DRUM BRAKES
SUBSECTION 7C
when the bands have been removed or the brake operating
3. Pins "C" and "D" should never come into contact with
mechanism has been disturbed, proceed as follows (see
the ends of the slots in links "K" and "J".
OPERATION CHECK. To be sure that the load drum brakes
1. If either brake actuating cylinder has been repaired or
are operating properly, perform the following steps:
removed, the cylinder must be bled to remove any air from
1. Lift a capacity load an inch or two off of the ground and
thecylinder and Iines. See Subsection 5A of this manual for
depress the drum brake pedal to hold the load. Move the
the cylinder bleeding procedure.
drum brake switch to the ON position. Slowly release the
drum brake pedal to see if the load will drift downward.
2. The set-up dimension for the brake release cylinder is
4-3/4 inches. Measure this dimension from the center of
the cylinder eyebolt to the edge of the cylinder. To alter this
dimension, rotate the cylinder on the eyebolt.
3. Adjust the brake band adjusting bolt to obtain a dimen-
sion of 1/2 inch of piston extension at the brake release
Reapply the drum brake pedal before moving
cylinder.
the drum brake switch to the OFF position.
4. The set-up dimension for the brake set spring is 7-3/4
2. Move the drum brake switch to the OFF position, and
inches of spring height. To obtain this dimension,loosen or
lower the load to the ground using the drum brake pedal.
tighten adjusting nuts "B".
3. If there was any downward drift of the load during the
5. Rotate adjusting nuts "C" to obtain a clearance of 1/4
test performance in step 1, the nut on the brake band
inch between pin "D" and the bottom of the slot in lever
adjusting bolt must be tightened (see Figure 7C-1).
"G". This should positron pin "D" near the top of slot "F" in
link "K".
4. Tighten the nut as much as is necessary to prevent the
load from drifting downward during the test described in
ADJUSTMENT CHECK. Perform the following checks to be
step 1.
sure that the load drum brakes are properly adjusted (see
5. The brake band must be tightened until the test de-
scribed in step 1 can be properly performed. Do not over-
1. Depress the drum brake pedal in the upper cab. This will
tighten the band to the point where the weight of the
extend the brake set cylinder and thereby apply the load
unloaded hook block is not heavy enough to lower the drum
drum brake At this point, pin "C" should not contact the top
rope when the drum control lever is in the neutral position.
of slot "L" (slot "L" is located in lever "G").
6. Adjust the band support turnbuckles so that the clear-
2. Move the drum brake switch (located in the upper cab) to
ance between the brake drum and the brake lining is equal
the ON position. At this point, pin "D" should not touch the
at all points around the drum.
top of slot "K" (slot "K" is located in lever "G"). Also, the
piston of the brake release cylinder should be projecting
7. See Subsection 5C of this manual for instructions on the
adjustment of the brake drum pedal.
about 1/2 inch from the cylinder body.
Figure 7C-3. Pedal Linkage Adjustment (2100J978)
7C-4
