February 2010

Caterpillar charges ahead with electric-drive truck

Caterpillar’s new F-Series model is the centrepiece of refined product line

By B. Dunn

Caterpillar’s trucks move more than half of the world’s mined rock, ore, coal and oil sands. In addition to investing in innovation, Caterpillar maintains its global edge by extending its industry reach to gather feedback on the performance of its products and the needs of their users from nearly 150 customers worldwide.

In response to what it has learned, the company refined every model it produces and introduced a new generation of models — the 793F and 797F mechanical drive trucks, with powerful new engines, and the 795F AC (alternating current), Caterpillar’s first electric drive truck.

"All of the F-Series mining trucks incorporate innovative design and engineering that enables them to deliver the lowest cost per tonne," says Ed McCord, Caterpillar’s mining truck product manager. "We see the addition of electric mining trucks as a complement to our mechanical drive trucks."

Customers drove Caterpillar to design an electric drive model

The company decided to introduce an electric drive model because customers demanded it, according to David Rea, mining truck commercial manager, Caterpillar Global Mining Division. Furthermore, the 795 fills the gap between the 793 with its 250-tonne capacity and the 797 with its 400-tonne capacity, he added. "The electric drive system delivers higher retarding capabilities, making it a popular choice in applications like steep downhill-loaded hauls at mine sites such as those in the Andes."

Caterpillar had originally built electric drive trucks in the late 1960s. However, given the technology then extant, the power train was relatively inefficient and the fuel consumption was higher than that of mechanical drive trucks. But with today’s AC advancements, Caterpillar decided the time was right to add an electric model to its arsenal once again.

"The electric drive system delivers higher retarding capabilities, making it a popular choice in applications like steep downhill-loaded hauls at mine sites such as those in the Andes."

As with the other F-Series models, the 795F AC is powered by the 16-cylinder Cat C175 engine, which provides 3,400 horsepower and a loaded top speed of 64 kilometres per hour.

The revamped diesel engine promises longer life between rebuilds, lower sound levels, improved altitude capability and improved fuel economy compared to the 3500 Series engine it replaces, according to Caterpillar.

An alternator behind the power plant converts mechanical energy into an alternating electric current.

One benefit of the electric drive is the easily accessed remote-mounted generator that allows servicing without the need to remove other major components. Another is the ability to quickly and separately service the axle-mounted motors that power the wheels.

Caterpillar to build 12 new 795 trucks in 2010

New technologies are incorporated throughout the 795F AC vehicle. Safety and operator confidence are enhanced by four-corner blended braking and retarding using Cat oil-immersed and cooled disc brakes as well as electrical retarding.

In addition, the radial arrangement of the retarding grids promotes more uniform air flow for better reliability. The fully integrated proprietary drive system is fully supported by Caterpillar.

After testing a pair of 795F AC prototypes at its development proving grounds in Tucson, Arizona, Caterpillar built a third, which is currently undergoing “on-the-job” field testing at a Rio Tinto copper mine in Utah.

The company plans to build 12 new 795 trucks this year for testing at sites around the world. If they deliver the intended performance results, commercial production will begin next year.

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