Semi Truck Heavy Haul Trailer Axle Spacings

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Discussion Overview

The discussion revolves around the design and weight distribution of a 5 axle tractor and heavy haul trailer combination. Participants explore methods for calculating axle load weights based on different axle spacings, considering both unladen and laden conditions. The conversation includes software recommendations and practical approaches to balance the weight across all axles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks to determine balance points for weight distribution across all axles of a heavy haul trailer setup, noting that the front steer axle will likely carry less weight.
  • Another suggests using a spreadsheet for calculations, while also mentioning the potential use of ANSYS workbench for a more professional presentation.
  • A participant expresses interest in software that can evaluate axle load weights based on varying axle spacings for their personal project.
  • One suggestion is to use the freeware program "BeamBoy" for quick calculations, though its accuracy is uncertain.
  • Another participant proposes creating a free body diagram in a spreadsheet, mentioning that axle ratings typically limit to around 12,000 lbs, but higher ratings are common in practice.
  • It is noted that axles can be rated for more than 12,000 lbs, with common ratings between 20-24 kips for 18 wheel configurations, and that spacing can affect legal capacity.
  • A participant emphasizes the importance of moving the fifth wheel hitch and rear trailer wheels to achieve better load balance and suggests that a free body diagram and equations could provide a quick solution.
  • Another participant recommends consulting a specialist for proper configuration and suggests a website for further information on axle tractors and trucks.

Areas of Agreement / Disagreement

Participants express a mix of opinions regarding the best approach to calculate axle load weights and balance. While some suggest practical methods like spreadsheets and free body diagrams, others advocate for specialized software or professional consultation. No consensus is reached on a single best solution.

Contextual Notes

Participants mention various software options and practical methods, but there is uncertainty regarding the accuracy and effectiveness of the suggested tools. The discussion also highlights the need for specific design considerations based on regulatory limits and engineering requirements.

Rodeodad
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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.
 
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I'd use a spread sheet, unless I thought ANSYS work bench would better impress the customer.
 
I am looking for a software application to evaluate the axle load weights that will occur by using different axle spacings through the overall length of the truck trailer combination.
I am building this for myself.
 
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.)
 
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
 
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.
 
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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