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I would say slack is a nessasary evil in couplers for longevity. If the tolerances were tighter they would probably have a much shorter lifespan and thus higher maintainance costs. just my 2 cents.
Yes we are on time but this is yesterdays train
.....Do they {by design}, get away with less slack on passenger trains simply because they are shorter and less tonnage...?
One would sure think it would be less difficult to operate a train {freight}, if less slack was "built in" to couplers, etc...
Does today's tonnage and power combination allow operation of a long freight train {if less slack was the condition}.....?
Is it a fact slack is benificial to getting a train started in some instances....?
One would think {by looking at the design}, the Triple Crown type trains have quite a bit less slack than normal rail cars consist has....but understand it is much less tonnage too...
Quentin
The tolerance issue notwithstanding, another use of slack that has gone by the wayside was using it to start a long, heavy train.
Before high horsepower, DP, and roller bearings, trains would often be started by bunching up the slack (while stopping, if possible), then pulling it out. The locomotive only had to start one car rolling at a time (albeit in rapid succession). I've been around trains when you could hear the slack action coming and going from your vantage point mid-train.
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...
....So it sounds to me {from the last statements above}, the act of coupling / uncoupling process relies more on slack in the operation of a train than does slack being used to start a train.
Does slack give starting a mile long train that much advantage when it only provides 50' or so to work with....Watched a 5 engine train on the Frankfort line here start last night {and didn't hear any slack...being taken up}, must have been stretched...{and just 2 of the engines were on line}, so that {the other 3}, were added dead weight....but it is level track here from where we watched...But it sounded like the engineer just notched lightly to start.....as he was to proceed slowly...{heard it on my radio}, so the diamond at CSX could be cleared by the time this train arrived there...just a mile or less ahead. Guess I'm saying the train seemed to move out very easy without using "Slack".
One reason for not hearing slack when starting is as a policy we try to stop with the train stretched.It allows for a smooth start for one and two keeps the malcontents from being able to pull the pin on you.
You now things are going good when you start up and as soon as the motor starts to move old fred gives a beep and says hes moving too.
To follow up, I understand that there will always be some slop in the knuckles, but isn't the majority of slack built in the drawbar or what ever you call it? It seems to me that a 75% reduction of slack would eliminate lots of the bad stuff and not hurt the good stuff that it provides. Am I being silly here?
Here is an interesting link that may apply in part. It appears that the "Association of American Railroads Cushioning and Draft Systems Committee" has very smart people to figure these thins out. (maybe) I quess I didn't realize just how many different types of coulpers there were in this world.
http://www.railwayage.com/mar01/drawbars.html
NO. Slack is not necessary technologicaly, it is built into railroad culture.
With distributed power and unit trains and further modifications it shouldn't exist. Look around to see what the rest of the world has of couplings. Not all systems have slack. Not all trains need to be so heavy. Some comodities could be shipped by rail if it wasn't for the crash bang service provided.
Railroad history has arrived with slack built into it.
Need my car use so much gas? No, not unless l felt like changing.
....After watching the live web cam available now on here viewing from the Netherlands.....I notice their trains consist {generally} include about 35 to 45 or so cars. And they really fly by the web cam at speed. I suppose a train that length would have much less slack to deal with.
Ted M.
got trains?™
See my photos at: http://tedmarshall.rrpicturearchives.net/
Ted Marshall wrote:As a railfan I really enjoy watching and hearing slack action, especially when it's a really long, heavy train with minimal power. Ex.: 150 car, 15,000 ton rock train powered by two SD40-2s. I can't imagine what it would be like to start that train if there weren't any slack in the couplers.
Imagine it without any banging of slack runout. If two SD40-2s can't start the train without "taking slack," they're not likely to move it more than a few carlengths, either. Taking slack was a steam-engine technique required by the very low starting tractive effort of the steam engine. It's virtually meaningless for diesel-electrics and straight-electrics which exert their highest tractive effort at starting.
Slack is still necessary to pull pins. Otherwise it has no great value. The larger issue is that maintenance of draft gear is a significant expense, which is why we've gone to fixed drawbar or articulated cars such as five-well double-stacks, spine TOFC cars, and permanent drawbar ore jennies as much as possible. Slack isn't that large of an issue in lading damage with proper train handling, and eliminating it is not high on the priority list.
RWM
Railway Man wrote:. If two SD40-2s can't start the train without "taking slack," they're not likely to move it more than a few carlengths, either......It's virtually meaningless for diesel-electrics and straight-electrics........
Say WHAT?!?!?!?
I'm sorry, sir, but I must respectfully disagree. Utilizing the properties of slack can be very helpful in certain operational situations.
zardoz wrote: Railway Man wrote:. If two SD40-2s can't start the train without "taking slack," they're not likely to move it more than a few carlengths, either......It's virtually meaningless for diesel-electrics and straight-electrics........Say WHAT?!?!?!? I'm sorry, sir, but I must respectfully disagree. Utilizing the properties of slack can be very helpful in certain operational situations.
So, if you absolutely need to take slack to get it started, how far are you going to get with that train? Will you be able to start it again on a hill?
I can't speak for Z, but I'd opine that the laws of momentum figure in here - it's harder to get something moving than to keep it moving. One would have to hope that you can keep the train up to a speed that will carry it over the rough spots.
As for starting it on a hill - I'd guess no. Not if it wouldn't start on the "flats".
This might be a case where the crew and dispatcher might have to work together to get the train over the road without hanging it up somewhere it can't be restarted.
Railway Man wrote: zardoz wrote: Railway Man wrote:. If two SD40-2s can't start the train without "taking slack," they're not likely to move it more than a few carlengths, either......It's virtually meaningless for diesel-electrics and straight-electrics........Say WHAT?!?!?!? I'm sorry, sir, but I must respectfully disagree. Utilizing the properties of slack can be very helpful in certain operational situations. OK, you're the throttle man, I'm a dispatcher. I should know better than to ever argue with an engineer. So, if you absolutely need to take slack to get it started, how far are you going to get with that train? Will you be able to start it again on a hill?RWM
When I was firing, my instructing engineer once started our train (2 engines, 125 cars, around 17800 tons) on a hill using slack. We had gone about 2/3 of the way up Mt. Vernon hill in eastern Iowa when the second engine shut down for some reason. We notified the dispatcher, who started to figure out who could shove us over the hill. This particular day one of the main tracks was out of service for maintenance work and we were stalled in the single track.
We were able to get the second engine running again. My instructing engineer took over and decided to try to get moving again. He took slack and started the train, one car at a time. We didn't set any speed records, but made it over the hill. Had we stopped about a mile further on, we would've been on the worst part of the grade and probably not have been able to start at all. We didn't need the shove, which was good because IIRC, we were the last eastbound for a while, and they were going to start going west thru the single track after we cleared.
Could he have started the train without slack? Maybe, but the tractive effort would've been so high that most likely a coupler or draw bar would've given first.
Jeff
....How does one "hold a train" on the hill under stalled conditions, and prepare it to take out the slack without it backing down the hill out of control.....? Does the engineer set the brakes on the following consist and push back against the applied brakes to undo the slack.....? Than what...?
Modelcar wrote: ....How does one "hold a train" on the hill under stalled conditions, and prepare it to take out the slack without it backing down the hill out of control.....? Does the engineer set the brakes on the following consist and push back against the applied brakes to undo the slack.....? Than what...?
I was wondering the same thing Q.
Jeff and Zardoz:
The question I think is this: Is taking slack a regular practice necessary to start a train, as it was in steam days? Or an exceptional and unusual practice? I think the other posters are asking if it's still a regular practice that if not employed will result in trains not starting.
My humble apologies if I overstated the case that it never occurs -- as we know in railroading there is always, somewhere, an exception to every rule.
....Maybe someone will come along Chad and give us an explaination of how they really can do that.....
Sorry if I've over read some of the posts on this subject,but here's mine.
First are we talking about the slack between the knuckes,or the slack caused by the the cushioned drawheads ?
There's roughly 1 car length of slack,or traveling distance in a 100 car coal train.
Now take a 100 car cushioned drawhead boxcar and it will be more.
But slack is necasarry for these reasons I see as working as Engineer .
If there wasn't slack in coal trains,the tonnage would be both hard to pull and stop because there would not be an opposite resistance.
In a time freight type car the slack prevents hard coupling and rough handling when stopping and starting a train,sorta stops those "Iotola of slackola " Engineers
But I'm sure theres those people with different opinions,but there's mine .
Collin ,operator of the " Eastern Kentucky & Ohio R.R."
If the train stalls on a hill, taking slack will do no good. The tonnage is too much, no matter what you do. If you stall, the only way to move up the hill is to double (triple, whatever) the hill.
However, there are locations where we would do a setout on a hill. Sometimes the tonnage dropped off is not sufficient to permit the train to get moving again if it is a solid train (slack all stretched). Same thing would apply if a pickup is done on a hill.
One does a brake set sufficient to hold the train, then gently back into the train (while the train brakes are still set) bunching the slack. Keep going until you bump into the wall (too many cars to shove). Then release the brakes while at the same time begin working the throttle as ambitiously as you dare, getting going as fast as you can (while not going so fast that you pull something apart). Hopefully the momentum of the cars already moving will be sufficient to get the rest of them moving.
Railway Man wrote: Jeff and Zardoz:The question I think is this: Is taking slack a regular practice necessary to start a train, as it was in steam days? Or an exceptional and unusual practice? I think the other posters are asking if it's still a regular practice that if not employed will result in trains not starting.My humble apologies if I overstated the case that it never occurs -- as we know in railroading there is always, somewhere, an exception to every rule.RWM
As far as I know, taking slack is not that necessary that often anymore, except for isolated locations that due to grade and/or curvature that will always require special operations. With the high-adhesion locomotives and all roller bearing cars, trains roll much easier these days.
Railway Man wrote: OK, you're the throttle man, I'm a dispatcher. I should know better than to ever argue with an engineer. So, if you absolutely need to take slack to get it started, how far are you going to get with that train? Will you be able to start it again on a hill?RWM
OK, you're the throttle man, I'm a dispatcher. I should know better than to ever argue with an engineer.
Engineers are wrong as often as anyone else. Each of us has our areas of relative expertise. That's why a good dispatcher will consult with an engineer if he has any questions about how to plan a meet or overtake; and a good engineer will consult with the dispatcher if there is any question as to how trains are to be blocked, prioritized, etc.
FYI: I left railroading years ago, and am now a truck dispatcher. I frequently ask my drivers about what would be the best way to do certain runs. The drivers are the ones actually at the customer location; they see what is going on; they are familiar with the territory; they know what their truck can do and cannot do; that's why I ask their advice. Sometimes they will ask me why I am routing them a certain way, and I always take the time to explain why (customer priority, late shipments, etc).
Regarding your question, no. Once you stall, all the slack fiddling will do nothing except create scrap metal. The only way to proceed after a stall is to double the hill.
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