Wheels:
Caterpillar pushes electric drive
Designers at Caterpillar are aiming to move more than dirt these days. They’re pushing electric drive, and it’s a powerful thing.
The company’s D7E is the first electric drive track-type tractor using modern technology. The revolutionary electric drive system developed for track-type tractors gives the D7E an optimum balance of power, efficiency, control, and maneuverability. Caterpillar says that the system delivers higher productivity, reduced fuel consumption, reduced operating costs, and longer drive train component life compared to other tractors in its size class. The company plans to commercially introduce the D7E in select markets during 2009.
The D7E is in the 60,000-lb weight range and is powered by a Cat C9 engine producing 235 hp (175 kW). Compared to its mechanical-drive predecessor, the Caterpillar D7R Series II, the company claims that the D7E will deliver 25% more material moved per gallon of fuel, 10% greater productivity, and 10% lower lifetime operating costs.
In the D7E power train, the diesel engine drives a generator to produce electricity that ultimately powers two AC electric drive motors, which are connected to a differential steering system. A traditional mechanical transmission is not needed, because the variable-speed electric motors serve the function of a continuously variable transmission. The electric drive train has 60% fewer moving parts compared to previous D7s. The electric system also provides power to auxiliary components so that no engine belts are needed.
“From an environmental sustainability perspective, the D7E uses substantially less fuel per hour — dramatically reducing the amount of carbon dioxide emissions,” says Caterpillar group president Stu Levenick. “This revolutionary design consumes fewer resources over its working life than any other track-type tractor in its class. All major components are engineered to be rebuilt or reused in the future.”
In addition to the electric drive system, the D7E incorporates many design improvements. Most noticeable to an operator is the industry-exclusive center post cab. The cab provides more all-around visibility and wider sight lines to the blade for better operator productivity and enhanced jobsite safety.
Other D7E features and benefits include:
- Electric drive train makes operator training easier, because there are no gears to shift.
- A spacious tilt cab provides a comfortable environment and allows ready access for maintenance. The electric air conditioning system is a self-contained module and is mounted outside the cab. Noise levels in the cab also are reduced by 50%.
- A single, larger blade lift cylinder replaces the traditional dual cylinders. It provides the power and stability of a dual-cylinder system but with less than half the parts — for reduced maintenance. It also aligns with the center post of the cab to enable enhanced visibility.
- The C9 engine with ACERT Technology meets U.S. Tier 3 emissions standards, and the tractor has been designed with Tier 4a in mind.
Source: Caterpillar
© Nelson Publishing, Inc. All Rights Reserved