With hi-power diesels these days is train slack still a must to start a long train a moving. Maybe cars could be manufactured with less slack or even very little. Wouldn’t this help in alot of cituations?
Welcome to the forum.
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.
Even if you take all the slack from between the knuckles you still have cuhioned drawbars to worry about. Some engineers can run a good train and have little slack action and others are just murderous. Then somedays you get them to switch spots lol. I know when I am having a bad day I try to calm down and take it a bit easier.I try not to be rough with the equipment as I like my conductors ( Usually) and dont want them to have to walk back and fix any problem I may have caused.
…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…
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.
Not to mention that it would be rather difficult to uncouple cars if there was no slack.
You would almost need a compressed air powered slack-removing wedge with spring withdrawl on each coupler. And even that would need a bleed valve in order to pull the pin with the trainline charged.
…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.
I think slack might be called a necessary evil. I don’t believe that slack was provided for the purpose of starting a train one car at a time, however, it was put to that use. As has been mentioned, couplers require a bit of slack to allow the knuckle lock to slide into position. The coupler parts are cast without machining, so they have a considerable dimensional tolerance. To allow for that tolerance, and for the fact that they are not lubricated, the parts must fit rather loosely. The accumulation of that looseness adds up to the coupler slack. Link and pin couplers had much more slack generally because there were a lot of manufacturers making the parts, which were not exactly and not always interchangeable. So they had more looseness to accommodate the greater variation of parts.
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.
Today’s automatic coupler is built into the culture. When you begin to change anything about the cars, they must still be compatible with the cars than have not yet been changed.
…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.
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
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. [xx(] 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
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.