A Method to Characterize Cyclic Error in the Track Geometry Waveform Available to Purchase

A method [1] has been found to identify the presence of multiple cycles of harmonic error within track geometry measurement waveforms. This cyclic track geometry error can produce a buildup of resonant motion in vehicles, but may not be readily apparent from viewing the geometry error because it is often masked by the complexity of the waveform. However, due to the resulting large accelerations and poor ride quality, the dynamic rail vehicle response to the cyclic error will be unmistakable when the wavelength is at or close to a resonant frequency of the car body. Cyclic geometry error usually is unobserved and left uncorrected by maintenance because the associated mid-chord offset geometry error is typically far less than the safety limit per FRA. However, by using a band-pass filtering function on profile and alignment space curve data from the Amtrak geometry car, the presence and magnitude of any cyclic error becomes apparent. Further, it was found that shortcomings in the software used to calculate instructions for the tamper limit the effectiveness of tampers to remove the longer wavelengths commonly associated with this cyclic error. Therefore, improved methods to surface track with longer wavelength error are also being investigated.