Early in the thread, Tree suggested this to me:
If you haven't already read Al Krug's excellent primer on railroad air brakes, you'll find it well worth your while. http://www.railway-technical.com/trains/rolling-stock-index-l/train-equipment/brakes/north-american-freight.html
I've now read it, and it IS excellent. I'd highly recommend it to anyone curious about air brakes. Thanks again, Tree.
Still in training.
BigJim Deggesty Friends, in my learning about braking, I somehoe missed something--what is the PCS? Thanks Pneumatic Control Switch: That is what knocks the power down when there is a penalty or emergency brake application.
Deggesty Friends, in my learning about braking, I somehoe missed something--what is the PCS? Thanks
Friends, in my learning about braking, I somehoe missed something--what is the PCS?
Thanks
Pneumatic Control Switch: That is what knocks the power down when there is a penalty or emergency brake application.
That's how I originally learned it, from reading railroad manuals before hiring out. The glossary in our Air Brake and Train Handling rule book now calls it the Power Cut-Off Switch.
Jeff
OvermodIf from a UDE, a crew might not respond quickly enough to bail off the independent, and the actual bailing off might not then be quick enough to avoid some flat-spotting, even a little of which means grinding of expensive wheelsets.
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ruderunnerBut can the engineer make the eot initiate emergency braking without placing the locomotives in emergency?
The Amtrak P42 has an explicit control that does precisely this, described in the orientation video (I watched it yesterday so it is fresh in my mind to confirm).
Emergency applies brakes on the locomotive as well as the train. This will cause wheels already significantly 'braked' by inverter action or back EMF to slide very quickly.
If from a UDE, a crew might not respond quickly enough to bail off the independent, and the actual bailing off might not then be quick enough to avoid some flat-spotting, even a little of which means grinding of expensive wheelsets.
If in actual declared emergency, the crew might not take the time to do the bailing off; some might be 'distracted' enough not to prioritize it as company management might like.
and a minor hijack since we've gotten into emergency braking...
I know the eot can activate the emergency function and it also does so if the locomotive goes into emergency. But can the engineer make the eot initiate emergency braking without placing the locomotives in emergency?
I would expect the results to be sort of like stretch braking a passenger train. Would this have any practical application?
Modeling the Cleveland and Pittsburgh during the PennCentral era starting on the Cleveland lakefront and ending in Mingo junction
What is the theory behind the system cutting out the dynamic brakes during an emergency air brake application?
Johnny
Randy Stahl There is a timing reservoir on the PCS switch that must be exhausted before the engine will reset from PCS. But yes, if you wait a bit you can reset PCS and continue using the dynamic brakes without releasing the train. This reservoir prevents fast cycling of the PCS switch, I think its 10-16 seconds delay.
There is a timing reservoir on the PCS switch that must be exhausted before the engine will reset from PCS. But yes, if you wait a bit you can reset PCS and continue using the dynamic brakes without releasing the train.
This reservoir prevents fast cycling of the PCS switch, I think its 10-16 seconds delay.
There was a way to beat an undesired penalty application too, but, I won't go into that here.
I think that potential technical issues with locomotive 2339 and its maintenance deserve their own thread - with some close inspection of the trial and its results when they occur.
Or you throw it in reverse ...
Ex-BNSF engineer raises safety concerns, claims wrongful terminationhttp://www.king5.com/article/news/local/ex-bnsf-engineer-raises-safety-concerns-claims-wrongful-termination/281-511346381
If you go into emergency and the dynamic brakes cut out, can you still use the independent brake on the locomotives to help slow you down?
(Edit): Never mind. I realize that the locomotives are included in the emergency braking. I should have remembered this. The old mind seems to be going.
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"A stranger's just a friend you ain't met yet." --- Dave Gardner
jeffhergertWait for the brake pipe to go to 0 and completely exhaust. Move the automatic brake handle from Emergency to Handle Off.
Your basic reset after an emergency application. Do it every day I run while I'm doing my locomotive brake test (or if someone cuts in the consist too quickly after a runaround).
Every now and then the gauge looks like it reads zero, but there's still air moving, so moving the brake handle to handle off won't reset the PCS. In a situation such as we're discussing, it might be hard to muster up the patience to let the pipe fully exhaust, but until it does, you're not getting your reset.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
"I think it was the instructor back in engineer's school at Salt Lake City who told us this. (He worked, when not instructing, mountain grade territory.) He said if you're going down grade and have to put the train in emergency and the PCS opens up killing the dynamics, to do this. Wait for the brake pipe to go to 0 and completely exhaust. Move the automatic brake handle from Emergency to Handle Off. This won't initiate a release, something you don't do until you're stopped, but will allow the PCS to reset. This restores dynamic braking capability.
He said it would work, but I'll probably never have the chance (nor do I want the chance) to try this. Most of our grades aren't that long. "
I discovered this once after stopping in emergency with the dynamic controller still in full on position. After the PCS reset the dynamic came back on, although without any load since the train wasn't moving. I later tried it with moving light engines and full dynamic brake control was indeed restored with the automatic brake pressure at zero.
When I was in Engineers school in Cumberland I asked the instructor if it wasn't a bad idea to eliminate dynamic braking when in emergency. It seemed like you would want to keep all braking power possible in an emergency situation. Some years later Chessie engines, or maybe it was CSX by then, were changed to retain dynamic braking in emergency.
They were set up that way by the time of the Sand Patch runaway.
zardoz jeffhergert It may be an option that's railroad specific, but our locomotives have a Dynamic Brake Holding Feature. When the engineer places the automatic brake valve in emergency and the PCS opens, this feature keeps the dynamic brake operative. I think all our modern engines have it. The older power may not. Jeff Jeff, the former CNW power did NOT have that feature (SD40-2 and earlier). Using the jammer when the dynamics cut out was a rather insufficient replacement, but it was better than letting the slack run out, especially if you had multiple locomotives! (I always carried a 1/4" Allen wrench for those "special" occasions, especially in the yard)
jeffhergert It may be an option that's railroad specific, but our locomotives have a Dynamic Brake Holding Feature. When the engineer places the automatic brake valve in emergency and the PCS opens, this feature keeps the dynamic brake operative. I think all our modern engines have it. The older power may not. Jeff
It may be an option that's railroad specific, but our locomotives have a Dynamic Brake Holding Feature. When the engineer places the automatic brake valve in emergency and the PCS opens, this feature keeps the dynamic brake operative. I think all our modern engines have it. The older power may not.
Jeff, the former CNW power did NOT have that feature (SD40-2 and earlier).
Using the jammer when the dynamics cut out was a rather insufficient replacement, but it was better than letting the slack run out, especially if you had multiple locomotives! (I always carried a 1/4" Allen wrench for those "special" occasions, especially in the yard)
Note in the Saluda Grade video that the Road Foreman has a special key that when inserted and operated will keep the dynamics working when there is a emergency brake application.
Never too old to have a happy childhood!
BaltACD mvlandsw "I've read articles about the big CSX Sand Patch derailment. Some say the engineer did not brake frequently enough to keep snow/ice from building up between the shoes and the wheels. Others say he cycled the brakes too much and, and, as you say, pisssed away his air. Maybe this is simply a difference of opinion which endures. ??" The brake applications to keep ice from building up on the brake shoes are done before you go over the top of the grade where you have time for the system to fully recharge before topping the hill. Releasing the air brakes while moving is not supposed to be done when descending the east side of Sand Patch. The Sand Patch runaway of 2009 or 2010 (don't have total photographic memory recall) happened in the midst of at 20+ inch blizzard in the mid-Atlantic states. Leaving Connellsville, where a helper was attached, The Engineer expressed reservations about taking the train down the mountain under the conditions - the Asst. Division Manager instructed the Engineer to proceed. After the engineer made his first brake application after cresting Sand Patch he knew he wasn't getting the proper level of retardation and placed the train in emergency - and the tripping of the PC switch cut out dynamic braking on the locomotives. After that is was ride the train down the mountain. The locomotives made the descent, the cars all piled up. I don't know if the engineer, after placing the train in emergency attempted by any means to reactivate the dynamic braking on the engine consist. At the time of this happening, the Baltimore Division Timetable for the Keystone Subdivision had no special instructions about conditioning the brakes to insure that the brake shoes were contacting the wheels, not blocks of ice built up on the brake shoes. Operating in the same area was the Huntington Division's Mountain Subdivision between Cumberland and Grafton over 17 Mile Grade, Cranberry Grade and Cheat River Grade. The Huntington Division Timetable did have a special instruction requiring engineers to condition their brakes before descending any of the grades mentioned. Subsequent to the incident, special instructions were implemented on the Keystone subdivision that mirrored those on the Mountain subdivision.
mvlandsw "I've read articles about the big CSX Sand Patch derailment. Some say the engineer did not brake frequently enough to keep snow/ice from building up between the shoes and the wheels. Others say he cycled the brakes too much and, and, as you say, pisssed away his air. Maybe this is simply a difference of opinion which endures. ??" The brake applications to keep ice from building up on the brake shoes are done before you go over the top of the grade where you have time for the system to fully recharge before topping the hill. Releasing the air brakes while moving is not supposed to be done when descending the east side of Sand Patch.
The brake applications to keep ice from building up on the brake shoes are done before you go over the top of the grade where you have time for the system to fully recharge before topping the hill. Releasing the air brakes while moving is not supposed to be done when descending the east side of Sand Patch.
The Sand Patch runaway of 2009 or 2010 (don't have total photographic memory recall) happened in the midst of at 20+ inch blizzard in the mid-Atlantic states. Leaving Connellsville, where a helper was attached, The Engineer expressed reservations about taking the train down the mountain under the conditions - the Asst. Division Manager instructed the Engineer to proceed. After the engineer made his first brake application after cresting Sand Patch he knew he wasn't getting the proper level of retardation and placed the train in emergency - and the tripping of the PC switch cut out dynamic braking on the locomotives. After that is was ride the train down the mountain. The locomotives made the descent, the cars all piled up. I don't know if the engineer, after placing the train in emergency attempted by any means to reactivate the dynamic braking on the engine consist.
At the time of this happening, the Baltimore Division Timetable for the Keystone Subdivision had no special instructions about conditioning the brakes to insure that the brake shoes were contacting the wheels, not blocks of ice built up on the brake shoes.
Operating in the same area was the Huntington Division's Mountain Subdivision between Cumberland and Grafton over 17 Mile Grade, Cranberry Grade and Cheat River Grade. The Huntington Division Timetable did have a special instruction requiring engineers to condition their brakes before descending any of the grades mentioned.
Subsequent to the incident, special instructions were implemented on the Keystone subdivision that mirrored those on the Mountain subdivision.
I think it was the instructor back in engineer's school at Salt Lake City who told us this. (He worked, when not instructing, mountain grade territory.) He said if you're going down grade and have to put the train in emergency and the PCS opens up killing the dynamics, to do this. Wait for the brake pipe to go to 0 and completely exhaust. Move the automatic brake handle from Emergency to Handle Off. This won't initiate a release, something you don't do until you're stopped, but will allow the PCS to reset. This restores dynamic braking capability.
He said it would work, but I'll probably never have the chance (nor do I want the chance) to try this. Most of our grades aren't that long.
My first experience with retainers was back in 1954 when my high school class trip was to Washington DC from/to Cincinnati. On the westward trip on #1, i spent significant time in the vestible and remember the trainman comming through the car and operating a valve. Upon my query, he told me he was activating the RETAINER. Gave me a little discription of its function. We were somewhere west of Cumberland (having bypassed it) on the grades and of course, the B&O E units didn't have dynamic braking. It was dark and the sight of all the sparks from the brake shoes as the train snaked down the hills with the headlight lighting up the path and the train windows glowing is something I will never forget. The retainers allowed the engineer to retain braking while recharging the trainline and the reservoirs.
mvlandsw"I've read articles about the big CSX Sand Patch derailment. Some say the engineer did not brake frequently enough to keep snow/ice from building up between the shoes and the wheels. Others say he cycled the brakes too much and, and, as you say, pisssed away his air. Maybe this is simply a difference of opinion which endures. ??" The brake applications to keep ice from building up on the brake shoes are done before you go over the top of the grade where you have time for the system to fully recharge before topping the hill. Releasing the air brakes while moving is not supposed to be done when descending the east side of Sand Patch.
quoted by mvlandsw"Some say the engineer did not brake frequently enough to keep snow/ice from building up between the shoes and the wheels. Others say he cycled the brakes too much and, and, as you say, pissed away his air.
I had thought it well-established that the 'cause' was outgassing from composition shoes, which over a critical speed (around 23mph on the relevant portion of the grade) prevent even a perfect air-brake system from physically holding the train. In that condition, the only thing that prevents a fairly rapid runaway (the outgassing effect only getting worse as momentum increases) would be dynamic braking -- which automatically disengages as emergency is applied; I believe units have to be equipped with a special 'key', as they were for Saluda Grade, that permits the dynamic to be kept on with a hard brake set (in conditions where skidding wheels is no longer an economic concern). Very likely only a small amount of additional acceleration will get you to the point that the number of axles of full dynamic that can be summoned up in the consist may not hold the train effectively either, even if sustained without skidding.
If I remember correctly the only thing the engineer 'did wrong' was assume the amount of dynamic he actually had working on his consist was sufficient to keep the train well below the 'critical speed'. By the time he realized that things weren't working right -- Katy, bar the door!
It is possible that union representatives or whoever would raise the 'ice on the brakeshoes' idea as a practical excuse for an accusation of poor train-handling judgment. But as noted, any icing would have been melted, and then kept from refreezing, by proper brake procedure prior to starting down the grade ... at least in proper practice.
Thanks all again.
Yes, earlier I meant to say “retainer.” (I am aware of car retarders in hump yards; years ago I used to go watch the action at Southern’s Inman Yard in Atlanta.)
"I've read articles about the big CSX Sand Patch derailment. Some say the engineer did not brake frequently enough to keep snow/ice from building up between the shoes and the wheels. Others say he cycled the brakes too much and, and, as you say, pisssed away his air. Maybe this is simply a difference of opinion which endures. ??"
Yes; thanks, Overmod. I did not even think about that presentation of descending Saluda--which had been presented to us twice. I did not remember the specific application of the double retainers, and I trust that our op appreciates your description of their use. It is possible that no grain went down Saluda 54 years ago, so the doubles were not mentioned in those special instructions.
I should, perhaps, have added the further instruction concerning descending from Ridgecrest to Old Fort--if the dynamic brake is working properly, it is not necessary to turn retainers up--which saves a lot of time in getting over the road..
Johnny, you might have posted the link to the "Mountain of Challenge" video, which for all its endearing hokiness and Huckleberry Hound narration does specifically discuss how retainers were used going down Saluda (cf. 8:00).
The context of 'high' and 'low' retainers I remember had to do with dedicated sets of hopper cars in heavy service, which deserved (and perhaps needed) more 'retained set' loaded than empty. You'd still want some measure of reserved braking on empty trains or cuts, but the right amount to retard a loaded train might cause enhanced skidding or even increased risk of derailment or stringlining if applied to empties. Hence two distinct positions.
You can compare the difference between such a mechanism and the 'load sensing' devices on, say, some centerbeam flatcars that control direct braking effort depending on the truck-spring loading or whatever.
My basic knowledge of retainers comes from a now 54 year old Southern Asheville Division ETT, which, of course, had SPECIFIC instructions on the use of retainers in going down to Spartanburg from Asheville. Once all auxiliaries have been charged to 100 lbs,all retaining valve handles were to be turned up after the brakes were inspected--single pressure valves were to be turned all the way up, and double pressure handles were to be turned up to a 45 degree angle. Once the engine had pulled a sufficient distance over the crest, the engineer was to make a full service application of the dynamic brake and make several air brake applications--and then release immediately so as to fill the brake cylinders and retaining valve pipes. From time to time, brake applications were to be made to keep the train going slowly enough so that a 5 to 8 pound reduction would be able to stop the train. At the bottom of the grade, the retainers were to be turned down, and full a inspection of the train was to be made.
Instructions for descending certain grades between Asheville and Murphy, and descending from Ridgecrest to Old Fort if there is no dynamic brake operating are also given, but not in such detail; all retainer valves were to be turned up. Nothing was said about turning retainers down at the bottom of these grades.
There was no further discussion distinction between the use of single and double retainers.
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