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Axle load distribution with equalizing 6 row trailer
2

Axle load distribution with equalizing 6 row trailer

Axle load distribution with equalizing 6 row trailer

(OP)
Hi,

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.

rmw

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