority defects were automatically marked for immediate repair. The gauge measuring system consisted of a pair of capacitive sensors which respond to the gaps between the sensors and their corresponding rail heads. Continuous gauge data was recorded on a two-channel oscillograph. One channel was used to record track gauge and the other was used to denote location information via coded signals manually introduced by the system operator. Verification of system performance was carried out by measuring dynamic gauge-widening effects on a carefully instrumented curve and by performing comparative unloaded measurements over many miles of track. Gauge widening under dynamic loading was observed, and the existence of this effect was verified.