dehusman
It takes 5-10 sec for the brakes to apply once the brake valve starts the application. A train going 30 mph is traveling 44 ft/sec. That's between 220 and 440 ft before you can start to control the train. In that time between 4 and 8 more cars may have passed over the point of derailment and derailed. In that 5-10 seconds and several hundred feet, there is a strong probability that one or more cars will have skewed to the point that one or more wheels have reached the ends of the ties. As soon as that happens there is no braking force that you can apply that will keep the train streched in a straight line. Once the wheels get off the ties, they will present a huge amount of drag and will decelerate FASTER than the brakes can decelerate the train. It doesn't matter whether you have ECP or conventional brakes, the rear of the train can't decelerate faster than the derailed cars.At some point the air hoses on the derailed cars, whch are now dragging on the ties because the wheels are on or off the ends of the ties, will part, putting the train in emergency. When that happens you have lost control of the situation.
You entire premise hinges on the conditions that only one car derails, it remains upright, in line, on its trucks, on tangent track, train line intact and there are no other external forces acting on it (switches, grade crossings, collisons with other vehicles, debris, etc). While that does happen, its an edge case.
I have seen too many derailments with the wheels went from the POD to the ends of the ties in one car length or less.
Dave,
With all due respect, I do not believe you are looking at the total picture of the system and response that I am describing. Instead, you are construction a scenario of failure based mostly on the conventional air brake system performance.
My premise does not (as you say it does) hinge on the condition that only one car derails, that cars remain upright, remain on their trucks, or that the train line remains intact. I do agree that the conditions of track curvature, or excess forces from encountering switches might defeat the system and cause an immediate jackknifing. It is not meant to prevent pileups in cases of collisions with other trains, or in the case of derailing the locomotives from various causes.
Sure it takes some time to move the brake linkage once the application has been signaled.
But until that happens, cars on both sides of the derailment are going to be rolling freely with no compression from the trailing cars that will tend to skew a derailed car. So, while the entire train is still rolling without braking, the dragging resistance of one or even several cars could easily be irrelevant to the momentum of the train. Having several cars on the ties does not mean that the system has lost control of the situation. I disagree with your basic premise that the first car to derail will create so much running resistance that it will decelerate the trailing cars faster than the braking can hold them back.
The response does not depend on putting the train into emergency upon the breaking of the first air hose. And the breaking of the first air hose will not put the train into emergency. The brakes are not controlled by brake line reduction.
I agree that certain circumstances will prevent this system from controlling a pileup. However, in the scenario that you paint as typical, a derailment happens and every car following that occurrence will derail at the same spot. Therefore, you conclude that several cars will be on the ground before any braking is initiated on the trailing cars. And with that many cars on the ground, you conclude that they will surely jackknife. I don’t believe that is a certainty if the train does not go into emergency, and if there is no braking initiated on the cars ahead of the derailment-- both of which will be the case.
It is trains moving at full speed that have the most energy that can be applied to causing a destructive pileup. But that same energy can be most effective in keeping the derailed cars in line and stretched despite their dragging resistance. Even the derailed cars retain the force of momentum. At the slower speeds, there is less momentum to accomplish overcoming of the dragging resistance, but that same lack of momentum will also mitigate the potential for a destructive pileup.
So, in my proposal, a braking response is initiated on the trailing cars the instant the first car derails. If it takes 5-10 seconds for that application to take hold, the derailed car or several derailed cars will drag. They may tip over. They may lose trucks. But they will stay stretched and generally in line even though braking on the trailing cars has not yet begun.
Even for as violent as this dragging process can be, it is not what causes the maximum resistance that is indicated by the severely compressed and flattened cars in a wreck. The resistance that makes that possible comes from piling up several cars into a heap. That heap becomes the immovable anchor that the enormous linear inertia of the trailing cars is directed against.
My point is to react to the derailment more proactively in order to prevent that pileup from beginning. It won’t prevent every pileup, but air bags in cars do not prevent every death or injury. I would expect this system to prevent a lot of pileups, and not just ones in rare occasions when things go just right.
