Equipment Spotlight: Articulated Dump Trucks

Articulated Dump Truck
Aggregates & Roadbuilding Staff
January 02, 2009
By Aggregates & Roadbuilding Staff
Some recent arrivals on the Articulated Dump Truck (ADT) scene
Case 335B and 340B articulated dump trucks are said to be ideal for demanding earth moving, quarry and road construction applications.  The 335B has a payload of 31.5 tonnes, heaped capacity of 20.2m3, total laden weight of 60 tonnes and an engine delivering  380 net hp (284 kW).The 340B has a payload of 36.0 tonnes, heaped capacity of 22.2m3, total laden weight of 65 tonnes and a 426 net hp (318 kW) engine.

These articulated trucks are powered by electronically controlled, Family IV Case diesel engines for clean, efficient operation. According to Case, these engines take advantage of the latest technology with variable geometry turbochargers to provide fast response and high torque rise in the toughest conditions. Meeting the latest emission regulations is not an issue with the high pressure fuel injection systems that efficiently mixes fuel and air for complete combustion. The 13 L engine powering the 335B and 340B is Tier III certified, fully serviced and supported by the Case two-year 2,000-hour engine warranty.
An electronically controlled transmission gives the operator the option of fully automatic or power shift control of six forward and three reverse gears. Modulated and precise clutch engagement provides smooth shifting for extended component life, reduced operator fatigue and maximized fuel economy, all lowering the cost per tonne of material moved. The standard, limited-slip powertrain automatically transfers power from the wheel that slips to the one that grips for greater traction. Limited-slip axles with Longitudinal Differential Lock Control for 6 x 4 operation, or front and rear axles for 6 x 6 can be combined under extreme operating conditions.

All Case articulated trucks have an integrated differential mounted directly to the transmission, thus eliminating a drive shaft and reducing the number of wear parts. The trucks reportedly offer best in class operator visibility, thanks to the sloping hood, large windows and floor-to-ceiling glass doors. Flat glass throughout the cab eliminates distortion and an optional rear-view camera and monitor make it easy to manoeuvre to either the loading or dumping locations.
The centrally mounted, the ROPS/FOPS cab structure is iso-mounted with heavy rubber bushings, pressurized and soundproofed to provide the ultimate in working environments while the tall, wide doorway provides easy entrance and exiting. The fully adjustable air suspension seat, tilting steering wheel and standard air conditioning with numerous diffusers provide operator comfort.

Operator controls include large analog, easy-to-read gauges and recognizable warning lights while low-effort control level commands the transmission, dump body and braking systems.

The B Series Case models are equipped with independent front suspension with both vertical and oscillating movement as well as long-stroke cylinders for excellent dampening. This gives the operator a smooth ride, which is particularly noticeable on the return leg of a high speed haul. The rear suspension of all Case articulated trucks is designed with fewer moving parts to reduce owning and operating costs, with dual, cast steel, rear suspension beams secured directly under the rear frame for trouble-free operation, long-term. In addition, the rear suspension design provides superior levels of traction and stability for improved performance.

The wide rear frame on Case articulated trucks delivers greater material retention and more equal weight distribution between the front and rear axles. This frame width makes it possible to mount the tandem walking beams directly to the frame, resulting in fewer parts and greater reliability and durability. It also allows for internal mounting of lift cylinders, between the frame rails where they are protected. With the lift cylinders mounted directly under the dump body, rather than on an angle, Case B Series Articulated Trucks take full advantage of hydraulic power for an efficient and controlled dump cycle.

The wider rear frame also makes a wider dump body possible and, as a result, the lower center of gravity provided by lower material carrying height improves stability under load. All Case dump bodies are built to accept body heating kits and can also be equipped with tailgates and extensions to match the machine to the application.

With a rated payload of 39.5 tonnes and a 24 m3 capacity truck body, the Caterpillar 740 Expanded Capacity Articulated Truck claims the biggest machine payload in the 36 tonne size class. Specifications for the 740 include a Cat C15 ACERT engine delivering net power of 453 hp (338 kW) and a seven forward, two reverse gear transmission with electronic autoshift. The 740 has a top travel speed of 54.7 km/h.

The 740 features differential locks that can be engaged and disengaged on the fly for faster cycle times in challenging underfoot conditions and on steep grades. According to Caterpillar, the 740 delivers excellent flotation and traction to haul efficiently in difficult terrain and maintains world class ride comfort contributing to faster cycle times.

The C15 engine with ACERT Technology optimizes fuel efficiency to get more work done per unit of fuel, while advanced intake air management and precise combustion control meets exhaust emissions regulatory requirements—U.S. EPA Tier 3 and EU Stage IIIa—without the exhaust gas recirculation system used on competitive engines.

The 7-speed automatic transmission features individual clutch modulation to ensure constant shift times even when the oil is cold. Controlled throttle shifting reduces power train stress and clutch wear by coordinating engine speed, torque converter lock-up and transmission clutch engagements. The differential locks on the 740 features oil-cooled clutch disc plates for reliable and durable operation. The operator simply chooses a level of lock-up using the dash switch and activates the system via a foot button, so eliminating the need to stop the truck before engaging or disengaging either of the two lock-up modes.
The Cat designed oil over nitrogen front suspension system is built to last and protect the frame from shock loads. The three-point front suspension oscillates plus and minus 6 degrees to provide a smooth ride, allowing the operator to travel at speed over rough terrain and softening impact loads on structures and components. Superior ride quality allows the operator to feel confident at high speed and ultimately results in better productivity. The latest rear suspension blocks are designed and built by Caterpillar, and the mounts have as much as five times the life of previous designs. Multi-plate, oil-immersed, enclosed brakes are fitted to both front and center axles. These brakes provide outstanding stopping capability while maintaining maximum durability.

The spacious, center-mounted cab has both an operator seat and a forward-facing, full-size trainer seat to support proper and thorough training of entry-level operators. The operator seat is a fully adjustable air-suspension seat that offers an excellent ride and reduces fatigue over long workdays while the steering column telescopes and tilts to allow adjusting for the operator. The low, sloping hood and placement of the cooling package behind the cab give the operator excellent all-around visibility. The large glass area and central operator position also aid the view of the work area.

The electrical system is said to be robust and durable with colour coded wires stamped with circuit identification numbers. Wiring harnesses are well supported throughout their lengths and feature heavy-duty Deutsch connectors and braiding for superior resistance to abrasion. The 740 is factory equipped with Cat Product Link. The system enables convenient remote monitoring and provides information to help keep jobs on schedule, maintain machine health and reduce owning and operating costs.

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