The Caterpillar 797 is a series of off-highway, ultra class, two-axle, mechanical powertrain haul trucks developed and manufactured in the United States by Caterpillar Inc. specifically for high-production mining and heavy-duty construction applications worldwide. In production since 1998, the 797 series represents Caterpillar’s largest, highest capacity haul trucks. The current, third-generation model, the 797F, offers one of the largest haul truck payload capacities in the world, up to 400 short tons (363 t) and has the highest payload capacity among mechanical drive haul trucks.
In 1997, Caterpillar decided to begin development of a 360 short tons (327 t) payload capacity haul truck to meet the demand from large-scale mine operators wanting to reduce operating costs at mines using 80 to 90 short tons (73 to 82 t) per pass shovels.Engineers at Caterpillar's Mining & Construction Equipment Division in Decatur, Illinois, created a new design for the 797 using computer-aided design technology. This was the first time CAD tools had been used extensively to design a Caterpillar truck.
Caterpillar first unveiled a completed 797 on September 29, 1998, at its assembly plant in Decatur, Illinois.
The first two 797s produced were transported to Caterpillar's Arizona proving grounds for testing. In the second quarter of 1999, the third and fourth 797s produced were the first to be placed in service with a customer at the Bingham Canyon Mine in Utah. Caterpillar put 18 additional 797s into service with mine operators worldwide as production development units.
Caterpillar began marketing the 797 in North America in 2000, with full worldwide marketing following in 2001. The first generation serial number prefix is 5YW.
Caterpillar introduced the 797B in spring of 2002, replacing the first-generation 797. Caterpillar increased the power output of the Cat 3524B engine to cope with the 797B's higher payload capacity of up to 380 short tons (345 t), a 20 short tons (18 t) improvement over the 797. The first 797B units entered service with customers in October, 2002.
Caterpillar introduced the latest 797 in the series, the 797F, at MINExpo International in September 2008. When Caterpillar began full production of the 797F in late 2009, the 797F replaced the 797B. The 797F comes equipped with a new, more powerful and more efficient Cat C175-20 engine and an increased payload capacity of up to 400 short tons (363 t).
The Caterpillar 797 series trucks employ mechanical drive powertrains in contrast to the diesel-electric powertrains of similar haul trucks offered by competitors. During initial development in 1997, a diesel-electric powertrain was considered for the 797, but this powertrain configuration was not developed because Caterpillar considered a mechanical drive powertrain more appropriate for market conditions at that time.
A gross 3,400 hp (2,535 kW) [net 3,211 hp (2,394 kW)] Cat 3524B HD EUI 24-cylinder,
displacement]], electronic unit injection, quad single-stage turbocharged, liquid aftercooled, four-stroke diesel engine powers the 797. The Cat 3524B HD engine is a tandem unit consisting of two 12-cylinder Cat 3512B HD engine blocks coupled to operate as a single engine with a combined displacement of 106 liters (6468 cubic inches).
A gross 3,550 hp (2,647 kW) [net 3,370 hp (2,513 kW)], quad turbocharged Caterpillar 3524B engine powers the 797B. The power rating of the 3524B is valid up to an elevation of 8,500 ft (2,591 m) or 15,000 ft (4,572 m) with a high altitude arrangement.
A gross 4,000 hp (2,983 kW) [net 3,793 hp (2,828 kW)] Cat C175-20 ACERT single block, 20-cylinder, electronic common rail injection, quad turbocharged, air-to-air aftercooled, four-stroke diesel engine powers the 797F. The power rating of the C175-20 is valid up to an elevation of 7,000 ft (2,134 m) or up to 16,000 ft (4,877 m) with a high altitude arrangement.
The 797 series haul trucks are equipped with a rear-axle-mounted, computer-controlled, seven-speed planetary transmission with a separate lock-up torque converter. Both transmission and torque converter use a common powertrain oil.
Each 797 wheel is attached to the axle using 54 - 36-mm nuts that are torqued to 2,300 lb⋅ft (3,118 N⋅m). A size 55/80R63 radial tire was developed by Michelin in conjunction with Caterpillar specifically for the first generation 797. The Caterpillar 797B and 797F run 4.028 m (13.22 ft) tall, 5,300 kg (11,680 lb) Michelin 59/80R63 XDR. Most first generation 797s have been retrofitted to use the 59/80R63 tires as well. Six tires are required per truck at a cost in 2009 of approximately US$42,500 per tire.
Major components of the 797 are manufactured and assembled at seven Caterpillar or supplier facilities located throughout North America, then shipped to the customer site for final assembly by Caterpillar technicians.
The engine is manufactured by Caterpillar in Lafayette, Indiana, and is then shipped to Caterpillar's assembly plant in Decatur, Illinois.
The transmission and torque converter are manufactured by Caterpillar in East Peoria, Illinois, and is then shipped to Caterpillar's assembly plant in Decatur, Illinois.
The axle assemblies are manufactured by Caterpillar in Winston-Salem, North Carolina, and are shipped to the customer site.
The tires are manufactured by Michelin North America at the US7 Earthmover Manufacturing plant in Lexington, South Carolina, and are shipped to the customer site.
The driver's cab is manufactured by Bergstrom Climate Control Systems' Contract Assembly division in Joliet, Illinois. Each cab is assembled by one person and requires forty hours to complete. The cab is shipped to the customer site.
The dump body is composed of five components: the floor, the two sides, the front wall and the canopy. The dump body is manufactured at Caterpillar Mexico in Monterrey, Mexico,as well as at least to a limited degree by WesTech of Casper, Wyoming in the western United States and shipped in component form to the customer site where it is assembled and welded into a monolithic structure before being joined to the frame during final assembly.
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