Caterpillar mining trucks overhauled

  • 09-Feb-2009 04:54 EST
Caterpillar 795F AC, static, at Arizona proving grounds.jpg

Caterpillar's 795F AC, offered only as an electric drive model, marks a new weight class for Cat.

Four new models of Caterpillar mining trucks will be rolled out over the next two years as a change to include electric-drive trucks takes effect (see "Cat makes an electric commitment to mining"). The 793F and 793F AC will be in the 240- to 250-ton (218- to 227-t) class; the ac-drive-only 345-ton (313-t) 795F AC will mark entry into a new size class for Cat; and the new mechanical drive 797F will be in the 380- to 400-ton (345- to 363-t) class.

The frame, the backbone of the vehicles, is a box-section design made from mild steel, castings, and forgings. Bodies vary by model but are designed specifically for the load to balance body life and performance. The 797F is available with mine-specific design (MSD) bodies only; the 795F AC can use a coal-specific body; and the 793F can use MSD, coal, or the MSD X body, which gives more durability.

The mechanical 793F has many revisions over its predecessor, the 793D. These include a new transmission with electronic clutch pressure control; a larger, fully enclosed drive shaft; and a 10% more powerful engine: a 2650-hp (1976-kW) 16-cylinder C175-16 ACERT diesel. This engine is also shared by the 793F AC and the 795F AC.

Larger castings mark changes to the frame, which has a redesigned torque tube and new multilink four-bar rear suspension. The cooling system has been simplified, and advanced surface technology on the struts and hoist cylinders double their lifespan.

Cat claims that four-corner retarding systems are safer than the electric rear axle only systems and offers hydraulic brakes on all four wheels of the F-series.

Walkways and ladders were improved also, with width being increased to 600 mm (24 in), the addition of multidirectional front stairs, and a power ladder option.

The 793F AC model shares the 793F’s chassis and cab. The entire F-series cab has been changed to improve ergonomics and visibility. The cab is 10% larger than the old 793D, with 40% more window area and new front railings. It has new mounts to cut vibration as well as laminated glass and sound suppression to keep down noise. Overhead features in the cab include radios and storage space as well as locations for other display modules, such as object detection or MineStar. Extra quiet versions, available on current models, are planned for the F-series.

F-series development began in 2004 and has since involved 22 prototypes, more than 800 people, and more than $280 million in engineering and testing.

Cat’s 795F, entering a new size market for the company, allows for direct competition with companies such as Komatsu and Terex. Cat claims the 3400-hp (2535-kW) engine provides equal or greater performance across the board vs. the Cummins QSK60, the current market leader in class.

Topping the Caterpillar mining truck range is the 797F, a mechanical drive truck with a 400-ton (363-t) capacity. It replaces the 797B and has increased rollover protection ratings, a top deck with improved visibility, simplified intake piping, and a new differential designed for reliability.

Power for the 797F comes from a 20-cylinder diesel, with cross-flow cylinder heads, common-rail injection, and multiple turbochargers, producing 4000 hp (3000 kW).

Beyond offering the new ac-drive system, Cat is looking further into other alternate forms of power such as trolley cables, gas turbines, and hydrogen fuel cells.

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