Equipment

Savings Dug Up with D7E Dozer

Reduced fuel consumption and lower service costs are just a few ways fleets can save with the Caterpillar D7E Track-Type Tractor, a hybrid system that combines diesel and electric power.

September 2009, Government Fleet - Feature

by Grace Lauron - Also by this author

Delivering greater fuel economy, increased productivity, and lower lifetime service costs than conventional tractors of equal weight and horsepower, the Cat D7E Track-Type Tractor is designed to meet the growing demand for powerful, maneuverable, fuel-efficient dozers.

A hybrid system in the sense that it combines diesel and electric power, the D7E’s electric drive system is built exclusively for track-type tractor applications and is the first of a wide range of new drive technologies Caterpillar is developing for use in off-road equipment.

Capable of moving more material per gallon/liter of fuel while costing less to maintain and service, the D7E was recognized in May for its contribution to improving air quality with a Clean Air Excellence Award from the U.S. Environmental Protection Agency.

Less is More
Caterpillar’s D7E cuts down on fuel consumption and also eliminates extra moving parts, helping fleets save ownership and operating costs. The powertrain oil system takes 50-percent less oil (volume) and lasts twice as long.

The D7E’s relatively smaller engine runs in a narrow range (between 1,500-1,800 rpm) to extend engine life. Electric drive eliminates the torque converter, powershift transmission, and related drive shafts used in all-mechanical designs. Using a generator, the D7E engine “doesn’t need to rev as high or lug down as low,” according to Caterpillar. The engine is also entirely beltless, dispensing the need for belt maintenance and replacement, said the manufacturer.

Increased drivetrain efficiency allows the D7E to deliver better performance from less horsepower. The Cat C9.3 ACERT diesel engine, rated at 235 net horsepower (175 kW) in the D7E, drives a powerful electrical generator that produces AC (alternating current).

With 60-percent fewer moving parts than a mechanical drive system, there are fewer components to wear out or potentially break down. The components have been designed to last up to 50-percent longer than a conventional drive system working in a similar application.

Advanced electronics provide DC (direct current) to power the accessory system. The modular heating and air conditions system, water pump, and battery charger are electrically powered for maximum reliability in varied conditions.

A heavy-duty, low-drive undercarriage is engineered for durable service in severe applications, such as logging and pioneering in rocky terrain. Both standard and low-ground-pressure configurations are available. Optional for the D7E is the Cat SystemOne undercarriage, which uses sealed pin-and-bushing cartridges and balanced-life components throughout — a design that can reduce undercarriage maintenance costs by 70 percent.

Productivity Boosted
Smoother operation and improved visibility are just a few factors helping the D7E boost productivity and enabling fleets to get more work done in less time.

With advanced maneuverability, the D7E has the ability to make lock-track pivot turns — a first for this type of equipment. Operation is smoother and easier with no gears to shift or clutches, according to Caterpillar.

The design of the operator station also helps speed up the work process. The cab’s single center post aligns with the exhaust stack, air intake, and single blade-lift cylinder to enhance forward visibility. The angled door and mating side panel expand sightlines to the blade. Interior sound level is quiet and an integrated display screen provides a range of machine status information. The tilting cab allows wide-open access to major components.

Efficiency and versatility are also built into the D7E work tool and control systems. Blade options include universal, semi-universal, straight, and angled configurations — all supported by heavy-duty, L-shaped push arms and controlled by a powerful, single lift cylinder. Available rear work tools include a multi-shank ripper, hydraulically driven winch, and a drawbar, which allows using towed implements and scrapers.

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