SUBSECTION 8D
BOOM HOIST BRAKES
GENERAL
This section covers the removal, relining, installation and
adjustment of the boom hoist brake and the boom hoist
planetary brake.
Several terms are often misunderstood when used in ref-
erence to brake bands on this machine. The following de-
finitions, as used in this manual, are as follows:
1. Brake Set. This means the brake band is tightened
around a rotating member to stop, or prevent, the rotationof
that member.
2. Live End. This is the end of a brake band to which force is
applied.
3. Dead End. This is the anchor end of a brake band.
Typically, most lining wear will occur at this end of the band.
BOOM HOIST AND PLANETARY BRAKES
(2100J1008-2)
DESCRIPTION. The boom hoist brake is a spring set, hy-
draulically released type brake. When there is no pressure
in the boom hoist brake cylinder, its piston is retracted and a
spring applies the boom hoist brake.
When the operator moves the boom hoist control lever back
to raise the boom, hydraulic fluid is directed to the boom
hoist brake cylinder. With hydraulic pressure applied to the
cylinder, its piston extends and applies force to the linkage
overcoming the spring and releasing the brake (see Figure
8D-1).
When the linings are new and the brake is in proper adjust-
ment, the length of the operating mechanism spring, with
the brake set (hydraulic pressure released), should be 7-
3/8 inches. When the brake lining starts to wear, this di-
mension will increase (with the brake set). See the Oper-
cylinder, its piston is retracted and springs release the
ator's Manual for the method of adjusting the brakes for
planetary brake.
normal lining wear.
The boom hoist brake should be relined when brake lining
When the operator moves the boom hoist control lever for-
thickness reaches 3/16 inch as measured at the dead end
ward to lower the boom, hydraulic fluid is directed to the
of the band.
planetary brake cylinder. With hydraulic pressure applied to
the cylinder, its piston extends and applies force to the link-
age to wrap the band around the drum and set the brake
The boom hoist planetary brake is hydraulically set, spring
released. When there is no pressure in the boom hoistbrake