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Because the body is not raised, the ejector truck can work efficiently on sites. As such, the truck can work on sites where stability issues or overhead obstacles limit the the use of conventional dump trucks.
The ejector body also offers clean load ejection to eliminate production-robbing carry-back, where material is not fully ejected from the truck.
The load ejection concept delivers many benefits. Material can be spread while the truck is moving to cut cycle time, decrease power train loads and reduce the amount of support equipment needed for spreading and dozing. The ejector also prevents material from adhering to the inside of the truck body after the dump, so payload can be maximised, improving productivity, reducing fuel consumption and lowering cost per tonne.
Ejecting a load without raising the body increases stability, so the truck can work on inclines, side slopes and in very soft underfoot. The truck is also useful in tunneling and underground applications and on sites where overhead obstacles, such as conveyors, power lines or bridges, interfere with dumping.
The reinforced ejector body is made from high-yield, heat-treated steel. Its top rails incorporate the same steel used on the Cat 769D off-highway truck. The ejector mechanism includes a high-strength blade and technology similar to that proven on Cat wheel tractor-scrapers. The ejector body is designed to work with small rocks though (up to 150mm diameter), so such a thing would not be suitable for applications like offshore projects, where moving bigger rocks is required.
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Aluminum
There are other projects from other manufacturers in the pipeline, too. One technical research paper suggests a design concept where even the largest non-road mining truck body could be made from aluminum.
This might sound ridiculous, as we all know that this material is just too soft for such use, but the academic study provides results of a field service history with developments in various designs.
The study, found on mining website onemine.org argues that aluminum truck bodies are not the novelty they might seem. Mention is made of current U.S. usage and predictions given as to future development of aluminum bodies in the mining industry. The paper notes that way back in 1932 an aluminum unit proved very satisfactory in service on the Hoover Dam project but at that time the only high strength aluminum alloys available were not weldable and with the high cost of construction, a sound economic case for an aluminum body could not be made.
After World War II, great advances in aluminum welding techniques, using the inert gas shield, combined with the development of high strength alloys with good welded properties and welding characteristics changed the whole picture. Welded aluminum bodies were rapidly developed and by 1958 attention was again focused on the use of aluminum for off-highway truck bodies.
The paper goes on to explain how a Canadian firm, Alcan, embarked on an extensive development programme to prove the durability and economics of aluminum truck bodies for the mining and construction industries. The first step was to design a prototype aluminum body which took particular advantage of the fact that the ‘modulus’ of aluminum is only one third that of steel.
A body was built and mounted on a 22-tonne truck . Very little information was available as to the order of stresses that were set up in off-highway truck bodies and so it was therefore decided to carry out more tests, which the paper looks at in detail – arguing that this material is lighter, cheaper and more durable than anything else. Time will tell is this analysis is correct.
Tipper bodies make up a good number of the specialist trailers on the road, but one look along any busy highway will show that there are many other types working in the region. One body style particularly in demand at the moment is tankers. Mostly these are carrying either fresh water… or the exact opposite.
However, some are developed for new and different applications. Gorica, for example, has just completed an order for some flour tankers. Remember – flour can be explosive, so care had to be taken in the design. “We had some problems that took us a while to get right, but we did, and the customer is extremely happy “ a manager at the fim said.
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