JackRussell wrote:smallfire85 wrote:
OK, I am not quite getting why it would be the case that a train traveling in the opposite direction would experience a gauge tightening. I would have expected a widening, no matter what direction the train was traveling.
You are correct, any train would have experienced widening traveling through that area in either direction.
The tightening I'm referring to doesn't mean tighter than standard gauge, but tighter than what the wheels were currently running through. According to the report, the wheels on the low rail of the curve dropped into the gauge of the track at the wide gauge/loose anchor location. However, the rapid transition to normal gauge squeezed the wheels between the rails more than normal, causing the wheels on the high rail to climb over the high rail and derail the train. Technically, there were two separate, related derailments, but the wheel climb derailment is a worse situation since your wheels are now out of the gauge.
Typically, the wheels handle gauge widening easier than tightening because it gives the wheels more room to maneuver. The issue arises when the rails go back into gauge. For trains traveling in the normal direction in this case, this return is more likely to be gradual due to the nature of the defect development, which lessens the chance of a derailment. For a train traveling in the opposite direction, the tightening is much more abrupt, which increases the amount of friction between the wheel and the rail and the chance of a wheel climb-type derailment.
There are so many factors that can contribute to a derailment, especially this one, it's not even funny. The condition of the track, the geometry of the track, the condition of the wheels, the speed of the train, the direction of travel, I think there's too much focus on this one defect that it overshadows the other factors, which in my opinion are just as important. If you look in the report, the train ran in reverse direction (with 3157 as the lead) for 900 feet before stalling due to the derailment. This means the entire train crossed the POD in the normal direction before reversing, which means that the first two cars traveled over the POD in the reversing direction
without incident. Fun stuff!
The reason I pointed out the gauge change issue was because that defect, though related to wide gauge, is viewed as a separate defect. Unless that defect was also deleted, I think there was still enough information in that exception report to identify and remedy the condition before the derailment occurred.
I'm sorry for such the long posts, its just that there's so much to look at and explain for people to have a real understanding of this chain of events.
