TM 10-3950-672-10
(4) Directional Control Valves. The directional control valves are four-way, three-position valves with either an
open or closed spool. The valves are grouped into valve banks permitting simultaneous independent
control of crane functions. Each bank contains an integral main bypass for system relief and an individual
circuit bypass relief valve.
j. Turntable Assembly and Swing Mechanism. An anti-friction roller bearing supports the superstructure on the
carrier and allows 360 degrees of continuous rotation (swing) in either direction. Swing is accomplished by a
hydraulically driven motor driving a gear reducer which in turn drives a pinion that drives the roller bearing. A
multi-disc-type brake that is an integral part of the gear reducer, is provided to stop swing, and hold the
superstructure in the desired position.
(1) Swing Motor. The hydraulic swing motor is a low-speed, high torque type. The motor provides indirect
drive power for turntable swing through the gear reducer.
(2) Swing Planetary Gear Reducer. The planetary gear reducer is a sun and planetary gear-type, driven by
the swing motor. The gear reducer has a ratio of 27.98: 1.
k. Boom Assembly. The boom is a 14 to 24 ft (4.2 to 7.3 m) two-section, full power boom and is trapezoidal in
design. Boom elevation is from -0 to + 70 degrees.
1. Hoist. The hoist provides power and speed for all load raising and lowering operations. A van-type,
hydraulic motor drives the hoist drum by means of a planetary gear reduction system.
A metallic disc hoist brake is an integral part of the hoist assembly in that it is a spring-actuated brake
which requires hydraulic pressure to release. In the event of a hydraulic system failure or if the load-drop
speed is too fast, the hydraulic pressure in the hoist down line will decrease. This decrease in hydraulic
pressure would cause the hoist brake to actuate which would then slow down or stop the hoist.
m. Outrigger System. The outriggers are integral with the carrier frame and are controlled and operated from the
cab. The outriggers are the oblique telescoping-type and consist of a removable beam and a cylinder assembly.
A level indicator is located in the cab near the F-N-R-transmission lever, to aid in leveling the crane.
n. Swivels. Electrical and hydraulic swivels are used to route electrical and hydraulic circuits from the boom to the
carrier frame. These swivels are mounted as a single assembly, and are installed at the center of rotation.
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