Articulated Trucks: Growing into Their Rough-Rider Image?

Articulated dump trucks exist solely to carry a heavy load fast over rough terrain. They have been in widespread use less than 20 years, and manufacturers are finally beginning to build trucks that will take the punishment a hard-hat cowboy can dish out after he's seen the brochure pictures of

"The first thing project managers do when they get articulated trucks is save money by cutting out maintenance on the haul roads," says Todd Perrine, equipment manager with Kokosing Construction in Fredricktown, Ohio. "One of the highest incidences of back injuries among equipment operators come from guys in artic trucks. They're getting thrown around in the cab."

With the guys who live and die by job costs planning to move dirt on rough roads, Perrine says the trucks seldom last as long as Kokosing would like. When he shops for articulated dump trucks (ADTs), he looks for an overbuilt drive train. The selection has been improving.

The ADT market leaders, Volvo and Caterpillar, draw their durability ace from being integrated manufacturers, meaning they build their own engines, transmissions, and other driveline components. Their proposition: If you build the drive system for maximum efficiency and durability, you can do a better job than those who buy components from vendors and assemble a driveline. The reasoning seems sound, but there are still plenty of ADT users who rent trucks for enough hours to justify a purchase. They prefer to rent because they don't know how long the machines will last.

Until Komatsu's entrance with the HM400-1 in 2001, Volvo and Cat were the only integrated ADT manufacturers. Komatsu has marketed its trucks largely from the durability angle, and the tactic seems to be affecting the intensity of ADT competition.

Komatsu's 40-ton truck rolled out on power-train components adapted from rock trucks and wheel loaders. And in a move that asserts its commitment to durability, Komatsu is the only manufacturer that puts the sealed, wet-disc brakes on their 30-ton truck that serious ADT contenders reserve for 40-tonners. (Caterpillar does include wet-discs on its 35-ton 735.) Relying on the sealed brakes as retarders, too, plays into the durability claim. Komatsu says it results in less stress on the drive train than transmission retarders, which transmit brake torque through the driveline out to the wheel ends.

Components improving

Of course, the ADT field is replete with stout trucks manufacturers have assembled from venerable off-the-shelf components to serve buyers who want to save some money up front. Comparing 30-ton models, Deere, Terex, the CNH brands (Case, New Holland, Link-Belt), and Moxy sell trucks whose list prices average nearly $70,000 less than the three integrated manufacturers. The hourly ownership cost of a $310,000 assembled machine is nearly $2.40 less than that of a $350,000 unit, even if the less expensive unit falls 10 percent (700 hours) short of the integrated machine's lifetime usage.

Most of the assemblers buy ZF's 6WG260 countershaft transmission, and all of them drive ZF axles with limited-slip differentials in their 30-ton and smaller models. The electronic controller in the new series of this ZF gearbox engages the oncoming gear's clutch before the clutch being released is fully disengaged. The result is uninterrupted delivery of torque. Reduced shock loading and larger clutch discs have stretched the anticipated life of the transmission to 10,000 hours.

Deere and Terex have the only trucks in the 30-ton class with planetary transmissions (both are ZF models). With no countershaft to spin, planetaries transfer more input-shaft torque to the axles. They also tend to be a little lighter and more rugged than countershaft alternates. That's why planetary transmissions are common in 35- and 40-ton ADTs. With the TA30 introduced last month, Terex upped the ante in the 30-ton class significantly by going to ZF's model 310. The same gearbox is used in some 40-ton ADTs.

The key benefits of virtually all engine/ transmission pairings today result from integration of electronic controllers. Linking the two computers allows wonders like simultaneously disengaging one clutch and engaging another, and adapting the clutch performance to manage driveline torque. You have to watch the tach closely to discern when the machine is shifting in the higher ranges.

Traction-control controversy

Virtually all ADTs have a switch the operator can throw to lock up the transfer case that proportions transmission output torque between the front and rear axles. Flip the switch and the drivelines fore and aft lock up to deliver equal amounts of power—it's sometimes called longitudinal differential lock. Only Volvo and Caterpillar continue to offer locking differentials for each axle. That's transverse diff lock.

Caterpillar challenged the long-established dog clutches that Volvo uses for transverse lock-up with wet-disc clutches. Discs allow the Cat operator to throw on 100 percent transverse lock even when the wheels are spinning.

All other truck manufacturers use limited-slip differentials for transverse traction control. The diff switch in their cabs is only for longitudinal lock. Limited-slip is always on, which makes the operator's job easier. It also makes the axles a little less expensive than lock-up clutches. Limited-slip proponents are quick to point out that it saves tires and driveline damage, and is quite effective in wheel loaders and other off-road equipment. But there's no guarantee they'll get your hardhat cowboy out of every quagmire that 100-percent locked axles will pull.

Creature comforts

Articulated-truck designers seem to be using sport-utility vehicles as a benchmark for cab comfort. Lists of creature comforts include power windows, heated mirrors with remote control, air-ride seats with adjustable lumbar support, and beverage coolers. The instructor's seat in the new Terex folds forward so you can use the lunch tray and cup holders mounted on its back (like in minivans). You get the impression the marketers would just love to add a six-disc CD changer and retractable running boards.

It's easy to take shots at the cab refinements because friction clutches and tractor seats were common on equipment as recently as 30 years ago. But the features are clearly intended to make operators more productive by keeping them more comfortable.

Productivity continues to be the articulated dump truck's overriding objective. It keeps material moving when hauls are wet or rough. Manufacturers are competing for share of this market (which has nearly tripled in size over the past 15 years) with more durable transmissions, axles and brakes. And that makes it easier to meet the objective.

Integrated from Fan to Finals

Caterpillar designs and manufactures the electronic transmission in the 700 Family specifically to match its engines and the unique power-delivery requirements of articulated haulers. Traction is controlled with wet-clutched differential locks that can be engaged on the go and achieve 100-percent lock up. The inter-axle and cross-axle diff locks, combined with a three-point front suspension that oscillates plus or minus 6 degrees, keeps the operator in the seat at faster speeds over rough terrain.

Number of models: 5

Tons payload: 25, 30, 35 and 40

New models: 735 and 740 Ejector Truck

Noteworthy features: The 740 Ejector Truck unloads without raising the bed, for improved stability. The 35-ton 735 has the latest electronic version of the 3406 engine, with an overhead camshaft. It's tied to a new eight-speed transmission, and the two components' computers manage shift torque, torque converter lock-up, and clutch engagements to reduce power-train stress. The 735 also has the fastest dump cycle of all the 35-ton trucks.

Little Haulers with Big Features

JCB replaced its 712 and 716 with the upscaled 714 and 718, aiming to bring higher-capacity haulers to site-prep and land-contouring contractors who work in limited space. The trucks work in either two-wheel drive or four-wheel drive modes, and have limited-slip differentials. The 714, with a heaped capacity of 9.6 cubic yards, fits well in off-highway applications where Class-8 dump trucks have been used.

Number of models: 2

Tons payload: 14 and 18

New models: 718

Noteworthy features: The JCB trucks are both powered by Cummins B series engines, and manage top speeds of 23 and 24 mph. ZF Smoothshift transmissions ease driveline shock. Electronic Monitoring System (EMS) watches vital functions and protects the operator and machine in the event of a system failure. It also logs vital statistics for comprehensive service records.

Lightweight Heavy Hitter

John Deere sells one of the lighter-weight trucks. At 40,100 pounds, the 300D, for example, is 8 percent lighter than the nearest competitor and 25 percent lighter than the heaviest. They're built by Bell in South Africa with Deere's PowerTech diesels replacing Mercedes power in the two smaller models, giving them the highest horsepower-to-weight ratio in the 25- and 30-ton classes. Deere claims the line has the best fuel efficiency in the industry, and the weight advantage promotes a go-anywhere image.

Number of models: 4

Tons payload: 25, 30, 35 and 40

New models: 250D, 300D, 350D and 400D

Noteworthy features: With total dump-cycle time (raise and power down) of less than 18 seconds, the 300D unloads more than a second faster than Caterpillar; three seconds faster than Volvo; and 22 seconds faster than the CNH brands.

Rock-Truck Reliability

Komatsu borrowed the engine from its 48-ton rock truck as the slightly derated heart for the HM400-1, its first articulated hauler introduced in 2001. That choice, along with borrowing the hydro-pneumatic suspension also proven in rigid dump trucks, set the rock-truck-reliability theme for the articulated HM Series. Komatsu's hitch articulates on tapered roller bearings that require no maintenance. The line challenges competitors' priorities by being the only make to include wet-disc brakes on a 30-ton truck.

Number of models: 3

Tons payload: 30, 35 and 40

New models: HM300-1 and HM350-1

Noteworthy features: Hydraulic retarder uses the service brakes on the front and center axle to eliminate braking stress carried down the driveline from a retarder in the transmission.

Significant Power Improvements

Terex launched the seventh generation of its articulated trucks with the introduction of the light end of the line last month. It marked the reintroduction of its 27-ton truck, which falls between Volvo's 26-ton truck and the CNH brands' light 30 tonner. Component choices in the new TAs suggest a significant upgrade. Cummins' QSM 11 engine in the TA30, for example, boosted gross horsepower to 350, and torque increased from 1,015 to 1,275 foot-pounds (giving Terex a 10 percent advantage over the most powerful 30-ton competitor). Terex expects hours to overhaul to stretch from 12,000 hours out to 14,000 hours. The TA30 also has ZF's new 310 planetary transmission, which appears in some 40-ton trucks.

Number of models: 5

Tons payload: 25, 27, 30, 35 and 40

New models: TA25, TA27, TA30

Noteworthy features: New models have fully hydraulic, dry disc brakes with dual calipers for 50 percent more friction area. The TA40 is expected to be upgraded to sealed, wet-disc brakes this month. The new hitch bearing is oil-lubricated.

Striving for SUV-Like Service

Only Volvo gives operators the option of selecting a 6×4 operating mode in a 6×6 truck to save fuel and tires in less-demanding terrain. Dog clutches in the differentials provide 100-percent lock up. Adding the oil-filled articulation joint that was introduced with the larger D Series trucks to the A25D and A30D eliminated the need for any daily or weekly service on these trucks. Greasing is required only at 250-hour intervals and fluid levels are electronically monitored. Like many artic-truck makers, Volvo has extended oil-change intervals to 500 hours for the engine; 1,000 hours for the transmission; and 2,000 hours for the transfer case and axles.

Number of models: 4

Payloads: 25, 30, 35 and 40 tons

New models: A25D and A30D

Noteworthy features: The electronically controlled Volvo D10B engine in the A25D and A30D complies with Tier II emission standards, and it brought 19 percent more horsepower to the 25-ton truck (now rated at 304 horsepower), and 8 percent more power to the 30 tonner (now at 323 horsepower). Hauling capacities also increased.

A Truck for All Buyers

Case, New Holland and Link-Belt articulated trucks all come from one Italian CNH-joint-venture factory, but by the time the brands deliver machines, each has developed unique value. There's no denying that the Cummins engines and ZF drive trains are identical. Each truck's value differs, though, in the combinations of standard equipment and support packages each brand uses to reach unique groups of buyers.

Case is considered the brand for the established contractor, so the Case cab is laid out in very traditional fashion. The warranty attracts experienced artic-truck buyers—it's a year of unlimited, whole-truck coverage; a second year of unlimited-mileage engine warranty; and the drive train is covered in years two and three up to 6,000 hours.

As a relative newcomer to construction, New Holland Construction pursues entrepreneurs with cutting-edge features. A rear-facing closed-circuit TV camera and monitor in the cab shows the operator what's directly behind the dump body. It's standard on New Holland trucks, but an option on Case. New Holland's list price is lower than that of the other CNH brands. List pricing is a deal-starting point that reflects the brands' strategies, though, and when money changes hands, it's doubtful anyone would see such a disparity between brands.

Link-Belt is a partnership between CNH and Sumitomo and operates as a freestanding company. The product line has strength in forestry, industrial, demolition and other niches. LBX customers tend to have expectations similar to Case customers, so the red and white trucks are similar to Case machines. Link-Belt buyers tend to expect high-spec trucks, so the rear-vision package is standard equipment. The 30-ton ejector body is expected back in Link-Belt's lineup in 2004.

Number of models: 7

Tons payload: 16, 25 and 30

New models: 25 and 30 tons

Noteworthy features: Three-stage telescoping dump cylinders are mounted inside the frame. Swing-out front fenders and electric-assist flip-up hood make service components easy to reach.

Stability Is Trump Card

Moxy's introduction of the MT36 Series II and MT40B Series II trucks early last year suggests a divergence from the weights and capacities of trucks built by Scandinavian neighbor, Volvo. Moxy continues to install bigger engines than the industry's heaviest trucks, though. Moxy's key points of difference have more to do with stability. The oscillation ring (the part of the hitch that allows the two halves of the truck to roll side-to-side independently of each other) is located in front of the hinge. The Norwegian manufacturer says this reversal of the typical order of hitch design ensures equal weight distribution to the front wheels no matter what the attitude of the truck's bed, or how tightly the machine corners. The free-swinging rear tandem housing pivots around a center mount allowing greater vertical wheel travel and good ground contact at extreme angles. The tandems are gear driven.

Number of models: 4

Tons payload: 26, 31, 36 and 40

New models: MT36 Series II and MT40B Series II

Noteworthy features: Rear frame slopes to the front, like a rock truck, to lower the center of gravity. ZF's upgraded 6WG260 transmission in the MT26 and MT31 is beefed up to handle the new trucks' increased horsepower, and the electronic controller promises smoother shifts.

Haul Truck Makes Tracks On- and Off-Road

British inventor David J. Brown's newest innovation is a 40-ton haul truck that works like an articulated dump truck off-road, but can be driven on the highway. Rear axles of the all-wheel-drive Multidrive M8-40 are mounted on a self-steering bogie, producing an outside turning radius smaller than some 30-ton articulated trucks at 29 feet 8 inches. It will run 50 miles per hour on the road; 32 mph with a load on. The vehicle is just an inch too wide for a normal license in most states.

A heavy-duty Dupont belt conveys the load out of the body like a live-bottom trailer, and the headboard sweeps the box sides clean like an ejector truck. The belt will unload the truck on the move (the load's center of gravity never changes) in forward or in reverse. Unloading time is 15 seconds. It's not a rock truck, but marketers say it has performed well hauling 12-inch shot rock. The conveyor is warranted for 4,000 hours, and because it's a common belt type, it can be replaced for about $2,500.

A Cat C15 engine is mated to an Allison automatic 6-speed. The M8-40 weighs 46,500 pounds (40 percent less than a comparable ejector truck and 30 percent less than a 40-ton dumper). The company says it burns about 40 percent less fuel than conventional artic trucks, and with a GVW well less than any 35-ton truck, that's not hard to believe.

Web Resources

• Specifications

  ConstructionEquipment.com

• Case

  case.com

• Caterpillar

  cat.com

• JCB

  jcbna.com

• John Deere

  deere.com

• Komatsu

  komatsuamerica.com

• Link-Belt

  lbxco.com

• Moxy

  moxytrucks.com

• Multidrive

  multidrive.co.uk

• New Holland

  newhollandconstruction.com

• Terex

  terex.com

• Volvo

  volvoce.com