As is well known, South African rigs have, in the past, been designed for the overload. It was all heavy 'macho' stuff with no glitter and shine - just lots of 'grunt'. The enforcement of overloading legislation by the authorities and the resultant fines and downtime have now have swung the accent onto the need to legally maximise payloads. In the past, tare was regarded as a mere figure needed to comply with the law. Now, the tare mass is one which operators examine carefully when purchasing a truck. The reason being that with the emphasis on legal loads, a low tare mass equates to a higher payload - and a higher payload equals higher profit.
In this new environment, going for the lowest tare without compromising on quality is what truck, trailer and body designers and builders are going for and one material which is helping them achieve their aims is aluminium. When operating under a philosophy of 'designing for the overload', aluminium has no place on the drawing board. Now, however, it is increasingly finding its way into areas where it would never have even been considered before. In this special interest report,
FleetWatch's Paul Collings investigates the trends and issues surrounding aluminium's role in the trucking industry.
Then, Now, the Future
Aluminium has been used as an alternative to steel in the automotive industry for well over half a century. Its relative lightweight and non-corrosive properties make it suitable for the construction of both truck trailer bodies and truck tractor components. Despite its adoption by forward-thinking trucking people, there exists much 'mystery' around the validity of aluminium as a truck body building material. Many transporters are reticent to adopt it as a major component of their rigs. Let's begin the 'demystification process' by investigating its origins and place in truck manufacturing in general.
Where does it come from?
Aluminium is nature's most plentiful metal and the third most common element in the earth's crust after oxygen and silicon. When certain rock types containing aluminium crumble, a type of clay soil called bauxite (named after the place where it was discovered in the early 1800's, Les Bauxis, in France) is formed. It is from this soil that aluminium is extracted. Bauxite mines in Australia, West Africa, Brazil and Jamaica provide global aluminium manufacturers with most of their necessary raw material. Bauxite, after being cleaned, yields aluminium oxide, which is then reduced (via electrolysis) to form primary aluminium.
The metal is actually a liquid at this stage of refinement and is transported from the electrolysis plant to the cast-house where alloying materials are added and the starting material for future manufacturing processes are made, including extrusion and sheet billets (aka ingots), foundry alloys and wire rod.
Aluminium billets are the raw material used in the extrusion process and can reach lengths of up to 6.5m with a diameter of 254mm. These billets are made in a wide range of alloys to render suitable tensile strengths and product properties necessary for different applications.
How is it made?
The aluminium products we see in our everyday lives have all passed through an extrusion process that begins with the preheating (to 450-500ºC) of a billet made of primary aluminium or recycled, secondary aluminium. The billet is then pressed under high-pressure (1500-3800 tons) through a die to create the shape of the extrusion. These dies are relatively cheap to make and can produce both solid and hollow extrusions. The extruded aluminium is then cooled and stretched to eliminate crinkles and stresses. From here, the extrusions are baked in a furnace at about 180ºC to 'age' the metal. The extrusions are then checked and delivered to the customer.
Why use it?
Ask any trucker why they like aluminium and they'll say "because it looks great." There are, of course, several other 'selling propositions' over and above the aesthetic. It's light (2700kg/m³), weighing about 66% less than steel and with the right alloy and design, aluminium is as strong as structural steel. It is also easy to cast, machine and join (it can be welded, brazed, glued and riveted).
Aluminium is a good conductor of energy, making it a favourable material for truck components that need rapid heat dissipation, like wheel rims and radiators. A big selling point is its resistance to corrosion due to the formation, on contact with air, of a thin layer of oxide on the metal surface. This makes aluminium the material of choice in corrosive environments like coastal areas. It is also non-toxic, making it suitable for food transport applications. From an environmental point of view, aluminium can be recycled many times over and requires less power to melt than steel, reducing the need for fossil fuels and other power generating resources.
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Use it for what?
Truck body builders have been using aluminium since the 1920's and the metal has proven itself to be a low-maintenance, durable and lightweight alternative to other construction materials like steel and wood. Commercial transporters over the decades have used aluminium as a cost saver and profit generator. South African transporters have traditionally stuck with the brute strength of 'tried and trusted' steel but are gradually moving towards new aluminium truck body designs for a host of duties, be they in solid, tipper, tanker, flat bed, dropside, mixer or refuse bodies. Even critical stress areas like chassis beams and wheel rims are now being built from aluminium.
Truck tractor manufacturers are also turning to aluminium to help reduced the tare mass and durability of their prime movers. Fuel tanks, firewalls, engine pulleys, condenser units, radiators and tool boxes are just a few truck components now manufactured out of aluminium.
Design considerations
There are many challenges facing designers of aluminium truck bodies and components. Every transport application has its idiosyncrasies, as does every trucking environment. Designs used for steel bodies are not suitable for aluminium construction. Engineers have to design with the specific material properties of aluminium in mind, using the optimum alloy while always focusing on the demands of the environment their design will find itself ultimately at work.
Into the vanguard
The only constant is change, as the saying goes, and the winners in the game of commercial transport will be those operators who embrace new technology. Aluminium is in its ascendancy as a fabrication material; on paper, it makes financial sense, both short and long-term. How seriously should it be taken when buying a rig? Let's hear what the experts have to say...
Footnote: Many thanks to Hulett-Hydro Extrusions for providing the source information for this introduction.
