Another real train question: Sometimes I’m on a bicycle at a local grade crossing watching a relatively slow (25 MPH) long freight pass through. Most all cars wheels make about the same noise but every once in a while one comes through with much louder wheel noise, but not the thump thump of a flat wheel. I know there are periodic hot box detectors to locate a failing wheel bearing that is overheated. But I would think that a failing bearing would make substantial, and different sound, than a properly operating one. Do railroad have any system to early detect a failing bearing based on excessive noise?
The noise of most pending bearing failures is ultrasonic, far above human hearing range, and if in the more-critical inside bearing the sound may be considerably muted. The kinds of catastrophic failure with audible breakup of running surfaces starts with a quiet crackle, but that only applies for a few miles of running before failure through the grease tribology will progress to overheating or seizure. In a very few cases – I have only experienced two – the truck will emit a high continuous ringing or squeal, but the likelihood of someone phoning that in between detector ‘suites’ is probably slight.
There is most definitely a place for audio detection of failing-bearing signatures, but it HAS to be on the car, unless you propose to have four carmen on each car every time a No. 1 brake test is done. (And probably you won’t catch it then if speed is too low or the bearing is cool).
Thanks for your knowledge and background info. Just thought I’d run this concept to the train brain trust.