New HELP! Weight distribution?

Discussion in 'Heavy Haul Trucking Forum' started by jrscott1970, Apr 24, 2015.

  1. jrscott1970

    jrscott1970 Light Load Member

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    I am new to pulling drop deck and RGN trailers. Can anyone tell me the proper way to load an item for weight distribution that can not move under its own power. Is there an easy formula for figuring out where to place the item according to axles and whether you have a dollie/jeep, so you get the weight equally distributed? I have to test on this and I'm not too sure how to figure it out on paper. Basically a square, overweight
    box that won't take up entire deck.
    Thanks for your help
     
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  3. otherhalftw

    otherhalftw R.I.P.

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    Is the weight equally distributed within the "box". First question will be where is the "center of weight" of the "package". If heavier on one end, this will add to the placement over axles.
     
  4. Heavy Hammer

    Heavy Hammer Road Train Member

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    See post #218 in the other thread where you asked this question...http://www.thetruckersreport.com/tr...iscellaneous-thoughts-ideas-questions-22.html
     
  5. Heavy Hammer

    Heavy Hammer Road Train Member

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    Load Placement Calculation 101
    Required values to be known;
    1-Empty weight of tractor
    2-Empty weight of trailer
    3-For more precise calculations, actual empty axle weights of unit* versus estimate
    4-Wheelbase of trailer. (Kingpin to center of trailer axle group. Center of two axles on tandem, center axle on tri, quad, 5, blah blah blah)
    5-Payload weight, more specifically and way more crucial the bigger you get, the COG of payload (C/G or COG Center Of Gravity, the center point of the weight of a load)

    Example: (round numbers for simplicity)
    1-22,000# fully rigged highway tractor
    2-11,000# combination step deck
    3-*Based on experience roughly 75-80% of a deck tare weight sits on the trailer axles...so
    11,500 on the steer axle
    13,000 on the drives
    8,500 on the trailer
    4-We are pulling a 48' step deck with 41' from the kingpin to the center of the tandem trailer group. 41' is 492".
    5-We are going to load a 47,000# load off a ship with their crane on a closed spread tandem! We only get one shot at this and we're good, so we're gonna get it right!
    This load is 15' long. BUT, the COG is 2'6" from center! So that means even though the load is 15' long, the center of the weight is 5' from one end and 10' from the other...the importance of this comes later.**

    The Formula Is:***
    X= (Target axle weight - Tare axle weight)
    Y= (X / Payload) ... Y is percentage of wheelbase to measure and mark placement of COG
    T= (Y * Wheelbase) ... T, that's our Target for the COG!

    So, in our example, we must land this load at max legal (US 80,000 GVW) axle weights
    X= (34,000 - 8500). So X is 25,500#.
    Y= (25,500 / 47,000). So Y is 0.5425 or 54.25% of the payload must sit on the trailer axles, which of course is 54.25% of the trailer wheelbase.
    T= (0.5425 * 492"). So our Target is 266.91" from the kingpin of the trailer.

    Now that we know our Target we measure out 266 15/16" from the kingpin and put a mark on the trailer here. This is where the COG needs to sit to properly scale this load. Remember, the target is the weight, not the dimension. If the load is balanced front to back, then you can use dimension.

    **Now here is where we show off how good we are. The trailer has a 24" kingpin setting. Add that to "T" is 290 15/16. We know that with the COG 5' in from the heavy end of the payload, we'll subtract the 60" (measurement from the front of the load to the COG, the real Target) and come up with 230 15/16" (19'2 15/16"). We'll hook our tape on the front of the trailer tell the loadmaster to set the front/heavy end of the load at that measurement and when it's right, we say "drop it, and cut it free."

    Oh yeah, you can actually use this exact same formula to calculate the "T" for the 5th wheel setting on your tractor as well and get the exact split for 12/34. This works for big multi-axle components as well, I use it all the time on my 9axle. The caveat to this formula is; variable control (regulator type drop axles) are exactly that, variable and throw things off.

    ***(It's a multi line and split formula when wrote down and I don't know how properly display it in this forum format, so I'll break it down, then see if I can get a scan of the "proper" formula and add it later.)
     
    Truckdobe, not4hire, xsetra and 2 others Thank this.
  6. jrscott1970

    jrscott1970 Light Load Member

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    Thank you so much Heavy Hammer. That's exactly what I needed. I'm a visual person, and can usually load ok without this, but real heavy stuff and rgn,drop decks had not been in my wheelhouse in the past. I needed to test this week on paper, and needed the formula. Im terrible at math, but lucky for me I have a smart wife who broke it out all down for me. God bless both of you. Keep safe.
     
  7. xsetra

    xsetra Road Train Member

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    G dang I'm glad I don't haul heavy. That just gave me a headache. Good information. Thanks
     
  8. TripleSix

    TripleSix God of Roads

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    They won't really be concerned with the answers that you put down on paper. The true test is whether or not you can explain your answers.
     
  9. Heavy Hammer

    Heavy Hammer Road Train Member

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    That's not heavy...the example is 5 axle at 80,000lbs.
    It's actually a real loading situation I've done several times.
     
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