Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Axle load distribution with equalizing 6 row trailer

Axle load distribution with equalizing 6 row trailer

Axle load distribution with equalizing 6 row trailer


I was wondering if I could gain some assistance in explaining how to calculate axle loads on a 6 row hydraulic "load equalizing" trailer.

For example the trailer is 13.99 m long, with 6 rows of axles with 8 tires per axle, axle spacing 1.83 m.  The trailer has a goose neck at the front hitched to the turntable on a prime mover.  See attached file for diagram.  The suspension is supposedly "hydraulically equalising dampened, trailing arm suspension."  Available suspension travel is 600 mm if that is relevant.

My question is, if a 50 t load is placed on the rear of the trailer 3 m from the end, how is the load distributed?  I don't understand how the suspension works and if the load is  actually equalized over the six axles or is higher towards the back where the load is.

If the load isn't equal, how does one work out the distribution in each axle?

Many thanks in advance.

RE: Axle load distribution with equalizing 6 row trailer

At best, the equalization works from wheel-to-wheel on the same axle, not necessarily across axles.

I would consider the footprint of the load and distribute its majority to the axles directly under the load, declining as you progress away from the load.  All axles will take some of the load...the stiffness of the deck will assure that.

RE: Axle load distribution with equalizing 6 row trailer

You don't say how long the 50t load is, but assuming it as a point load, then it is roughly over or centered over the centerline of the last and second from last axles.

If the suspension is "hydraulically equalized" (I suspect pneumatic air bags) then the load will cause the trailer deck to drop somewhat.  The load levelers on each axle will adjust their positions to bring the deck back to its original position, loading each axle as needed to do so to the extent of the air (or hydraulic) pressure available.

So assuming that the deck doesn't deflect or buckle, each axle will take the load necessary to return the deck to its original position which is the set point of the load leveling valves.  

Since the trailer is supported at the goose neck, some of the reacted load will transfer to the driver (which is not a bad thing with respect to maintaining traction for a 50t load.

So, I see the load being carried by axles loaded with a bias toward the rear lessening as each axle position approaches the goose neck connection point.

It is all dependent on the deck position and the amount of load transferred to the driver.

That is the nice thing about air rides; each axle doesn't know that any other axles exist, it only knows that it wants to inflate the bags in order to satisfy the load leveler valve position set point.

This can be a problem when a single axle tries to cross over a hump.  That is why some air suspensions will have maximum pressure limiters; to keep that axle from trying to lift the entire load of the trailer at which time the rest of the axles would be just happy to unload their bags.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close