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Construction Equipment Guide
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Thu December 05, 2013 - National Edition
The Cat 770G and 772G off-highway trucks have been designed with major advancements in emissions control technology, transmission and traction control systems; frame, drive train, and cooling system enhancements; added operator amenities; and serviceability improvements. Many of the features introduced on larger Cat G Series trucks are being incorporated on the new 770G and 772G models. With nominal rated payload capacities of 40 and 52 tons (36.3 and 47.1 t), respectively, the new trucks use Cat C15 (770G) and C18 (772G) engines, with net power ratings of 477 (770G) and 550 (772G) hp (356 and 410 kW).
Engines and Cooling
Available in Tier II/Stage II, Tier III/Stage III, and Tier IV Final/Stage IV configurations, the engines can be programmed to achieve the customer’s specific fuel economy goals. Two programmable modes are available: economy and adaptive economy.
Economy mode lets the customer select a derate value between .5 percent and 15 percent. Then, at the touch of a button, economy mode applies steady power deration across all portions of the haul cycle. With adaptive economy mode, the truck monitors power demand, delivering fuel savings when possible and horsepower when needed, to optimize fuel economy throughout the haul cycle.
For further fuel savings, the new auto neutral idle feature automatically places the transmission in neutral gear after the brake is applied for more than 15 seconds while in a forward gear. This reduces parasitic drive train loads and provides major fuel efficiency improvements. Once the operator removes his foot from the brake, the transmission re-engages. This is completely transparent to the operator. Also, a hydraulically driven, on-demand cooling fan reduces power draw on the engine by operating only when required and only at the speed required.
Tier IV Final Components
The Caterpillar solution for Tier IV Final exhaust emissions on the C15 and C18 engines is selective catalytic reduction (SCR). This technology has several stages.
The Cat clean emissions module injects diesel exhaust fluid (DEF), a solution of about 33 percent urea and 67 percent demineralized water) into the exhaust to react with any residual NOx to create ammonia. This exhaust is routed through an ammonia oxidation catalyst where it reacts with oxygen to create inert water and nitrogen.
The 5.6 gal. (21.2 L) DEF tank, located next to the fuel tank, is formed of tough plastic. The DEF tank will need to be refilled at the same time as the diesel fuel tank, so service personnel can fill both tanks at the same time. The cab gauge cluster includes a DEF level gauge.
Because the trucks work in extreme temperatures, engine coolant is routed to the DEF injector to keep it cool and to the DEF tank to thaw frozen DEF.
Drive Train, Frame Refinement
The new transmission control system, advanced productivity electronic control strategy (APECS), provides a number of benefits, including improved shift quality, faster acceleration, better speed on grade and faster cycle times.
This new control strategy modulates shift points to match optimum operating speed and torque, minimizes torque spikes during shifts and reduces stress on the drive train, which increases drive train component life. The control strategy also provides greater operator comfort and control and reduces material spillage.
An optional advanced traction control system uses the service brakes instead of the park brake components to modulate wheel slip. This change in design makes the system much more responsive to traction loss in the lower speed ranges, and improves speed on grade in wet, slippery conditions. This new system also assesses front wheel steering angle when determining traction slippage and adjusts the degree of allowance in wheel speed differential that naturally increases between the inside and outside wheels when the machine is turning.
By assessing steering angle, it compensates for the outside wheel turning at a higher speed to improve traction.
Wheel stations feature a one-piece wheel-and-hub design that simplifies servicing and reduces leak potential. The single-piece design reduces removal and installation time and the risk of brake cooling oil leakage. The new 19-in. Duo-Cone seal is a cast design that optimizes sealing performance by reducing linear velocities at the sealing interface. Additionally, cooling oil velocity has been reduced, lowering pressure at the Duo-Cone seal and further reducing the potential for leaks. Wheel stations are interchangeable (left and right), reducing the number of replacement parts. In addition, the design reduces the number of seals, improving reliability and simplifying the system.
Frame designs for the 770G and 772G have been modified to more precisely balance weight and durability requirements, providing frames tailored to the truck payload capacity while maintaining robust service life. Welds in critical stress areas are double-sided and ultrasonically tested to ensure integrity. High strength steel is used throughout the frames to absorb the stress of impact loads, and proven box section construction manages torsion loads.
Operator Environment and Safety
The 770G and 772G have a new four-post ROPS/FOPS structure that is integral with the cab. The center cab position provides ample interior room and creates a walk-in style cab, allowing the operator to easily enter and exit. The cab is mounted to the frame to dampen sound and vibration, and with the new Cat Series III optimized seat system, the 770G and 772G provide the operator support and comfort throughout the day with long-term durability.
To further enhance operator comfort, the cab comes standard with a left-hand power window and a right side sliding window for excellent cross ventilation. Also standard is an electronically controlled air conditioning system that allows the operator to set a preferred temperature that the system will maintain throughout the day.
Operator safety is enhanced with handrails, lighting, and a low effort stair step system using a star pattern tread plate on the walkways, allowing the operator to safely get on and off of the truck. A new rear-hinged door provides immediate accessibility to the cab, and new hand rails on the ROPS posts facilitate safely cleaning the front windshield.
The 770G and 772G now come standard with VIMS 3G, the Caterpillar vital information management system, truck production management system (TPMS), TMPH (ton mile per hour) / TKPH (tonne kilometer per hour) tire management system, and product link (standard or cellular). The advisor display in the cab provides an on-board interface for these information systems.
VIMS 3G provides diagnostic and prognostic information on the machine’s critical components allowing for maximum uptime and improved maintenance and serviceability.
The truck payload management system (TPMS) incorporates speed based re-weighing capability to monitor and store up to 2,400 cycles of payloads and productivity data.
The TMPH/TKPH system notifies the operator when manufacturer tire capacity has been exceeded and provides the operator with a warning.
All routine service points are accessible from secure platforms or from ground-level access, enhancing technician safety. Three spin-on fuel filters ensure fuel cleanliness, and the primary fuel filter incorporates a water separator and an electric priming pump.
Filters in the steering, braking, and transmission/torque converter circuits are sized to provide 1,000-hour service intervals, and a brake wear indicator on the rear wheel groups is a standard feature. An in-cab, fluid-monitoring system is available.
In addition, the Cat ET (electronic technician) service tool provides access to stored diagnostic data through the Cat data link, including the status of all engine parameters (throttle position, speed, timing, and fuel flow/consumption), plus data from transmission controls, including gear selection and shift times.