Posted on 09/25/2004 11:03:26 PM PDT by Cincinatus' Wife
A few items to throw into the pile that I have access to..
The BNSF train originated in Eagle Pass, TX.
The "new" boxcars were new construction from a plant in Mexico.
Angle cocks (hand valves) control the flow of air throught the brake pipe.
At the point of the uncoupling, the angle cocks were closed on both cars, on the one left coupled to the train and the one that was part of the roll-away. The air was "bottled" in the rear 50 cars and the brakes were inoperative.
The uncoupling lever was lifted which opens the knuckle and separates the couplers.
There is a .34% to .92% westward descending grade from the point of the uncoupling.
Evidence was found on the east car of the cut that rolled indicating the presence of a "UDA" on the railcar. Empty water bottles - clothing - papers - excrement.
Tracker dogs were used, first on the rail car which they got a good hit on. Tracked the scent along the railroad, through a wooded area and onto the sidewalk of Commerce St. in San Antonio. Along the sidewalks for a few hundred yards and then to the curb where the scent dissappeared as if the person/persons got into a vehicle..
Hundreds of "UDA" are pulled off of and from under trains across the southwest daily..
wideminded,
Angle cocks were turned on two cars then the pin was lifted between the two, uncoupling the cars. By turning the angle cocks, the air is "bottled" in the cut and the brakes will not set when the train line is separated. Had the angle cocks not been closed, the cut of cars would have likely not rolled more than a few hundred feet because the train line would have been "broken" and the brakes would set up in an "emergency application". Hope that helps..
WOW!
That's a lot of information.
***At the point of the uncoupling, the angle cocks were closed on both cars, on the one left coupled to the train and the one that was part of the roll-away. The air was
"bottled" in the rear 50 cars and the brakes were inoperative. ***
Is that normal?
Of course the RR should bear first responsibility.
But this lax (crimminal) attitude sets trains up for terrorist use.
kemosabe, the railroad knows the cause. It is not "mythical". It real and provable. And, it is possible to have a "rolling disconnect" and not set the brakes. Of this I speak from hands on experience.
Yep, that's normal.
Like having water flowing through a garden hose.. The nozzle is closed first - then the faucet is closed. You still have water in the hose, under pressure, until you open the nozzle and release. The release is what casues the pressure to drop in the hose and in the air brake lines. This drop in pressure sets up an imbalance in pressure and causes the brake pistion to operate and set the brake against the wheel.
I did some more reading on train braking online and noticed that this is probably the most plausible explanation, although it was not discussed in the article. Some other ways a runaway train could occur include:
1. If the boxcars had been idle long enough to have empty auxiliary air tanks and the crew did not connect up the brake lines to charge them.
2. If the train had braked hard several times in succession just before the cars were decoupled, the auxiliary air tanks would be depleted, leaving no force on the brakes.
Sorry, I hadn't read your post #22 before my last post.
Yes, but this would tend to suggest a deliberate--rather than accidental--uncoupling, would it not?
Also, I thought that trains had a motion sensor on the rearmost car which maintained radio contact with the engineer (a function formerly performed by the brakeman in the caboose). So shouldn't the engineer have discovered that something was amiss, unless somebody also sabotaged the motion sensor?
The way I read it they were turning the manual brakes on the car (the big wheel) that sets individual brakes.
>>>>I'm puzzled, though--wouldn't uncoupling cars on a moving train cause all the brakes along the entire train to get automatically thrown pretty quickly? Or did whoever uncoupled the cars cap the brake lines to prevent that from happening?
Sorry to get back so late... work keeps getting in the way.
1) Yes, this was a deliberate act on the part of the trespasser/vandals.
2) The BNSF train was equipted with an EOTD. In the initial interview with the BNSF train crew, they claimed that they had been having problems during their trip with losing linkage/connectivity between the locomotive and EOTD. They would have to stop and relink electronically. They claim that while they were stopped for the signal, they got no information from the EOTD that the rear of the train was moving AWAY from them. (it reads out footage between the lead unit and the EOTD)
The EOTD device is being tested as well as the readouts from the "blackbox" on the locomotive.
Had the angle cocks NOT been closed, the brakes would have set up on the entire train as soon as the "glad hands" on the air hoses uncoupled. Since the trespassers/vandals closed BOTH angle cocks, the train line was kept intact and no "emergenty application" of the brakes occured.
The hand brakes (big wheel) does set up the brakes on an individual car but did not come into the play at any time during this event.
Typical that San Antonio would blame the UP....instead of their own immigration problems. I get it is a "sanctuary city" like LA, etc where they dont deport people.
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