Jim200 Euclid The key point I would like to know is the derailment speed for that train entering the curve, and whether maximum braking starting upon the engineer's relization of the circumstances, would have prevented the derailment. I would like to know whether the brake application was mostly ineffective, as the engineer has stated, and if so, why? There is a lot of info in the locomotive event recorder graphs in the link below, but it takes time to understand the squiggly lines. Figure 2 shows the trip from Seattle versus time in 50 second increments, and shows that the engineer slowed from 70mph to 30mph in about 60 seconds and accelerated from 0.0mph to 77mph in about 140 seconds. It also shows that the engineer made several 10 psi reductions in brake pipe pressure, but the brake cylinder pressure remained at 0.0 psi. However, the speed shows that the train was braking, which would indicate problems in brake cylinder data. Figure 3 shows that in the last 10 minutes and about 14 miles, the engineer made about 28 changes to the throttle as he was trying to maintain a top speed which varied from 76mph to 83mph with four times below 79mph and seven times above. Figure 4 makes the data in the last 3 miles even easier to read. Near 1.5 miles from the end of data and the locomotive at 80mph, the engineer reduces throttle from T4 to T2 and it takes 7 seconds for the tractive effort to reduce. At 3/4 miles and 81mph the engineer reduces the throttle from T2 to Idle in four seconds, and it takes 8 seconds for the tractive effort to go to zero. Two seconds after Idle with the locomotive at 82mph, the engineer applies about 8 psi reduction in brake pipe, and one second later the brake cylinder pressure rises to 14 psi in 2 seconds. One second later the locomotive hits 83mph for 3 seconds and presumably the alerter sounds. The locomotive is now at 1/2 mile. 12 seconds later the locomotive slows to 80mph, but even with 1/4 mile to go, the engineer does not apparently know where he is. 4 seconds later with a little more than 1/8 mile to go, the engineer recognizes the danger and reduces the brake pipe by an additional 11 psi over 5 seconds and the brake cylinder pressure rises to 48 psi. The locomotive remained at 80mph for about 1.5 seconds, but because the speed is not plotted in 0.1mph increments, it is difficult to determine exactly. The final speed recorded after 6 seconds of increased braking is 78mph. It is doubtful that emergency braking would have saved the day, but maybe somewhere there is data showing this. https://dms.ntsb.gov/public/61000-61499/61332/616699.pdfhttps://dms.ntsb.gov/public/61000-61499/61332/616699.pdf (Apparently the NTSB reorganized their website and this link on the 501 locomotive event recorder doesn't work)
Euclid The key point I would like to know is the derailment speed for that train entering the curve, and whether maximum braking starting upon the engineer's relization of the circumstances, would have prevented the derailment. I would like to know whether the brake application was mostly ineffective, as the engineer has stated, and if so, why?
The key point I would like to know is the derailment speed for that train entering the curve, and whether maximum braking starting upon the engineer's relization of the circumstances, would have prevented the derailment.
I would like to know whether the brake application was mostly ineffective, as the engineer has stated, and if so, why?
There is a lot of info in the locomotive event recorder graphs in the link below, but it takes time to understand the squiggly lines. Figure 2 shows the trip from Seattle versus time in 50 second increments, and shows that the engineer slowed from 70mph to 30mph in about 60 seconds and accelerated from 0.0mph to 77mph in about 140 seconds. It also shows that the engineer made several 10 psi reductions in brake pipe pressure, but the brake cylinder pressure remained at 0.0 psi. However, the speed shows that the train was braking, which would indicate problems in brake cylinder data.
Figure 3 shows that in the last 10 minutes and about 14 miles, the engineer made about 28 changes to the throttle as he was trying to maintain a top speed which varied from 76mph to 83mph with four times below 79mph and seven times above.
Figure 4 makes the data in the last 3 miles even easier to read. Near 1.5 miles from the end of data and the locomotive at 80mph, the engineer reduces throttle from T4 to T2 and it takes 7 seconds for the tractive effort to reduce. At 3/4 miles and 81mph the engineer reduces the throttle from T2 to Idle in four seconds, and it takes 8 seconds for the tractive effort to go to zero. Two seconds after Idle with the locomotive at 82mph, the engineer applies about 8 psi reduction in brake pipe, and one second later the brake cylinder pressure rises to 14 psi in 2 seconds. One second later the locomotive hits 83mph for 3 seconds and presumably the alerter sounds. The locomotive is now at 1/2 mile. 12 seconds later the locomotive slows to 80mph, but even with 1/4 mile to go, the engineer does not apparently know where he is.
4 seconds later with a little more than 1/8 mile to go, the engineer recognizes the danger and reduces the brake pipe by an additional 11 psi over 5 seconds and the brake cylinder pressure rises to 48 psi. The locomotive remained at 80mph for about 1.5 seconds, but because the speed is not plotted in 0.1mph increments, it is difficult to determine exactly. The final speed recorded after 6 seconds of increased braking is 78mph. It is doubtful that emergency braking would have saved the day, but maybe somewhere there is data showing this.
https://dms.ntsb.gov/public/61000-61499/61332/616699.pdfhttps://dms.ntsb.gov/public/61000-61499/61332/616699.pdf
(Apparently the NTSB reorganized their website and this link on the 501 locomotive event recorder doesn't work)
The lack of pressure indicated in the brake cylinder in the event recorder would indicate to me that the engineer actuated "bailed off" the independent brake in the earlier brake applications. That he did not do this in the final brake applications before the incident.
Not a problem in the recorder data.
Jeff
jeffhergert Jim200 Euclid The key point I would like to know is the derailment speed for that train entering the curve, and whether maximum braking starting upon the engineer's relization of the circumstances, would have prevented the derailment. I would like to know whether the brake application was mostly ineffective, as the engineer has stated, and if so, why? There is a lot of info in the locomotive event recorder graphs in the link below, but it takes time to understand the squiggly lines. Figure 2 shows the trip from Seattle versus time in 50 second increments, and shows that the engineer slowed from 70mph to 30mph in about 60 seconds and accelerated from 0.0mph to 77mph in about 140 seconds. It also shows that the engineer made several 10 psi reductions in brake pipe pressure, but the brake cylinder pressure remained at 0.0 psi. However, the speed shows that the train was braking, which would indicate problems in brake cylinder data. https://dms.ntsb.gov/public/61000-61499/61332/616699.pdfhttps://dms.ntsb.gov/public/61000-61499/61332/616699.pdf (Apparently the NTSB reorganized their website and this link on the 501 locomotive event recorder doesn't work) The lack of pressure indicated in the brake cylinder in the event recorder would indicate to me that the engineer actuated "bailed off" the independent brake in the earlier brake applications. That he did not do this in the final brake applications before the incident. Not a problem in the recorder data. Jeff
Jim200 Euclid The key point I would like to know is the derailment speed for that train entering the curve, and whether maximum braking starting upon the engineer's relization of the circumstances, would have prevented the derailment. I would like to know whether the brake application was mostly ineffective, as the engineer has stated, and if so, why? There is a lot of info in the locomotive event recorder graphs in the link below, but it takes time to understand the squiggly lines. Figure 2 shows the trip from Seattle versus time in 50 second increments, and shows that the engineer slowed from 70mph to 30mph in about 60 seconds and accelerated from 0.0mph to 77mph in about 140 seconds. It also shows that the engineer made several 10 psi reductions in brake pipe pressure, but the brake cylinder pressure remained at 0.0 psi. However, the speed shows that the train was braking, which would indicate problems in brake cylinder data. https://dms.ntsb.gov/public/61000-61499/61332/616699.pdfhttps://dms.ntsb.gov/public/61000-61499/61332/616699.pdf (Apparently the NTSB reorganized their website and this link on the 501 locomotive event recorder doesn't work)
As I understand it, it was the final application when the engineer became aware of the curve just ahead; that the he says did not take hold. He said he chose a service application at that point rather than an emergency application because he said that he had been taught by Amtrak that the service application would stop the train just as quickly as the emergency application, and that Amtrak preferred the use of the service applcation for such an emergency. And then the engineer also stated that he was surprised by the fact that his service application did not feel like it was taking hold.
I assume that the data showing sevice applications resulting in no cylinder pressure (highlited in blue) is from earlier in the trip and not the case with the final brake application before derailing.
SD70Dude 243129 Damn phone!!#%÷×+\% In the interest of proper training: How to quote Now you are qualified!
243129 Damn phone!!#%÷×+\%
Damn phone!!#%÷×+\%
In the interest of proper training:
How to quote
Now you are qualified!
Thank you for your 'tech support'.
"he said that he had been taught by Amtrak that the service application would stop the train just as quickly as the emergency application. "
That is absolutely untrue!!
243129 "he said that he had been taught by Amtrak that the service application would stop the train just as quickly as the emergency application. " That is absolutely untrue!!
So, is there some other possible reason why Amtrak would hold the erroneous beleif? Is it possible that they see some downside to an emergency application, and would prefer not to use it? I think that may be possible. I am not saying that they would be correct in that position, but I think it is possible that they have convinced themsleves that the emergency application should be avoided. Of course this all assumes that the engineer was accuately describing what Amtrak had told him about the service application being equivalent to the emergency application.
Euclid 243129 "he said that he had been taught by Amtrak that the service application would stop the train just as quickly as the emergency application. " That is absolutely untrue!! I am assuming that you mean what is untrue is the claim said to have been made by Amtrak that the service application would stop just as quickly as the emergency application. If that is so, why do you think Amtrak would make such a claim? They may hold that as an erroneous belief, but it seems so basic to understand that there is a reason for the emergency application being available. The reason is the occurrance of an emergency. If the service application could get the job done as well as the emergency application, why have the emergency application function available? So, is there some other possible reason why Amtrak would hold the erroneous beleif? Is it possible that they see some downside to an emergency application, and would prefer not to use it? I think that may be possible. I am not saying that they would be correct in that position, but I think it is possible that they have convinced themsleves that the emergency application should be avoided. Of course this all assumes that the engineer was accuately describing what Amtrak had told him about the service application being equivalent to the emergency application.
I am assuming that you mean what is untrue is the claim said to have been made by Amtrak that the service application would stop just as quickly as the emergency application. If that is so, why do you think Amtrak would make such a claim? They may hold that as an erroneous belief, but it seems so basic to understand that there is a reason for the emergency application being available. The reason is the occurrance of an emergency. If the service application could get the job done as well as the emergency application, why have the emergency application function available?
You assume correctly and if that is true Amtrak should be held criminally responsible.
EuclidHe said he chose a service application at that point rather than an emergency application because he said that he had been taught by Amtrak that the service application would stop the train just as quickly as the emergency application, and that Amtrak preferred the use of the service applcation for such an emergency.
I already posted the air brake requirements frm the PRIIA 305-005 specification about 10 pages back:
Full-service, air only for a single locomotive from 125 mph, the stopping distance shall be no more than 9,000 ftEmergency, air only for a single locomotive from 125 mph, the stopping distance shall be no more than 8,000 ft
And: Pneumatic priority shall be given in emergency and dynamic priority in service rate applications (blended braking)
That translates to brake decelerations of 1.27 mph/sec for full service and 1.43 mph/sec for emergency application, air only.
The Talgo Series 8 cars have brake decelerations of 2.3 mph/sec in full service and 2.7 mph/sec in emergency. See page 32:
www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf
I can only see on paper that the difference between full-service and emergency brake deceleration is much smaller than I expected. How blended braking fits into the picture I don't know.
What influence this has on train behavior under different brake application others I ask others to evaluate.Regards, Volker
Volker,
I do recall you posting that information a while back. I am convinced that the emergency application is typically faster, but Amtrak’s alleged statement to the contrary makes me at least wonder if there could be an exception for certain trains. I doubt that there is, and I also believe that Amtrak may have never told the engineer of 501 that the two braking application will produce the same effect. But also, as I mentioned earlier, I think anyone might find reasons to have preferred to use a service application instead of the emergency application when faced with what would constitute an emergency situation. We have had discussions about that point before in the General forum.
Maybe this will all come out in the NTSB report, but I am just framing questions at this point. So I ask what the difference is in stopping distance for two different brake applications with the locomotives and rolling stock that made up #501.
Here is another question: I understand that the service application takes more time to propagate throughout the train, whereas, the emergency application propagates faster because each car dumps its share of the brake pipe charge. But with each of the two applications, what is the maximum amount of brake cylinder pressure that results?
I looked at page 32 in the link on Talgo equipment where it gives braking deceleration. I assume this is with maximum application to an individual car brake. When applying this information to a whole train, would there not also be an additional time advantage for the emergency application due to its quicker setup from car to car throughout the train?
" When applying this information to a whole train, would there not also be an additional time advantage for the emergency application due to its quicker setup from car to car throughout the train? "
Absolutely.
I reposted the decelerations trying to base the discussion, why the engineer said/concluded full service and emergency application have the same effect, on some data.
The Talgo Series 8 differs from other trains that it is quite short, 672 ft without locomotive, and has disk brakes on all wheels but not unusual for passenger cars.
I found information about brake propagation rates in two different sources.
- Service application: 50 ft in 0.1 sec = 500 ft sec- Emergency application: 950 ft/ sec (from NTSB report)
How true I don't know.
I think the Talgo brake data are correct for all brakes applied only.Regards, Volker
I don't have access to any notes or substantive material, but I recall that Amtrak's blended braking (dynamic + service) is specifically intended to produce 'net' deceleration equal to emergency air-only. (Isn't that mentioned in the P42 orientation?) That would account for the muddled perception that 'service is equal to emergency'. (Note also that for ECP braking the difference between full-service and emergency can be very small, even on long freight consists about 3%, since ECP actuates all the valves virtually simultaneously and actuation time is relatively short)
A question that arises is whether blended braking in a consist like 501's involves a dynamic contribution from both units or only the lead.
From personal observations over the years -
Those in trouble tend to generate some kind of narrative that is intended to minimize their culpability in the incident. Stating that service and emergency apply the same level of braking power is consistant with such a fantasy narrative.
Never too old to have a happy childhood!
The big difference with ECP is stopping distance between ECP and conventional air braking with ECP showing a profound advantage in shortening that stopping distance--but-- that is only with a service application used in the comparison of the two braking systems. With an emergency application, the ECP advantage is very small.
So the claim that ECP offers a great advantage is, in my opinion, disingenuous since it is precisely the emergency application where stopping distance is the most important. And there, the ECP advantage is negigible.
There is an APTA Recommended Practice 13. APTA PR-E-RP-014-99: Recommended Practice for Diesel Electric Passenger Locomotive Blended Brake Controlhttps://www.apta.com/resources/standards/Documents/APTA-PR-E-RP-014-99.pdf
The paper recommends a substitutional type of system where the maximum blended braking force equals that of the friction only system.
A second system is supplemental were the blended braking power exceeds the friction only system. A supplemental type system should be used only to meet unusual railroad physical characteristics.
The APTA RP is part of the PRIIA 305-005 specification.
So the question remains how much difference remains between full service and emergency application.
With the above probagation rates it is 1.4 sec (full service) to 0.7 sec (emergency)
Regards, Volker
What is the maximum level of friction that the wheel-rail interface will support without sliding? Is that friction level different in braking or in traction?
On a freight train I would say the traction friction is higher because of the locomotives wheel-slip control.
In the case of Amtrak #501 I'm undetermined. The Talgo Series 8 trainset has disk brakes with wheel-slide protection and anti-slide systems.
I assume that the Talgo train can provide enough friction to attain the brake decelerations of 2.3 mph/sec and 2.7 mph/sec.Regards, Volker
Edit: Another plus for passenger cars is the small difference between loaded and empty on passenger cars.
VOLKER LANDWEHRThe Talgo Series 8 cars have brake decelerations of 2.3 mph/sec in full service and 2.7 mph/sec in emergency. See page 32: www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf
See page 32: www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf
Why is the rate of deceleration higher with the emergency application than with the service application?
Perhaps because it was required?
When you look a few posts up you find the requirement for the Charger (air-only).
9,000 ft braking distance in full service (1.27 mph/sec) and 8,000 ft in emergency (1.43 mph/sec)Regards, Volker
Euclid VOLKER LANDWEHR The Talgo Series 8 cars have brake decelerations of 2.3 mph/sec in full service and 2.7 mph/sec in emergency. See page 32: www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf Why is the rate of deceleration higher with the emergency application than with the service application?
VOLKER LANDWEHR The Talgo Series 8 cars have brake decelerations of 2.3 mph/sec in full service and 2.7 mph/sec in emergency. See page 32: www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf
Because the air is totally and completely 'dumped' as opposed to gradually reduced with a service application.
Air brake 101.
243129 Euclid VOLKER LANDWEHR The Talgo Series 8 cars have brake decelerations of 2.3 mph/sec in full service and 2.7 mph/sec in emergency. See page 32: www.whsra.com/sites/all/files/Shannond/20111103%20Talgo-Western%20High%20Speed%20Rail%20Alliance.pdf Why is the rate of deceleration higher with the emergency application than with the service application? Because the air is totally and completely 'dumped' as opposssed to gradually reduced with a service application. Air brake 101.
Because the air is totally and completely 'dumped' as opposssed to gradually reduced with a service application.
I understand that, but here is why I ask: The specifications give a rate of deceleration for the Talgo equipment during braking with an emergency application and braking with a service application. The rate of deceleration is expressed in mph per second. I assumed that this was simply the rate of deceleration with full brake cylinder pressure developed. That would be the entire expression of the measure.
And if this were the case, the expression of deceleration would be with the brake fully applied to one or more cars. If this is how the specification is measured, the difference in the speed of propagation between a service application and an emergency application would be irrelevant. Of course, in a practical sense the speed of propagation is relevant because it takes more time for a service application to propagate through a long train than it does for an emergency application.
But if you are measuring just the deceleration of car braking in mph per second, the effect of application propagation would be set aside. If it were not set aside, then you would have to qualify the measure by including the length of the train; and the total stopping distance. I don’t see that in the specification of mph per second.
This is why I earlier asked what the maximum brake cylinder pressure is for a service application and an emergency application. If the pressure is the same for both applications and if we are just measuring deceleration aside from the effect of propagation time; then the rate of deceleration should be the same for both applications. That is why I asked why they differ.
Here is an interesting read about freight train brake: https://www.quora.com/How-do-trains-stop
Quote: ......One factor to take into consideration is that the auxiliary reservoir on each car is 2500 cubic inches in volume. The brake cylinder on the other hand is only 1000 cubic inches in volume. This result is a 2.5:1 ratio in air pressure between the reservoir and the cylinder................The emergency reservoir, which we have not discussed until now is larger than the aux reservoir, boasting 3500 cubic inches, giving it a 3.5:1 ratio to the brake cylinder.................
A gush of air is sent through the train causing a chain reaction that moves at 930 feet per second rather than the service rate of 540 feet per second. Additionally, 77 lbs of force is exerted on each brake cylinder rather than the max service application of 64lbs..................
I think passenger cars will be equipped similarly.
Yes it is air brake 101 but not what Joe tried to explain.Regards, Volker
I understand what Joe explained about the difference between the speed of application of an emergency application and a service application. As my above comment indicates, what I don't understand is the specification for braking deceleration for the Talgo equipment for the emergency and service applications.
It seems to lack some details, or it is stated as an industry standard expression, and the missing qualifiers are part of that industry standard and therefore not stated.
These missing qualifiers would be the weight and speed of the train, the speed of brake propagation in the application process, the maximum cylinder pressure, the propagation of that cylinder pressure, and the total stopping time from start of application to stopping. Maybe some of that is left out to get to the pure brake deceleration rating. We don't know. But, in any case, just the factor of train speed alone raises the question of how one can give the rating as just one rate of deceleration, because the rate of deceleration would increase as the speed drops. It would not be a constant. So perhaps the rate expressed is the average of some overall set of test conditions that are not stated.
What I want to know is how many feet it would take to stop from an application at 80 mph for each type of application.
VOLKER LANDWEHR Yes it is air brake 101 but not what Joe tried to explain.
Yes it is air brake 101 but not what Joe tried to explain.
"Because the air is totally and completely 'dumped' as opposed to gradually reduced with a service application."
"tried to explain" ??? What was not clear in my statement?
243129"Because the air is totally and completely 'dumped' as opposed to gradually reduced with a service application." "tried to explain" ??? What was not clear in my statement?
You explained it perfectly in the most fundamental terms. But my question was asked in repsonse to the brake deceleration specification for the Talgo equipment which I quoted from Volker's comment offering that specification. It is the specification that is unclear to me. I don't know that it includes the effect of dumping the trainline directly from each car versus exhausting it from a single point (or multiple points from DPU).
So when I asked why the rate of deceleration was faster with an emergency applicaiton, I was not referring to an airbrake 101 question. I was asking a question about the terms of the Talgo specification.
243129 VOLKER LANDWEHR Yes it is air brake 101 but not what Joe tried to explain. "Because the air is totally and completely 'dumped' as opposed to gradually reduced with a service application." "tried to explain" ??? What was not clear in my statement?
Because it doesn't answer the question "why is the brake acceleration higher in emergency than full service". The answer: The emergency reservoir is larger than the auxilliary reservoir leading to a higher ratio emergency reservoir/Brake cylinder volume and higher pressure in the brake cylinder.
The question was not "why do the brakes apply faster in emergency".
The emergency braking seems to be a two part story: Faster propagation rate and higher deceleration because higher brake cylinder pressure.
I know that passenger train brakes are different with e.g. higher pressures etc. So I can't say if the same mechanism is followed but the only way to increase brake power and deceleration on equipment with only wheel brakes is increasing the preasure in the brake cylinders, I think.Regards, Volker
EuclidWhat I want to know is how many feet it would take to stop from an application at 80 mph for each type of application.
I think that can't be calculated from the Talgo specs. We don't know the brake decelerations at 80 mph. The given data seems to be the absolute maximum and is not constant over the speed range.
We know the propagation rates (about 540 ft/sec and 930 ft/sec) but we don't know the time from trigerring the car brake until the brakes are fully applied.
Perhaps a quote from the PRIIA Bilevel Passenger Rail Car, Chapter 7 Brakes specs gives some more information though it doesn't make it easier:
A train consisting of five bi-level cars built to this specification (in any combination of car types) and one F59 locomotive (or equivalent) shall have a minimum full service braking rate of 1.35miles per hour per second (mphps) at 125 mph increasing to and maintaining an average of 2.00 mphps at speeds of 70 mph or less.
The instantaneous full service deceleration rate shall not exceed 2.75 mphps nor be less than 1.25 mphps.
The emergency brake rate shall not be less than 2.50 mphps at speeds below 70 mph.
The cars shall be loaded to AW2 condition.The Contractor shall verify that the brakes are fully functional under all operating and environmental conditions found in PRIIA Specification 305-912. Locomotive dynamic braking shall not be used to determine compliance with specified brake rates.
"Why is the rate of deceleration higher with the emergency application than with the service application?"
This is the question I answered.
243129 "Why is the rate of deceleration higher with the emergency application than with the service application?" This is the question I answered.
In my opinion you answered a different question.
The Talgo's emergency application deceleration rate is not higher than full service (2.7 mph/sec vs. 2.3 mph/sec) because of the dumped air but because the brake cylinder pressure and therefore the brake force is higher.
Euclid didn't ask for the propagation rate difference (E. 930 ft/sec vs FS 540 ft/sec), the question you answered.regards, Volker
The above quote shows my question in response to Volker posting the deleration rates above my question. In my question, when I said, "Why is the rate of deceleration higher...", I meant why is it higher in the Talgo specification. I did not mean why is it higher in general airbrake performance principles.
The Talgo specification starts with braking fully in effect, so it does not include the effect of propagation. That being the case, I would assume the deceleration is greater for the Talgo emergency application (once fully applied) due to there being greater pressure in the brake cylinder during an emergcy application as opposed to a maximum service application.
Questions about the braking not apparent
1. If a SC-44 goes into emergency does that sutomatically activate loco sanding ?
2. Are the Talgos ECP and especially with full service and emergency ?
3. Dis the P-42 trailing mirror the SC-44 electronically emergency and sanding ?
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