Shouldering the Load

July 26, 2013

Today’s trend on the construction site is for contractors to have the ability to meet their goals of higher production per man hour-essentially, the ability for one operator to move more dirt in a workday.

The partner in that endeavor is the dump truck, be it a rigid frame or articulated.

Caterpillar’s latest offering in the field is the Cat B series of articulated trucks. The Cat Ejector articulated trucks (available in 31- and 42-ton payloads) are designed by Caterpillar to be a fully integrated and engineered solution that, instead of lifting the dump body up in the air to discharge the load, pushes the material out of the body.

“This has several advantages,” says Anthony Pollock, product-marketing supervisor. “The load can be spread evenly while the machine is moving, thus allowing layers of material to be put down without the need for a dozer to spread out a dumped pile of material. The Cat Ejectors also can discharge their loads statically in a pile, if required, like a conventional tipper machine, and can get into tight spaces by allowing discharge with the tractor steered at an angle-something not recommended for conventional tippers due to machine stability.”

The Cat Ejectors also can discharge material on a side slope, or a fore/aft slope, an operational “no go” for conventional tippers because of the possibility of overturning the machine, Pollock says.

“This also applies to discharging the load in areas of very poor underfoot conditions, where the advantage of the Ejector is that it does not need to raise the dump body high in the air, thus reducing the chance of machine instability,” he adds.

Pollock points out that if operating in poor underfoot conditions, traction aids will have to be used for a higher percentage of the time.

“Cat’s B Series fully Automatic Traction Control (ATC) provides the ultimate in traction, without the need for any intervention at all by the operator having to think about when to engage differential locks with switches or buttons,” he says. “With new or less experienced articulated truck operators, the choice of articulated truck manufacturers’ traction control system is a big consideration to avoid machine abuse and costly repairs of reduced fuel efficiency.”

When underfoot conditions start to deteriorate, Cat’s ATC system automatically senses the slightest wheel slip within micro-seconds and responds by proportionally engaging clutched differential locks in each axle and/or in the longitudinal transfer gearbox between the tractor and trailer.

“The whole system responds so quickly that, to the outside observer, individual wheel slipping on these machines is a thing of the past,” notes Pollock. “The system also proactively engages the longitudinal clutch as the machine enters certain grades, automatically anticipating the machine’s requirements.”

Site safety also is of primary importance, says Pollock.

“Cat B Series provides extensive handrails for the operator, with easy, three-point contact access up onto the machines,” he says. “Cat articulated trucks also provide wide, stable walkways when entering and exiting the cab without the need to try to exit the cab door and climb down the steps in one operation.”

The company’s articulated trucks also provide punched steel anti-slip walkways where mud from boots passes through the tread plates.

Caterpillar articulated trucks also feature electro-hydraulic secondary steering that automatically activates if a there is a steering pump failure.

“This feature works in forward and reverse, and at all machine speeds, including with a stationary machine and a dead engine,” says Pollock. “This allows the easy adjustment of the machine steering angle when loading an AT onto a low-loader with a dead engine.”

Pollock points out that the key to Cat’s power train is that the truck always remains in true six-by-six drive, with fully open differentials for the best possible efficiency in getting power to the ground over difficult or undulating terrain.

“Only when any slippage is detected does the ATC system respond-and in a measured and proportional way appropriate to the level of wheel slippage,” he adds.

Another aspect of the integrated systems design approach is Cat’s Advanced Productivity Electronics Control Strategy (APECS) software control.

It is “based around always making sure that the machine is in the correct gear to provide the best traction, lowest noise, and highest fuel efficiency,” says Pollock. “Another benefit of APECS is improved acceleration and maintenance of speed on grades. Cat’s APECS system senses torque and allows the machine to shift up into a higher gear when it can, without having to wait for higher engine revs. Electronically controlled clutch engagement provides smooth, quiet operation, even with sudden downshifts required on steep grades.”

Pollock says the hitch is the key principle in the machine.

“It’s the main difference between a rigid or off-highway hauler and an articulated truck,” he says. “Allowing the tractor and trailer to oscillate and articulate independently, combined with six-by-six drive, is what gives the articulated truck its versatility in all terrains and all weathers.”

Cat’s rear suspension joints, together with the walking-beam suspension, allow all six wheels to be in contact with the ground at all times.

The hitch must be 100% reliable and provide years of trouble-free durability, Pollock says. The Cat design features a cast steel head bolted to a forged steel oscillation tube.

“The metallic properties of the head and the tube need to be quite different,” says Pollock. “The head needs to be tough with good ductility and impact resistance, while the tube needs to feature hardened surfaces that are highly resistant to wear. That’s why we design our hitches in two halves from two different materials and then bolt them together.”

The B series is available in engine emissions compliance levels to meet all worldwide markets, Pollock says.

Over the nearly two years that the B Series has been in the field, Caterpillar has studied fuel consumption under a wide variety of field conditions. In one example, the less-regulated version of the 740B is returning an average of 10% less fuel consumption than its predecessor, Pollock notes.

The E-Series is John Deere’s latest offering in the articulated dump truck (ADT) market is the E-Series. The series is highlighted with three models: the 370E, 410E and the 460E. The 460E is the John Deere’s largest ADT ever to hit the market, according to Mark Oliver, ADT product marketing manager, John Deere Construction and Forestry.

Additionally, John Deere has two D-Series models: the 250D Series-II and the 300D Series-II.

“The E-Series ADT family is a customer-driven, ground-up design with three models built to meet and exceed the durability, productivity, and uptime needs of contractors,” says Oliver. “John Deere worked closely with road builders, site developers, and the mining, quarry, and aggregate segments to develop three trucks that are purpose-built to reliably handle various payloads and move materials faster and more efficiently.”

Productivity, durability, and ease of service were the major drivers of the E-Series program, Oliver says.

“Our goal with the E-Series was to provide contractors with the most productive ADT available that would also exceed their long-term durability goals,” he says. “New John Deere axles that were specifically designed for an ADT application are one example. Our axles are independent circuits that are pressure lubed and filtered. The wet disc brake system also is cooled. These items combined will provide our customers the reliable, long life they expect from ADT axles.”

The addition of more automated features such as Auto Dump and Auto Differential Lock also makes it easier to train operators and make them more productive faster, Oliver adds.

There are a lot of factors in determining what size articulated dump trucks contractors should use in their application, Oliver points out.

“One of the most important decisions is choosing the right size ADT and matching it to the loading tool,” he says. “Most ADTs are loaded with an excavator. It is vital for efficiency of the excavator and for maximum production of the ADT to have the excavator take full passes loading the truck.

“If it takes one extra excavator cycle with only a half bucket to top off the ADT, it is not efficient for the excavator,” he says. “If the excavator does not put in that last half bucket, you don’t optimize production for the ADT. Choose the ADT size that allows for four to seven full buckets from the excavator.”

Haul road distance and haul road condition are the most important factors to consider in choosing an ADT as opposed to other truck forms, such as rigid frame trucks, Oliver says.

“ADTs are designed to operate in conditions such as deep mud and severe slopes,” he points out.

Doosan offers iT4 technology on its articulated dump trucks to meet the new emissions requirements.

“We use an SCR system instead of the EGR method that uses DPF filters and regeneration,” says Brian Bereika, ADT product specialist. “The SCR system is much simpler, operates at lower temperature, and doesn’t have filters to clean and replace. Instead, urea is injected into the exhaust system as an aftertreatment to remove the nitrous oxide.”

Bereika says Doosan also offers 10% higher horsepower on its ADTs with much higher torque, along with higher 44T payload its DA40 or 40T ADT. Auto lubrication and an onboard weighing system are now standard to offer simplified maintenance and longer component life.

Doosan designs its ADTs with “a very simple driveline that allows the tires to remain in contact with the ground in all conditions,” notes Bereika. “This provides maximum power and traction to the ground and better stability.”

The 30T and 40T ADTs are Doosan’s most popular sizes. The new iT4 models, DA30 and DA40 are still almost all in dealer rental fleets.

“Contractors will tend to use 30T on smaller-size hauling jobs and 40T for the larger, high-volume ones,” Bereika says. “Other determining factors include the size of loading equipment to be used, the length of the haul, and the time allowed to accomplish the task. Tailgates are the most common option on ADTs, but not always necessary or an advantage, so that decision has to be considered as well.”

Bereika points out that while ADTs are capable of operating in almost all site and weather conditions, they do have their limits.

“They can navigate very deep mud and climb or descend steep gradients, but they must be operated with safety first,” he says. “They weigh more than 150,000 pounds, travel more than 25 mph, can be overturned, and can descend steep gradients fully loaded. There are a lot of dynamics going on at once. Operators need to be trained on how to operate them safely and fully understand how to use the different braking systems. They sometimes are the most expensive equipment on the site.”

Terex Construction offers a full complement of articulated dump trucks and rigid-frame off-highway trucks. Information on the company’s line of trucks can be found at

The trucks can be seen in action on these YouTube videos: and

When it comes to selecting a truck that best meets a contractor’s needs, an articulated truck is a “very adaptable product,” says Ken Emmett, product manager for Terex. “It can easily work in hostile conditions such as wet, frozen, and underdeveloped job sites, and with its all-wheel drive and articulation it often works where other equipment can’t go, often because it can get to a job site and back without being disassembled.”

Articulated trucks can operate in more places than a rigid frame truck, he adds.

“The superior traction of the all-wheel drive articulated truck, combined with a suspension design that can keep all the wheels on the ground in very rough terrain, make it a winner in off-road competition,” Emmett says. “Articulated trucks are used to pioneer and build the roads for the rigid trucks to use.”

In contrast, rigid frame trucks are designed for haul road conditions that are smooth and predictable, Emmett says.

“Haul roads in quarries are generally well established,” he adds. “Haul roads in mines are not as well established, but generally far better than those on a site where an articulated truck will be used.”

There are many considerations to choosing one type of truck over another, Emmett points out.

“One consideration of the articulated truck is that it is generally smaller than the rigid trucks found on a job. Therefore, the rigid has an advantage of transporting more material per cycle,” he says. “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.”

The big “if” in this equation is whether or not the rigid can actually go on the terrain the articulated truck can go on, says Emmett.

“If the rigid can’t move, the articulated truck wins,” he points out.

The most significant advancement in the Terex articulated truck is the vehicle’s electronic technology, says Emmett. State-of-the-art computer systems in the manufacturing process enable the production of better grade steel and to heat-treat materials better, he adds.

High-tech computer systems allow Terex to utilize computer-controlled ultra high-definition plasma tables and welding tools for a machining process as accurate as possible.

“The electronic technology installed on Terex Generation 9 articulated trucks allows our transmissions to shift at the proper times relative to load and speed, as well as helping the brakes and retarders to be applied appropriately,” says Emmett. “Also, Terex articulated trucks are equipped with electronic technology that allows them to run high-powered, Tier 4, interim-compliant diesel engines that decrease fuel consumption and reduce the trucks’ exhaust emissions.”

All Terex articulated trucks are equipped with state-of-the-art computerized systems that communicate to each other through a CAN-bus system, designed for peak efficiency.

“This technology indicates factors to operators such as the truck’s body being up, when a truck component needs servicing, where the component is and what it is doing,” says Emmett. “For example, Terex truck models equipped with a tire inflation warning system know if a tire is low on nitrogen, and it will indicate to the driver which tire it is and how long before it needs replacing.”

Through the CAN-bus system, the Terex truck data can be transmitted via satellite to almost any location globally, enabling operators, fleet managers and service technicians to be kept up-to-date on the truck’s condition.

Terex trucks are designed for the highest capacities per class to move more material per trip and a high power-to-weight ratio for faster material movement.

“Terex off-highway trucks are designed to keep productivity levels high, fuel consumption low and cycle times short,” Emmett says.

The adoption of Tier 4 technology offers fuel economy advantages.

“Contractors need to move more material per gallon of fuel,” Emmett points out. “Because Terex buys, not builds, engines and transmissions, we are able to source the best combination of engines and transmissions from the premier suppliers in the industry.”

That strategy is designed to construct trucks that run faster and haul more, improving productivity and lowering operational costs.

In addition to meeting the new emission standards, Terex Generation 9 articulated trucks equipped with Scania engines are designed to deliver fuel efficiency and low maintenance costs for low total ownership cost for the end user, says Emmett.

The Selective Catalytic Reduction engine in Terex Generation 9 articulated trucks requires nothing more than to have the diesel exhaust fluid (DEF) tank topped off when the truck is fueled, Emmett says.

“The DEF is environmentally benign, costs far less than diesel, and application is as simple as adding windshield wiper fluid to the truck,” Emmett says. “When the truck needs the DEF tank filled again, an indicator light signals the driver in advance of the actual need.”

In addition to reduced emissions being easier on the environment, it’s also good for the truck, Emmett points out.

“Trucks simply run better and longer when less crud is ingested into the engine,” says Emmett. “Terex articulated trucks are designed with highly accurate fuel-injection systems, which means no excess diesel fuel is washing down the cylinder walls and increasing engine wear.”

Emmett says the most significant advancement has been the introduction of wet brakes, replacing dry brakes, along with a retardation system.

“Retarding on Terex Generation 9 trucks is supplied by a standard engine brake and transmission retarder to ensure maximum control in loaded, downhill hauls,” he says. “These features give the driver a feeling of security, knowing he can stop a loaded hauler heading down hill without brake fade. It also reduces operating costs. A dry brake truck can consume upwards of 5% of the truck purchase price over 10,000 hours maintaining the dry brakes. Wet brakes all but eliminate this cost and increase uptime.”

All models in the Terex Generation 9 range benefit from oil-cooled multiple-disc brakes on each axle, providing extended brake component life, reducing service intervals and operating costs, and improving overall braking performance compared with traditional dry-disc brake systems, says Emmett.

Volvo CE’s articulated haulers have attracted faithful users since their introduction in the 1960s, but with the introduction of what the company calls its Hauler Chassis, which allows customers and body builders to adapt standard haulers into special purpose vehicles, the range of their applications has been greatly expanded.

Delivered without load body or hoist cylinders, the base machine allows modification to meet the specific off-road transport needs such as water tank, hook lift, ejector body, or fifth-wheel configurations for pulling a wide range of trailers.

The drive train features as standard an Automatic Traction Control (ATC) system that automatically engages/disengages the six-wheel drive. The system detects any slippage and applies the appropriate drive mode for optimum traction. In good conditions, the four-wheel drive mode reduces fuel consumption, tire, and mechanical wear.

The F-Series is fitted with “dog clutch” differential locks in all three axles, which help maximize grip in difficult conditions. When applied, they ensure all wheels rotate at the same speed, maximizing traction in severe operating conditions, e.g., deep mud. All differential locks can be engaged, on the fly, by stepping on the floor-mounted button helping maximize traction in tough conditions.

The A25F and A30F are fitted with fully hydraulic brakes and dry discs on all wheels, while the bigger A35F and A40F are fitted with oil-cooled wet discs. Additionally, all machines feature retarders. The A25F and A30F feature a hydraulic retarder and Volvo Engine Brake (VEB), the latter consisting of a compression brake and exhaust retarder. The larger A35F and A40F also feature VEB but, instead of a hydraulic retarder, use the wheel brakes. There is also an optional Trailer Brake Valve that enables the adaptation from the chassis hydraulic system to the trailer air brake system.

At Bauma 2014 at Stuttgart, Volvo CE announced that it has developed a new engine system that meets Tier 4 Final (US) emission reduction requirements that come into force on January 1, 2014, through a combination of in-cylinder and external solutions as well as selective catalytic reduction (SCR) technology. The system has undergone rigorous testing to prove its suitability in a variety of heavy-equipment applications including ADTs.

By applying SCR, a technology its trucks have used since 2005, Volvo’s solution incorporates an aftertreatment catalyzer that reduces NOx levels by injecting a urea-and-water-based reduction agent. When the reduction agent-diesel exhaust fluid in the US-is heated by the exhaust, it produces ammonia, causing a chemical reaction that converts NOx to nitrogen and CO2, both of which are naturally found in the air.

Mack Trucks offers a full range of construction trucks in its Mack Granite and Titan by Mack truck series. The models are available in horsepower ranges from 325 to 605 horsepower.

The company’s latest entry in the construction market is the Mack Granite Medium Heavy Duty (MHD), available in a four-by-two configuration in both class 7 and class 8.

Mack Trucks also has introduced the new mRIDE spring suspension for on- and off-road use.

“Paired with Mack axles, the mRIDE suspension has an industry-leading ability to articulate over rough and uneven terrain and still maintain excellent ground contact and traction,” notes Curtis Dorwart, vocational marketing product manager for Mack Trucks. “In addition, the mRIDE is more stable and significantly lighter than other suspensions and is almost maintenance-free, requiring no lubrication.’

Navistar’s primary vocational vehicles are International WorkStar and PayStar, which serve as the main platforms for dump trucks. A dump body can be accommodated on other products, such as TerraStar and DuraStar.

“Articulated dump trucks would likely be produced by the body builder, and our vehicles could haul them,” notes Elissa Koc, manager of communications for Navistar.

WorkStar is a heavy-duty diesel truck constructed with a range of power train combinations of up to 475 horsepower and 1,700 lb-ft of torque. Key features include a new sloped hood for greater visibility, a strong “mega-bracket” and cross-member design to support radiator and dual front tow pins, a design for REPTO and transmission-mounted PTO applications, Diamond Logic electrical system on-board diagnostics to monitor all vehicle components to reduce downtime and keep the operator informed of its status, and an ergonomic center panel designed for easily accessible auxiliary switches.

PayStar features a five-piece cross-member system and Huck-bolted chassis components, 120,000-psi rails, and a resisting bending moment (RBM) up to 4.87 million in-lbs designed for maximum strength-to-weight ratio.

The International TerraStar is now available in a four-by-four configuration, says Koc.

“This is a purpose-built commercial truck built from the same DNA as its larger brother, the DuraStar,” she says. “We designed the TerraStar from the ground up to be a commercial truck. The TerraStar four-by-four features a gear-driven Fabco Transfer case designed for higher loads and better durability than chain-driven transfer cases. It also features a commercial-grade Allison 1000 series transmission. In addition, the TerraStar has best-in-class frame rail strength of 80,000 psi.”

The DuraStar features a setback axle for maneuverability and a tight turning radius, a Diamond Logic electrical system for diagnostic help, offering a standard convenience package with parking brake alarm and pre-trip exterior light checks, and easily integrates control of body and equipment mounted to the truck.

The truck also features an optimized drive train performance, which matches transmission shift points with engine power curves, designed for better responsiveness, reliability, and fuel economy. It also has a sloped hood and swept-back, curved windshield design for a broad view of the road.

Komatsu offers a Tier 4 interim solution.

“The automatic regeneration and over 95% passive regeneration system has recently been introduced on the HM300-3 and HM400-3 articulated trucks,” says Craig McGinnis, product specialist for Komatsu America Corp.

McGinnis points out that regeneration is used to remove soot that collects in the diesel particulate filters.

“Komatsu’s Tier 4 interim engine solution operates with 95% passive regeneration, using normal exhaust temperatures,” he says. “Active regeneration occurs automatically, allowing the operator to continue working without interruption.

“Along with the reduced fuel consumption of the Tier 4 interim engines, the new articulated trucks also feature improved traction control, the Komatsu Traction Control System,” notes McGinnis. “This automatic system keeps you moving in adverse conditions by reducing wheel spin to maintain forward momentum. The HM300-3 and HM400-3 also feature an updated, quiet cabin and a new monitor panel. The new operator seat is higher capacity, air suspension, and heated.”

The rigid frame trucks, such as the HD325-7 and HD605-7, feature MacPherson struts, which contribute to ride comfort and the truck’s tight turning radius.

The company’s satellite monitoring systems, Komtrax and Komtrax Plus, offer managers and owners a detailed operation history of their machines, McGinnis says.

“Tracking everything from fuel consumption, to working modes, to idle times, to maintenance intervals, Komtrax provides a unique view of the equipment, which helps manage maintenance time, idle time, and reduces costs.”

User interface is similar across all of Komatsu’s Tier 4 product lines.

“If you know one monitor, you know them all,” McGinnis says. “This simplified interface allows operators to easily move between machines if required. Rearview monitors are also standard, increasing operator convenience and awareness.”

Articulated trucks also come with standard Komatsu Traction Control System. The automatic system requires no input from the operator and is designed to help increase productivity.

This year, Allison Transmission has introduced its 5th Generation electronic controls, which offer a variety of features to further improve fuel economy and vehicle performance for the specific needs of any rugged-duty application, notes Steve Spurlin, executive director of global application engineering and vehicle integration for Allison Transmission.

The new controls include load-based shift scheduling, reduced engine load at stop, shift energy management, vehicle acceleration control, and the enhanced converter load release.

Allison 5th Generation controls are designed to provide flexibility in specifying maximum fuel economy.

“To maximize transmission protection, Allison’s advanced prognostics, which are calibrated to the vehicle’s particular operating requirements, monitor various operating parameters to determine and alert when service is due,” says Spurlin. “This not only provides maximum transmission protection, it eliminates unnecessary oil and filter changes.”

Allison’s fully automatic transmissions have been designed for conditions calling for durability and reliability and thus fit rugged-duty operating requirements, Spurlin says.

The company’s Continuous Power Technology is designed to “deliver smooth, seamless, full-power shifts with superior startability and gradeability,” notes Spurlin. “On-road, this results in shorter trip times. Off-road, Allison Automatics provide precise traction control. While manuals and automated manuals cause the drive wheels to hop and do damage to the drive train, Allison Automatics achieves just the right amount of traction for load and ground conditions.”

When Ray Mosley, founder and a partner of the Resource Management Co., located in the area of Nashville, TN, sought to add new vehicles to his dump truck fleet five years ago, he thoroughly researched the options, considering life cycle costs and contacting other dump truck fleet owners.

Resource Management Co. is a utility and site contractor. The company is in the dump truck business and does rock conveying. The company began in 1989 with a few dump trucks and now has 100 employees and 26 tri-axle dump trucks, four slinger trucks, and 35 pieces of excavating equipment.

Mosley determined that specifying Allison Automatics for his company’s T800 Kenworth trucks was the way to go for his operation.

“We were looking for a way to take the shifting away from the drivers because the manual transmissions have some inherent problems if you didn’t operate them properly,” Mosley notes. “We were trying to take that task away from the driver. Allison has a pretty good name in the industry, and it’s been around for a long time.”

Other factors came into play as well.

“We wanted to reduce the shock to the drive train,” Mosley says. “We wanted to reduce driver fatigue. We wanted to find a piece of transmission that would be low maintenance. With manual transmissions, we always have to adjust the clutches, replace the clutches, or replace broken axles for the drivers who misuse the equipment. Allison seems to be a fit for eliminating all of those problems.”

A team from the Resource Management Co. visited the Allison plant in Indianapolis, IN, for a tour.

“They have a test track up there, and we got to use the product and put it through some tasks we felt were relevant to our business, and liked it,” Mosley notes, adding his company is poised to order more.

“We’ve serviced them as Allison recommended,” he says. “So far, we don’t see any wear item or issues where we are concerned about in the longevity of the product. We feel like they’ll last the life cycle of the vehicle.”

Be it a rigid frame or an articulated dump truck, there are several factors for contractors to consider when selecting the right truck for their operation:

  • Capacity—Capacity should be measured in cost per yard of material moved.
  • Power-to-weight ratio—The better the ratio, the more productive the truck will be on the job.
  • Mechanical systems—Does the truck have the latest technology, such as a superior suspension system?
  • Recommended maintenance intervals—The longer the intervals, the more time the truck is working and making money.
  • Engines and fuel consumption
  • Product and dealer support
  • Size—“Contractors need to make sure they are matching the right truck to the job,” says Emmett. “Before they go shopping for a truck, they need to know how much material they have to move. They should also ask themselves what kind of material they are hauling. What distance do they need to haul the materials? Also, off-highway trucks always are part of a system of equipment working together, so contractors need to match the truck to their other equipment—for example, what kind of loading tool do they have?”
  • New versus used—Sometimes, contractors believe it’s best to buy used off-highway trucks rather than new. Emmett suggests the following criteria in making that decision: project length, future potential, funding availability, reliability, labor costs, tax benefits, emission requirements, fuel consumption, fleet size and related labor, and cost per yard/ton haulage requirements.
  • Productivity and fuel—In selecting the right specification for a vehicle, performance, productivity, and fuel consumption should be taken into consideration, Spurlin points out.

“Contractors should consider the load profile, duty cycle, speeds, topography, and other vehicle details, such as engine, drive axle arrangement, and tires when making their selections,” he says, adding the company provides software and representatives who can assist in the specification process to ensure contractors are maximizing their transmission experience.

Dorwart agrees, saying a contractor should understand what is being hauled and how to maximize payload and productivity. “Many times, a smaller displacement engine will provide more than enough power, will reduce weight and have no adverse effect on productivity,” he says.

Site access, haul road widths, haul lengths, and space available at the loading/dumping area are all important factors to consider. “These may restrict the physical size of the articulated truck that can be utilized on the assumption that a larger articulated truck is usually more cost-effective than several smaller ones,” Pollock says.

Road and ground conditions are important considerations, too. “Hard-packed, well-maintained roads are best suited for rigid frame trucks,” says McGinnis. “These types of applications are usually longer term, allowing time for roads to be established and maintained. For off-road-type hauls with muddy, sloppy roads, an articulated truck would likely be the ideal tool. Komatsu’s HM trucks are designed for rougher roads, often when the haul road is frequently changing.”

The next factor to consider would be the amount of material to be moved as well as the haul distance.

“This will give an indication of what size truck is needed as well as how many trucks are needed,” McGinnis says.

The physical characteristics of the job site also should be taken into account.

“This can include the loading tool,” McGinnis points out. “The loading tool will dictate the loading height requirements of the truck. Also, the dumping area should be considered. If dumping into a hopper, for example, the dump clearance should be checked along with any overhead restrictions, such as power lines or doors.

On-highway transportation should be considered when selecting a truck, McGinnis says.

“Articulated trucks are easier to move from one site to another and could therefore make them more ideal for a contractor who frequently moves jobs,” he adds. “However, in the case of a large quarry with little chance of moving to another location, a rigid truck could be more appropriate.”

Operators should be aware of the haul distance when selecting a truck, McGinnis points out. “Of course, longer hauls will burn more fuel and be paramount on managers’ minds,” he says. “However, haul roads can also be too short. When haul distances are extremely short, it is usually then better to use a wheel loader in a load-and-carry application. It would basically take more time to load and unload the truck than it would to just carry the material with the loader.”

Vehicle durability should be top of mind for any business owner when matching the right truck to the job application, Koc points out.

Dorwart advises that contractors should not “over spec,” getting a truck that is too heavy. “Don’t cheat your driver out of a really good driver’s seat,” he says. “Specifying for some interior upgrades and aluminum wheels will pay back at resale and keep a driver happier. Ask your drivers what works for them.”

As for the availability of loading tools onsite, “There would be no point in specifying a 40- to 45- ton articulated truck if the only excavators or wheel loaders available on site were too small to efficiently load the articulated truck,” says Pollock. “In general, the optimum number of passes for both excavator and wheel loader loading is between four to six, depending on machine and bucket sizes.”

About the Author

Carol Brzozowski

Carol Brzozowski specializes in topics related to resource management and technology.

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