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Using aluminium trailers will improve payload potential and help ease the congestion problem, says Tony Paterson. |
Roads may be compared to the blood circulation system in the body, says the Aluminium Federation of South Africa's Tony Paterson, an engineer who believes that solutions to problems caused by overloading lie with trailer designers, operators and traffic officials.
"The human circulatory system is divided into three categories; arteries (which transport oxygen), veins (which transport deoxygenated blood and contaminants to be cleaned by the kidneys) and capillaries (which distribute oxygenated blood to the tissues and form the link between arteries and veins). The system moves nutrients from one part of the body to another and carries 'emergency services' to places of need. As is the case with the road network, dysfunction may be caused by local collapse or blockages of one type or another. With sufficient dysfunction, congestive heart failure occurs, rendering the heart incapable of supplying the necessary oxygen to the body," says Paterson
There is a school of thought that believes a good way to reduce road congestion is to allow trucks to carry heavier loads, thereby reducing the number of trucks on our roads. This sounds plausible in theory, but the reality is such that as our roads get older, they wear out, which leads to local collapse, which in turn results in congestion, Paterson continues. As the road network becomes more stressed the equivalent of congestive heart failure occurs and the system can no longer support the economy.
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Road repairs cost the tax payer millions of rands every year, not to mention the stress caused by idling away valuable time in road repair queues. |
Heavy maths
"If we support overloading, the rate of road deterioration will increase. The wear on a road is a function of the axle mass to the power of around 4.2. This implies that 21 000 motor cars of mass 750kg on each axle causes as much damage as a single rear, single wheel truck axle with a gross mass of 16 tons (8 tons per axle assumed)," explains Paterson. "If we overload the axles by just one ton, the number of motor cars causing equivalent damage rises to 34 000, a two tons increase is equivalent in damage terms to 53 000 cars. Thus the effect on road life from overloading is very significant."
Lighten tare
While most operators respect the legal restraint on axle load, "there is always the 20% rogue element that gets away with what it can, effectively at tax payers' cost," adds Paterson. "Responsible operators need to investigate ways to help ease congestion and the use of aluminium in trailer fabrication is one avenue to achieve this. Typically, an aluminium truck body may be expected to yield a 15% to 20% increase in payload, not only reducing congestion but also enabling the same load to be transported in fewer vehicles, which saves the operator in capital outlay on truck purchases."
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New vehicle testing facilities like the one at Donkerhoek will enable traffic officials to comprehensively check loaded vehicles, suspensions included. |
Improve suspension
Another factor to bear in mind and one that is sorely overlooked by many transporters is that a poorly maintained vehicle suspension system will transfer greater effective wheel loads than will a well maintained system, Paterson explains: "As a well maintained system evens out the stresses to the road (and the chassis), over a longer period the impact on the road wear and tear reduces. Research carried out buy AFSA with the same trailer and load on different road surfaces show a stress increase of three times between paved roads and gravel roads. The poorly maintained suspension system is likely to show a similar impact, this reducing both vehicle and road life."
With this in mind, Paterson concludes that "traffic officials should check not only the overall mass of the vehicle but also the state of repair of the suspension system. Both will contribute to better life from our road infrastructure."
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