Caterpillar hosted an international trade press event on June 22-24 in Peoria to showcase the D7E, its track-type-tractor with electric drive that was first unveiled at ConExpo 2008.

According to Dave Nicoll, product execution manager, “Our engineers were given a blank sheet of paper to design this. That doesn’t happen often at Cat.” Nicoll explained that because of this unique opportunity to design the tractor from the ground up, Cat’s engineers were able to make many changes in the new cab.

More than 100 patents have been requested in association with the D7E; some are still pending. Some of the most innovative features on the new tractor include its center-post design that offers 35% improved visibility, along with the dedicated steering pump, beltless engine, exclusive center-post cab and single lift cylinder.

Keith Heiar, senior project engineer for track-type tractors at Caterpillar, describes the best features of the D7E.

But the most compelling feature of this dozer is definitely its electric drive train. Cat is now labeling its D7E as a diesel electric hybrid. The machine was recently recognized by the EPA with a Clear Air Excellence Award.

Mike Betz, engineering manager for the D7E, discussed the components of the electric power train in contrast to the D7R power train. The D7E’s power train uses a generator, motors, and power electronics instead of a torque divider and powershift transmission.

It is powered by a Cat C9.3 ACERT 235-hp engine. “It’s 5 horsepower less than what we offer today [in the D7R] but we get more power to the ground,” Betz said.

Betz also described the power inverter as the “heart of the electric drive” since it controls the motors. The power inverter provides DC power for machine control and accessory systems, provides AC power to the propulsion module, and matches power output to each job’s needs.

According to Cat’s engineers, the D7E performs better with machine control and guidance systems due to its distributed hydraulics, single lift system and dedicated steering pump

Betz said, “This question comes up all the time: ‘Will it work in environments that tractors are used in today?’” His answer was a resounding yes. He noted that 18 D7Es are currently running at customer sites, and they have logged more than 50,000 machine and lab development hours to date. He also noted that the entire electric drive system is fully sealed and liquid cooled.

Comparing the D7E to the D7R, Cat claims that the D7E consumes 10-30% lower fuel per hour and moves 10% more material per hour. This claim that the D7E will help contractors do more with less was supported by four contractors who attended the event to tell about their experiences testing out the machine on their jobs. They reported that their operators were excited by the visibility, maneuverability and power of the D7E.

Dan Plote, president of Plote Construction Inc. (Hoffman Estates, Illinois), said the D7E provided “consistent strength with no sure and no slowdown.” He added, “Amazingly, [the D7E] is keeping up pound for pound with our D8T. We’re saving over 30% in fuel and pushing the same amount of dirt everyday.”

Mike Betz, engineering manager for the D7E, explains the basics of the D7E’s electric drive train during a machine walk-around.

Cat’s Nicoll also promoted that the D7E will offer more uptime because its drive train eliminates “nuisance items” such as belts, alternators and clutches.

The performance of the machine is also playing into its ability to work with machine control and guidance systems. According to Wesley Reetz, D7E tractor project engineer, “The D7E has tested better than any other tractor with AccuGrade.” He attributed this to the D7E’s distributed hydraulics (which decrease lag because the dozer valve is closer to the lift cylinder), its single lift system (which is simplified for better response) and its dedicated steering pump (which provides simultaneous implement control).

Cat dealers are now taking orders for the D7E, which will initially be available in the U.S., Canada, Europe and Japan. Limited production is slated to begin this October, with full production in early 2010.