jeaton Getting a signal to the valve is only part of the system. The valves are operated by electricity. I don't think there is any practical method of getting the required power to the valves other than via wire cable.
Getting a signal to the valve is only part of the system. The valves are operated by electricity. I don't think there is any practical method of getting the required power to the valves other than via wire cable.
Thanks, I forgot about the the power. Batteries would be silly.
Railway Man jchnhtfd The only question I have about it -- and I'm sure the railroads have thought of this! -- is what happens if the system (by which I mean the whole system -- especially including signalling and dispatching) becomes set up with using the vastly improved stopping capabilities of trains with ECP brakes -- and something goes wrong with the electrics. I assume that the normal air brakes would still work (dump the air and the brakes apply, just as they always have) but if the engineer is expecting the better braking from the ECP, and it turns up missing, what happens? Or, if the ECP system senses (maybe through an upgraded FRED) that it has failed -- that the signal isn't getting through -- does it make a warning? Does it apply the brakes like 'old fashioned' air? Or... ? Otherwise, I can see a whole raft of advantages to it! It fail-safes to plain-old air braking. The ECP is an overlay system, not a stand-alone system, as you surmised. You cannot respace signals or adjust block limits for ECP braking unless everything is equipped with ECP braking and the ECP system becomes stand-alone. However, if this never happens, it's not that big a deal. The touted benefits of tighter signal spacing (as well as the floating block potential touted as a benefit of PTC), are almost impossible to realize in practice on a Class 1-style railway unless one's railway just happens to be a 1,000-mile-long, 251-style, double-track railroad, with no work events, crew changes, maintenance events, or crossover events, and identical trainsets with identical power. In other words, a railroad that looks like the Washington Metro but much longer. Even if one could figure out a way to make every train ECP and always brake on an ECP-type curve, and figure out how to dispatch it to take advantage of the reduced block lengths -- which I am unconvinced is possible -- in practice the net time savings is unlikely to be economically significant versus other expenditures that could be made. ECP does have a substantial economic benefit for increasing train length, train tonnage, and fuel economy, and that's a pretty good thing. I never worry too much about picking the last apple on the tree when I can fill my bushel baskets with everything in easy reach. RWM
jchnhtfd The only question I have about it -- and I'm sure the railroads have thought of this! -- is what happens if the system (by which I mean the whole system -- especially including signalling and dispatching) becomes set up with using the vastly improved stopping capabilities of trains with ECP brakes -- and something goes wrong with the electrics. I assume that the normal air brakes would still work (dump the air and the brakes apply, just as they always have) but if the engineer is expecting the better braking from the ECP, and it turns up missing, what happens? Or, if the ECP system senses (maybe through an upgraded FRED) that it has failed -- that the signal isn't getting through -- does it make a warning? Does it apply the brakes like 'old fashioned' air? Or... ? Otherwise, I can see a whole raft of advantages to it!
The only question I have about it -- and I'm sure the railroads have thought of this! -- is what happens if the system (by which I mean the whole system -- especially including signalling and dispatching) becomes set up with using the vastly improved stopping capabilities of trains with ECP brakes -- and something goes wrong with the electrics. I assume that the normal air brakes would still work (dump the air and the brakes apply, just as they always have) but if the engineer is expecting the better braking from the ECP, and it turns up missing, what happens? Or, if the ECP system senses (maybe through an upgraded FRED) that it has failed -- that the signal isn't getting through -- does it make a warning? Does it apply the brakes like 'old fashioned' air? Or... ? Otherwise, I can see a whole raft of advantages to it!
It fail-safes to plain-old air braking. The ECP is an overlay system, not a stand-alone system, as you surmised.
You cannot respace signals or adjust block limits for ECP braking unless everything is equipped with ECP braking and the ECP system becomes stand-alone. However, if this never happens, it's not that big a deal. The touted benefits of tighter signal spacing (as well as the floating block potential touted as a benefit of PTC), are almost impossible to realize in practice on a Class 1-style railway unless one's railway just happens to be a 1,000-mile-long, 251-style, double-track railroad, with no work events, crew changes, maintenance events, or crossover events, and identical trainsets with identical power. In other words, a railroad that looks like the Washington Metro but much longer. Even if one could figure out a way to make every train ECP and always brake on an ECP-type curve, and figure out how to dispatch it to take advantage of the reduced block lengths -- which I am unconvinced is possible -- in practice the net time savings is unlikely to be economically significant versus other expenditures that could be made. ECP does have a substantial economic benefit for increasing train length, train tonnage, and fuel economy, and that's a pretty good thing. I never worry too much about picking the last apple on the tree when I can fill my bushel baskets with everything in easy reach.
RWM
Falcon48 ECP isn't necessarily an overlay system. As it is implemented, it is likely to be deployoed as a "stand alone" system on cars used exclusively in dedicated train service (I believe this is what NS is doing in its intial installation), but as an "overlay"system on cars which are freely interchanged. Eventually, as the car fleet is fully equipped, the "overlay" feature won't be necessary (that is, assuming the system works reliably), but that probably won't happen in our lifetimes.
ECP isn't necessarily an overlay system. As it is implemented, it is likely to be deployoed as a "stand alone" system on cars used exclusively in dedicated train service (I believe this is what NS is doing in its intial installation), but as an "overlay"system on cars which are freely interchanged. Eventually, as the car fleet is fully equipped, the "overlay" feature won't be necessary (that is, assuming the system works reliably), but that probably won't happen in our lifetimes.
You and beauleiu are correct, I'm out of date on this.
By the way, I was able to witness some ECP tests at Wabtec, I was there for another reason (I'm not a mechanical person any longer) and got to drop in -- it's impressive as heck to witness 150 brake valves apply all at once.
I had not considered the need for electric power transmission when I was considering a wireless alternative to the car-to-car connectors. However, I found the following reference in this: http://www.tsd.org/ecpbrake.html
From the link: “Two alternatives are under consideration for the signaling means that will be adopted as the interoperable standard for the 'physical layer' (a) wireless and (b) trainline.”
Perhaps this is obsolete information at this point, but if the wireless alternative were implemented, it would seem that an electric cable would be used only for power and the control function would be wireless.
In looking at the Booz/Allen/Hamilton FRA final report, I see that they show an electric cable with car-to-car connectors as separate from the air hoses. They do not go into any detail on the electrical connectors, nor how they are operated for connecting and disconnecting.
I suppose that if there is a problem with the reliability of the connectors, it would emerge over time with repeated disconnecting and reconnecting. And being that the initial application of ECP is to dedicated consists, the connector weakness may not be so apparent because they are not being repeatedly connected and disconnected.
We had the same probelms roughly in the OTR industry in the llate 90's all trucks built after April 1,1997 had to have ABS on them however it was April 1 1998 before the TRAILERS had to have it on them per the DOT and FMCSA. So for over a year you had brand new trucks with ABS dragging around trailers without it and let me tell you stopping in the mountains in a snow storm was FUN. What the FRA is going to have to do to battle the Connector issue is say hey the OTR industry has used this 7 pin connector for 60 years and they have it also has multiplexing capablities now since 2003 any trailer ABS faults have to appear on the Dashboard of the truck pulling the trailer. Plus they are easy to DC at the end handle rough handling if you forget to unhook them they will pull apart without any damage and a easy to reapir and replace in the field.
BucyrusI had not considered the need for electric power transmission when I was considering a wireless alternative to the car-to-car connectors. However, I found the following reference in this: http://www.tsd.org/ecpbrake.html From the link: “Two alternatives are under consideration for the signaling means that will be adopted as the interoperable standard for the 'physical layer' (a) wireless and (b) trainline.” Perhaps this is obsolete information at this point, but if the wireless alternative were implemented, it would seem that an electric cable would be used only for power and the control function would be wireless. In looking at the Booz/Allen/Hamilton FRA final report, I see that they show an electric cable with car-to-car connectors as separate from the air hoses. They do not go into any detail on the electrical connectors, nor how they are operated for connecting and disconnecting. I suppose that if there is a problem with the reliability of the connectors, it would emerge over time with repeated disconnecting and reconnecting. And being that the initial application of ECP is to dedicated consists, the connector weakness may not be so apparent because they are not being repeatedly connected and disconnected.
An electric cable may not be necessary with wireless control. There are several ways that power could be generated on the car, the simplest being an axle driven generator. A slightly more exotic approach would be the work being done at MIT using electric dampers to replace shock abosrbers, instead of heating the oil in the shocks, the dampers generate electricity.
The downside is that the technology does not exist for RR freight cars and thus would have to be developed and tested for several years. The upside is that the wireless system might be functional with some non-equipped cars in the mix.
erikemAn electric cable may not be necessary with wireless control. There are several ways that power could be generated on the car, the simplest being an axle driven generator. A slightly more exotic approach would be the work being done at MIT using electric dampers to replace shock abosrbers, instead of heating the oil in the shocks, the dampers generate electricity.The downside is that the technology does not exist for RR freight cars and thus would have to be developed and tested for several years. The upside is that the wireless system might be functional with some non-equipped cars in the mix.
Wireless communication of real-time status from each car's braking system to a processor integrated with the controlling locomotive, and bullet-proof, no maintenance, self-contained power supply? This would be extremely attractive from an operating department, network-capacity point of view.
It's kind of late so do not expect this to have decent cohesiveness
1. brake shoe dust(Metalic) real bad for any kind of electrical connectors. hot & corrosive. (ever see the end of a box car a container or a truck trailer used in tofc service. you will see to orange/brown streaks on the end). That metalic dust is real nasty on electrical connectors in addition it does all kinds of nasty things to data signals.power needed. Solution put a solar panel on roof of car.electrical cable/ air brake microwave.
an electrical cable suffers from the above. using the air line for a microwave guide presupposes that all the brake hoses will be converted to a design that can be used as waveguide.(brake hoses are made of rubber or rubber like compounds. rubber by itself can not be used as wave guide(like using a open window to keep flies out). to do this you would need to have a hose that is more like a a steel pipe.
from the document.I like sound of the other things you can do if you have a data signal. I didn't think about that. You would be able to send all kinds of data back and forth from cars as a car in the consist (of a train) could call for help if it was having trouble.(burglar alarm) The possibilities are endless.
I'll try to get back to re edit this later, when I am a little more awake.
Rgds IGN
Solar panels in a railroad environment are high-maintenance, high-theft, unreliable, items. They get dirty quickly in a dusty environment or when exposed to diesel exhaust (like a train!). You can imagine how much sunlight they will actually "see" after a trip through a tunnel district. They're unsuitable for anything that's supposed to be fail-safe. Many railroads are removing them and going back to good 'ol utility power on a pole for wayside signal and grade-crossing signal applications. Often the "removal process" is accelerated by your local helpful thieves. They're OK for things like ballast cars that by definition have a lot of manpower attached to their use on an everyday basis, and aren't expected to wander around the countryside on their own for years on end like the typical freight car does, or in yards that are secure.
I would think that the generators on every car would be a nightmare for the mechanical department. It means more parts that will eventually break. It seems like that would cause cars to be bad ordered more often.
"No soup for you!" - Yev Kassem (from Seinfeld)
Not that I know how it would be done, wouldn't the best approach to be to harden the connector to the effects of environmental damage? Everthing will get dirty, but some metals are corrosion resistant. (Gold comes to mind, but last I heard, railroads don't own any active gold mines.) I wouldn't expect to see 100% reliability, even conventional air lines fail from time to time.
"We have met the enemy and he is us." Pogo Possum "We have met the anemone... and he is Russ." Bucky Katt "Prediction is very difficult, especially if it's about the future." Niels Bohr, Nobel laureate in physics
Jeaton have you even looked at what I have written. The OTR industry has been using the same 7 pin pigtail connector for 70 years to power the trailer lights. It now provides the power for the ABS system and others it has to deal with Ice Snow Grease from 5th wheels and drivelines hitting the ground if the driver forgets to stow it getting wrapped around drivelines and such. Yet it functions at as close to 100% reliebilty as you can get. In all the time I drove OTR the only problem I ever had with one was when it would not get a good ground solved that by a shot of WD-40 every time. Also easy to connect and the connectors are RObust at each end and standardized. I had to bring a trailer that was kept at a customers in for roof repairs sucker was built in the 50's and truck was a 90 model guess what I had no problem hooking up to it. Also the box that the cable hooks into is weather proof and sealed so no corrison issues inside and the pins are corrison resistant already. Called take an Idea from teh OTR truckers for once OK they use this standard part on all trailers might be what the RR industry needs to get ECP off the test track an into regular service.
Ed-I did see your post. Question though, are those plugs hardy enough that they can be routinely pulled apart any time the trailer is dropped just by pulling the tractor away or is the disconnect done manually?
For loose car (mixed) freight trains, the glad hand design of the air hoses allow an automatic disconnect when the cars are separated. If I understand the system, the electric brake cables are also built to pull apart in the same manner.
edbentonJeaton have you even looked at what I have written. The OTR industry has been using the same 7 pin pigtail connector for 70 years to power the trailer lights. It now provides the power for the ABS system and others it has to deal with Ice Snow Grease from 5th wheels and drivelines hitting the ground if the driver forgets to stow it getting wrapped around drivelines and such. Yet it functions at as close to 100% reliebilty as you can get. In all the time I drove OTR the only problem I ever had with one was when it would not get a good ground solved that by a shot of WD-40 every time. Also easy to connect and the connectors are RObust at each end and standardized. I had to bring a trailer that was kept at a customers in for roof repairs sucker was built in the 50's and truck was a 90 model guess what I had no problem hooking up to it. Also the box that the cable hooks into is weather proof and sealed so no corrison issues inside and the pins are corrison resistant already. Called take an Idea from teh OTR truckers for once OK they use this standard part on all trailers might be what the RR industry needs to get ECP off the test track an into regular service.
The ECP electrical systems share designs, materials, systems, and ideas with truck braking electrical systems. It's the same manufacturers with the same suppliers.
From what I can find, it seems clear that the connectors have had issues with reliability. It is unclear to me whether those issues have been resolved. The initial development effort has been concentrated on a system that works. Ultimately, that system has to be made practical and reliable enough to withstand day-to-day operation on loose car freight trains. It would be interesting to learn how much of that phase is completed. I would not be surprised if very little of it has been completed.
When I look at the mechanical design of freight car components such as couplers, air brake equipment, trucks, and handbrakes, I see a kind of robustness and simple elegance that meets the challenge of reliability in an environment of extreme heat and cold, ice, rain, snow, mineral and metal dust, chemical corrosion, vibration, shock, and neglect. The component designs able to meet these challenges have been perfected over more than a century of trial and error. The solutions were not obvious at the onset. Once nuts and bolts seemed like the logical way to fasten freight car trucks together. But nuts and bolts could never be kept tight, so they designed trucks that don’t need nuts and bolts to hold them together.
In these early stages of ECP, the most daunting prospect is the conversion of the whole fleet. But the sudden introduction of complex electro-mechanical-pneumatic systems that can meet the rugged reliability challenge posed by freight cars may be yet to emerge as a daunting prospect in its own right.
Here is an explanation of the connectors and how they work:
http://findarticles.com/p/articles/mi_m0BQQ/is_4_48/ai_n25337860/pg_1?tag=content;col1
From the link:
“The physical wagon-to-wagon wireline connection was standardised a few years ago by the Association of American Railroads (MR). It uses a connector similar in operation and appearance to the traditional end-of-wagon air brake hose "gladhand" connector. During uncoupling, the electrical connectors separate by themselves along with the brake hoses. During train formation, they are connected by a brakeman in much the same fashion as the air hoses, with a negligible increase in the time required to make two connections, rather than a single one.”
Q. Does the ECP system have a feature that will drain the reservoirs?
Speaking of features, a key one that intrigues me is the ability to make a graduated release. It seems that would make it easier to control speeds on a down grade to keep a train right at the allowed speed. I suspect a good engineer who knows the terrritory is able to set conventional brakes to stay close to the speed limit and not go over, but safety would suggest a little too much brake rather than not enough. If I have it right, the feature would also eliminate the need to set up retarders, but I don't know if that is now done very often.
From a dispatch point, wouldn't the graduated release make stopping a train heading down grade on a passing siding safe in almost any circumstances?
Not that operations will become all that much more fluid, maybe except in mountain territory.
jeatonQ. Does the ECP system have a feature that will drain the reservoirs?
I can see how all-or-nothing release can hasten running out of air, and graduated release would therefore make running out of air less likely. But is there any type of control or sensing with an ECP system that could absolutly fail-safe prevent running out of air while moving?
jeatonQ. Does the ECP system have a feature that will drain the reservoirs? Speaking of features, a key one that intrigues me is the ability to make a graduated release. It seems that would make it easier to control speeds on a down grade to keep a train right at the allowed speed. I suspect a good engineer who knows the terrritory is able to set conventional brakes to stay close to the speed limit and not go over, but safety would suggest a little too much brake rather than not enough. If I have it right, the feature would also eliminate the need to set up retarders, but I don't know if that is now done very often. From a dispatch point, wouldn't the graduated release make stopping a train heading down grade on a passing siding safe in almost any circumstances? Not that operations will become all that much more fluid, maybe except in mountain territory.
Jay, only the air-brake and train-handling people could answer that one. I sure can't.
As you know there are three secret languages inside the railway: air-brake, operating rules, and signaling, each with their own high priests (Road Foremen of Engines and Master Mechanics, Chief Dispatchers and Rules Examiners, and Signal Engineers and Maintainers, respectively), temples, and vile initiation rites. I have the secret Train Dispatcher handshake and decoder ring, and the signal people indulge me as long as I sit in the back row, don't talk too much, and sound appropriately respectful, but I'm not even allowed into the foyer of the RFE/MM temple. Randy Stahl has got some pull there, I think.
This page has an incredible amount of very well written, understandable information on the functions of railroad air brakes:
http://www.railway-technical.com/brake2.shtml
The third paragraph down called Successive Applications describes running out of air from too many sets and releases in too short of a time. It also includes the classic colorful body function name for this predicament.
Bucyrus This page has an incredible amount of very well written, understandable information on the functions of railroad air brakes: http://www.railway-technical.com/brake2.shtml The third paragraph down called Successive Applications describes running out of air from too many sets and releases in too short of a time. It also includes the classic colorful body function name for this predicament.
I assume it would be possible to run out of air, at least of sufficient pressure to be effective, but it is less of a problem with ECP brakes. ECP continues to charge the brake line and provide air to the reservoirs when the brakes are set. Not so with standard air brakes.
Railway Man jeaton Q. Does the ECP system have a feature that will drain the reservoirs? Speaking of features, a key one that intrigues me is the ability to make a graduated release. It seems that would make it easier to control speeds on a down grade to keep a train right at the allowed speed. I suspect a good engineer who knows the terrritory is able to set conventional brakes to stay close to the speed limit and not go over, but safety would suggest a little too much brake rather than not enough. If I have it right, the feature would also eliminate the need to set up retarders, but I don't know if that is now done very often. From a dispatch point, wouldn't the graduated release make stopping a train heading down grade on a passing siding safe in almost any circumstances? Not that operations will become all that much more fluid, maybe except in mountain territory. Jay, only the air-brake and train-handling people could answer that one. I sure can't. As you know there are three secret languages inside the railway: air-brake, operating rules, and signaling, each with their own high priests (Road Foremen of Engines and Master Mechanics, Chief Dispatchers and Rules Examiners, and Signal Engineers and Maintainers, respectively), temples, and vile initiation rites. I have the secret Train Dispatcher handshake and decoder ring, and the signal people indulge me as long as I sit in the back row, don't talk too much, and sound appropriately respectful, but I'm not even allowed into the foyer of the RFE/MM temple. Randy Stahl has got some pull there, I think. RWM
jeaton Q. Does the ECP system have a feature that will drain the reservoirs? Speaking of features, a key one that intrigues me is the ability to make a graduated release. It seems that would make it easier to control speeds on a down grade to keep a train right at the allowed speed. I suspect a good engineer who knows the terrritory is able to set conventional brakes to stay close to the speed limit and not go over, but safety would suggest a little too much brake rather than not enough. If I have it right, the feature would also eliminate the need to set up retarders, but I don't know if that is now done very often. From a dispatch point, wouldn't the graduated release make stopping a train heading down grade on a passing siding safe in almost any circumstances? Not that operations will become all that much more fluid, maybe except in mountain territory.
Hmmm. Since the Chairman and CEO is probably from Law, Finance or (heaven help us) Marketing, that probably explains why those guys have to grovel for sufficient funds to run their shops.
When you drop a trailer you have to remove the pigtail however it takes 5 seconds or less to do it from the trailer you just pull it out of the box it is in on the trailer. In the winter it might take 10 seconds or so. If you forget to remove it will never forget to again because you will hear this nasty slapping sound when the pigtail slams into the back of the tractor and leaves a nice dent in it.
If you cut and paste this link, it opens a PDF that has nice photos of a lot of the ECP equipment details including connectors. They do appear to be a twist type of glad hand like the air hose connectors. Somewhere I think I read that the electric line is 120 volts. Here is the link:
rsac.fra.dot.gov/document.php?type=meeting&date=20071025&name=NS+ECP+Brake+Implementation-10-25-07.pdf
I appreciate narig01's comment about rubber hoses as waveguides (like using an open window to keep flies out). You need something for the waves to bounce against. Perhaps a wire braid, such as some plumbing connections have, would work. I am reminded of the first work with UHF in ham radio back in the late forties; there was quite a bit of discussion of using metal tubing in the tuning circuits. (I was interested in ham radio back then, but I never got into it.)
Still, you need power to work the system, so it is not enough to transmit a signal to the car valves. It seems to me that enough objections to scotch it have been raised against the idea that each car have its own power source.
I trust that the people who create a workable system will be willing to learn from the trucking industry and will not attempt to re-invent the car-to-car connections all on their own; from what Ed Benton says, the system he knows works quite well, and it is fit for railroad service.
Bucyrus, I looked at that link to the NS’s application you provided. It truly is informative. The stand-alone system certainly has a great advantage in that the brake pipe is used only to provide air to the car reservoirs and thus there is much less danger that the reservoirs will be depleted. Of course, in unit train operation, there is little occasion for the connectors to be separated. In other operation, when cars are set out, would it not be possible to plug the connector into a dummy connector to protect the contacts (taking a few seconds more)?
Johnny
Johnny,
What you describe may be a feature, but I am not sure. They show that extra pigtail connection, but I don’t quite understand the functionality with it. The brake component manufacturers may also make truck brake equipment, and some of that equipment might be usable for ECP and truck systems. But I would not necessarily conclude that the same connectors could be used for both applications. Perhaps some of the design requirements overlap so they can share common attributes. Since air hoses part automatically upon uncoupling, it is understandable why they would want that same characteristic for the electrical couplers in order to avoiding the work rules complications of another added labor task. Although they are adding the one task of manually coupling the electrical connectors.
ericspI would think that the generators on every car would be a nightmare for the mechanical department. It means more parts that will eventually break. It seems like that would cause cars to be bad ordered more often.
That's one of my concerns as well, which is why I suggested that the generators would have to be tested for a few years before even thinking writing regs mandating their use. There is a lot of work being done on "energy harvesting" for wireless sensors, an example is using the vibrations from a motor to generate power for a wireless sensor.
There's also quite a bit of work being done on self-assembling wireless networks, which would be a natural for a train. As RWM suggested, having each car report sensor readings could be very useful, with sensors for trainline pressure, brake cylinder pressure, brake-arm force, wheel vibration (think flat spot detector) and bearing temperatures.
Hell a standard 7 pin connector that the OTR industry would do that NOW for you guys. Use the Center pin for your Power supply have the top wire for the Gorund wire and then use the rest as needed. Btw there are Multiplexers out there tha would be able to tell you vai a computer which car and axle have the failure on them and were at. The OTR industry has been using them since 2004 without any issues on Doubles and Triples including the Dollies to hook them up leading to 5 different hook up and vechiles up to 140 feet long with only 12 volt systems . Now for the RR industry I know they will have to beef up things but it could be done easy.
Here is a very current, informative summary of ECP brakes:
http://www.railway-technical.com/brake3.shtml
It mentions that with ECP brakes, the E stands for Electronic, as opposed to earlier developments with Electro-pneumatic where electro meant electrical.
Another source mentions that the electric cable carries 120 v.a.c. Other sources mention using the line as a platform system for monitoring all kinds of functions such as bearing temperature, wheel problems, load temperature, tank car pressure, hand brake set, etc. If there happens to be a connector failure, the system can tell you which connector it is.
The cable can also be used to control distributed power in a train.
What I find really surprising is this from the above link, which relates to what has been brought up in this thread:
“Each car has a rechargeable battery to provide the high power requirements when solenoids need to be activated. When the high power is not being used, the batteries will trickle recharge from the communications/power cable. (If the train uses radio communication the batteries will recharge while the car is in motion via an onboard generator creating power from the motion of the car, either an axle generator, or natural frequency vibration generator or some other type of device.)”
jeaton Railway Man jeaton Q. Does the ECP system have a feature that will drain the reservoirs? Speaking of features, a key one that intrigues me is the ability to make a graduated release. It seems that would make it easier to control speeds on a down grade to keep a train right at the allowed speed. I suspect a good engineer who knows the terrritory is able to set conventional brakes to stay close to the speed limit and not go over, but safety would suggest a little too much brake rather than not enough. If I have it right, the feature would also eliminate the need to set up retarders, but I don't know if that is now done very often. From a dispatch point, wouldn't the graduated release make stopping a train heading down grade on a passing siding safe in almost any circumstances? Not that operations will become all that much more fluid, maybe except in mountain territory. Jay, only the air-brake and train-handling people could answer that one. I sure can't. As you know there are three secret languages inside the railway: air-brake, operating rules, and signaling, each with their own high priests (Road Foremen of Engines and Master Mechanics, Chief Dispatchers and Rules Examiners, and Signal Engineers and Maintainers, respectively), temples, and vile initiation rites. I have the secret Train Dispatcher handshake and decoder ring, and the signal people indulge me as long as I sit in the back row, don't talk too much, and sound appropriately respectful, but I'm not even allowed into the foyer of the RFE/MM temple. Randy Stahl has got some pull there, I think. RWM Hmmm. Since the Chairman and CEO is probably from Law, Finance or (heaven help us) Marketing, that probably explains why those guys have to grovel for sufficient funds to run their shops.
With that caveat (excuse) in mind, I have a few observations:
(1) "Graduated release" is a very important advantage of ECP. I suspect the readers of this forum know what that is but, in case there are any that don't, "graduated release" refers to the ability to make a partial release of the train brakes by releasing them in increments, rather than "all or nothing". With current, non-electronic technology, it's not possible to use a "graduated release" feature on freight trains. One reason is that on a long train, the increase in train line pressure that would trigger a partial release won't be uniform from front to rear, so the resulting release won't be uniform (in fact, it may not even happen towards the rear of the train), which can set up unaccepatable in-train forces. It is possible to use "graduated release" in passenger trains (and most do) unless they are unusually long (i.e., the Amtrak Auto-train). Locomotives usually have a selector switch that allows the locomotive to be set for either "passenger" service (with graduated release) or "freight" service (no graduated release). If you think of a fheavy reight train going down a steep grade, you can see how useful a graduated release feature would be. Right now, if the brakes are set too much, the engineer must entirely release the brakes and then reapply them, which can result in a runaway (or, as you state, may require the train to come to a stop and the car retarders to be manually set). ECP allows the engineer to kick off just as much braking force as he/she needs.
(2) While I don't know this as a fact, I assume that it is possible to deplete the car reservoirs by repeated, closely spaced brake applications on an ECP system, just as it is with a conventional system. What causes this phenomena is the inability of the train line to fully recharge the car reservoirs between closely spaced brake application (kinda like trying to repeatedly flush your toilet before the tank completely refills). However, ECP should improve the situation. The reason is that, in an ECP system, the train line is simply an air supply line. This means it can be replenishing the air tanks to full operating pressure even while the brakes are applied (it may also permit the use of control valves on the cars that allow the air to replenish faster than current ones, but I don't know that as a fact). In a conventional system, the brakes are applied by reducing pressure in the train line. This means that, when the brakes are applied, the train line can only replenish the car tanks to the reduced pressure in the train line, not to full operating pressure (unless the retarders on the cars are manually turned on).
(3) One of the other posts in this thread suggested that "graduated release" would allow less air to be used when making a full brake release. Based on what I know of the technology, that isn't correct. The air pressure in the car reservoirs is "used" when the brakes are applied (i.e., that's when it moves from the car reservoirs to the brake cylinders). The "release", whether graduated or direct, simply exhausts brake cylinder pressure to the atmosphere. In fact, in a conventional system, graduated release may actually consume marginally more air in making a full release. That's because, in conventional graduated release, the locomotive must increase train line pressure enough to get a full release rather than just a partial release. In a non-graduated release, it just takes a small increase in train line pressure to get a complete release. However, the increment is probably not enough to make much of a difference particularly since, with curent technology, graduated release isn't used on long trains.
Falcon48(2) While I don't know this as a fact, I assume that it is possible to deplete the car reservoirs by repeated, closely spaced brake applications on an ECP system, just as it is with a conventional system. What causes this phenomena is the inability of the train line to fully recharge the car reservoirs between closely spaced brake application (kinda like trying to repeatedly flush your toilet before the tank completely refills). However, ECP should improve the situation. The reason is that, in an ECP system, the train line is simply an air supply line. This means it can be replenishing the air tanks to full operating pressure even while the brakes are applied (it may also permit the use of control valves on the cars that allow the air to replenish faster than current ones, but I don't know that as a fact). In a conventional system, the brakes are applied by reducing pressure in the train line. This means that, when the brakes are applied, the train line can only replenish the car tanks to the reduced pressure in the train line, not to full operating pressure (unless the retarders on the cars are manually turned on).
I don't know enough about the ECP implementations to say you are right or wrong, but I would also think it is possible to deplete the air supply by multiple closely spaced brake applications.
I would suspect that ECP would make running out of air much less likely than with the current system. A typical scenario for running out of air is on a down grade, the engineer makes an application, realizes that he is braking too hard, releases the brakes and then has to make another application before the reservoirs recharge, finds out he over did it again at which point he's lost most of the pressure. With graduated release, there is no need to release the brakes completely, which reduces the amount of air needed if braking needs to be increased again. The situation would be even better if ECP allows for full recharging of the reservoirs during an application.
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