Help on bridge law formula for semi dump

Discussion in 'Tanker, Bulk and Dump Trucking Forum' started by T-800, Aug 24, 2018.

  1. NightWind

    NightWind Road Train Member

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    It's all about the distance between the steer axle and the back axle on the trailer. Keep in mind that unless you have a spread you'll still have to get the axles correct
     
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  3. bigguns

    bigguns Road Train Member

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    You MUST take into consideration the inner bridge which is axle 2 to axle 5 or axle 2 to axle 6 if you have a tri-axle.
     
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  4. T-800

    T-800 Light Load Member

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    This is the part that confuses me. If this is the deciding factor, than I need a 40’. But if it’s axle 1 to axle 5, I can go shorter. I don’t know which one to go off of
     
  5. Slowpoke KW

    Slowpoke KW Heavy Load Member

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    Both
     
  6. special-k

    special-k Road Train Member

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    Afaik the inner bridge is from the rear drive axle to the first fixed axle on the trailer not the rearmost axle.
     
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  7. T-800

    T-800 Light Load Member

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    So I will need a 40’ then. Dang
     
  8. BKLusk64

    BKLusk64 Light Load Member

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    By federal bridge law you need 51feet center of axle 1 to center of axle 5 for 80,000 lbs. Then you also need at least 36 feet from axle 2 to axle 5 to carry 68,000 lbs. 12+34+34. If you can legally carry more than 12,000 on your steer axle you might be able to shorten up the 36 feet between axle 2 and 5.

    Hope this helps
     
  9. T-800

    T-800 Light Load Member

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    Well if that’s the case I’m curious to know what the length on a 36’ would be. I wonder if I could get away with a few inches short

    Edit* I mean what the king pin to rear axle is.
     
    Last edited: Aug 25, 2018
  10. MACK E-6

    MACK E-6 Moderator Staff Member

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    If your trailer is a tri-axle, you can have 32 feet from the front drive to the rearmost trailer axle, but then you need to have a long enough tractor to still have 51’ from the rearmost trailer axle to the steer.

    With the trailer axles though trying to max the steer axle out should become a non-issue. You’ll just have to get used to running slightly tail heavy.

    I’ve seen dump trailers consisting of a shorter bucket mounted on a longer chassis. Something like that might be what you’re looking for.
     
    Last edited: Aug 26, 2018
  11. T-800

    T-800 Light Load Member

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    I’m needing a frameless for weight. Thank you for the info. That was more what I was looking for. I found a 36’ frameless tandem but wasn’t sure if it would work with the inner bridge
     
    Last edited: Aug 25, 2018
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