properties with truck designs, creating
truck bodies that fit their specific
operation, maximise their fleet’s
hauling capacity and save time.
On the surface, it appears as though
one truck body is pretty much the same
as another, varying only on seemingly
small things, such as floor length or
side height. However, there is much
more to the design than meets the eye.
While almost any heavy-steel
fabrication shop can weld together the
basic components of a truck body –
floor, sides, front slope and a canopy –
the key to maximising productivity
and payload begins long before a piece
of metal is even touched.
Angles and ratios
The first step in engineering a truly
custom truck body is working with the
mine to understand the characteristics
of the materials it is hauling and how
the materials will pile or heap inside
the truck body. Traditional body
manufacturers design a body around a
single, standardised angle of repose,
which is the angle of maximum slope
at which a heap of any solid material
will stand without sliding over itself.
Coal is often thought of as heaping at
3-to-1 and overburden has a generic
2-to-1 heap ratio. The problem with
relying on this generic data is that it
makes it all but impossible to
accurately predict a load, while
designing a truck body.
When designing a custom truck
body, it is best to use as accurate and as
much information as possible. A heap
ratio using a material angle, or angles,
of repose is one data point that will be
needed in this design process. This
data is taken from the mine that the
bodies are being designed for and it
will provide the most accurate
information to provide a unique truck
body to tackle the mine’s individual
characteristics. This calculation affects
the required size of the truck body to
attain the maximum capacity for the
material being hauled.
Because of the variety of properties
and materials in overburden, the
calculation is not nearly as simple.
Unlike coal, the make-up of
overburden can change drastically
from one location to the next, making
determining the angle(s) of repose a
difficult task. A unique way of
handling this is to use a predictive load
modelling system that measures the
angle(s) of repose and factors in basic
geometry, material properties and
loading tools at the mine site, as well as
a truck chassis’ weight distribution and
centre of gravity, to predict how the
overburden will heap in a truck body.
This gives the engineers the critical
clues needed to design the most
effective body design.
In the predictive load modelling
process, multiple angles of repose are
obtained by examining photographs,
video, or 3-D scans taken from a
variety of perspectives – generally,
side-to-side, front-to-rear and rear
angles – of the material as it lies
naturally loaded in a truck. Sometimes,
all of the angles turn out to be the
same. Other times, multiple angles are
present, which need to be taken into
Overburden material varies between mines, which is why engineers scrutinise material
information, including 3-D scans, photographs or video, from each mine to determine
the best design for that application.
Before it is fitted to a truck, some custom manufacturers test their bodies through
virtual simulations to achieve optimum weight distribution and centre of gravity, as well
as reinforce load-bearing areas.
44
|
World Coal
|
June 2015
