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The
dump truck does not have the most sophisticated name in construction
equipment, but it can be the contractor’s best friend. By Paul Hull |
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In children’s picture books, a dump truck often resembles a big red or yellow box on huge wheels with an equally huge driver grinning in the cab. The dump truck that’s best for your projects is not necessarily the biggest, its color might not be red or yellow, and its wheels might not be huge, but your driver (and you) will be grinning if the vehicle works with efficiency and is reasonably comfortable. Comfortable? Was it only in recent years that manufacturers realized that these tough trucks are the daytime homes of drivers who are not always big men? Today’s trucks ensure that a qualified driver of any size is comfortable enough to work a productive day’s shift. It’s all in the arithmetic. If your driver is tired and distracted for the last three of eight or nine hours, the final third of his day’s work may be slower and less accurate. It is not a question of brand name; it’s a matter of design. When Volvo’s A35D and A40D articulated haulers were awarded the prestigious German Red Dot Award, it was their "combination of engineering precision with safety and comfort" that was a winning criterion. "The designers [Nya Perspektiv Design] succeeded in both appearance and functionality," notes Tony Helsham, president and CEO of Volvo Construction Equipment. Some of driver comfort is in the actual handling of the controls: the steering, the power, the dumping. I do not have the physical strength of Hercules (nor Xena), so I was surprised when I climbed up into a Volvo truck with more than 20 tons of rock and debris in the back and found that steering around tight corners, uphill, and downhill took less effort than the same maneuvers in my own car. Slamming gears and being nicknamed "Bruiser" might have been yesterday’s images of a tough guy, but today’s dump truck driver is appreciated more for his ability to complete a cycle quickly and keep the job going on schedule. "Any truck driver who treats the vehicle the way a boy abuses his toy trucks–banging them here and there, ignoring the terrain, and never looking under the body to assess damage–may lose his job today," comments Steve Murphy, with 20 years of truck experience and based near Davenport, IA. "He deserves to. There’s no excuse today for poor truck performance." An aspect of driver comfort seldom mentioned is that the improvements in seating have meant that a greater number of drivers now wear their seat belts. Previously, driving over uneven terrain could cause major discomfort to a seat-belt user, so more than half of all truck drivers did not buckle up. That has changed, to everybody’s benefit. The cab, the positions of the controls, the legroom, and the adjustability of the seat might be as important as the shape of the truck’s bed and hood. Before plunging into what is new and helpful in dump trucks, let’s go back to 1957. That is the year the engine in small-town contractor Dean Myers’s truck was made. There are thousands of United States contractors with only one truck, and they might value it more than others value their fleets. "I need a truck that runs" is Myers’s basic requirement. "The running includes the engine and the dumping mechanism. It does not include the outward appearance, because that doesn’t help much in our work." An interesting comment made by Myers’s daughter Kay Lynn (who is an academic star in college and drives the truck in the summer) was that she was surprised how much better the gears were in the truck than in her personal car of a much later vintage. "Truly, it’s easier to drive." In the hands of a good driver, a dump truck (even an old one) can maneuver and reverse with unmatched precision. "My dump truck is a 1952 Ford, and it serves me well," asserts Guy Schultz. Similar to thousands of other contractors nationwide, he serves small communities within a radius of about 50 mi. "I look after all my equipment, and I might take a lot of convincing to buy a new truck for its looks or for features that would not help me much," he adds. Our conversations show that many contractors agree. Are They Construction Machines?
Most of us do not perceive trucks the same way as excavators, loaders, and dozers. "Since trucking is not a construction contractor’s business, International has developed the Integrated Dump Truck to make it easier for customers to buy and own a truck," explains Steve Keate, president of the truck group for International Truck and Engine Corporation. "With the chassis, body, and other components engineered as a single unit, the result is higher performance and value." International’s Integrated Dump Truck can have an aluminum or steel body, with lengths from 10 to 19.5 ft. and side heights from 24 to 54 in. The 13,200-lb. capacity (steerable) and 20,000-lb. capacity (rigid-lift) axles are available to meet any state’s legal load requirements. The truck can also have a heated- and insulated-body option for easier unloading in very cold weather. "We try to expand our income-producing season, and anything that helps to offset winter’s freezing is worth consideration," say contractors such as Keith Mitchell in Montana and Robert Burk in New York: states where the weather can stop the work season too soon if you don’t plan countermeasures. Contractors in Minnesota, North Dakota, Michigan, Maine, and Wisconsin agree. "Severe service" is how International describes such trucks as the 5500i and 5600i for contractors. It makes sense that the challenges of construction sites are more severe than those of interstate and other paved highways. Special attention was paid to the cab in the design of this series, and the benefits that International claims are those that contractors nationwide are listing as most important: improved driver comfort and convenience, greater reliability, higher quality, enhanced serviceability, and improved visibility. Good maneuverability of the 5500i is helped by the 40º turn angle and the 425 tires. That model has the set-forward axle; the 5600i has the traditional set-back axle to maximize front-axle loading. An indication of the importance of trucks in construction–especially for contractors who have to haul away dirt and debris–is the number of manufacturers who are now offering, or considering the production and marketing of, trucks specifically for our sector of the industry. You are probably familiar with Caterpillar, Komatsu, Volvo, International, Moxy, Terex, Freightliner, and Sterling, but have you investigated the trucks presented by Link-Belt, Hitachi, John Deere, JCB, Thwaites, and Multidrive? In the first group mentioned, Sterling’s Acterra models (classes 5-8) have capacities from 19,000 lb. and horsepower ratings from 170 to 300. Not all require the driver to have a commercial driver’s license. The sight lines close to the truck–frequently difficult at smaller sites–are improved by the design of the hood with its sharp slope. That same improvement in visibility for the driver is why Terex’s new TA25 and TA30 (both articulated) have hoods that are 7 in. lower than before. It’s for those situations when the driver needs to see as close as possible to the front of the truck. All the information you could possibly want about trucks is readily available from the manufacturers’ distributors. It takes some reading, but it’s well worth the study before any purchase.
"When you are busy every day, as we always hope to be, it’s not easy to follow a recommended maintenance schedule for vehicles," admits Bob Carlsson, a contractor in Minnesota. "Most of us contractors don’t have dedicated technicians. We do the checks ourselves, for things like the fluids, and wait our turn up at the local truck-service place for more complicated problems and repairs." That’s why some of the less noticed improvements are the most important. Standard oil-change intervals have grown helpfully in recent years–International’s 7000 Series intervals extend to 15,000 mi. now. The location of the cooling system can make a difference, too, because some grading and excavation sites seem to love attacking that vital part of a truck if it is too near the ground. When a truck is out of action for repairs, its value as a work tool is zero. An interesting observation from a contractor who uses Caterpillar trucks is that he can have a remanufactured engine (done to the standards and warranty of a new engine) in two to three days, whereas it might take a week or two for an overhaul. The difference in cost is difficult to assess, because it depends on the condition of the old engine. Sometimes an overhaul is a little less than a "reman," and sometimes it’s a little more. The warranty could make the whole difference to your situation. A remanufactured engine from Cat often offers a warranty of 12 months, while the warranty on an overhaul may be only three or six months. Some medium remanufactured diesel engines can give warranties up to 150,000 mi. Each type of construction machine claims to be the true workhorse at the site, but it is easy to make a case for the dump truck. Loaders, excavators, telescopic handlers, skid-steers–they all load trucks. One of the most publicized capabilities of those loading machines is the height to which they can raise their loads. For most projects by grading and excavation contractors, it seems that 10 tons or less is a common capacity required of a truck. Contractors who know the digging and loading capacities of their equipment can quickly assess the best-size dump truck for them. Dump trucks carry and dump, but they also serve as the towing vehicle for many contractors. "We often use a flatbed behind the truck for a skid-steer and wheel loader," relates Gary Harper of Glasgow, MT, who has been driving dump trucks since he was a teenager. He works for Knoll’s Ready-Mix but is hauling earth (transferred by a telescopic crane from a concrete bucket to a skid-steer loader and then to his truck) from the excavations for add-on construction at a hospital site. "At the site, the trailer is unhitched and all the machinery is ready to go, including the truck, which is now working as a dump truck." It’s a practical use of equipment, but make sure the truck pulls only a reasonable load. Carrying the load is important; how to dispose of it is just as important. Dump trucks have traditionally dumped. In other words, the back goes up and the load falls out. Some trucks use a side discharge. Some don’t raise the load. All the methods work well, and it comes back to whatever is best for your usual applications. That might mean your trucks should be only as big as the feeding capacity of your excavating machines. At the building of a resort on the Caribbean island of Tobago (which included a hotel, a golf course, condominiums, a marina, villas, a bird sanctuary, and a shopping complex), contractor Gregori International used two Volvo A25s and an A30. Maximum haul distance was about 2 mi. "The best target we moved in a single night was 1,830 cubic yards over a distance of almost a mile," says Nick Clark, project manager. "The trucks could have moved more, but we were restricted by the maximum performance of the dozer and excavator." The trucks for that project dumped their loads to the rear.
The alternative to dumping the load is ejecting it. Some Caterpillar trucks offer this option. The advantages are that the discharge of sticky materials is easier and more complete, and the operator can dump the load while on the move (to spread materials at the dump site and reduce cycle times). Since this ejector system eliminates the need to raise the body, a truck can dump on sideslopes and is more stable when dumping on steep slopes or unstable ground. Another practical advantage is that the driver does not have to worry about overhead cables and structures. In Europe, David Brown has designed similar trucks for several years. Multidrive Ltd.’s M8-35, for example, is an ejector body truck for a 35-ton payload. "We have had decades of learning and solving the problems of traditional ADTs [articulated dump trucks], and we have incorporated significant advantages into the Multidrive trucks, with patented drivelines and ejector body systems," explains Brown. "High- or low-density materials with abrasive, sticky, granular, or rocky characteristics pose no problems. We have even done concrete spreading. All such materials can be safely flat-discharged on the move–forward or reverse or high-heaped static–in just 15 seconds."
A type of dump truck that has not become popular yet in North America is a big brother of what Europeans call the site dumper. Thwaites is one of the leaders in this field. Thwaites’s Alldrive 7 Tonne (with a maximum safe load of 7 tons) doesn’t look like a dump truck, but it does handle a load that is quite normal at many construction sites. We don’t see this kind of vehicle trundling along the interstate, but we do see its value for grading and excavation contractors when the materials stay at the site. It can travel up to 16 mph (with four speeds), and the engine is a Perkins 1000 series with 106 bhp. It’s not a dump truck, but is it showing us one possible direction for handling tons of materials on-site? In a similar train of thought, if you are wondering exactly what you want your everyday truck to provide, you might check the capabilities of Freightliner’s Unimog (popular in Europe as a Mercedes brand) and some of the Mitsubishi Fuso models (such as the 2001). At the other end of the scale, you can expand the capabilities of a dump truck. "The Strong Arm gives you the payload of an 18-wheeler with a 10-wheeler," comments Rusty Hoffpauir for Strong Industries in Houston, TX. "It is put on the rear of heavy-duty trucks like dump trucks and concrete mixers to increase payloads. It has been used often for asphalt, but its usefulness for transporting materials from large excavation sites could be significant." The extension and axle added by Strong lengthen the dump truck by 13 ft. (or 5 tons) and fold away when not required. It was developed to meet the stringent specifications of federal bridge laws. It has also been called a flying tag axle, a booster, a stinger, and a trailing tag. We noticed that the trailing axle does not interfere with normal dump truck operations because the axle toggles up and toward the front to clear the rear of the vehicle. Some 80% of concrete trucks made today have trailing axles; they could be the future of dump trucks for owners with big payloads. Articulated trucks are gaining popularity in North America. Construction-equipment manufacturers who have not been associated with them previously have now decided to enter that sector of the market. New Holland Construction has just announced its first ADT: the AD250. "It will expand the full line of construction equipment offered by our company," points out General Manager of Marketing Kirk Gillette. "This six-wheel AD250 should be ideal for use on sites where there are slopes or soft ground, places like housing developments, land reclamation sites, industrial parks, and golf courses."
Among the features offered on this first-of-the-new-line ADT from New Holland Construction are centralized greasing that requires only two locations for lubricating the whole machine and a locking brake to hold the vehicle steady and stable during loading and unloading. The steering is fully hydraulic, and there is a backup system that allows steering of the truck if the primary-steering function is lost. The truck’s load capacity is 13.9 yd._ struck and 17.4 yd._ heaped. Payload is 50,707 lb., maximum speed forward is 30 mph, and minimum turning radius is only 322 in. Many dump trucks we see around the thousands of smaller communities in the US (with populations of less than 50,000 but home territory to many grading and excavation contractors with work on utilities, housing, and publicly funded projects) have rigid configurations, and they go well on paved roads or at sites where the terrain is reasonably flat. The weather plays an important part in most construction–especially, perhaps, for grading and excavation–because its friendliness or hostility can affect the ground before and during the work. There has been broad acceptance of articulated trucks (as compared with rigid-frame, off-highway trucks) because they often cope better with poor terrain and adverse weather conditions and because they have high flotation, a relatively light weight, and large tire footprints. When the ground is soft or the roads are rough, articulated trucks with three axles tend to perform better than those with two because of their lower ground pressure. But a two-axle unit will handle most poor ground conditions and can carry rockier material. The total resistance of the ground at your site is a consideration too. Total resistance is the grade plus the rolling resistance, with the latter reckoned to be about 3% for a gravel road or compacted dirt and as much as 8% for a soft-earth backfill. The weight, load, and tire size affect a vehicle’s response to those ground conditions. The grades at the site are also factors in hauling efficiency, with articulated trucks climbing steeper grades (up to 35%) than rigid trucks (short grades to 20% but more reasonably 8-10% on continuous grades). Three-axle articulated trucks seem to have an advantage on poor terrain, but the free-swinging tandem housing on Moxy trucks is designed to give even better ground contact, whatever the ground conditions. On some undulating terrain, says Moxy, competitive articulated trucks without that design feature might leave an axle floating in the air rather than gripping the ground. The sloping body design of the MT26 and MT31 trucks also promotes good stability at uneven sites and facilitates tipping and load ejection because the slope allows a wider rear part of the body. "The sloping rear frame ensures a low center of gravity, good stability, and excellent weight distribution to the front axle," notes Tina Eckeroth, marketing director for Moxy. "The articulation hinge system always ensures equal weight distribution to the front wheels, even when the vehicle is turning. Our trucks also have permanent six-wheel drive to help them meet the challenges of rugged terrain. We are now offering our Plus 1 concept to US contractors. We think our trucks go one step further than our competition for features like engine power, traction, larger loads, better stability, and low fuel consumption." These trucks feature Scania engines, Komatsu or ZF transmissions, and 400 Hardox hardened-steel plates in bottom, front, and sides. Tipping time is 15 seconds. The MT26 and MT31 offer two alternative standards for the user: the HighLine and the Effective Line. The former has more standard equipment available for its cab, while the latter is more of a basic, no-frills truck to suit those for whom price is critical. The suspension system of Caterpillar’s D400E II articulated ejector truck (with a rated capacity of 40 tons) has the same goal: keep the wheels in contact with the ground. "The front axle is mounted on a swinging-cradle subframe arrangement," explains Mark Sprouls, who has done independent studies of truck design and performance for Caterpillar and others for several years. "This pivots on the front frame and allows a cushioning movement in the vertical plane. The body-load stresses go straight to the suspension system rather than being absorbed by the truck’s frame. That, in turn, makes for a more comfortable ride and a longer life for the frame." For the rear axles, the mechanical balance-beam suspension lets all four rear wheels stay on the ground to improve both traction and flotation. Dump trucks are everywhere.
Many of those you see are old, battered … and still going.
There are few construction-equipment items as friendly and hardworking;
few that have proved themselves to be so easy to use and helpful
to own. Now much more comfortable, with excellent hydraulics and
ergonomic controls to boot, the new models will probably still be
working when their current drivers are talking about today as the
"good old times" of grading and excavation. Paul Hull writes on construction and environmental topics for several international magazines.
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