Cat gets fresh with new undercarriage for compact loaders

  • 08-Sep-2008 11:39 EDT
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Caterpillar's new compact rubber-track loaders combine a newly engineered suspension-type undercarriage with the chassis of their multi-terrain loader counterparts.

Caterpillar's new compact rubber-track track loaders, the 279C, 289C and 299C, combine a "freshly engineered" suspension-type undercarriage, designed and built by Cat, with the chassis of their multi-terrain loader counterparts, the 277C, 287C and 297C. Cat says the tracked loaders were designed specifically to "deliver solid traction and reduced wear on sites with sticky, rocky soils."

The fully suspended undercarriage employs four independent torsion axles for improved ride and bucket-load retention.

All three models feature two-speed drive systems, with a maximum speed of 8.5 mph (14 km/h) in second range. The electrohydraulic joystick control of the drive motors delivers straight-line tracking, and electronic torque management optimizes productivity. Cat-exclusive drive motor seal guards that protect the motors from damage and extends the lives of seals and final drives.

Models have rated operating capacities of 3200, 3850, and 4150 lb (1451, 1746, and 1882 kg), at 50% of tipping load. Lift-arm-path design is radial for the 279C and vertical for the 289C and 299C.

A highlight of the design is a robust new undercarriage. It uses an external-type sprocket, steel track rollers and idlers, conventional spring-type (grease-adjusted) recoil mechanism, and rubber tracks that incorporate the reinforcing strength of steel—both as steel cords that run longitudinally through the tracks and as steel inserts at the sprocket-engagement points. The design emphasizes durability and aggressive traction, suiting it particularly well for applications in which maintenance, operator technique, and underfoot conditions might present challenges.

Because the undercarriage is suspended via a pair of torsion axles on each side of the machine, each track assembly can flex independently, resulting in a softer ride for the operator, reduced shock loads through the machine, and minimal spillage from the bucket in rough going. With nearly 70 in (1767 mm) of track-on-ground, which Cat calls class-leading, the 18-in (457-mm) wide rubber tracks exert low ground pressures, while providing added traction and long service life.

Powering all three of the three new loaders is the Cat C3.4T diesel engine, an inline, four-cylinder, turbocharged model with a 3.3-L displacement. Net-power ratings are 82 hp (61 kW) for the 279C and 289C, and 90 hp (67 kW) for the 299C.

The engine is designed with high-load-carrying bearings, induction-hardened cylinder liners, forged-steel/super-finished crankshaft, positive-displacement gear-pump lubrication system, and a gear-driven coolant pump.

The engine powers a two-speed hydrostatic drive system that was engineered to electronically balance torque and speed delivered to the tracks, a feature designed to enable optimum performance and fuel efficiency in any application, whether aggressively digging in a sticky clay bank, loading trucks, or doing drawbar work.

Electronic control of the drive system allows continual fine-tuning of the engine, drive pumps, and drive motors to deliver controlled tractive effort, but always in combination with ample hydraulic power for the implement (lift and tilt) and auxiliary circuits.  Standard hydraulic flow is 22 gal/min (84 L/min), and rated system pressure is 3335 psi (230 bar). The auxiliary-hydraulic system uses a large variable-displacement load-sensing pump, provides a continuous-flow feature, and incorporates heavy-duty, flat-faced quick-disconnect couplings.

For applications requiring added hydraulic power, Cat offers the optional High Flow XPS auxiliary-hydraulic system, which delivers 33 gal/min (125 L/min) at a system pressure of 4061 psi (280 bar). The XPS system allows the machines to efficiently handle work tools such as a cold planer or a brush cutter.

A mechanical quick-coupler is standard, and a hydraulically controlled coupler is available. For added control, the optional Advanced Machine Information and Control System allows the operator to select the level of loader-arm and bucket responsiveness, while also providing ten work-speed selections.

To enhance controllability and ease of operation, the new models are equipped with a foot throttle, which allows the operator to adjust engine speed to suit the application, while also reducing sound levels and conserving fuel. This feature complements the independently adjustable joystick controllers, which are console-mounted to provide ample forearm support. The operator station is equipped with a suspension seat.

An optional enclosed ROPS (rollover protective structure) cabin is sealed, pressurized, and heated, with ventilation air filtered to eliminate dust. An air-ride seat and air-conditioning is also available. The design positions the seat and surrounding enclosure to enhance visibility, and a quick-release door and safety interlock system prevent accidental machine movement.

Lift-arm safety braces are designed for easy use, and routine-maintenance features include a rear door that swings open 90° to provide ready access to service points. Also, the cab tilts up for wide-open access to drive-system and hydraulic components.

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