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Box or U-shape tipper design?

There are many types of tippers and dump trucks and trailers. Each one should ideally have a fit-for-purpose design. And they have many names.

A dump truck, known also as a dumping truck, dump trailer, dumper trailer, dump lorry or dumper lorry or a dumper for short, is used for transporting materials (such as dirt, gravel, or demolition waste) for construction as well as quarries and mines. A typical dump truck is equipped with an open-box bed, which is hinged at the rear and equipped with hydraulic rams to lift the front, allowing the material in the bed to be deposited ("dumped") on the ground behind the truck at the site of delivery. In Europe, Australia, Africa and India the term dump truck applies to off-road construction plants only and the road vehicle is known as a tipper, tipper truck, tip lorry, tipper lorry, tip truck, tip trailer or tipper trailer.

But regardless of their name and their design, a good dump truck should be lightweight yet strong and durable, as well as cost-effective. The most common dump body designs are the traditional box, and the U-shape, sometimes called half-pipe, half-round, elliptical or curved design.

The flexibility or innovation potential of a design depends on the deformation limits of the body. If mild steel is specified for a rigid box design, a lot of stiffeners are needed that will add extra weight to the body. If the bending and deformation limits are not the main problem, you can design a lighter-weight body without the same amount of stiffeners and achieve a more versatile design.

Box shape tipper design considerations

Heavy loads in a box body put pressure on the insides of the body depending on gravitational movement. The pressure is usually greater at the bottom than at the sides. This means that there will be maximum stress at the corners in a box shape design.

In this type of design, the corners are often joined together with welds. When you use high-strength steel like Hardox® wear plate, the parent material is often stronger than the welded joint. This means that the weld will be placed where the stress is at its highest, which is not preferable.


Box tipper body design

U-shape tipper design considerations

In a U-shape design, sometimes called a half-pipe design, part or all of the body is rounded in the shape of a U.

The actual shape can vary, from a squarer cross section to a more rounded cross section. The corners of the body can be bent in various ways.

The main method of forming the corners is to use a press brake, which is more flexible and can bend a longer section than a roller bending machine. Because the U-shape does not have any corners and the load distribution is over the entire design, the stress is not centered. The risk of placing welds in high-stress areas is therefore lower with the U-shape design. Finally, because the U-shape lacks sharp corners, it usually has a longer service life.

U-shape tipper body design

Benefits of U-shape over box tipper shape

A U-shape design presents many advantages over a box shape design:

  1. With a rounded shape, thinner steel gauges can be specified and fewer stiffeners used than with a box shape. The resulting structural optimization also brings a reduction in weight.
  2. It is potentially cheaper to produce, with fewer component parts and less welding.
  3. The contoured body optimizes material centering, reduces carry-back and improves load discharge (see illustration below for load distribution differences between box shape and U-shape designs).
  4. Without stiffeners the center of gravity is lower and the load carried is more stable.
  5. Because a U-shape body is rounded, material does not get stuck in any corners, making clean-up easier.
  6. A larger tailgate opening allows larger stones to be discharged.

Load distribution for a box tipper design (left) and a U-shape tipper design (right).

Exploded illustration of a U-shape tipper with the main components separated.

The information in this report is only applicable to SSAB’s products and should not be applied to any other products than original SSAB products. 

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