Results 1 to 7 of 7

Thread: A question about the Milwaukee Road Slug Sets

  1. #1
    Join Date
    Mar 2011
    Location
    MP44.2 Worcester, MA
    Posts
    165

    Default A question about the Milwaukee Road Slug Sets

    Hi all,

    I recently downloaded the Milwaukee Road Slug Set. It is beautifully done however I have a question about the engine physics. It is my understanding that a slug is a locomotive with the prime mover removed. A slug is used for increased traction.

    The slugs in this set are 1500 HP, minus a small percent for efficiency. Since there is no prime mover in a slug the HP rating should be zero. These locomotive sets are actually ABA configurations.

    I have noticed the same issue in several other slug downloads available on this site.

    Also, I leave it to the physics gurus to determine what the maximum pulling force should be.

    Fred

  2. #2
    Join Date
    Oct 2006
    Location
    Lancaster, Pennsylvania
    Posts
    2,226

    Default

    https://en.wikipedia.org/wiki/Slug_(railroad)

    You'll note that while they do not have a prime mover, they do have traction motors which are supplied from the main locomotive(s). So slugs having HP values is accurate, then.

  3. #3
    Join Date
    Aug 2007
    Location
    Carolina's
    Posts
    2,644

    Default

    Some of the slugs Milw and C&NW built, retained the engine for ballast weight. Some had concrete blocks fitted.

    The electric motors picked up their power from the A units. Usually 1 truck of the slug got power from one A unit. The other truck from the other A unit.

    Robert

  4. #4
    Join Date
    Dec 2012
    Location
    Netherlands
    Posts
    18

    Default

    A mother-slug combination is basically a 2-part locomotive with only a prime mover in the mother. So the power output of the prime mover is equally divided between the traction motors of the mother and the slug.

    I don't think it's possible to set up a slug in OR of MSTS so that it draws power from the mother. So you'll have to mimic this behavior by adding a power rating to the .eng file of the slug. But it also requires derating of the power of the mother unit(s). So the MILW slug set F7A-slugB-F7A units should each have a power rating of 1000 (minus a small percent for efficiency). This because the power output of the F7A's = 1.500*2 = 3.000 hp. This total power is shared by the three units, giving them 3.000/3 = 1.000 hp each.

    The above only works when mother and slug have the same number of powered axles. For a 6-axle (SD40) mother and a 4-axle slug the numbers are 3000/10 = 300 per axle. So the mother power rating should be 6*300 = 1.800 and the slug rating should be 4*300 = 1200.

    Wim
    Last edited by brama; 12-08-2019 at 04:20 PM.

  5. #5
    Join Date
    Mar 2011
    Location
    MP44.2 Worcester, MA
    Posts
    165

    Default

    The lead and rear engines in the set have a total 1500hp + 1500hp or 3000hp. It makes no difference how many motors the slug has. There is only 3000hp for all the motors to draw from. A traction motor cannot supply its own power.

    In the MSTS/OR world this problem could solved by reducing the slugs MaxPower value to zero hp.

    There is a further problem that these are road switchers and would probably cut out automatically at about 35 or 40 mph. At that point the pulling force suddenly disappears and the engine becomes dead weight. I don't think there is any way of doing this in the .ENG file.

    Fred

  6. #6
    Join Date
    Jan 2005
    Location
    USA
    Posts
    306

    Default

    If you reduce the slug's power to zero you won't be able to take advantage of the slugs tractive effort. You will be towing a dead unit around. The closest thing to do to mimic the real thing is what was mentioned above, divide the HP between the mother units and the slug. But then if you later decide to use the mother units alone with out the slugs then you will have to again adjust the power setting back to full HP.

    Ron

  7. #7
    Join Date
    Mar 2011
    Location
    MP44.2 Worcester, MA
    Posts
    165

    Default

    Ron,

    It looks as if I'll have to reduce the HP of each unit to 1000 HP. Since this download came with consist files, if I reserve these engines for the slug consist, I won't have to worry about switching the MaxPower back and forth.

    Fred

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •