These mammoth pieces of equipment have been called beasts of burden. That is changing, however, as manufacturers are designing newer models for fuel efficiency
These mammoth pieces of equipment have been called beasts of burden. That is changing, however, as manufacturers are designing newer models for fuel efficiency by maximizing the payload-to-weight ratio. Regulatory requirements also have facilitated the transition to better fuel economy.
Safety also is a major concern and stopping power has become more of a priority. Several manufacturers are reinventing braking configurations, John Deere has integrated its braking system with a transmission retarder, and Komatsu has auto retard control speed for downhill travel.
SUSTAINING HAULAGE WITH LESS FUEL
The Komatsu HD785-7 weighs about 366,000 pounds and has a 100-ton capacity. The Tier-II 12-cylinder engine delivers 879 kW at 1,900 rpm. It has a high-pressure, common-rail injection system and air-to-air aftercooler turbocharger. The company says it has high torque at low speed, faster acceleration and lower fuel consumption than its predecessor.
The haul truck operates in power or economy modes and also has variable horsepower control, which detects the presence of a load. The automatic transmission is configured with seven forward and two reverse gears.
The machine is equipped with four-wheel retarder ìAP-FOUR (Anti-pitching four-wheel oil-cooled multiple disc retarder)î that applies retarding force on all four wheels. The retarder absorbs 1,464 horsepower. Auto retard control speed allows the operator to set downhill travel speed to maintain constant speed.
The cab has a five-way adjustable seat and a tilt-telescopic steering column. A suspension seat dampens vibrations. An instrument panel monitors critical machine functions. Problems are recorded in the monitor and indicated as service codes.
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The Terex TA40 articulated haul truck weighs 151,579 pounds with a 30.3-cubic-yard heaped capacity. The maximum payload is 42 tons. It is powered by a Tier-III compliant Detroit series 60 turbocharged diesel engine that generates 450 horsepower.
The company says that the six-wheel wet-braking system allows downhill haulage and can be combined with the standard engine-brake retarder and variable-range transmission retarder. A direct-mounted Allison HD 4560 planetary gearbox is electronically controlled with six forward speeds and one reverse. The company says, an integral lockup clutch improves fuel economy and operator selectable top gear increases control. Outboard transmission retarder is standard.
A high-roll center is achieved with four trailing links on the front suspension. Each axle is coupled to the frame by three rubber-bushed links and a transverse link. Pivoting inter-axle balance beams equalize load on each rear. Pivot points on leading and trailing links are maintenance-free. The three axles are in permanent all-wheel drive with differential coupling between each axle. Heavy-duty axles with fully-floating axle shafts and outboard planetary reduction gearing are standard.
Hydrostatic power steering by two double-acting cushioned steering cylinders is supplied by a variable displacement / piston pump. Secondary steering is provided by a ground-driven pump mounted on the dropbox. An audible alarm and warning light indicates when the secondary system is activated.
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The 6900XD 40-ton dump is designed to minimize cost-per-ton hauled as compared with traditional ADTs and rigid frame off-road dumps, according to Western Star Trucks. The machine is configured for speed, stability and fuel efficiency. According to the company, on maintained terrains and hauls that exceed half a mile, the 6900XD is 35% more fuel efficient than competitive articulated and rigid dumps in the same payload class. On longer hauls in excess of 12 miles, the truck has posted average fuel consumption of 7.13 gallons per hour.
The truck has heavy-duty Allison 4500RDS automatic transmission, and planetary gear drive axles for axle ratios between 10:1 and 12:1. This design produces less reduction gearing, power loss and heat in the transmission compared with high-maintenance drop boxes and transfer cases used in articulated and rigid haulers.
The 6900XD is equipped with 10 14R25 tires and has top speed of 43 mph. Smaller diameter tires (with reduced rolling resistance) offer better fuel efficiency and cycle speed than larger diameter, low-pressure flotation tires at a reported 40% lower replacement cost.
The truck uses a dry drum brake design versus wet disc brakes that are said to consume higher amounts of fuel due to inherent drag from rotating discs. The 6900XD is equipped with a standard Jacobs compression brake; optional hydraulic transmission retarder provides 600 British horsepower.
Constructed of Hardox 400 steel, the dump box has low-profile sides, with a scowled end to secure large boulders and reduce hydraulic cylinder stress upon boulder impact. Auto-lift tailgate is designed to maximize material loading while a full cab guard protects the cab from falling debris.
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The John Deere 400D articulated dump truck has a 65,960 pound net weight. The Mercedes Benz OM501LA engine has six cylinders and delivers 413 horsepower. The engine also has an integral exhaust brake and an engine valve brake. The truck has 6◊6 drive configuration.
The truck has an Allison 4500R ORS automatic engine-mounted planetary transmission with lock-up torque converters, integral output retarder and adaptive shift control. Maximum speed is 32 mph.
It has a new operating station with a short-sloped hood. Mirrors provide a panoramic rear view. It has a tilt-telescoping steering wheel. The air-suspension seat is adjustable and is positioned behind the front axle. Air conditioning is standard. A standard sound-suppression package reduces noise levels. The truck has a 128-gallon fuel tank and a 47-gallon hydraulic reservoir.
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Michelin's XDR quarry tires have deep, longitudinal, and transversal grooves. The company says the tread design distributes ground pressure evenly and is 15% deeper than most radial E4 tires.
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