I had raised this question sometime before, I believe, but got no takers, so one more go-around: If a train is running downhill, or a cut of cars somehow gets disconnected from a longer train and begins a descent, what kind of gradient would we be talking about before the cars or runaway train becomes “unstoppable”? Once a train or cut of cars has built up momentum, is there some kind of mathematical or engineering formula that can explain how much force or what kind of machinery would be needed to stop said train? What exactly could a RR dispatcher do at this point to stop the train? My point of reference was an incident several years ago in LA, where a UP train or cut of cars apparently rolled down the tracks, all the way from one point around West Covina (or somewhere around there, I forget the RR name for the location) all the way down to a point close to the main UP yards (I can’t remember this name either[banghead]. Any takers?
…Sorry I can’t contribute a measured answer to the “required to stop a cut of cars” on a certain downgrade, but if a cut of cars is disconnected by breakeage of some kind wouldn’t that cut of cars go into emergency at the moment the train air line was disconnected from them…?
I know you are posing the question of when a cut of cars “is” coasting downgrade under the conditions they can…Don’t know how one answers that…except some equal counter force has to be applied to equal force that is bringing the cars downhill…Don’t know how one applies a figure to it.
If the train comes in two, and the entire train has air - both sections will go into emergency an stop. However, there are instances where cars can roll away:
1.) Cars don’t have air to begin with. - no or not enough hand brakes set.
2.) The train had air, but sat so long, the air bled off and the brakes released - again no or not enough hand brakes set.
3.) Train has been cut by vandels that know to close both anglecocks. Prevents the air from going down.
4.) Someone bottled the air and didn’t set enough hand brakes. As the air equalized in the brake pipe, the brakes released.
If the train runs away, there isn’t much the DS can do, except keep people out the way, and the railroad lined up. Although a good DS will know where the hollows are the could bring it to a stop.
MOW could put out a derailer, but depending on how fast the runaway is going, the could be a hazardous endeavor.
Usually though, if feasable, transportation could chase it down with another engine, or they might let is roll into a hollow and stop on it’s own.
If the cut is small and moving slow, it’s also possible to get someone onboard to the cut to apply hand brakes. Or, if the air is bottled, reach in and open the anglecock, there-by putting the cut in emergency.
Everything Nick said but if a DS has his wits about him (this day and age its takes a DS, corridor manager, and who knows what to eqaul one good old DS) they line the cut into a siding in the middle of nowhere. Generally once the cars hit the switch, do to speed and physics, the cars will derail themselves. Stopping the train and leaving one hell of a mess! Then everybody gets a potty break!!!
Would opening the valve (stop****) at the end of the consist also put the train into Emergency? Of course, catching up with it to make that happen may not be a piece of cake…
What about activating the uncoupling lever between two cars? Or does there have to be slack in the train to allow the pins to lift and the knuckles to open?
Using an anglecock on a moving cut of cars is very unlikely to be a winning strategy. The placement of the valve near the coupler makes it next to impossible to reach, especially while moving. The odds of falling under the train even trying this manuver are substantial. Also, even if it worked, there is likely no air in the cut so opening the anglecock would not apply the brakes. If air was bottled, this might work, but otherwise, no. Same problem with the cutting lever. Also, you are correct that this would require at least some slack. Best bet is to tie handbrakes or chase the cut with locomotives and other cars with air and couple on. Then apply brakes on other equipment. This practice is extremely dangerous as well, but I have seen it work before. Also, a light engine might be able to catch a single car or very small cut by matching speeds and applying brakes, I have successfully done this before with a loaded covered hopper and a single yard engine (GP38) where another railroad was kicking cars and had one get away in a neighboring yard. Speed was just over 20 when we coupled.
None of these practices are recomended, but in an emergency one has to make the best choice under the circumstances. Always take the safe course…
in partial reply to another aspect of the initial question. It is quite possible – fortunately, also quite rare – for a train with everything in working order to run away. This tends to make for a very bad day for the crew… I won’t even try to give a certain speed above which figure for you, as it depends on way too many variables: total weight of the train, % effective braking, availability or not of dynamics, air temperature, are any brakes frozen (snow/ice)?, previous braking history, etc.
The basic problem, though is that each brake (wheelset or dynamic) can only absorb just so much energy, and no more. In the case of dynamics, it’s power: there is a maximum horsepower that a given engine with given dynamic brakes can absorb. In the case of wheelsets, there is a maximum power for steady state, and at speeds above that, a maximum total energy, before the wheel and shoe temperatures get so high that you have no brakes at all. So… if the crew heads down a grade and they don’t have enough energy absorbing capability, they are going to run away. Possible scenarios (and all of these have happened!): somebody goofed and they were just plain going too fast at the top (rare); the crew was counting on dynamics on all the engines, and one or more were not operating; there was an obstruction in the main air line and they had reduced braking on part of the train; the train was heavier than the crew was told it was; the brakes were partly frozen…
In trucking a mountain would win if your speed is too high for the availible effort generated by your brakes to stop. The amount of braking availible depends starting with traction, road surface and ends with the total vehicle mass and weight.
Not to scare anyone but on certain passes we allowed the rig to be pulled to top speed by gravity for several miles and it worked out to about 118-125 mph on a 6% we needed to get to flat ground before we could safely bleed off the speed. One of the few times in my life Ive felt negative gravity without flying.
We do think that “Final Speed” at which no recovery is possible exists somewhere above 120 but not more than 200. Need a math whiz to work it out. Ive seen 150+ in a car but usually had a mile or so to make the stop or at least knock it down.
I dont think today’s railroads are capable of holding the track much beyond 90 mph because the flanges are only so deep, once they rock out of the rail that’s it.
Riprap, there are a lot of variables, with a heavy freight train on a 2.2 percent downgrade, the maximum safe speed is less than 25 mph. With a train of empties it will be a few mph faster, not too much though. Passenger trains will be quite a bit faster. The most immediate concern is are all the dynamic brakes working properly, and how many " tons per operative brake" does the train have. Over 100 tons per operative brake, average, and train handling on downgrades steeper than about 1.5 percent becomes crucial. Each freight car has one brake system. So a loaded coal car weighing 143 tons is well above 100 tons per operative brake, of course several empties will offset this. It is the average for the whole train.
Safety Valve, the limiting factor is how much force the rail can withstand before the fasteners break, or the rail breaks. On the high-speed line in Germany the ICE trains between Cologne and Frankfurt descend 4 percent grades at 186 mph under 75 percent dynamics. The Au River bridge is especially spectacular almost like a rollercoaster. The train comes out of a tunnel and goes from full throttle to 75 percent dynamics and straight down a 4 percent grade to the river bridge, immediately its back to full power for the 4 percent climb out of the river valley to a summit in another tunnel.
There is nothing but the flanges to keep the train on the rails. Think of the tremendous downforce at the bottom. conversely there is lifting moment at the top transitions which are also taken at 186 mph. I imagine that they do not have curves during the top transitions.
Almost 30 years ago the UP had a ballast train runaway on Cima Hill in Southern Nevada. Cima Hill is very close to
I would think that in either case,the train would(1) stop and the conductor would notify the DS that the train was in emergency and the rest of the train was also stopped and (2)the runaway cars would be switched to a siding if avail.or (3)in the case I heard of once where a coal train DP unit didnt recv the signal kept pushing the remainder of the train til it got close enough to be stopped with the rest of the stopped part of the train ,that may cause a derailment…(Does that sound right?).[2c] Danny
Back in the mid '70s the BN had an exercise built in to one of the loco simulators that showed if a 100 car coal train (all 263,000lb loads) reached at speed of 63mph on a descending 1.3% grade before an emergency brake application took place and the grade continued at 1.3% the train could not be stopped due to the fact that the brake shoes would burn off before a stop could be reached. This was using air brake only with no dynamics.
Over the past 40 some years I have seen two cases where a moving train with a fully charged air brake system broke in two and one piece did not stop from an emergency brake application like it is supposed to. Both times it was because an air hose wrapped itself around the uncoupling lever rods and kinked itself so the emergency application did not take place. The first time we left the caboose and rear 40 cars around Utica, IL. We were going by Ottawa Yd when the condr asked on radio if the brakeman had found anything yet (both trainmen were on head end). The 2nd time was the head end went into emergency and the rear end near did not. Upon walking the train the brakemen found butted knuckles and the air hose wrapped. I’m sure you all will say “That can’t happen” that’s what I thought too, until it did.
The following is a cut and paste from the TRAINS NewsWire for 10/09/2006: No details of what happened beyond the fact, that apparently a train went out of control while puling or shoving cars into an ore dumping system.
It seems that even when all things appear to be nominal and in a normal order there is the problem of an out of control runaway, with a unit supplying air, and breaking power. Does anyone have any further info on this line? Or What happened?
Runaway on Quebec’s Cartier Railway
October 9, 2006
PORT CARTIER, Quebec -A Cartier Railway unit ore train ran away at Port Cartier in northeastern Quebec on the morning of Oct. 6 as it was entering the ore dumper. The two-man train crew was slightly injured when they leapt from the locomotive. A third person working in the dumper was also sent to the hospital. The provincial worker health and safety board and Transport Quebec are investigating the cause of the accident. It is not known at this time how long it will take to clear the derailed cars and repair the ore dumper.
Opened in 1960, the isolated Cartier Railway is a wholly owned subsidiary of the Quebec Cartier Mining Co. and operates 259 miles of track between Port Cartier, on the north shore of the St Lawrence River, and Mont Wright, the location of an iron ore mine. The railroad has no outside rail connections. - John Godfrey
In a case of a break-in-two with empties or lightly loaded cars in front of loads the rear will almost certainly impact the front section hard. The locomotives will continue to pull for a few seconds creating separation then lighter front will slow more quickly. allowing the rear to catch up. The DPU incident was on the UP in flat Nebraska and was a malicious vandalism, opposing anglecocks were closed and the pin had to have been lifted, after the train left North Platte Yard. The DPU pushed section of the train was following the headend pulled section, a witness reported that the separation was nearly a mile when it went past them at a grade crossing. There is no way the train could have passed the 1000-mile Inspection in North Platte like this, so that someone did this between the time the carmen issued the release and the time the train departed.
Beaulieu has the correct information about this incident. The train was stopped by putting it into emergency. The rear half also went into emergency, and everything was (eventually) hunky-dory.