Slack, a wondrous thing in concept, theory and application.
Let's work an idea that braking power/effort of a/group of cars, while varying,, affects slack, and thus, different speeds within a train. That speed within the train blows into importance when the difference is like holding a piece of string between your fingers and pulling on it...or instilling a loop of slack and then pulling them apart....right?
Said that, and some may wonder where's this is goin?'
This is about "little train's,' on big 'roads: 'tween four to eight thousand feet trains powered on only the head end.
On very gently rolling right of way with a high throttle position effectively, slack thus stretched, widen on the throttle, more slack is pulled out. Time a minimum reduction, in your mind, like an NFL Quarterback, the additional stretch...but follow with an automatic application arriving at the end of the train when reduction of the throttle reduces speed fastest, low or no throttle and surely, kick off the (auto) brakes coming into the restrtiction
Slack action happened. while releasing through the restriction of speed, while with little. slack had the time to readjust to what was the tolerable state that got the train this far.
Now the slack is there for the massaging.
It's your railroad: drift, bunch or strech... ya' have to do some thin'
Six inches per normal coupling car sounds reasonable - 1/2 inch or so in the coupler, 2 1/2 inches in the draft gear on each end of the car, maybe less....then you have cushion under frame cars that can have a couple of feet of travel.
Never too old to have a happy childhood!
BaltACD GM1361 What is taking slack in the following sentence? CAUTION: Taking slack is not a recommended method forstarting a heavy train on a heavy grade. Short brake releasetimes will release the brakes on the entire train, and the rearportion will begin rolling backward while the head portion isstarting forward, easily causing a train separation. Couplings between cars have some 'slack' in them - potentially on the order of 1/2 inch to a inch per coupleing + the movement of the draft gear on each end of the car. As train lengths increase, the amout of 'free moving' slack in the train also increases. Improperly controlled slack action is the primary cause of shattered coupler knuckles and pulled out draft gear. The action described in the 'CAUTION' is a situation where the entire train is stopped on a ascending grade. The engineer has 'bunched' the slack in the train, so that each coupling has the maximum slack distance to move before starting to pull on the car behind it. In the procedure being cautioned, the air brakes are applied on the entire train. As the engineer begins to start the train, adding power to the locomotive consist, he is also releasing the air brakes - pulling the slack out and starting each car individually from front to rear. The caution refers to the fact that the brakes will release on the rear of the train before the starting secquence of pulling out the slack has gotten to the rear of the train. Gravity will have the entire portion of the rear of the train pull against the starting head end of the train as a 'solid unit' with a much higher draft force than the engineer intends with his starting sequence. The high draft force is easily capable of shattering a coupler knuckle or finding the weakest draft gear, thus stopping the train and necessitating additional actions being taken.
GM1361 What is taking slack in the following sentence? CAUTION: Taking slack is not a recommended method forstarting a heavy train on a heavy grade. Short brake releasetimes will release the brakes on the entire train, and the rearportion will begin rolling backward while the head portion isstarting forward, easily causing a train separation.
What is taking slack in the following sentence?
CAUTION: Taking slack is not a recommended method forstarting a heavy train on a heavy grade. Short brake releasetimes will release the brakes on the entire train, and the rearportion will begin rolling backward while the head portion isstarting forward, easily causing a train separation.
Couplings between cars have some 'slack' in them - potentially on the order of 1/2 inch to a inch per coupleing + the movement of the draft gear on each end of the car. As train lengths increase, the amout of 'free moving' slack in the train also increases. Improperly controlled slack action is the primary cause of shattered coupler knuckles and pulled out draft gear.
The action described in the 'CAUTION' is a situation where the entire train is stopped on a ascending grade. The engineer has 'bunched' the slack in the train, so that each coupling has the maximum slack distance to move before starting to pull on the car behind it. In the procedure being cautioned, the air brakes are applied on the entire train. As the engineer begins to start the train, adding power to the locomotive consist, he is also releasing the air brakes - pulling the slack out and starting each car individually from front to rear. The caution refers to the fact that the brakes will release on the rear of the train before the starting secquence of pulling out the slack has gotten to the rear of the train. Gravity will have the entire portion of the rear of the train pull against the starting head end of the train as a 'solid unit' with a much higher draft force than the engineer intends with his starting sequence. The high draft force is easily capable of shattering a coupler knuckle or finding the weakest draft gear, thus stopping the train and necessitating additional actions being taken.
Very informative response! What is the total distance a freight car will move before it begins to pull the car behind it? Someone told me years ago that it was in the neighborhood of six inches, i.e. three inches for each car. I have no idea whether he knew what he was talking about.
BaltACDI saw one bulletin wherein the experienced engineers were being instructed to train the trainee engineers on the art of 'stretch brakeing'.
That is good to hear. I can remember when one prominent Regional RFE told us that "There will be no more air brake artists out here"! What a maroon!!!
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We are allowed to stretch brake, but not to power brake. The difference? What throttle notch you're operating in. They consider operating in notch 6 and below to be stretch braking, above that and you're considered to be power braking. For awhile, they had changed the meaning of stretch braking to only being in notch one or two, anything higher and you were power braking. Someone with actual experience running trains must have been able to get them to change it back.
Even though stretch braking is allowed, it's still preferred to be used when other more fuel efficient methods aren't practical. They do stress dynamics, almost to the point where young engineers are afraid to use air. One time I had a student who needed to get slowed down right away because the approaching train on the adjacent track went into emergency about a mile away from us. Instead of immediately setting air, he was going to notch down on the throttle and go into dynamics. I told him to use air and get the speed down, you don't know if the train who lost his air did so because a hose came apart or he's got cars derailed across the tracks.
Jeff
Deggesty Balt, from what you say, somebody in management is aware of reality. Perhaps, someone who has had much experience in running an engine?
Balt, from what you say, somebody in management is aware of reality. Perhaps, someone who has had much experience in running an engine?
The company's Chief Transportation Officer still maintains her Engineer's Certificate and does qualification runs as required by law to keep it current.
Johnny
BigJim efftenxrfeThere needs to be a realization that combined train air brakes and dynamic brakes are what is needed for downgrades.That is exactly right. Having a good air/DB balance set up going downhill can quickly go sour if a unit loses its DB. As for complete DB failure, now a days, the company goes ape+#@* if an engineer tries to learn how to power (stretch) brake. It was an art I was fortunate to learn before all of this fourth grade hall monitor techno-blabby wizardry was installed on the units. An engineer needs to know how to do this just in case use of retainers.
efftenxrfeThere needs to be a realization that combined train air brakes and dynamic brakes are what is needed for downgrades.
As for complete DB failure, now a days, the company goes ape+#@* if an engineer tries to learn how to power (stretch) brake. It was an art I was fortunate to learn before all of this fourth grade hall monitor techno-blabby wizardry was installed on the units. An engineer needs to know how to do this just in case use of retainers.
I was reading through my company's Engineers Bulletins - I saw one bulletin wherein the experienced engineers were being instructed to train the trainee engineers on the art of 'stretch brakeing'. While stretch braking is not the approved braking method, there are locations and situations where this method is called for. The company desires to have their engineers know the proper way to do stretch braking, even though it is not the approved general method of braking. The experienced engineers would not be 'down graded' for stretch braking while they were training someone.
As for complete DB failure, now a days, the company goes ape+#@* if an engineer tries to learn how to power (stretch) brake. It was an art I was fortunate to learn before all of this fourth grade hall monitor techno-blabby wizardry was installed on the units. An engineer needs to know how to do this just in case something fails so that he can handle the train safely.
As for retainers, I know that eastbound coal trains out of Bluefield, W.Va. used retainers on about the head 20-30 cars as it is a long way down to the foot of the mountain. I don't know if they still do. My grades weren't that long and the profile such that we didn't have to use retainers. I don't think their use would have been discontinued. I'm sure there are plenty of grades out west and some here in the east that require the use of retainers.
I see no mention of retainers. I assume they are not used anymore. When was their use discontinued?
This is tough.
Big Jim ain't working on what we considered "track" that was exceptional.
On SP, mountain grade rules kicked in at 2%.
Good train handling and survival required doin' the right things!
Absolutely, no dependence on the dynamic brake's ability to regulate train speed or holding ability or independent is mentioned; it must be mentioned that on mountain grades, neither expecting contemporary independent brakes nor automatic train brake app's to hold trains is realistic.
The DB can fail; all locomotives DB brakes fail if the control circuit breaker trips, ain't nothing left.
There needs to be a realization that combined train air brakes and dynamic brakes are what is needed for downgrades.
Holding trains on descending mountain grades while recharging after stopping, no problem if you're a mountain qualified engr. on SP..
BaltACDin most cases having all the locomotives with their brakes applied are sufficient to hold a already stopped train
One thing that changed how much a unit will hold on a grade was the advent of composition brake shoes and then the change on six axle trucks from three brake cylinders per side to two per side. Trains that were normally able to hold a train in the yard as hand brakes were released started rolling away.
As for setting hand brakes to charge the trainline, this is only effective if a very heavy brake application has been made. Under normal situations a ten pound reduction will be more than enough to stop a train on a grade. Having the conductor go back and set brakes is only making him do unnecessary work and is a waste of time.
If an engineer has been smart and not used a lot of air to stop his train, the dynamic brake will keep the train in check long enough to charge the trainline enough to where a heavy application is needed to control the speed.
As far as train makeup is concerned, the yardmasters only have to worry about placement of dangerous cars, trailing tonnage behind empty 89ft. flats and shiftable loads placed away from dangerous cars or the very rear car on the train. There has also been some rules placed in effect about load/empty placement in auto rack trains. This is not to say that load/empty placement does not effect train handling, but, train crews don't get to pick and choose the makeup of their train.
But what about the independent and the dynamic? Say I have stopped on a downgrade, and now get the signal to proceed. I have the independent fully applied. (Of course I understand that dynammics only work when the train is moveing,indeed are only effective above a certain speed.) Now I make a full release. The train is still standing, and I take the time to allow the train line to be pumped up before releasing the independent. Can I release the independent gradually to ease the train into motion, and then as the train picks up speed engage the dynamic brake, assumng there is one, to hold the speed down to what I consider safe and prudent, using just enough dynamic to do so? Or does the independent have to be released completely at once also?
daveklepper I understand. Also, obviously one does not need to use power to get the train up to any speed wanted on any significant downgrade. What question comes to mind: If one gives only a partial release, will the increase in brakeline pressure propogate more slowlly through the train line than if one gives a full release? Because if the speed of propogation is the same, then if one is stopped witih a full or emergency application, on a downgrade, it would seem prudent to release the brakes slowly, charge the train line up slowly, so that the train eases into motion, but still has some brakiing effort. However, I see that if the pressure build-up propagates too slowly front to rear, one can easily have a break-in-to, with the brakes released at the front and still fully applied at the rear - or one can develop flat spots on the rear cars. The conductor setting handbrakes makes sense. I presume setting say one-fifth or one-fourth of them staring from the front and workiing toward the rear is usually sufficient in your territory. How does the conductor get back to the locomotive as it starts rolling when the brakes are released? I imagine he starts with the rearmost handbrake applied and works toward the front, but still he might be several car-lenths awa from the locomotive when the train begins rolling. Do you then use the independent to make sure the train does not exceed walking speed until the conductor reboards? I can see a problem with that if there are a bunch of empties righit behind the power. Is this problem always solved by proper blockiing and locating the empties to the rear of the train consistantly?
I understand. Also, obviously one does not need to use power to get the train up to any speed wanted on any significant downgrade. What question comes to mind: If one gives only a partial release, will the increase in brakeline pressure propogate more slowlly through the train line than if one gives a full release? Because if the speed of propogation is the same, then if one is stopped witih a full or emergency application, on a downgrade, it would seem prudent to release the brakes slowly, charge the train line up slowly, so that the train eases into motion, but still has some brakiing effort. However, I see that if the pressure build-up propagates too slowly front to rear, one can easily have a break-in-to, with the brakes released at the front and still fully applied at the rear - or one can develop flat spots on the rear cars.
The conductor setting handbrakes makes sense. I presume setting say one-fifth or one-fourth of them staring from the front and workiing toward the rear is usually sufficient in your territory. How does the conductor get back to the locomotive as it starts rolling when the brakes are released? I imagine he starts with the rearmost handbrake applied and works toward the front, but still he might be several car-lenths awa from the locomotive when the train begins rolling. Do you then use the independent to make sure the train does not exceed walking speed until the conductor reboards? I can see a problem with that if there are a bunch of empties righit behind the power. Is this problem always solved by proper blockiing and locating the empties to the rear of the train consistantly?
Operating in mountain territory, train make up is critical - load & empty placement, long and short cars coupled to each other, long empty cars in the train and a host of other conditions that have caused derailments in the past and now have 'Train Handling' rules that cover those situations. It is a real challenge for a yardmaster to build a train and follow all the applicable rules that apply to trains operating through mountain territory.
On freight trains you either apply the brakes, apply them more firmly or release them entirely. Freight train braking systems cannot be modulated like the brakes on your automobile. Passenger train braking systems do permit a graduated release of the brakes and their brake valves have two settings - Passenger & Freight. It a passenger car is handled in a freight train the brake valve needs to be in the Freight setting.
When recovering from a stop on a descending grade, the last brake to be released by the engineer is the independent locomotive brake - in most cases having all the locomotives with their brakes applied are sufficient to hold a already stopped train - they would not be sufficient to stop the train were it moving.
daveklepper Given either situation, with a heavy, mixed car type and load and empty, freight stopped either in the siding or on the main, would not you make a gradual release, and then let the train start rolling without power, just gravitiy starting it, to give yourself the maximum amount of time to recharge the brake line in case you have to make another brake application? And then start applying power to bring the train up to what you consider safe and prudent operating speed (which could still be less than track speed) only when you know that the brake line is fully charged?
Given either situation, with a heavy, mixed car type and load and empty, freight stopped either in the siding or on the main, would not you make a gradual release, and then let the train start rolling without power, just gravitiy starting it, to give yourself the maximum amount of time to recharge the brake line in case you have to make another brake application? And then start applying power to bring the train up to what you consider safe and prudent operating speed (which could still be less than track speed) only when you know that the brake line is fully charged?
My territory has some heavy grades. When a train is stopped on one of these grades, for whatever the reason - Conductor ties on hand brakes to hold the train, then the trainline can be recharged and the brakes released, then the hand brakes can be released.
guetem1or run him into the hole on an ascending grade.
Going uphill the heavy/long train is going slow to begin with. It also has the advantage of being able to stop easier on the uphill grade and use an automatic brake reduction heavy enough to effect a complete brake release throughout the train when leaving.
On the other hand (And a lot depends on the speed of the siding, the slower the speed allowed the more critical the situation) the heavy/long train descending into the siding has much more to worry about. Today's heavy trains seem to have plenty of GO power, but, they are limited in how much Dynamic Brake can be on line. Thus, descending the grade, there is more tonnage than the units can hold back, forcing the use of an automatic brake application. If you had to make a heavy brake application to stop the train, it is going to compound your problems when you have to knock the brake off to leave as now you do not have a fully charged brake system.
Operating on a less than fully charged brake system is a crap shoot. Especially, if more than one brake application has been made. Because when released, the brakes are not fully charged and they do not apply in the same way as they did when charged (some will apply, some will not). It's completely different feel. You have to sneak up on just the right amount of air to apply. You want enough to hold the train, yet, you don't want to put too much on and stop, forcing another round of the pissing contest thus getting you deeper into trouble.
Keeping the heavy train on the descending main is much better for him. If he needs to stop and a brake application is needed to do so, then, upon brake release he has much more time before the train gets up to speed in order to charge the brakes in case they are needed again.
now Fred's post got a belly laugh out of me! I would not have wanted to be on the carpet for the Super's tongue lashing on that one either! Now as a dispatcher it is my job to know the territory and know where the grades are and try not to let a train's track warrant run out on the "wrong" side of a hill. Unfortunately the mechanical Gods do not always cooperate and if a train stalls due to a dead motor, it'll always be in the worst place. Also you learn for train meets to try not to stop a heavy train or run him into the hole on an ascending grade. Train compliance rules nowdays help to mitigate a lot of the problems mentioned earlier, but once in a while the yard will get behind the power curve and kick a train out of the yard that is out of compliance, Galesburg are you listening???? But when that happens usually there is a trainmaster or chief dispatcher who catches it and makes the train stop and switch it into compliance on line, usually plugging your main line for an hoour and a half!!!!
Paul of Covington A couple of questions for engineers and conductors: When driving in your own vehicle and coming to a stop sign or red light, does a part of your mind think about slack control? Also, when approaching a traffic light, do you ever find yourself "calling the signal" in the back of your mind?
A couple of questions for engineers and conductors:
When driving in your own vehicle and coming to a stop sign or red light, does a part of your mind think about slack control?
Also, when approaching a traffic light, do you ever find yourself "calling the signal" in the back of your mind?
From the time I can remember, until my sister who is 11 years younger than me turned 16, my father referred to every traffic light he ever saw as a "board". Red board, green board, whatever. It was only when he started to teach her how to drive that he began referring to them as "lights".
rfpjohn's post gets the award for the funniest thing I heard all day.
Bruce
So shovel the coal, let this rattler roll.
"A Train is a Place Going Somewhere" CP Rail Public Timetable
"O. S. Irricana"
. . . __ . ______
GM1361Does taking slack here mean to bunch the slack or stretch the slack?
This thread has covered both aspects of slack - stretched and bunched. Proper contol of slack by the engineer is critical in the safe operation of trains that are being operated today.
Slack can be a tool for the engineer to use and at the same time a condition that is his potential enemy when he cannot control it's movement within his train. The decisions of when and where to apply power must be made with consideration of where the slack is in the train and how the application of power will affect the movement of the slack in the train know what terrain the train will be traversing. Likewise using the various braking systems available (independent locomotive brake, trainline air brakes, dynamic brakes) must be done with consideration of where the slack is and how the particular braking action will affect the movement of the slack in the train on the terrain the train is operating over.
Paul of Covington;
I do find myself wanting to ring the bell going by highway construction workers accompanied by that nagging worry that I've forgotten about a work authority.
Fred BoyerThe train was probably down to 5 MPH as it went into the yard leads.
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"A stranger's just a friend you ain't met yet." --- Dave Gardner
With the size of todays trains - most always more than a mile long and in some cases two miles long - the engineers biggest consideration in train handling is slack control - both draft (pulling slack out) and buff (slack running in) forces. While the conductor and flagman no longer ride in the caboose to complain about a engineers train handling - broken knuckles, pulled out draft gear and derailed cars are monuments to a engineers less than ideal train handling techniques.
This is not a problem on just hills. I have a photo of a bulkhead flat loaded with I beams that has just the tail end of the coupler left in the pocket. The engineer started too fast, front of the train got moving, but the rear was stopped. Lots of steel cars at the back, and a lighter train in front. Broke the coupler in the pocket, the front was moving, of course, the train came apart, and went into emergency. Unfortunately, the rear has some movement by this time, although it went into emergency too, the front stopped quicker than the rear. Damaged the end of the car when they came together again. Indiana is flat ground around here.
I also witnessed the opposite happen when a train came into a yard in southern Indiana. Front had 20 cars of steel scrap, rear was lighter cars. The train was probably down to 5 MPH as it went into the yard leads. The conductor, wanting the train to stop, radioed "dump it". Engineer went into emergency, front stopped, the last two cars were empty auto racks and they went about 4 feet into the air at the coupling. Didn't stay around to hear the superintendent discuss this one with the crew.
Holy crap. It's unfathomable the amount of knowledge needed to properly operate a train. Not just what the controls do and the rules and signals but also how to control the entire train. I can only imagine that an engineer with over 30 years experience would think that another engineer with only 10 years experience would be considered a rookie. I used to want to be an engineer but after reading numerous articles and forums like this, I'm glad I didn't. My head would explode...lol. My hats off to ALL you engineers. Truly another job that is underpaid.
I should have figured out that power isn't necessary for the diesels to roll back a bit, just releasing the brakes. Sould have been obvioius to me.
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