Equipment Specs

Rock Truck

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1999 Komatsu HD785-5 Rock Truck
Rock trucks are a type of off-highway truck used to transport large amounts of material such as dirt, rocks, and coal across unpaved roads on construction sites, gravel pits, and in open-pit mines. These trucks, even empty, are too heavy for public roads, and typically carry loads of 100 to 300 tons.[1] For transportation, they must be broken down into various parts, and reassembled at job sites. Although these trucks are designed to move on unpaved roads, they must be driven on smooth surfaces in order to run; uneven roads can twist or crack a rock truck’s frame, ruining its suspension.[2] These trucks, powered either mechanically or electrically, and vary in their number of tires. They are loaded with the assistance of another piece of equipment, such as an excavator, and they unload from either their underside, or from the rear.


[edit] History

[edit] The Need for a Better Truck

The need for heavy-duty off-highway trucks became apparent in the early 1930s,[3] when excavators were being used for dirt-moving jobs. These shovels were relatively advanced in comparison to the corresponding light-framed highway trucks that were being used to move dirt at the time. With their wooden bodies and narrow wheels, these trucks would often get stuck in the mud. Additionally, their frames would often become damaged while being loaded with rocks by the excavators.

[edit] Mack Trucks for the Hoover Dam

Although various attempts to develop a heavier-duty off-highway truck were made through the years, rock trucks were really introduced during the construction of the Hoover Dam, beginning in 1931.[4] At this time, Mack Trucks modified some of their highway truck models for use in the project. Specifically, the Mack AC and AP were designed for use at the Boulder Dam. Following this, the company decided to introduce an entire line of specialized off-highway trucks. Its line expanded until the company abandoned its off-highway endeavor in 1981.

[edit] Euclid’s Specialized Rock Trucks

In 1934, Euclid Road Machinery was the first company to focus on rock trucks specifically built for off-road use. The company’s offerings in this market were very successful; consequently, many other truck manufacturers embarked on a similar endeavor.

[edit] Trailer Type Haulers

In the 1940s, a new type of rock truck was introduced. Companies such as Caterpillar, LeTourneau, M-R-S, Dart, and Euclid first manufactured these trailer type models, pulled by two- or four-wheel tractors. Today, companies that make tractors for these units are Caterpillar, Euclid, and Komatsu, and specialists such as Maxter Industries Ltd manufacture the corresponding rear- and bottom-dump trailers with capacities up to 290 tons.[5]

1996 Caterpillar 777D Rock Truck

[edit] Bigger Trucks Need Bigger Parts

After World War II, the need for larger rock trucks was increasing, but was limited due to the size of engines, transmissions, and tires that were available. In response to this, Euclid began incorporating twin power—doubled-up engines, drive trains, and drive axles—to their trucks to enable heavier loads to be carried. An example of one such truck is Euclid’s LLD 50-ton rear dump, which was the largest truck in 1951,[6] the year of its introduction. This truck used two Cummins NHRS engines and had a combined horsepower of 600. By the 1960s, single-engine trucks were in use again as more powerful components were available. Dual power, however, was used once again in the 1970s when the truck capacity demands surpassed available components size for a second time.

[edit] Electric-wheel-drive

A significant advancement arose in the late 1950s with the introduction of electric-wheel-drive for rock trucks.[7] This system made use of a diesel engine that drove a generator to provide DC electric current for a motor in each driving wheel. One of the first such rock trucks to be introduced was produced by R.G. LeTourneau with the Anaconda Co. in 1959. The articulated truck was known as the TR-60, and had a capacity of 75 tons.[8] The same year, Unit Rig, a division of Terex, introduced a diesel-electric truck they called “Lectrahaul.” By 1979, 2,500 Lectrahauls had been built—its M-200 was the world’s largest truck when introduced in 1968.[9] Today, the largest offering from Unit Rig, now a division of Terex, is the AC electric-wheel-drive, 340-ton capacity MT-5500.[10] There is currently an on-going debate over which trucks, mechanical or electric-drive, cost the least per ton hauled.

[edit] Ralph Kress’ Contributions

It is argued that one of the most influential people in the rock truck industry was Ralph Kress.[11] Kress was involved in the advancement of Dart, LeTourneau-Westinghouse, Caterpillar, and Kress Corp.

Kress’ career in off-highway trucks began in 1950 when became general manager of Dart Truck Co., where he developed the Dart 75-TA, the world’s largest truck at its introduction in 1951.[12] Fifteen years later, Dart became the first manufacturer to introduce a mechanical drive truck with a regular two-axle configuration to have a capacity greater than 100 tons.[13] Dart was acquired by Unit Rig in 1984.

In 1955, Kress became part of LeTourneau-Westinghouse (Wabco), where he worked as a consultant, designing a 30-ton rear dump truck, part of a line known as the Haulpak. This truck included such features as a triangular box shape, which lowered the center of gravity, an offset cab, forward sloping windshield, and short wheelbase. These elements became standard in most rock trucks for the next forty years. In 1984, Wabco became a division of Dresser Industries Inc; in 1988 the Komatsu Dresser Co. (KDC) was formed. Today, Haulpak trucks are marketed under Komatsu Mining Systems.

After his accomplishment with Wabco trucks, Kress moved on to Caterpillar. There, he began developing Caterpillar’s line of electric-drive trucks. By 1969, Caterpillar had decided to stop manufacturing electric trucks.

As a result of Caterpillar’s decision, Kress moved on to work at the company founded by his son Ted: The Kress Corp. It was there that Kress developed the Kress Hauler, a mechanical drive 150-ton rigid framed bottom dump truck with a rear engine and 180-degree steering. This truck, able to haul loads at a speed of up to 60 miles (97 km) per hour, can also turn its four front wheels 90 degrees to the truck frame – this enables very tight turns. Kress rigid-frame bottom dump rock trucks are currently the largest coal carriers available.[14]

[edit] The New Face of Euclid

Euclid became a division of General Motors in 1953. Fifteen years later, the parent company was required to cease production and sales of rock trucks for four years, in addition to giving up the Euclid brand. As a result, GM introduced Terex products as a way to continue manufacturing earthmoving products.

[edit] The Titan

In 1972, GM began manufacturing rock trucks again, and introduced their Terex 33-series. This product line included the Model 33-19, more commonly known as the Titan. This truck, unveiled in 1974, had a 350-ton capacity, was 67 feet (20 m) long, 26 feet (7.9 m) wide, and weighed 509,500 pounds (231,105 kg). Its gross vehicle weight was 1,209,500 pounds (548,620 kg). This massive rock truck was powered by diesel-electric-drive, with a 16-cylinder 3,300 horsepower GM engine. Additionally, the truck was mounted on 10 tires that each measured 11 feet (3.4 m) in diameter.[15] The truck, now on display in Sparwood, British Columbia, Canada, held the title of the world’s biggest truck for 25 years.

[edit] Breaking the Titan’s Record

1982 Terex 3307AA 40-ton Rock Truck
Though the Terex Titan held an impressive size record for over two decades, its title was taken in 1998 by Caterpillar’s 797. This truck, with mechanical drive and an automatic power-shift transmission, boasted a 360-ton capacity, was 30 feet (9.1 m) wide, and had a gross vehicle weight of 1.2 million pounds (544,310 kg).[16]

Liebherr-America Inc. was on its way to breaking the Titan’s size record when it acquired Wiseda in 1995 and formed Liebherr Mining Truck Inc. With the purchase of this Oklahoma-based large diesel-electric truck manufacturer, Liebherr began to introduce a number of massive rock trucks, with capacities from 200 to 360 tons. The T282 (originally the KL-2680), one of the largest trucks available today, was unveiled in 1998. This model is comprised of MTU or Cummins engines, with a capacity of 340 tons and a combined horsepower of up to 3,200.[17] Recently, Liebherr has introduced the IL-2600, with a 300-ton capacity. This truck was designed to decrease structural weight so that the payload-to-weight can increase. The IL-2600 has four in-line rear wheels, and a rear frame with no lateral support—its strength is taken from a fortified truck box.

[edit] Other Contributing Manufacturers

Many companies have contributed to the advancement of rock trucks over the decades. In 1943, M-R-S introduced its Mississippi Wagon, a bottom-dump four-wheel trailer pulled behind a four-wheel tractor. This truck had a unique feature that enabled hydraulic weight transfer between the trailer and tractor.

In 1958, the English Aveling-Barford Co. developed their SN-series, 30- to 35-ton capacity trucks powered by Rolls Royce C8TFL or GM12V71N engines that reach speeds of up to 33 miles (53 km) per hour. Today, the company offers the RD-series, originally known as Centaurs, a line of rigid frame trucks ranging from 17 to 65 ton capacities.

1963 saw the introduction of International’s major advancement into the market with the Payhauler 180. This 45-ton four-wheel drive rigid-frame rear-dump truck included tires all around. The front of the truck was the same size as the rear, and its weight was distributed equally on each wheel. This truck was very successful for construction sites and surface mines with soft ground. The line was subsequently expanded and renumbered as 330, 340, and 350 until International sold the line in 1982 to a new company named Payhauler Corp.; Terex Corp. has owned Payhauler since 1998. The improved 350, now known as the 350C, continues to be sold to a niche market.

In 1971, in the midst of the rising popularity of electric-drive trucks, Rimpull emphasized their “Back to Basics” approach, manufacturing mechanically driven bottom-dump rock trucks. Today, the company manufacturers mechanical-drive rear-dumps with capacities ranging from 85 to 120 tons. Rimpull’s bottom dump line has been expanded to include the CW-180, with a 180-ton capacity, and the CW-280 with a 300-ton capacity and 1,600 horsepower.

[edit] Common Manufacturers

[edit] Additional Photos

1975 Euclid 201TD Rock Truck
2002 Euclid-Hitachi EH1100 Rock Truck
2003 Caterpillar 769D Rock Truck
Wabco 35C Rock Truck

[edit] References

  1. Haddock, Keith. The Earthmover Encyclopedia. Motorbooks: 2002.
  2. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  3. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  4. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  5. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  6. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  7. Alves, Michael and Haddock, Keith and Halberstadt, Hans and Sargent, Sam. Heavy Equipment. Crestline: 2003
  8. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  9. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  10. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  11. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  12. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  13. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  14. Haddock, Keith. Giant Earthmovers. MBI Publishing: 1998.
  15. Alves, Michael and Haddock, Keith and Halberstadt, Hans and Sargent, Sam. Heavy Equipment. Crestline: 2003
  16. Alves, Michael and Haddock, Keith and Halberstadt, Hans and Sargent, Sam. Heavy Equipment. Crestline: 2003
  17. Alves, Michael and Haddock, Keith and Halberstadt, Hans and Sargent, Sam. Heavy Equipment. Crestline: 2003