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Thread: What decides how many locomotives for a train?

  1. #1

    Default What decides how many locomotives for a train?

    Experience or formula?
    Ostentatiously humble.
    My patients' arrhythmias straighten themselves out!!
    Innocent by reason of sanity.

  2. Default HP Assignments

    Quote Originally Posted by Robert Gift View Post
    Experience or formula?
    Wow, big question. I'm not a motive power dispatcher, but as I understand it, there's a formula for how many horsepower to assign per ton over a particular district depending on how fast you want the train to go. Flat midwest will take less HP per ton than climbing mountain grades. A hotshot will have more HP per ton than a drag freight. Others can fill in better than I, I'm sure.

  3. #3

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    I think it also depends whether the locomotives on hand are AC or DC traction.

  4. #4

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    My buddy is one of our Power Coordinators for Roseville, we call them RH1. (It stands for Round House 1) So he is the one who gets the train info then has to build the consists for the train. Here is his answer "Kinda hard to put into words...it deals with tons per axle. A loco has a ratio that each traction motor can pill. Of course the bigger the unit the more the traction motor can handle."

    When I asked if it matters if the train is on flat land or mountains he said "Yes it does."

    Althought this is only a half assed answer it came from the horses mouth.
    Chris AKA: Youngest Old Timer
    Machinist for Uncle Pete in Roseville CA

  5. Default

    TPA (Tons Per Equivalent Powered Axle) usually determines how many engines.
    Im looking for "She Who Laughs On Her Knees"

  6. Default

    The short answer is 'formula informed by experience'.

    A particular train will have a horsepower per ton (or tons per equivalent powered axle for you younger folks) requirement. This is a fairly strict formula that depends on the terrain (grades, curves) and speed (slow freight, higher speed intermodal). If train MRVPT has 8,000 tons and requires 2.2 hpt then you need 17,600 horsepower worth of locomotives.

    Usually, however, there isn't much variation, because often times the central power desk will stipulate that a certain train ALWAYS has to run with at least 2 units because those units are then needed on another train. So, even if that particular day's train tonnage may be low, you still have to send it out with 3 units otherwise the power desk will have kittens because you've now totally screwed up the outbound train planning for the next couple of terminals. And, if you've got more tonnage than normal, there isn't usually an extra unit sitting around with nothing to do, so you reduce tonnage instead.

  7. Default Al Krug's website

    This has answered a lot of questions I had:

    http://www.alkrug.vcn.com/rrfacts/rrfacts.htm

  8. Default

    On CN we use Hp per ton to calculate the number of locomotives to use on a train. Other factors come into play too such as restrictions on the number of driving axles. Some subdivisions only allow 12 or 18 driving axles per locomotive consist.
    Tyler

    Long Live GE!!

  9. Default

    Quote Originally Posted by Ed Sand View Post
    Usually, however, there isn't much variation, because often times the central power desk will stipulate that a certain train ALWAYS has to run with at least 2 units because those units are then needed on another train. So, even if that particular day's train tonnage may be low, you still have to send it out with 3 units otherwise the power desk will have kittens because you've now totally screwed up the outbound train planning for the next couple of terminals. And, if you've got more tonnage than normal, there isn't usually an extra unit sitting around with nothing to do, so you reduce tonnage instead.
    Also, just because there are 3 or however many locomotives in a consist does mean that they are all online and working to move the train.

  10. #10

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    Thathought also occurred to me because I was the only passenger on a 20-seat commercial flight from San Francisco to Santa Barbara. I asked why they flew it rather than have me depart later or go on another airline. They needed the aircraft to depart from Santa Barbara.

    Is it better to have less locomotives working harder than more working less?
    Withome furnaces, it is better to have a smaller furnace working harder than larger furnace working less.
    Ostentatiously humble.
    My patients' arrhythmias straighten themselves out!!
    Innocent by reason of sanity.

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