Caterpillar 797 Mining Truck 301
mechanical power train information to optimize truck performance, extend component life, and
improve operator comfort.
The engine uses a hydraulically driven fan for efficient cooling. The fan design and oper-
ation also reduce fuel consumption and noise levels. The engine and its components are
designed to minimize service time, which helps keep availability of the truck high.Efficient Mechanical Power Train The 797 power train includes a new torque converter with
lockup clutch that delivers high mechanical efficiency. The new automatic-shift transmission
features seven speeds forward and one speed reverse. Electronic clutch pressure control (ECPC)
technology smoothes shifts, reduces wear, and increases reliability. Large clutch discs give the
transmission high torque capacity and extend transmission life. The transmission and torque
converter enable the truck to maintain good speed up grades and to reach a top speed of 40 mph
(64 km/h).
The differential is rear mounted, which improves access for maintenance. The differential
is pressure lubricated, thus promoting greater efficiency and long life. Wide wheel-bearing
spread reduces bearing loads and helps ensure durability. A hydraulically driven lube and cool-
ing system operates independently of ground speed and pumps a continuous supply of filtered
oil to each final drive.
Oil-cooled, multiple disc brakes provide fade-resistant braking and retarding. The elec-
tronically managed automatic retarder control (ARC) is an integral part of the intelligent power
train. ARC controls the brakes on grade to maintain optimum engine rpm and oil cooling.
Automatic electronic traction aid (AETA) uses the rear brakes to optimize traction. A combi-
nation of constant-displacement and variable-displacement pumps delivers a regulated flow of
brake-cooling oil for constant retarding capability and peak truck performance on downhill
grades.Electrohydraulic Hoist Control New hoist hydraulics include an electronic hoist control, inde-
pendent metering valve (IMV), and a large hoist pump. These features allow automatic body
snubbing for reduced impact on the frame, hoist cylinders, and operator. This design also allows
the operator to modulate flow and control overcentering when dumping.Serviceability Caterpillar designed the 797 to reduce service time thus ensuring maximum
availability. Routine maintenance points, such as fluid fill and check points, are close to ground
level. Easily accessed connectors allow technicians to download data and to calibrate machine
functions, thus extending maintenance intervals which further increases availability. The 797
is also designed to make major components accessible, which effectively reduces removal, instal-
lation, and in-truck maintenance time for all drivetrain components.
To allow technicians to raise the truck body inside a standard-height maintenance build-
ing, the canopy portion of the body is hinged so that it can be folded back. In the folded and
raised position, the 797 body height is no higher than the 793, Caterpillar’s 240-ton-capacity
(218-metric ton) mining truck.Testing Several 797 mining trucks were tested at the Caterpillar proving grounds. Mine eval-
uation performances were also done during 1999 – 2000. The test results are used to correct
unexpected problems and fine-tune various components of the truck. The 797 has been avail-
able commercially worldwide since January 2001.62080_10_ch10_p251-302.qxd 5/22/10 12:32 AM Page 301
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