I was wondering this when a train has to go into emergency how long does a train to stop there was one time that I did get to a see a train go into emergency and I think th train stopped in no more then 30 seconds but now I could be totally wrong but. I would really like to know so if anyone knows can you please pass it along to me. [:)][:)][bow][bow]
It depends on how heavy and how fast the train is.
It depends on more than just that. Train length is a big factor. Temperature, pressure, and even humidity are factors.
I’ve thought about use of eddy current brakes and electrical connections. This would allow the train to brake fully at each car immediatly. Only a signal current is used, the rest could easily and cheaply be generated by the motion of the car. The only real problem with the system is on steep grades. Eddy brakes can slow the train down but not stop it. The cars would roll at a tiny fraction of a MPH. This could be fixed with a parking brake that positively stops the train if it’s moving at less than say a 1/4th a MPH. It would only engauge when the brakes are not released.
The installation would likely cost less than current design and have very little maintenance. The problem is implementing it. A design could be done that can use pressure to sense braking needed and allow new designs to work with old designs. Eventually it could be completely transferred to the new design and thus the hybrid would not be needed any longer.
…Can a train of a given length be stopped {via emergency application}, quicker now that FRED releases air from the rear too {assuming that is correct}…? And by theory, why does it take a long train more distance to stop than a short one…? Assuming line pressure exhausts as designed…or does the length of the train have an effect on exhausting the brake line…?
I have read where the pressure drop travels at about 800 ft. per second down the trainline. on an 8000’ train that would take ten seconds to reach the rear end. If the EOT dumps the air at the same time I would think you would save 5 seconds anyway.
The short answer is that it takes too long for a train to stop.
I suspect that physics has something to do with all of this. Specifically, inertia. If you have a 6500 ton train doing 60 miles an hour, there’s a lot of energy that has to be expended to bring that train to a complete halt. I doubt the brakes completely stop wheels from rolling… and even if they did, we would probably see the wheels skidding along the rails, if they didn’t spread or derail first.
Take a look at the length of skid marks on your local highway. (There are plenty of them.) Figure on local speed; think about the weight ratio and go from there. One of the cliches I have heard is that an automobile getting hit by a train is like an automobile hitting a beer can. That gives you a rough weight ratio.
Now you know why I flunked chemistry in college.
Erik
…My thoughts have wondered around this subject…By theory I keep thinking a 5 car train and a 100 car train should stop within reasonably the same space…If…and of course it’s just theory, each car has equal brake capacity as each and every other one and if the brake line would exhaust right now…{suppose that’s the problem}, long 100 car train could stop in similar amount of space as 5 car train…
I can’t give you the best answer, but usually- under “normal” conditions-the formula is 100’ for every mile per hour of speed,plus another 100’ per hundred tons trailing load.( If the train is accelerating, this distance/tonnage ratio won’t apply.) Momentum is a very important factor in the equation, that is why one has to allow for train speed to the degree we have to in the formula. Go to Operation Life Saver’s website for more 411. I have looked at it and I have more respect for how difficult it can be running a train,some times.“Dumping the air” is somthing most engineers try to avoid, since one never is totally certain how the train behind you will react when the air is dumped.
Busting it from the rear is a last ditch effort…
It would have the effect of cracking the whip on the train, with the locomotive at the end of the whip…guaranteed to break the train if the loads are on the head end.
The engineer has to flip a switch on the head end device to blow it from the EOT…most sill use the train brake handle to plug it…
If you dump it from the head end, and nothing happens, or you’re pretty sure they all didn’t bust, then you plug it from the rear.
Say a train breaks in half, the air sets up from the break, and runs away from that separation…the cars closest to the break dumps, then the next, then the next, all in progression away from the break in both directions…
Dumping from both ends at the same time would have the effect of stretching the train in the middle, and get you a drawbar or a knuckle at least.
In a normal emergency application, the air exhaust from a large pipe under the cab, the train line dumps from there, and the pressure drops on each car backwards from the locomotive…as it takes a fraction of a second for each brake valve to “sense” the drop in the train line from the car ahead of it, then to trigger the brake valve, the longer the train, the longer the progression from the “break” be it in the cab via the brake valve, or a separation in the train somewhere, so the longer the train, the longer it takes.
Air density and temperature can have an effect too, the colder it is, the denser the air is, the longer it takes.
It’s a simple, primitive system, but it works, quite well, because it is so simple.
That’s the basics…I am sure someone will jump in here with a super technical explanation, but it really is simple.
Ed
…Yea, Ed…understand all the items involved you mentioned…Guess my example can never happen in reality. It would just be possible on paper such as comparing my 5 cars and 100 cars…and assuming no slack and none of the other varibles…just the fact each car COULD have the air exhausted at the same time then the two lengths of cars {traveling at a steady speed}, then could stop at the same distance…
Was reading the rest of the replies…maybe this might help.
All the brakes do not apply at the same time.
Each valve on each car senses the pressure in the train line…if a break occurs, the cars nearest the break sets up, and exhaust the train line, which the next cars brake valve senses, and follows suite, so forth and so on…away from the break.
However long it takes the pressure drop in the train line to work its way back away from the break (or the brake valve in the locomotive) is the deciding factor…the more cars you have, the longer it takes to set the brakes up on all of them…add in the weight, speed, track condition, weather factors…there is no set time it takes to stop a train in emergency, each one will act different, depending on all the factors mentioned.
Ed
When you have a 130 car train it still takes 10’s of seconds for the wave to get to the end of the train if the FRED isn’t opened. At 65 MPH, that is nearly 100 feet per second. The distance traveled. The train would travel over a quarter mile before the braking becomes very effective. At that point, the train has gone well over a quarter mile.
I had a train go in emergency caused by a blowen air hose in the middle of the train. I was running a 16,000 ton coal train we were doing 50mph and from the point that the emergency application occured it took a mile for the train to stop, so tonnage and speed has a lot to do with time and distance for the train to stop. I know this has nothing to do with emergency application, last night I was running a 5,500 train that got tagged by the detector with a defect I took 10psi out of the brake pipe let the etd tell me the pressure drop at the rear and dropped another 3psi and so forth down to a full service in that controled stop it took a mile and a half to stop the train.
Rodney
Ed and Rodney speak from long experience. It takes a long time to stop a train is the bottom line. And they aren’t exagerating with the problems that come from dumping the air, whether on purpose or if the train brakes. The rules say if you do that, you walk the train – and if the train is of any size, the odds are that you will find a car on the ground. Or worse.
Some passenger equipment is fitted with additional electric valves which, if all goes well and things are smiling, can and do apply the brakes on all the cars at once, which helps a lot. The backup is, of course, the normal air – and if the electrics don’t dump the car, the air will, later.
One thing to remember: the system may seem primitive, but it really isn’t – it’s very sophisticated but, at the same time, unbelievably simple and about as close to fail-safe as you can possibly get.
…I would imagine the electric system to dump the air simutaneously on each set of brakes on each car makes a big, big difference how long it takes to stop a train compared to waiting for each car to loose brake line psi and hence then apply that car’s brakes…
True, but the cost of maintaining such a system nation wide on the thousands of freight cars makes it use financially prohibitive.
Add in the time factor of having to hook up such a system on each and every freight train…
Passenger cars, on the other hand, tend to run in the same corridor, with the same equipment coupled together, and due to the “value” of the cargo, get more scrutiny after each run, incurred higher maintenance cost, and require a different set of handling skills…so electric brakes make sense, both from a maintenance and a customer satisfaction standpoint.
The equipment required would not survive the impacts a freight car takes in a hump or flat yard, even the hard joints of a normal couple up…and unlike most passenger cars, most do not have a cushioned drawbar or a cushioned under frame to absorb the impact.
Ed
…No question Ed…I was still thinking in terms of tight coupled passenger cars…I fully understand that is not possible on freight cars that go all over the country and as you say maintenance concerns and of course the connections would not be very possible to maintain either…without problems.
Oh, it’s not as bad as all that, in 33 years, just sitting here thinking about it, I can think of three times I’ve been on a train in emergency that was actually on the ground and none of those three times were times that were initiated by a crew member, they were undesired emergency applications.
Someone said the engineer will do all he can to avoid getting into a situation where he has to place a train in emergency. I strongly agree, it’s usually most unavoidable when automobiles are involved or, even worse, pedestrians and trespassers. Other times trains are placed in emergency are when, perhaps, a engineer overplayed his hand, so to speak, not a good situation to get oneself in.
We was taught in engine school that air took 9 seconds to travel from the 1st car to the 100th car.Now that’s after shooting the brakes.But like already mentioned several factors go in to account the time it takes a train to stop.I shot my brakes after hitting a car at a crossing at 40mph on a coal train and 3 motors,with 128 loads,It was on level ground dry rail,and took half of a mile to stop.
A 6,000 ton train travelling at 60 mph would take about a mile and a half to stop in emergency.