First I know this is ancient (1989) history but I caught a program on it this morning on the National Geographic Program. Link to Wikipedia article of original incident. That made me think of a couple of questions:
-The engineer was given incorrect info about train weight and braking power. What was done to correct this from happening? Has anything been done? I couldn’t find an answer to that.
-Why does putting on the Emergency Brake cut out the Dynamics? The only answer I can find had a long winded explanation that had something to do with wheelslip. Given that the engines involved (I think-could be wrong!) were ‘older’ even at the time, would ‘modern’ engines (SD70XXX or ES44XX or comparable EMD/GE power) fare any better? Why or why not?
what has changed bulk shipment are weighed, paper work is better but we are still over tonage and under powered. as far as engines go the power is cut off when in emergency do to not wanting to slide the wheels, this is still practice today on new engines put your train in emergency and the power is knocked down. the only differance is with the electronic brakes it takes longer to recover from a emergency brake application either intentional or not.
So the engine automatically goes into idle as a result of Emergency Brakes being applied? Wouldn’t the Dynamic Brakes help slow the train further, even with EB applied? Or would it be better to use a Full Service application and Dynamics?
modersn locomotives let you continue in dynamic braking during an emergency application, they will shut down if in power, but they now have what is called dynamic brake holding. I’m not sure when this feature started but it has been around awhile, some SD40-2’s do have this feature, and most locomotives after this time have the feature.
I’m not sure what has been done with problem of overloaded cars, but I believe they have to be weighed during or right after loading.
I seem to recall that the cars were not overloaded as in maximum allowable weight. The problem was weight of the contents of the cars was entered incorrectly into the “System” and thus the train list info the crew received indicated each car weighted about 30+ tons lighter.
The “Fix” if I recall correctly was no more guessing at the weight of some contents. If the actual weight was unknown, then the weight went into the reporting system as maximum allowed for the car. In this case that would be 131 tons.
Another factor was the locomotives involved did not have all have operating dynamic brake and the engineers involved had no way to determine this. That problem has not been resolved to this day, the engineer still doesn’t know if dynamic brake is operating properly except on the controlling unit until he uses it.
Whenever I went into emergency and was in dynamic brake the dynamic brake would stop working and indepenent brake pressure applies and since your train is probably already bunched in since you were in dynamic that is ok but whenever I go into emergency I bail the engine brakes off just a touch so that you won’t get serious run in from the engine brakes setting up which could also cause a derailment and serious flat spots on the wheels .
It is important to know where the heavy cars are at in your train . If I got alot of empties on the head end and the middle is heavy as well as the tail end you would not want to get excessive with dynamic brake .
I got to run the IC simulator one time and talk with the instructor. IC had a rule of no more than 16 axles of dynamic braking as it would prove too much braking for most instances. Don’t know if that sheds any light on the subject but excess dynamic braking apparently can act like going into emergency when it is applied.
Or if you have some cars that have longer draw bars and the get shoved in the corner and all of the weight from the train behind , something will have to give .
Dynamic is nice but it must be used carefully . Generally I will use it going down hill to control train speed . I don’t like to use it going thru curves or turnouts as much . When I first became a engineer instructor told me something and it kind of stuck in my brain . He said using dynamic , don’t put too much on too soon or take it off really quick . It’s a gradual process , start applying easy that way you don’t get too much run in and when you feel that your train is completely bunched in use all you need . Taking DB off , do it gradually as well .
You can also use DB and air together . If I am going to stop and DB is not enough to stop the train I will use this method .
Will an engineer please correct me if I’m wrong, but doesn’t dynamic braking depend on the wheels actually turning to get the braking? I think that the faster they turn, the stronger the braking (this was at least true until extended-range braking and AC traction motors came into use). So putting a locomotive into emergency, in an attempt to stop the motion of the wheels, is rendering the d/b less useful anyway, right?
When the air goes, the PCS (pneumatic control switch) cuts the power. The engines go to idle, and amps go to zero. If my train dumps, I usually bail off until the train stops. Otherwise, flat spots on the motors can happen, as the engine brakes apply harder. Some older engines didn’t have the PCS, and were able to run away from a wreck.
I haven’t been in dynamics when the air goes, so I do not know what happens. I would think the PCS cuts dynamic as well.
Usually above 15-20 lbs on the engine brakes will cause the dynamics to kick out. I haven’t tried this, either. The rotating wheels in dynamic causes retardation, so stopping the wheels from turning is less than desireable. Normal dynamics work best between 15-25 mph. Some work good down to 10 mph, and I’ve heard AC traction engines can go down to 0 mph.
Paperwork has changed since that wreck. A crew that takes charge of a train is supposed to receive written info on how the train lines up; number of loads, number of empties, where the loads are in the train, how the power is running, which engines have dynamics, which ones have dynamics cut out, if the brakes work as intended, etc. This info is supposed to be left by the outbound crew.
How does dynamic function compare at 40ish MPH versus 20ish MPH? That’s the speed that the train was going when the engineer first applied his DB in this situation (according to the show anyway). Is this function hampered at higher speeds? What if he’d had AC traction vs DC-which motor ‘does’ DB better?
The faster one is going the more dynamic brake retarding is potentially available. Note: potentially. Whether it actually is or not is very much dependent on the particular type of engine involved and how its controls are set up.
What you don’t want to do if you can possibly help it is stop the wheels rotating – either engines or cars – as you get a lot less retarding from a sliding wheel than from a rotating one.
One of the booby traps with a train which is heavier than you think it is – and it has caused several wrecks – is that there is a very definite limit to how much energy, total, the brakes on the train (including the dynamics) can absorb before they get too hot to function. The total energy is related to the square of how fast the train is going. If each car is heavier than you think it is, the maximum safe speed going into a grade is less than you think it is – and once she starts to run, the only thing you can do is pray or jump.
I saw that show, and spent most of it laghing about the UP SD70s pushing from the rear, (they didn’t exsist back then) and the animation of the actual crash with a UP loco lettered Southern Pacific![D)]
The real thing I would DEFINETLY not laugh about, but all the RR related goof-ups were rather funny. [:-^]