Several manufacturers have also upgraded the suspension designs. For example, Volvo is launching a computer-controlled hydraulic suspension for its A35/40. "Besides dramatically improving comfort and productivity, it provides anti-roll and self-leveling functions by allowing cross flow between cylinders and back to the tank," says Goodman.
Likewise, Terex touts the benefits of its independent front suspension (IFS). "With coil over damper units and half shafts, the truck rides measurably better than non-IFS trucks," claims Emmett. "The advantage translates directly into the potential for a more comfortable ride for the operator. The reduction in vibration in the truck may also increase the life of components."
The advent of ejector bodies adds a new dimension to articulated models. "We are seeing a greater acceptance of our ejector truck design," says Schreifels. "By ejecting the load out the back of the truck on-the-go instead of stopping to raise the body, contractors are seeing faster cycle times, down-sized support equipment and the versatility to go places a raised-body truck wouldn't work (under power lines or bridges, spreading on slopes, underground mining, etc.)."
Then there is the emergence of articulated water trucks. "The adoption of articulated trucks as water trucks is a major change to the construction industry," says Emmett. "By combining the go-anywhere ability of the articulated truck with a stable, low-profile water tanker, the new breed of road maintaining water trucks is advancing quickly."
Rigid-frame trucks offer economy
In the right conditions, a 45-ton or smaller rigid-frame truck can be a cost-effective solution. "The justification is simple," says Emmett. "If the haul roads will support application of the rigid, the rigid will be less expensive to operate. But you must consider footing, road width, weather and all of the associated items that impact upon traction."
Sites with well-maintained permanent or semi-permanent roads are good candidates for a rigid-frame truck. "The ideal site for a small rigid-frame truck is a fixed location with excellent haul roads," says Schreifels. "Rigid-frame trucks have demonstrated the lowest cost per ton in applications with good haul roads. If you are worried about productivity in changing conditions, then an articulated truck may be a better fit."
It all comes down to the economics of hauling more material per cycle. Generally, rigid-frame trucks on a site are larger. "Therefore, the rigid-frame has an advantage of transporting more material per cycle," says Emmett. "And that cycle will most likely be on a smoother road. The cycles will be faster and the costs associated with operating, such as labor, fuel, maintenance and ownership, will be less per unit hauled."
Rigid trucks tend to be a more mature product than articulated trucks, but there have been some developments in this market. "Wet brakes are now standard on most brands and computerized drivetrains are common," says Emmett. "The next big leap will be with the introduction of Tier IV engines."
He adds, "There is some movement toward hybrid rigid trucks, but the development is in its infancy. However, climbing fuel prices will help push this forward."
Caterpillar recently introduced center-mounted cabs on its 40- and new 50-ton rigid-frame trucks. "The cab on all of our quarry and construction trucks (40 to 100 tons) is more spacious and has more glass area for better visibility than previous models," says Don Weinhold, market professional at Caterpillar. In addition, there are rear vision cameras for better visibility, automatic retarders and engine brakes, ground level lockouts and other upgrades, which increase the performance and safety of the current generation of rigid-frame models.
Alternative option emerges
In addition to traditional rigid-frame haul trucks, there are other unique options available, including one offered by Western Star Trucks. The company has collaborated with J&J Truck Bodies & Trailers to offer the 6900 XD 40-ton dump. It is designed to maximize shift productivity through efficient fuel consumption, fast cycle times and operator comfort.
This truck features 110,000-lb. planetary axles, a Detroit Diesel 60 Series engine, a fully automatic Allison 4500 RDS transmission and a purpose-built dump box. It boasts stable loaded top speeds of more than 40 mph in the right application.