I was watching a UP freight train go by the other day and I noticed on a few of the cars the trucks would pass by with a loud bang bang bang..what causes this? And why dont they fix it?<br>thanks<br>Alan<br>



adofmsu@aol.com

Those banging noises that you heard were made by flat wheels. The most common causes of flat wheels are dragging cars with hand brakes set, sliding wheels and sticking brakes. The surface of the wheel becomes gouged and can create a double flange eventually, which would derail the train. Occasionally a traction motor on a diesel electric locomotive will freeze up, causing the wheels on the associated axel to lock up and slide, creating flat spots on the wheel. Such an incident caused a terrible accident years ago on the Illinois Central. A traction motor on the trailing unit of the City of New Orleans's locomotive (E-8s) froze. A flat spot developed and went unnoticed for a good distance, later estimated to be 40 miles. The wheel gouge became deep enough to create a double flange. When the train came to the next turnout, it derailed, killing a large number of passengers.<br>



envlink@voyageronline.net

A flat spot on a wheel must meet a set of minimum dimensions as outlined in the AAR Interchange Rules before it can be considered a defect which will bad order the car. The defect can be a single flat spot of a certain size, or multiple flat spots of lesser size at close proximity to each other. If/when a car inspector locates the defect, he/she must determine if it is bad enough to bad order the car. If not, the car continues on it's way, thumping along until the flat spot grows to the minimum required size for bad order. An inspector employed by the car's owner may elect to bad order the car prior to the defect becoming too large if he/she so desires (but whoever heard of a railroad doing preventative maintenance?). However, if the car is owned by another company (railroad, car lessor, etc.), the flat spot must meet the minimum requirements before that wheel set can be changed out. After all, you wouldn't want the local garage replacing parts on your car that didn't need to be. That would be dishonest!<p>Brian Wise<br>



thewises@apex.net