Machine Matters: Artic athletes

Relocating large amounts of material is a team effort and sending the best player in at the right time is the key to any team’s success. When the playing field is rugged and too tough for the average hauler, it’s time to send a large articulated dump truck into position.

Built to work in miserable conditions and muscle through the worst muck, articulated dump trucks are the haulers of choice for moving heavy material short distances over wet or rocky ground conditions. Unlike on-road or rigid-frame trucks, an artic truck flexes at the joint where the cab and body meet and oscillates 360 degrees to allow all six wheels to maintain equal contact with the ground. Typical on-road dump trucks won’t accept the constant strain of driving over boulders, slogging through mud up to their axle caps carrying 80,000 pounds of wet gravel over mediocre access roads that didn’t exist yesterday. Twisted frames, rollovers, punctured tires and engine damage can quickly put an end to such a truck’s productivity. K.C. Clarendon, product consultant for ADTs at John Deere, sums it up simply: “ADTs are for use in conditions where nothing else will work.”

The North American ADT market continues to grow. Working above ground or even deep in a mine (see “Dropping in” section), ADTs provide up to 50 tons of hauling capacity and despite their heft, are still maneuverable in tight locations thanks to their independent front cab and tight turning radius. Six-wheel drive gets these trucks up and over debris and boulders. Large balloon tires ‘float’ the machine through sand and mud.

Large ADTs are strictly off-road vehicles and need to be trailered to the jobsite. Once on the job, their maximum speed is around 34 miles per hour and they are best used for short hauls of up to five miles.

Renting to know you
High initial purchase costs of around $400,000 per unit in this size class means most contractors rent these units. In fact, Dave Wolf, marketing manager at Case, says 80 percent of new ADTs are in production as rental units. After these units have been on the rental market for two to three years, they become less expensive and contractors buy them.

With all good teams, matching each player’s talents to the other’s strengths maximizes the effectiveness of the overall line up. With this in mind, it’s worth your time to do some quick calculations before renting one or more artic trucks.

First, look at how much material you’re moving. Calculating the amount of material and the time you have to move it is the first part of your production equation. Pairing the most efficient loading equipment with the right size truck is the second. Steve Moore, senior product manager for Komatsu, says figuring the number of fully loaded passes will tell you what size truck you need. “A small truck may rent for $7,000 a month and seem less expensive than renting a larger truck for $15,000 per month. But if you are repeatedly filling and waiting for the smaller vehicle to complete the haul cycle or sending out the larger truck at less than capacity, you won’t be saving money in the long run,” Moore says.

Another thing to consider is what support loading vehicles are available for the job. Ideally, three to five passes by the loader or excavator should fill the truck for maximum efficiency.

Next, figure out the entire haul cycle, from the time it will take to load the truck, drive to the unloading site, dump the material and drive back to the starting point. Articulated truck manufacturers include estimated dump times in their sales information. Remember to include the time and equipment you’ll require to maintain at least a minimal access road in and out of the jobsite – if there even is a road.

Finally, consider how long you have to complete the job. If you have a lot of material that needs to move in a short time, don’t assume you’ll need the largest truck. Depending on your loading machine’s capacity, it could be more cost effective to rent several right size trucks that give you faster cycle times time than to rent a too-large truck that takes too long to fill, dump and return. You want to make sure both your loader and your trucks keep moving all day without lag time waiting to get loaded and unloaded.

Rules of the off-road
Large articulated trucks sport big tires and intimidating profiles and should be approached with respect. Manufacturers make their ADTs easy to drive but that doesn’t mean any rookie laborer should hop in the cab and take off.

Manufacturers offer some ADT training, but because running an artic does not require the same skills as a well-paid heavy equipment operator, often the least experienced (i.e., cheaper) person on the job usually gets the keys to the truck. That’s not the case everywhere, however. In Europe, for example, when a contractor rents an ADT, the rental agreement includes a licensed driver to operate the truck. While there are no legal requirements in the United States governing who can drive an ADT, that may be changing. Currently, Florida is considering a ADT driver certification process, similar to those required for forklift operators.

When renting an articulated dump truck, make sure the person who will be responsible for operating it has the experience or training to drive it safely. Passing the pee-in-the-cup drug test isn’t a good indicator of a new employee’s ability to handle an 80,000-pound machine. Most rental dealers are able to provide limited training to your potential ADT operator – take advantage of what they offer.

Bigger and better
New models and features on ADTs are making them adaptable to a growing number of applications and their increased flexibility lets contractors tackle a wider variety of jobs.

This fall, Moxy Trucks will begin selling its new MT51 in North America. With a payload capacity of more than 100,000 pounds, Kevin O’Donnell, vice president of sales and marketing for Moxy, says the MT51 is the largest ADT made. Like all of Moxy’s artic trucks, the MT51 has permanent six-wheel drive that provides constant equal power to all wheels, creating maximum traction. Moxy’s articulation system positions the swing point hinge behind the turning ring, and allows equal weight distribution to each wheel in uneven terrain. The company’s signature sloping rear frame, dipping 7 degrees from hinge to tail, articulates independently from the front wheel suspension system. The independent action of the frame and cab lets all six wheels maintain contact with the ground and provides driving stability. The MT51 is powered by a Cummins QSX15 510-horsepower engine.

Push it
When is an articulated dump truck preferable to a scraper? Ken Emmett, construction product manager at Terex, says that while scrapers are self loading and can be extremely efficient in a level grade area, an articulated dump truck easily competes on steeper grades and in poor ground conditions.

Ejector blade systems like those found on Caterpillar’s 740 Ejector artic trucks let the truck discharge its contents while moving forward, without raising the truck bed upright. On sites with restricted overhead space limitations, the Cat 740 Ejector can spread material in a smooth, constant flow, without starting and stopping mid-flow. The 740 Ejector’s on-the-go spreading function is especially effective on side slopes when raising the truck bed could cause the truck to become unstable and tip over. The ejector blade feature also reduces the need for additional spreading equipment, resulting in faster cycle times and fewer machines on site.

The Terex TA40 also has an ejector body option. Terex gives this example of how the ejector body can shorten the cycle time. “Think about a haul that takes 520 seconds,” Emmett says. “Now put an ejector body on that truck and eliminate 80 seconds of ‘turn and dump’. The cycle time is reduced to 440 seconds and if the truck carries 30 yards each pass, production goes up from about 170 yards an hour to 200 yards an hour, rising almost 18 percent.”

Dropping in
An example of a using big truck in a small space comes from K.C. Clarendon, product consultant for John Deere. Joliet Sand & Gravel, 45 miles southwest of Chicago, operates a underground sand mine. Needing a powerful hauler that could maintain traction in sand and work in a confined space, Joliet Sand & Gravel chose a Deere 400D articulated truck. Its lower ground pressure and lighter footprint lets the 400D ‘float’ over sandy ground conditions and reduces rolling resistance.

The trick was getting the truck into the mining area so it could haul limestone to a crusher. The company blasted out sections of the mine – two and a half miles down – then dropped in the Deere 400D. The mine’s ceiling was high enough to allow the truck bed to tip up but the rock walls imposed strict boundaries. The Deere ADT maneuvered well in the mine’s limited operating space says Clarendon. “The turning radius on the 400D is less than that of a standard pick up truck, making it easy to drive in confined areas.”

Smart suspension
Volvo’s new Full Suspension (FS) on its E-Series articulated haulers is in part a response to Europe’s new whole-body vibration legislation, which requires contractors to monitor and assure their operators don’t exceed a set vibration threshold. While vibration standards are not regulated in the United States, Volvo’s product manager Buddy Goodman says the other benefits on its FS system will keep U.S. drivers more comfortable and reduce cycle times.

When combined with higher-than-recommended travel speeds, cab jostling can create operator fatigue, medical claims and lost production time. Smart suspensions like those found on Volvo’s A35E S and A40 E FS artic haulers are bringing smoother rides and easier operations to the off-road field. Available in North America this month, the A40E offers automatic leveling and stability control on all six wheels. Sensors constantly monitor the truck’s load and ground conditions. Working with the machine’s engine control unit, the high and low pressure accumulators allow the shock absorbers to automatically self-level, keeping the truck at a neutral level of balance when going around corners and twisting terrain. The FS system allows operators to travel at higher than average speeds with less vibration, which the company says will significantly reduce cycle times and increase productivity.

Keeping a low profile
The Case 340B articulated dump truck increases its stability with its lower profile and wider bed. “By widening the bottom of the 340B’s bed, it can carry material down lower. That provides a more comfortable ride for the operator and keeps the bed more stable so there is less chance of a rollover,” Wolf says. The 340B is the largest of the Case ADT line up, with a rear frame design that houses the lift cylinders internal to the rear frame, protecting them from damage should a rollover happen. “The position of these cylinders also lets us take full advantage of our hydraulic power. The cylinders lift straight up instead of at an angle, providing more power,” Wolf says. To increase the 340B’s tractive effort the front driveline is mounted under the center of the cab and has an integrated transmission-mounted differential that transfers power directly to the front wheels, eliminating the drive shaft.

Machine management system standard
Komatsu’s HM400-2 articulated dump truck uses the same Komatsu SAA6D140E-5 engine found in their WA500-6 wheel loaders and PC600 excavators. Its front and center axle brakes act as a retarder, allowing the truck to go down steep grades quickly and safely. Komatsu’s Komtrax machine management information system is standard on all models and sends constant vehicle health, location and performance statistics to the contractor’s computer. An optional exhaust kit sends warm engine exhaust through the body of the truck to keep materials soft in cold weather conditions.