As new technology has allowed rigid-frame haulers to swell their payloads to as much as 400 tons (363.6 tonnes), the primary application of large rigid trucks has shifted more and more to large earthmoving sites and mining operations.

During the same period, the argument for articulated haulers in construction has strengthened, primarily due to their surer footing on uneven ground. Where the two cross over, there are difficult choices to be made, dependent on variables such as haul road surfaces, gradients, uptime and, of course, initial and overall cost.

At this year’s Bauma, Volvo Construction Equipment will unveil (possibly literally) its new A60H articulated hauler, a 55-ton (50-tonne) capacity machine, set to do battle with Bell Equipment’s equally impressive B60D ADT.

The question is, why has Volvo chosen this moment to produce its biggest-ever hauler? While the 40% payload increase on Volvo’s A40 model will reduce the per-tonne cost and increase productivity, manufacturers have previously resisted the temptation to go big and enter such a niche market – literally between the natural territories of the two types of hauler.

Volvo says it is responding to increasing demand among its customers for haulers with larger payloads. It adds that the A60H is a viable alternative for customers currently using rigid dump trucks operating on soft, uneven or steep roads.

Along with optimising production, Volvo says the new hauler helps reduce costs, as the need for maintenance of haul roads is minimised.

As a further selling point, the A60H comes nicely equipped with technology to ensure optimum performance, including intelligent monitoring systems, such as MATRIS, CareTrack, and the Volvo On Board Weighing System.

The operator experience also promises to be good; within the Volvo Care Cab design, a centrally-positioned seat offers good all-round visibility, while comforts include climate control and low noise levels, as well as enhanced steering and suspension.

Bell Equipment first introduced its own 60-ton-class ADT, the B60D, at Bauma Africa in 2013, where it was hailed as being in many ways an improvement on rigid haulers of the same capacity, given its ability to perform well on variable haul road surfaces.

At its launch, it signalled a blurring of the lines between rigid and articulated machines, with Bell confident the B60D would win the argument with South African mine and quarry owners, due to its manoeuvrability on difficult terrain. Haul roads, therefore, require less maintenance, significantly lowering costs.

The B60D has two driven axles, giving it a 4x4 capacity. Its rigid truck frame style, adds to its strength, both literally and as a unique selling proposition.

While the biggest articulated machines do battle with rigids, the lower-capacity ADTs are largely having things their own way, with sales of rigid haulers in construction falling away over the past three years.

Scottish firm McFadyens Contractors have been using the Bell B30D ADT for five years and, after signing a contract to work on a forestry roads project, opted to buy a second used B30D, as well as a new B30E.

The company’s managing director, Billy McFadyen, said, “Our existing Bell dump truck has proven its reliability, while operators have confirmed that they like the comfort and functionality within the cab.”

When a project calls for the regular transportation of heavy loads, it’s imperative that the uptime of haulers is maximised. With its recently revamped TA400 ADT, Terex Trucks has focused heavily on the increased durability and protection of components, including upgraded hydraulic hoses, electrical interfaces, transmission mountings and brake pipes.

In order to prolong the life of hydraulic components, the company has introduced magnetic pressure filters that reduce the risk of contaminants entering the system, and keep the hydraulic oil clean.

The TA400 also features force-cooled multi-disc brakes, an electronic activated exhaust brake and a six-stage modulating transmission retarder. Terex Trucks claims the ADT’s high-performance oil extends service intervals to 6,000 hours and says the truck’s drivetrain, with longitudinal and limited slip transverse differential locks, is able to maintain traction, even on the most difficult ground.

Again, operator comfort is high on the agenda in this market, and Terex Trucks has included anti-vibration mounts for both engine and cab, as well as cushioned stops on the steering cylinders. Machine performance information has also been improved, with diagnostics including oil quality, oil levels, filter life and various fault codes.

The TA400 Gen 10 will be launched at this year’s Bauma and will be available globally in Tier4 final in Europe and North America and in Tier 2 in non-regulated countries.

The company promises further models in the articulated hauler range later this year and in 2017.

Meanwhile, proclaiming the unfailing strength and reliability of its rigid haulers is Hitachi, which offers the EH1100-5 65-tonne class hauler to compete against the big ADTs on construction sites and quarries.

It boasts either a Tier 2 Cummins 760-hp engine or an MTU series 2000 engine, as well as an Allison H6620A automatic transmission.

As for the handling argument, the EH1100-5 has an active traction control system which has been refined to control wheel spin in wet and muddy conditions.

In terms of usability, the cab’s dashboard has been replaced by a 25 cm screen, which can also be used to troubleshoot and diagnose machine issues.

Taking a relatively even-handed view on the rigid v articulated argument is Roy Haaker, product line director for wheel loaders and articulated dump trucks at Doosan. He says, "It is clear that some of the ADT suppliers are moving up towards 50 t metric and higher. The rigid dump truck has never been a true competitor in real ADT applications (such as motorway construction and quarry overburden removal), however the ADT is trying to take some of the market share from that of rigid dump trucks.

“This is due to the fact that the ADT can combine both jobs, carrying load from A to Z in almost any application - where the rigid dump truck has to give up when slopes are too steep or there are soft/bad ground conditions, the ADT can overcome these hurdles without any problem.”

Mr Haaker continues, "The large ADT only has this advantage on large jobsites, as transporting it from one site to another becomes more difficult, similar to RDT. So indeed you may see some of the smaller quarries replacing RDTs by larger ADTs, to maintain the same production and to combine more jobs, increasing the return on investment. It is however a given fact that the ADT has a shorter life time than the RDT - it is a more complex machine and costs more to maintain.

"So, I agree the large ADT could be a competitor for smaller RDT but only in special applications. I do not see an ADT taking over completely from the smaller RDT, as maintenance/repair costs are higher and the larger the ADT, the more difficult it will be to use in typical ADT applications so the advantage becomes smaller."

Doosan recently launched new versions of its DA30 and DA40 ADTs, meeting Stage lV/Tier 4 Final engine emission regulations.

The trucks feature an articulation hinge behind the turning ring to provide equal weight distribution to the front axle. Doosan states that the hinge, in conjunction with a free-swinging rear tandem bogie, guarantees permanent 6-wheel contact and drive for equal power distribution on difficult terrain, negating the need for electronic aids such as traction control.

John Deere says it listened to its customers’ feedback on safety, efficiency and productivity before updating its E-Series ADTs with a raft of additional features. To a best-in-class differential lock and powerful transmission retarder, John Deere adds ground-level access for all daily service requirements, as well as a tyre pressure warning system and optional onboard weighing system.

Again, the cab is upgraded, allowing for enhanced operator concentration and efficiency. Sealed and pressurised to keep out both dust and noise, the controls are low-effort and the air-suspension seat is heated and high-backed.

With the E-Series, John Deere also offers operators its Ultimate Uptime package, which includes inspections, both pre-delivery and as a follow-on benefit, as well as three years of telematics, machine health prognostics and remote diagnostics and programming capability.

Caterpillar is another of the major players in the hauler market, and is currently promoting its C2 Series ADTs, ranging from 26.5 tons (24 tonnes) to 31 tons (28 tonnes). All of these smaller machines feature powerful engines and advanced transmission control, along with all axle wet brakes and automatic traction control.

In terms of engine design, all three of the new Cat models are available in US EPA Tier 2/Stage II equivalent, Tier 3/Stage IIIA equivalent, or Tier 4-Final/Stage IV configurations, to meet worldwide emissions standards.

Happily straddling both rigid and articulated trucks, Philippie-Hagnbuch’s (PHIL’s) rear eject bodies system incorporates a blade that simply pushes material out of the back of the dump truck’s bed. As the body of the truck does not need to be raised, drops can be made in areas with limited height clearance. Material can also be dropped with the truck in motion, allowing for a more even spread, if required.

Pushing flat from front to back, the system enables trucks, be they ADTs or RDTs, to maintain a low centre of gravity, meaning drops can be made on steeper gradients and on softer ground.

The PHIL system also claims to eject more of the load – even stubborn material that can become plugged to the floor or side of a standard hauler – as the sweeping motion of the blade is said to eliminate virtually all material.

Minimising maintenance, the rear eject system utilises one hydraulic cylinder to operate both the blade and the tailgate mechanism. So, as the blade begins to move material towards the rear of the truck, the tailgate mechanism, located at the sides of the body, also move back, lowering the tailgate.

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