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Semi Truck Heavy Haul Trailer Axle Spacings

  1. May 28, 2012 #1
    I am try to build a 5 axle tractor(twin steer,tri-drive)
    to pull a heavy haul trailer(jeep 2axle, trailer 3axle, booster 2axle).
    Overall truck/trailer length 120 feet.

    I am trying to determine balance points to equally distribute the weights on all axles.
    I do know that the front steer axle will not carry equal weight.
    It will probably be less than the others.

    A CAD program that would allow me to test the different positions with different weight factors unladen and laden would help.

    I do not know which thread to post to to ask for help.
  2. jcsd
  3. May 29, 2012 #2
    I'd use a spread sheet, unless I thought ANSYS work bench would better impress the customer.
  4. Jun 3, 2012 #3
    I am looking for a software application to evaluate the axle load weights that will occure by using different axle spacings throught the overall length of the truck trailer combination.
    I am building this for myself.
  5. Jun 3, 2012 #4
    If you just want "quick and dirty", you might try the freeware program "BeamBoy". I have no idea how accurate it might be for your project.

    (FYI: Version 2.2, released in 2001, is the latest version. It's available from numerous download sites.)
  6. Jun 7, 2012 #5
    How about just a free body diagram in the spreadsheet like the other poster suggested. I believe most tires or axles are rated for 12000lb's, that will be your limited factor
  7. Jun 7, 2012 #6
    Axles can be rated for much more than 12kips. That is part of the design engineer's job to specify how much capacity he/she needs. But if it is to haul heavy loads on the road, then the maximum axle capacity will be specified by whichever DOT has jurisdiction. 20-24 kips per axle is quite common for the 18 wheel configuration, with a maxium gross weight of 80 kips, unless you buy over weight permits. Spacing the axles further apart can also get you more legal capacity.

    But a modern truck can be adjusted over a great range to balance the loads out between the axles. The fifth wheel hitch on the tractor can be moved forward or aft, and often the rear trailer wheels can be moved on a rail.

    As two of us have already mentioned, the best and simplist solution is to draw a free body diagram and write your equations, and then kick out a quick spread sheet. If someone were to give you the perfect software for this application, you could have a solution much quicker with the spread sheet than you could install, learn, and set up the software. This is one of those problems with a five minute solution.
  8. Nov 11, 2012 #7
    That is part of the design engineer's job to specify how much capacity he needs. I think you should ask for the opinion of specialist to configure it correctly. Or if you want to know more about axle tractors and other trucks I recommend you to visit this site. http://heavyhaulingjobs.blogspot.com/
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