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Thread: BNSF Tier-4 ET44C4 and GECX ET44AC Demo Units (Big Blues)

  1. #11
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    That sounds great!

    Once all these new lines of physics have been finished are we going to be able to add them to multiple .eng/.wag files using RR?
    Borislav
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  2. #12
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    OK, it took a little longer to compile than I estimated, but here it is. This data sheet shows model, nominal transmission efficiency, gross horsepower, adhesion, continuous tractive effort, and minimum continuous speed. If you know the weight of the unit (I could not list that as some units vary widely (for example with the SD40-2, Milwaukee had some as light as 356,800 pounds, while Burlington Northern had some that weighed 419,500 pounds)), you can multiply the adhesion X weight to get starting tractive effort. In the SD40-2 example, The Milwaukee unit would have about 94,550 pounds of starting tractive effort, while the BN unit would have about 111,168 pounds of STE. They both would have the same CTE so above 11 mph the heavy unit doesn't do more, and it adds to the consist weight, but it will start a heavier train. The adhesion values assume good quality clean rail in dry weather, thus these are the optimum, weather and debris will degrade the adhesion. You will note, my data is internally consistent. When you look at a site like DieselShop, the data is NOT internally consistent. All these except the Erie are freight gearing, CTE would drop and MCS would increase for faster gearing. George Elwood's site has many operators manuals for locomotives, which will expand on how gearing effects TE and speed.
    Attached Files Attached Files

  3. #13
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    Thank you, Bob!

    I don't think I understood how to get the STE.
    Borislav
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  4. #14
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    Let me explain. A DC electric motor, at very slow speeds develops an almost vertical increase in torque. This condition can't be tolerated very long, but it does mean that for any reasonable horsepower (kilowatt), a diesel electric locomotive is limited not by power, but rather by weight on the driven axles and adhesion. If you know what a locomotive weighs, then you get the starting tractive effort by multiplying the weight by the adhesion, for example if the locomotive weighs 429,000 pounds and has a nominal adhesion of 35%, then it's starting tractive effort is 429,000 * 0.35 = 150,150pounds of force = 667.9kN of starting tractive effort. It can only stay in that condition a few moments, but it is enough to start a train rolling. As speed builds the electric motor's torque crosses the adhesion limit, and the ability of the locomotive to pull the train becomes limited by the torque production of the electric motor. This becomes constrained by short term ratings and continuous tractive effort, which is a function of electric motor ability to absorb current. As speed increases the motor needs more and more power to accelerate the train, and to maintain track speed. If you don't need a very high track speed, then a heavy lower powered locomotive will suffice (this is why the iron ore roads used SD7s to pull heavy trains, they had no competing traffic, so speed was not an issue). I hope this helps!
    BTW, adhesion is limiting also for AC designs, but the explanation is a little more complicated.
    BTW2 this applies to a unit with all axles driven. If the unit has A1A trucks, then the adhesive weight would be 2/3 the total weight if you ignore weight transfer (appropriate for older A1A designs) and using about a 15% increase for weight transfer in latest A1A units (415,000*0.6666*1.15*adhesion).
    Last edited by plainsman; 03-06-2019 at 01:36 PM.

  5. #15
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    Note, a SD45, a SD40, and a SD39 that all weigh the same, will have the same starting tractive effort (they have the same adhesion), and the same continuous tractive effort, since they have the same traction motors, even though they have different horsepower. The additional power is only needed if you want to pull the train faster, or accelerate more quickly away from stops).

  6. #16
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    Quote Originally Posted by plainsman View Post
    Note, a SD45, a SD40, and a SD39 that all weigh the same, will have the same starting tractive effort (they have the same adhesion), and the same continuous tractive effort, since they have the same traction motors, even though they have different horsepower. The additional power is only needed if you want to pull the train faster, or accelerate more quickly away from stops).
    Well I just learned something new. I always thought they were diffrent weights, due to some haveing diffrent fuel tank sizes.

  7. #17
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    Hi Michelle,
    Typically they are different weights, the SD39 usually lighter, because it isn't usually put in long distance service, so it is lighter. But Milwaukee Road had some extra light SD40s at 356,800 pounds (some routes had some very weak bridges) and Burlington Northern had some SD40-2 units that weighed over 420,000 pounds. Most commonly, the SD40 would be the heaviest on most roads, because it was the long distance heavy haul locomotive. The SD45 usually was a little lighter, as it was run on light fast trains, often reefers and TOFC. The SD39 was usually lighter still, as it was often more a shortline and yard roustabout. But there could have been a road that had all three the same weight.

  8. #18

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    Hello there.

    Do you guys know of anybody who might have a GECX Blue repaint of an ET44AC? I got the UP Salad Bowl and will work the same way as the CP Mactier Evolution. I noticed on ORTS screenshots a picture of a GECX ET44AC demo unit

  9. #19
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    Sir,

    I made the GECX 2022 and 2025 unit some time ago. However, it's rather old, and needs some updates. The FA needs to be rebuilt, and it needs a new ENG file.

    Don't expect a release anytime soon, but it's not out of the question.
    Parker B. - A Misplaced Midwesterner.

  10. #20

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    One i did a while back. SFCAN048.jpg

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