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Thread: Slack and yank?

  1. #1
    Join Date
    Dec 2019
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    Default Slack and yank?

    Hi sorry I am still not up with all the train terms and so am just wondering what Slack and yank actually mean in say OR or real life for that matter - I had thought it related to if a train starts too fast or a sudden acceleration, but is this right? And can it happen in OR - when I play I never find that my engine ever starts too fast, everything is always gradual and if I happen to start to fast then wheel slip stops me - I am not deliberately wanting coupler breaks but I have been reading other players experiences in OR and Run8 and it does sound exciting to have to deal with the challenge of possible breaks .
    Also I am hardly an experienced engineer so I would anticipate making mistakes - which I think is a big part of the appeal of Sims - train, racing and flight Sims especially - that one can progressively get better, so if I am driving and not having any breaks happen, I presume I am doing a good job yes? Or does it depend on the train set and it's properties?
    I read another post from a while back where someone was unable to climb a grade with a train simulations trainset on a route despite to their knowledge such a climb from 0.8% being possible and one comment was that some 3rd parties just aren't familiar enough yet with OR- so it does depend on the trainsets?

  2. #2

    Default The 'Why of Slack'

    I asked a Union Pacific engineer "How do you start a heavy, 10,000 ton, train." Her answer was "One car at a time." So in real world rail operations, that is the reason for slack.
    There have been some discussions at Elvas Tower regarding how OR handles slack.

    I watch a lot of cabride videos. Tram rides through the citys of Europe also has me hooked!
    That being said that the absolute longest freight consist I've seen in all Europe railroads cab ride videos (youtube) was 45 wagons with most having 25 to 30 wagons.
    The reason is simple. the couplers have NO slack at all. Thus starting tonnage usually runs about 1000 to 3000 metric tons as some videos publish consist specs. Quite interesting.
    The 3000 ton is pure speculation from when I observed two electrics pulling 11 tankers.

    Some links:
    Freight: https://www.youtube.com/watch?v=eb6fV5eyjp8
    Tram: https://www.youtube.com/watch?v=MoPBANJY_qA
    Freight: https://www.youtube.com/watch?v=QCx9Qa7ZRUE
    Tram Incidents: https://www.youtube.com/watch?v=mshJ7L3VGj8

    Enjoy,
    ............Vince ..............
    ...... Author NECv4 .......
    .... LIRR BUILD PHOTOS ....
    .............LIRR VIDEO.............
    ...... Eschew Obsfucation ......

    On the The Statue of Liberty in New York Harbor there is a Tablet. On it is written:
    "Give me your tired, your poor, your huddled masses yearning to breathe free,
    the wretched refuse of your teeming shore, send these, the homeless, tempest-tossed to me,
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  3. #3
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    Doreen, Victoria, Australia.
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    Default

    >unable to climb a grade

    We have a thing called a "ruling grade load" for each hill and each engine.
    When you build a train you have to take into account, grade and speed.
    Passenger trains typically have 5 - 10hp/tonne.
    Freight trains can have 1/2 - 5hp/tonne.

    Slack is the amount of gap in the coupler when done up.
    When you have 200 cars the slack can be 6 feet or more if the couplers are well worn.
    Cheers
    Derek

  4. #4
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    Default

    oh my - wait 6 feet? what does even look like? i am still learning about the different couplers out there - how is that possible? is that for some kind of loose coupling?

  5. #5
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    Default

    Quote Originally Posted by Heruraha93 View Post
    oh my - wait 6 feet? what does even look like? i am still learning about the different couplers out there - how is that possible? is that for some kind of loose coupling?
    That is six feet over the full length of the 200-car train.
    IBM XT i386; 512Kb RAM; 5.25" FDD; 1.4Mb FDD; 5Mb HDD; VGA 256-colour graphics card; AdLib soundcard; DR DOS 6.0; Windows 3.0

  6. #6
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    Default

    ah right okay that makes more sense, i was thinking 6 feet between cars which seemed crazy to me but then i am not up with all the ways waggons get coupled.

  7. #7
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    Quote Originally Posted by Vince View Post
    The reason is simple. the couplers have NO slack at all. Thus starting tonnage usually runs about 1000 to 3000 metric tons as some videos publish consist specs. Quite interesting.
    No, it isn't. There's plenty of slack in the couplers. A far more practical reason for the max. length of freight trains is the general length of yards and sidings. Because of the high frequency passenger services, freight trains are often held in sidings and loops for many times during their full run. Obviously, you don't want freight trains which are longer than these sidings. Many shunt yards, most of which date back to early steam days, also have limited length. That's what sets the maximum length for freight trains (about 35 4-axle wagons here in the Netherlands, for instance).

    Regards,
    Rob Roeterdink

  8. #8
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    Search mendip rail jumbo trains.When I was driving trains,we had a train of maybe 30 odd loaded PGA wagons fitted with instanter couplings.I would estimate the slack would be 15 to 20 feet which required very careful handling to avoid broken couplings and "snatches".

  9. #9
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    Default

    Hi Folks,

    I think Peter started work on coupler slack in ORTS but I don't think it's done... While we have the animation modeled - the physics don't seem to be there - as the locomotive must overcome the friction of the entire train to start it moving - as opposed to the "one car at a time" as mentioned above... I've done some pretty comprehensive testing and reading on steam trains - the controlling friction limiting the length of a train should be the friction between 5 MPH and 10 MPH - not the startup... In ORTS it is definitely the startup...

    Regards,
    Scott

  10. #10
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    Default

    There is slack in the couplings in OR, but it is minimal and gives the impression of having none on starting. Once rolling, slack action can be observed along the train under braking and acceleration
    Beer is not a matter of life or death, it is much more serious than that.

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