Reminding buyers of the essential characteristics that keep the popularity of the articulated dump truck (ADT) on the rise, Joe Sollitt, product marketing manager, haul trucks and motor graders, Komatsu America, sums up this way:
“Applications where less-than-ideal haul conditions exist—such as poor or slippery ground conditions, tight switchbacks, or low ceiling heights—are ideal fits for ADTs. These machines are conventionally used in applications that range from site preparation to overburden removal in quarries, and from reclamation projects to transporting fly ash at coal-burning power-generation facilities. Versatility is what makes these trucks so popular in fleets of all sizes.”
ADT Cost of Ownership
Size Class Purchase Price (avg.) Hourly Rate* (avg.) To 21 tons $229,000 $65 22-27 tons $369,000 $98 28-32 tons $466,000 $109 33-35 $565,000 $127 36 tons & up $682,000 $144
*Hourly rate represents the monthly ownership costs divided by 176, plus operating cost. Unit prices used in this calculation: diesel fuel, $3.46 per gallon; mechanic’s wage at $52.33 per hour; and money costs at 2.125 percent.
But ADT versatility goes beyond the conventional. Henrik Larsson, product manager, Volvo Construction Equipment, says the company’s Hauler Chassis ADTs can accommodate such rear-mounted equipment as a fifth wheel, hook-lift system, platform body, tanks, concrete mixer, container haulers, and ejector body. He notes, too, that the company’s A40G FS (full-suspension) model—which replaces conventional suspension with a hydraulic cylinder, accumulator, and level sensor at each wheel—is finding increased work towing scrapers, given its ability to maintain high speeds in rough terrain.
According to Neville Paynter, managing director for Bell Equipment North America, the company has developed the engineering capability to extensively modify base ADTs to accommodate user needs. Such efforts, he says, have included fuel and lube trucks, fire trucks for use in mountainous terrain, slag-pot haulers in steel mills, and low-profile trucks for underground mining and limited-access applications.
Latest ADT Models
Most ADT manufacturers offer their trucks sans the conventional body. Caterpillar, for example, says Scott Thomas, product application specialist for articulated trucks, has special “bare chassis” models in the company’s new C Series truck line—725C, 730C, 735C, and 745C—which features all the standard articulated-truck options, he says, in both standard and extended-wheel-base configurations.
High-speed transport of large volumes of mundane dirt and rock, whether on a highway construction project or in a quarry, remains, however, the ADT’s primary application, which is facilitated by another of its qualities:
“Compared with other types of equipment, the ADT is relatively simple to operate, and this appeals to companies dealing with less-experienced operators,” says Mark Shea, product consultant, ADTs, John Deere Construction & Forestry. “With an increase in less-experienced operators, machine owners are asking for added safety and productivity features. For example, John Deere has automated certain functions, such as traction control, downhill decent control, drive-line assist, and activation of the retarder with a touch of the brake.”
Also on the list of operator-friendly features are dump-assist systems that simplify the operator’s job by allowing a “one-touch” operation for readying the truck to unload—automatically shifting the transmission to neutral, setting the brakes, and initiating body raise.
ADT market facts
The ADT’s stellar qualities aside, the market for these machines—which range in load capacity from around 25 to 45 tons—has not been without its trials in recent years.
Brian Bereika, Doosan ADT product specialist, helps to put numbers to the ups and downs of ADT sales. From a prerecession high of around 5,000 units annually in North America, the largest single market for the ADT, says Bereika, sales dipped to just slightly more than 1,000 units in 2009. Since then, sales have climbed fairly steadily, despite a relatively flat 2012, and have been reasonably healthy over the past three years, says Bereika, with 2015 sales anticipated to be around 3,300 to 3,500 units.
Bell’s Paynter notes another significant market development: “The North American ADT market has certainly seen a turn from outright purchase of machines to a ‘rental’ or ‘rent-to-buy’ market over the past years. Dealer and customer remarks about the reasons for this include confidence in engine-technology, opportunities for global resale of machines, product-cost increases (primarily for new engine technology), and lack of long-term work contracts.”
What the rental and end-user markets do share, however, is an affinity for larger ADTs, a trend that apparently has been developing for some time: “When the market hit a peak in 2006,” says John Deere’s Shea, “the trend toward 40-ton-class machines had already begun. This trend is continuing as owners watch profits and realize that the more material moved with a gallon of fuel and the fewer the operators, cost savings accrue.”
Based on a recent Doosan study investigating the overall ADT market, says the company’s Bereika, the 40-ton truck has a significant presence in the rental sector and in the light-mining and quarry sectors. In the latter application, he says, larger ADTs in some instances are replacing small rigid-frame haulers in the interest of allowing operations to continue when weather and ground conditions might shut down rigid-frame haul units.
Says Komatsu’s Sollitt: “It’s evident from market data as well as OEM model offerings that manufacturers are increasing horsepower and payload capacity when introducing new models. The market for trucks up to 26 tons and that for units in the 30-to-35-ton class have been slowly shrinking, and the market for the largest trucks, those with 35-ton and larger capacities, has absorbed that share.”
Innovation in articulated dumpers
When asked what concerns ADT users have today, Volvo’s Larsson listed what he called the “first four concerns” as “uptime, uptime, uptime, and fuel efficiency.” In ADT applications that might yield the slimmest of margins on a ton of material moved, profitability obviously hinges on keeping the truck moving—and at low operating costs.
“Daily service is something the operator is doing every single day,” says John Deere’s Shae, “and it takes time away from moving dirt. It’s becoming more and more important to minimize service time by making these routine chores easy and safe to perform.”
To that end, manufacturers have responded with designs that save time, such as ground-level routine maintenance, convenient fill points for fuel and diesel exhaust fluid, and key-on checks of fluid levels. In the wider scope of time-saving innovation are extended drain intervals for engine oil and hydraulic fluid, as well as tire-pressure-monitoring systems that are invaluable for helping avoid the downtime (and danger) associated with improper tire inflation.
Regarding fuel economy, Bell’s Paynter makes the point that a truck’s basic design has a fundamental effect on fuel economy, saying that since a truck spends 50 percent of its life unladen, the more weight it carries, the greater the contribution to operating costs and component stress. Among major design goals, he says, are reducing weight without compromising the machine’s structural integrity, reliability, or longevity, while balancing power-to-weight ratios for optimum traction, acceleration, and hill-climbing capacity.
Potential improvements in fuel economy for today’s ADTs also derive from the efficiency of the Tier 4-Final engines that most use and from the telematics systems that most include as a standard feature. Via telematics, truck owners can identify excessive idle time (caused perhaps by inefficiencies in job-site layout), excessive fuel burn resulting from an engine that might be in poor tune, as well as fuel-wasting driving habits among the fleet’s operators.
Telematics systems also are being used extensively in conjunction with on-board weighing systems, which most ADTs offer as either a standard or optional feature. Weighing systems, which use varied methods to capture payload data, help protect the truck from overload and also convey vital production data via the telematics system to the manufacturer’s website interface.
“As truck fleets increase, on-board weighing systems and telematics will become more important for effective fleet management,” says John Deere’s Shea. “Customers are realizing that the fleet must run at the highest possible performance level, and [these systems] allow them to dial in top performance.”
Continuing refinement of automated traction-control and retarder systems seems also to qualify for recent innovation for ADTs. These systems have a number of benefits, including simplifying operation, increasing safety margins on downhill runs, reducing inadvertent abuse of the truck (perhaps by engaging a differential lock at precisely the wrong time), and, overall, boosting production by promoting more consistent cycles.
Although specific designs for these systems vary among manufacturers, automatic traction control essentially works by locking the truck’s inter-axle differential and axle differentials as required (without operator intervention) to provide optimum traction, and automatic retarder control regulates the truck’s speed on downhill runs by activating one or more braking functions.
Caterpillar’s automatic-retarding-control system for certain of its new C Series models, for example, activates the trucks’ compression brake, selects an appropriate transmission gear, and applies the service brakes as required to control speed. The John Deere E Series models allow the operator to select the degree of retarding force for a given operation; the retarder responds when the throttle is lifted, and then fully engages when the operator touches the brake. In addition, a descent control in the E Series functions as a downhill cruise control, maintaining the speed of the truck at which the operator lifts the throttle.