Train becoming uncoupled -
https://www.youtube.com/watch?v=S1wytAllGkY
Never too old to have a happy childhood!
BaltACD Once a wheel hits the ground in a derailment, all predictability of what the ultimate outcome will be is gone.
Once a wheel hits the ground in a derailment, all predictability of what the ultimate outcome will be is gone.
Euclid jeffhergert Euclid Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible. Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs? Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens. I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now. Jeff What was the reasoning for having the PCS open to cut out dynamic braking in the event of a U.D.E., when that was in the design? And what is the reasoning for having newer engines maintain dynamics in the event of a U.D.E.? What would be the benefit of applying dynamic braking during a U.D.E.? It seems like it might be problematic.
jeffhergert Euclid Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible. Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs? Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens. I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now. Jeff
Euclid Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible. Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs?
Does the dynamic brake control system recognize the U.D.E. and respond by automatically stopping dynamic braking at the moment the U.D.E. occurs?
Depends. A UDE will open the PCS which cuts power or dynamics. Newer engines and those retrofitted will maintain dynamics when the PCS opens.
I don't know if this feature is an option or standard on new engines. I know we have this feature on most, if not all road engines now.
Jeff
One element of the reasoning is to prevent a secondary impact between the two parts of a train that has broken in two because of a broken knuckle or pulled out drawbar. Wether the reasoning is appropriate or not is open to discussion. Releasing Dynamics when the UDE trips the PCS would leave BOTH parts of the train with only emergency air braking as the primary and only braking - theoretically allowing both parts of the train to have similar stopping distances.
If the UDE trips the PCS but the Dynamics aren't released, theoretically the head end will stop BEFORE the rear end of the train. If the rear end runs into the stopped head end of the train there is a distinct possibility of a derailment at the impact point.
The above applies to when a train has head end power only. With DPU's in the power make up - all bets are off. Jeff Hergert would be the authority on that aspect of train dynamics.
Any UDE interjects wildly acting in-train forces, even on level tangent track; when those force begin acting on a train in graded terriory - all bets are off, especially when it happens on descending grades where a high level of curvature has been built to get the grade to manageable levels for ascending the grade.
The reason they want dynamics to keep working when the PCS opens, and other things can cause the PCS to open, is for trains operating in heavy grade areas. Mountains.
The PCS doesn't know if it's open due to a train separation, air hose bursting, or if the engineer (or conductor) just placed the train in emergency. Going down a heavy grade you want to maintain all the braking effort possible. I believe it was some of the runaways that brought about changes.
Say you have a freight train in dynamic braking, and you suddenly experience a U.D.E., thus triggering an automatic air brake “Emergency” application, which will stop the train as quickly as possible.
Reading467 Euclid, I printed the Locomotive Event Recorders Specialist's Factual Report in an attempt to compare the lead loco (NS 4178) with the DPU (4412) parameters during the timeframe starting at 2042 hrs, roughly 12 minutes before the emergency brake application. The engineer starting using the dynamics on the lead and 2nd unit (NS 4224) just before 2050 hours. The DPU's throttle was in notch 8 until 2051:40, returning to idle at 2052:10 (the 10 seconds is an approvimate reading from Figure 4. According to the Operations Group Factual Report, the crew received the HB Warning at 2053:00, based on recordings taken from inside the cab of 4178. The head end DB was in notch 2. The DPU was at idle. The engineer notched the head End DB to 5 and the DPU was also in DB 5 when the emergency application was initiated at 2054:24. I believe the answer to your initial question of where the pileup started is in the Track Factual Report, section 3.1.: "Additional wheel flange derailment markings were observed in the gauge of the track starting about 120 feet west of Pleasant Drive Railroad Crossing at milepost PC 49.2. These derailment markings were observed to the inside gauge portion of the track and run parallel with the north running rail and extend eastward to where the north derailed wheel strikes the Pleasant Drive Railroad Crossing (Note 6)." So, that's the apparent cause of the pile-up: the derailed north wheel of axle L1 of Covered Hopper GPLX 75465 hitting the grade crossing structure after the failed bearing on the other (south) end of axle L1 burned off, thereby separating the train line and causing an emergenecy air brake application.
Euclid, I printed the Locomotive Event Recorders Specialist's Factual Report in an attempt to compare the lead loco (NS 4178) with the DPU (4412) parameters during the timeframe starting at 2042 hrs, roughly 12 minutes before the emergency brake application.
The engineer starting using the dynamics on the lead and 2nd unit (NS 4224) just before 2050 hours. The DPU's throttle was in notch 8 until 2051:40, returning to idle at 2052:10 (the 10 seconds is an approvimate reading from Figure 4. According to the Operations Group Factual Report, the crew received the HB Warning at 2053:00, based on recordings taken from inside the cab of 4178. The head end DB was in notch 2. The DPU was at idle.
The engineer notched the head End DB to 5 and the DPU was also in DB 5 when the emergency application was initiated at 2054:24.
I believe the answer to your initial question of where the pileup started is in the Track Factual Report, section 3.1.: "Additional wheel flange derailment markings were observed in the gauge of the track starting about 120 feet west of Pleasant Drive Railroad Crossing at milepost PC 49.2. These derailment markings were observed to the inside gauge portion of the track and run parallel with the north running rail and extend eastward to where the north derailed wheel strikes the Pleasant Drive Railroad Crossing (Note 6)."
So, that's the apparent cause of the pile-up: the derailed north wheel of axle L1 of Covered Hopper GPLX 75465 hitting the grade crossing structure after the failed bearing on the other (south) end of axle L1 burned off, thereby separating the train line and causing an emergenecy air brake application.
zugmann jeffhergert If you read the report, it states that NS requires a train that gets a warm bearing alarm to start slowing, but not stopping until the train has cleared the detector. Our instructions are about the same. Using air brakes instead of dynamics could possibly cause a false reading on another car. A critical alarm requires stopping as soon as it is received. Even if the train is still on the detector. Non-critical alarms you clear the detector, as the detector won't even tell you specifics until you do.
jeffhergert If you read the report, it states that NS requires a train that gets a warm bearing alarm to start slowing, but not stopping until the train has cleared the detector. Our instructions are about the same. Using air brakes instead of dynamics could possibly cause a false reading on another car.
A critical alarm requires stopping as soon as it is received. Even if the train is still on the detector. Non-critical alarms you clear the detector, as the detector won't even tell you specifics until you do.
Again for us, an immediate stop is only required for a defect tone given by a detector that only checks for dragging equipment. We have been having more dragging equipment only detectors beeing put in service, usually at wayside signals, because of the use of concrete ties. Drag a wheel over one and the tie is considered defective.
Overmod Euclid, the emergency occurred due to the derailment. The thing you want from the event-recorder data in the docket, not the report is the rate of change of the throttle control going into full dynamic.
Euclid, the emergency occurred due to the derailment. The thing you want from the event-recorder data in the docket, not the report is the rate of change of the throttle control going into full dynamic.
While this is not a hot box induced derailment - it is enlightning as to some of the dynamics that happen when cars hit the ground - for whatever the reason from a train moving at track speed.
https://www.youtube.com/watch?v=LYubpuIe3cw
Reading467 Euclid, go back to either the STB Public Hearing Docket or the Final Report Docket, download the Event Recorder file and then you can see what actions were taken by the engineer and the corresponding reactions of the DPU (which was located after the 109th car) both before and after the point of derailment. There are three time frames to examine- the third set has the shortest timeframe and most relevant details
Euclid, go back to either the STB Public Hearing Docket or the Final Report Docket, download the Event Recorder file and then you can see what actions were taken by the engineer and the corresponding reactions of the DPU (which was located after the 109th car) both before and after the point of derailment. There are three time frames to examine- the third set has the shortest timeframe and most relevant details
jeffhergertIf you read the report, it states that NS requires a train that gets a warm bearing alarm to start slowing, but not stopping until the train has cleared the detector. Our instructions are about the same. Using air brakes instead of dynamics could possibly cause a false reading on another car.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
jeffhergert I don't agree with not using air brakes to stop the train after receiving an alarm. The admonishment is to use good train handling procedures. I understand the argument, but anything that changes the train dynamic quickly or harshly would cause the burned off wheelset to come out of alignment and cause the train to derail. Excessive dynamics too quickly will increase buff forces. That could "throw" the wheelset out of line and derail, just as much so as applying the air brakes. Heat generated from using air won't cause a hot bearing to deteriorate faster. Heat from brakeshoes would be at the the wheel's outer edges. A low spot in the tracks or switch frog might cause the alignment to be thrown off just enough. Jeff
I don't agree with not using air brakes to stop the train after receiving an alarm. The admonishment is to use good train handling procedures. I understand the argument, but anything that changes the train dynamic quickly or harshly would cause the burned off wheelset to come out of alignment and cause the train to derail. Excessive dynamics too quickly will increase buff forces. That could "throw" the wheelset out of line and derail, just as much so as applying the air brakes. Heat generated from using air won't cause a hot bearing to deteriorate faster. Heat from brakeshoes would be at the the wheel's outer edges. A low spot in the tracks or switch frog might cause the alignment to be thrown off just enough.
daveklepper After receiving the report from the third detector, the3 engineer nbegan slowingv the vtrain, intending to stop, using only dynamic breaking. Why not blended braking for a faster, non-emergency, service stop? Probably because he cdecided tread braking would heat the wheel even more. Thanks, Overmod, and comment, please?
After receiving the report from the third detector, the3 engineer nbegan slowingv the vtrain, intending to stop, using only dynamic breaking. Why not blended braking for a faster, non-emergency, service stop? Probably because he cdecided tread braking would heat the wheel even more.
Thanks, Overmod, and comment, please?
If you read the report, it states that NS requires a train that gets a warm bearing alarm to start slowing, but not stopping until the train has cleared the detector. Our instructions are about the same. Using air brakes instead of dynamics could possibly cause a false reading on another car.
Our detectors, and others that I've heard over the years, initially don't give what the defect is or it's location. They only do so once has cleared the detector or the train has stopped on the detector. Stopping movement on the detector fools it into thinking the train has cleared it. Then the detector announces type of defect and location(s) in the train.
Most of the time, a detector that checks for hot bearings also checks for other types of defects such as dragging equipment, etc. That's part of the reason a train is allowed to clear the detector. Our dragging equipment only detectors do require an immediate stop if an alarm is given, but doesn't give location until stopped. Knowing where each kind of detector is located is part of knowing one's territory.
Many years ago, when I was a conductor, my train had a bearing burn off. We were going slow through a hand throw crossover after single tracking around a MOW track project. This required going over a detector slow enough that it was giving trains crossing over false alarms. Every train ahead of us got a hot box alarm and had to stop and inspect. They all found nothing. Our turn and we had the same alarm. After clearing the detector and receiving the type of defect and location, we stopped and I got off. The engineer pulled the train ahead. (Yes, as long as it's not a key train, needed excessive power, no dust or smoke seen from back in the train, and now not operating on concrete ties, we can pull the defect location up to the conductor.) I had him stop about 20 axles short so I could start inspecting the 20 axles before the indicated location, which was about half a mile behind the enginees. Using the temp stick, I started checking as I went. When I got to the indicated bearing, it wasn't there. The truck frame was dragging on the ground. When we stopped, the bearing had seized up and stopped rolling, twisting off like a piece of plastic. you could see this on the axle where the bearing had been. They sent the wheel truck out (we were about 20 miles from there was one.) I watched them change out the wheel and then was releived on hours of certain shortly after they were done.
Euclid BaltACD Euc - are you trying to contend that if the engineer had power braked, hard enough to keep the slack stretched throughout the train that there would not have been a multi-car derailment? I would not draw that conclusion because of all the variables. But yes; I do think that method of braking could have prevented the pileup; but not the way it was configured in this incident. In any case, there would not be any "power braking." Power would not be applied as though the objective was keep the train stretched such as when going down a grade. What would act to keep the train stretched in this case would be only the dynamic braking. And also, it would be only dynamic braking of DPU engines; only those behind the car with the hot bearing. They would be decelerating the train in a way that would keep it stretched through the location of the hot bearing. There would also be no dynamic braking ahead of the hot bearing car because that would have the opposite effect of having the train bunched behind the head end, and for some distance toward the hind end. The car with the hot bearing was very close to the head end (I recall about 20 car lengths), so probably would have been in bunched slack if dynamic braking were applied by the head end power. So, no braking at all at the head end. This is far different from the way braking was actually applied upon hearing the detector warning. Most of it was applied to the head end because they had at least two units and they were very near the car with the hot bearing. Even with the head end dynamic braking having the wrong effect, significant motive power using dynamic braking to resist the momentum from behind the hot bearing car, may have been able to offset the bunching coming from the head end; but only if that trailing DPU was near enough to the hot bearing car. As I recall, the DPU first behind hot bearing car (there may have been only one DPU in that location) was quite a long distance back. And it also had the hind end cars behind it, pushing ahead, so unless head end dynamic braking was off, braking this consist from DPU way back in the train may have been futile with the head end dynamic braking bunching the slack near the head end. And also there is this point: If dynamic braking was off at the head end and only applied to DPU behind the hot bearing; I would not conclude that braking from a trailing DPU should be agressive for the purpose of stopping as quickly as possible. I would gamble on trading quickest stopping time for minimizing the dynamic brake tension coming forward from behind the hot bearing car. This gamble would take a little longer to stop the train.
BaltACD Euc - are you trying to contend that if the engineer had power braked, hard enough to keep the slack stretched throughout the train that there would not have been a multi-car derailment?
Euc - are you trying to contend that if the engineer had power braked, hard enough to keep the slack stretched throughout the train that there would not have been a multi-car derailment?
You are so far over your ski's you are out jumping reality and the laws of physics to a crash landing.
nah... nevermind.
BaltACD If you get a Hot Box indiciation from a Defect Detector or from a employee or someone along the right of way - YOU DO NOT USE AIR BRAKES to bring the train to a stop, except as a last resort.
If you get a Hot Box indiciation from a Defect Detector or from a employee or someone along the right of way - YOU DO NOT USE AIR BRAKES to bring the train to a stop, except as a last resort.
Euclid... We are now officially told that the train braking had nothing to do with the derailment. We are told that the train derailed when the failing bearing burned off the axle, and then at the same moment, the burned off axle caused the derailment. All I would like to see is some evidence to back up that assertion. Where is the science?
Had the engineer applied the air brakes, the axle would have rung off once the brake shoe applied pressure to the wheel tread. Tread air brakes require that the axle be 'solid' in order to allow the pressure of the brake shoe to apply the braking force to the tread. Once the brake shoe applies force to the wheel tread, it will then displace the wheel if the axle is no longer strong enough to hold the wheel in its designed position.
BaltACD Euclid ... Also, I think it is fair to say that all burned off axles cause a derailment, but they don’t always cause a pileup. Critical element in whether there is a pile up of one variety or another - what was the speed of the train when the offending car 'hit the ground'.
Euclid ... Also, I think it is fair to say that all burned off axles cause a derailment, but they don’t always cause a pileup.
Critical element in whether there is a pile up of one variety or another - what was the speed of the train when the offending car 'hit the ground'.
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