Cat wheel loaders get new axles

  • 19-Jun-2008 07:47 EDT
Cat 938H scooping gravel.jpg
Caterpillar’s new 938H wheel loader features differential lock for both axles and load-sensing, variable-flow hydraulics for dependable tractive effort, increased rimpull into the pile, and a 16% increase in lift force compared to the previous models, according to Cat.

Front differential lock, load-sensing hydraulics, and a new ACERT engine highlight Caterpillar’s new 938H wheel loader and IT38H integrated toolcarrier. Locking differentials are designed to provide dependable tractive effort in poor underfoot or tough loading conditions, and the load-sensing hydraulics can help both loaders deliver improved cycle times. Additional features help to aid machine health monitoring and service.

Powered by a 6.6-L inline six-cylinder Cat C6.6 diesel engine, both loaders deliver 180 hp (134 kW). Certified to meet U.S. EPA Tier 3 off-highway emissions regulations and international emissions standards, the engine is capable of maintaining peak engine power over a broader engine speed range as compared to the 938G II and IT38G II machines these loaders replace.

Equipped with the company’s own ACERT technology, the C6.6 engine’s cylinder head incorporates a new cross-flow design that facilitates air movement, and the turbocharger is equipped with a ‘smart’ waste gate that provides precise, reliable control of the boost pressure. ADEM A4, Cat’s engine management electronic control module, monitors engine conditions and regulates fuel delivery and other parameters to manage load and performance. An engine idle management system maximizes fuel efficiency and offers four idle control speeds to meet application requirements. To feed the common fuel rail, the engine employs an oil-lubricated high-pressure fuel pump that has been designed to be tolerant of alternative fuels.

An electronically controlled variable-speed on-demand fan monitors and cools engine coolant, transmission oil, and air inlet manifold as needed. The cooling system is isolated from the engine compartment by an insulating, nonmetallic shield.

Both loaders feature countershaft powershift transmission, which was introduced with the previous series. Designed and built by Cat, the transmission features an automatic shift capability that allows full-power speed and directional changes, helping to boost cycle times and productivity. Control throttle shifting helps to regulate engine speed during rapid, high-powered shifts to preserve component life and smooth out the shifting, and an electronic clutch pressure control system modulates the individual clutches.

Load-sensing variable-flow hydraulics supply hydraulic flow and pressure to the loader’s implements only on demand, offering full hydraulic forces at any engine speed. Implement control is improved compared to the previous system with the incorporation of a new S3PC priority proportional pressure compensation valve that allows the simultaneous use of the raise/lower and rack-back/dump functions. The new loaders provide increased rimpull into the pile and a 16% increase in lift force compared to the previous models, according to Cat.

Both loaders feature a new axle with front differential lock or an optional automatic differential lock for both front and rear axles. The automatic differential lock monitors machine operation and locks during the dig cycle or when tires slip. Locking the axles—whether automatically or manually—allows the loader to deliver improved traction with less tire wear, lower fuel consumption, and less generated heat. Differential lock, which replaces limited slip, can be engaged while the loader is in motion.

Rigidly mounted to the frame, the front axle supports the weight of the loader and withstands internal torque loads and external forces. The rear axle is designed to allow ±12° oscillation so all four wheels can remain on the ground when traveling over uneven terrain. The loaders’ articulated frame incorporates a durable plate engine frame and a robotically welded two-plate loader tower. The solid-plate engine end frame resists twisting and distributes impact loads.

A two-piece counterweight is integrated into the loader’s structure. Linkage for the 938H is a single-tilt Z-bar design, while the IT38H uses an integrated toolcarrier linkage and includes parallel lift for various materials-handling tasks.

Service points and sight gauges have been grouped together for easier daily servicing, and the grill and cooling cores swing out for cleaning. Other serviceability options include brake wear indicators, remote pressure taps, an automatic lubrication system, and SOS services, in which engine, transmission, and hydraulic oils can be sampled via easy-access valves for quick analysis.

The operator’s cab includes a six-way adjustable seat with automotive-style lumbar support and adjustable armrests, maximized visibility to the bucket with distortion-free glass to the floor, optional rearview camera, and low-effort load-sensing steering with tilting steering column. Key machine controls have been located within the operator’s reach, and implement pods have been restyled for operator comfort. A standard transmission switch allows operators to keep their hand at the implement control levers while making directional shifts, and an optional joystick with integrated forward-neutral-reverse switch can replace the lift and tilt levers.

An in-cab messenger display provides real-time data for monitoring machine performance, the engine, and other diagnostics. Cat Product Link, a standard feature, provides a two-way flow of information between the loader and the Cat dealer that is extended to the owner’s desktop computer.

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