Low Loaders

On mining sites, there is a need for rubber-tyred low-loaders to move large
items of equipment from one part of the site to another. This is particularly the
case for crawler-mounted equipment, where excessive undercarriage wear
can occur during extended travel. Such items of equipment can weigh in
excess of 300 tonnes.

The Swing Wheel Low Loaders are rear-loading heavy equipment low loaders, with a unique method of swinging the wheels aside to permit loading on a fixed, inbuilt ramp at the rear of the machine. Loadquip have delivered 300, 385 and 450 tonne payload versions of the swing wheel low loader.

To date, the low-loaders used to transport such equipment have been
supported on a multiplicity of tyres small enough in diameter to fit beneath the
platform. It is quite common to use 32 wheels, arranged in four rows of eight
wheels each. A complex system of load-equalisation apparatus connects the
wheels together to ensure that the load is spread as evenly as possible over
all of the wheels over a range of uneven road conditions, and brakes are
provided for each wheel set.

There are a number of disadvantages associated with this approach. Firstly,
the equalisation system cannot function over a sufficient range of wheel travel
to accommodate severe road irregularities, resulting in tyre and suspension
damage. Secondly, the spread of support over such a large area results in
severe tyre scrub during cornering, again damaging tyres and suspension
components. Thirdly, the large number of small brakes used (typically 16)
leads to problems of uniform application, and these brakes are inherently
unsuited for continuous retardation on downgrades, as they overheat quickly.

These shortcomings may be overcome by utilising single axle assemblies
from large mining trucks in place of the multiple-axle designs currently in use.
Tyre-scrub, and its attendant high maintenance costs for both tyres and
suspension systems, is greatly reduced. However, the tyres from these
machines, which are typically up to 4 metres in diameter, are too large to fit
beneath a load platform with a reasonable loading height.

If they are installed outboard of the load platform, the vehicle becomes very
wide, and cannot negotiate normal mine roads easily. If they are placed
behind the load platform, it becomes impossible to load equipment over the
rear of the load platform. While it is possible to load some types of equipment
from the side, this is not feasible for long loads such as overburden drills.

To overcome these problems Loadquip has developed a patented swing
wheel arrangement whereby standard off highway truck wheel assemblies are
connected to the outer rear corners of the low loader via hydraulically
actuated swinging arms. These arms move the wheel assemblies between a
travel position behind the load platform and a loading position substantially
outboard of the load platform. The swing axis is inclined so that the wheels
swing upwards; clear of the ground as well as outwards.

This allows the load platform to be lowered all the way to the ground after the
wheels have been swung outwards to facilitate easy loading. Jacks are
included to raise the rear wheels clear of the ground before the wheel
assemblies are returned to the travel position.

The use of large off highway wheels also permits the use of large enclosed
oil-cooled disc brakes with spring applied emergency brakes. Such systems
are designed to meet the requirements of Australian Standard 2958, providing
safe and reliable fade-free braking and retardation in accordance with the
requirements of this standard. Retardation on the trailer axles allows such
low-loaders to descend long grades safely with full loads on board. Based on
the above principles, Loadquip has developed designs for low-loaders in
excess of 450 tonnes in capacity. All designs are fully-engineered and utilise
finite-element analysis techniques to identify areas of high stress. Castings
have been used in many of these areas such as the swing arms, to produce
fatigue-resistant structures.