SUBSECTION 7A
HOIST SYSTEM
GENERAL
Left and right drum planetary systems are included on
these drums. The planetary assemblies are identical on the
This section describes the components required to trans-
left and right drumswith a planetary brake band around the
mit hoist torque from the drumshaft to the hoist drums.
planetary drum. To raise a load, the drum clutch is engaged
The hoist system consists of the drumshaft, drum brakes,
and shaft rotation is transmitted through the clutch to the
drum cltuches and drum pawls as shown in Figure 7A-1.
drum spool and lagging. The lagging rotates in the same
DESCRIPTION
direction as the drumshaft to take up on the hoist line and
raise the load.
The hoist system is powered by the upper engine through
the chain driven drumshaft. The drumshaft and drum
When lowering a load with power lowering, power is
clutches turn continuously while the engine is running and
transmitted through the planetary system which reverses
torque converter is engaged. However, the operator must
the direction of the shaft rotation.
engage one of the hoist clutches to rotate a hoist drum.
Hydraulically operated pawls engage the ratchets of the
The third drum is installed on the left end of the boom hoist
drums to prevent the rotation of the drums when the opera-
shaft. The third drum rotates only when the third drum
tor so desires. The pawls should be adjusted as described in
clutch is engaged.
Subsection 7E.
Figure 7A-1. Hoist System
