PREVENTIVE MAINTENANCE
SECTION V
To prevent a live boom condition from occurring when both
pawls become disengaged from the ratchets as the linkage
crosses the neutral position, carefully check the adjust-
ment of the drum and planetary pawls as follows (see Fig-
ure 5B-5):
Lower the boom to the ground before per-
forming any maintenance work on the pawls.
1. Inspect the pawls to make certain that they pivot freely
on the shaft.
2. Check for 0.132 inch clearance above the pawl cylinder
spring guide with cylinder retracted, and adjust this dimen-
sion by means of the jam nut and spring guide, if neces-
sary.
3. The distance between the pivot pin and the top of the
support bracket should be 3 inches. Adjust to this dimen-
sion by means of the jam nut adjacent to the support
bracket.
Figure 5B-4. Drum Pawls
4. With the boom hoist lever in neutral, make certain the
boom hoist drum pawl is fully engaged in the ratchet teeth
and the length of the pawl spring "A" is approximately 2-
NOTE
1/16 inches. Adjust to this dimension by means of adjust-
ing nut "A". if necessary
lt may be necessary to push the drum control levers to
the "lower" position momentarily to engage the
NOTE
pawls in the drum teeth.
The length of pawl spring "A" may vary slightly; how-
Release the left and right drum pawl switches and allow
ever, the length of the pawl spring "B" must be set at
them to return to the OFF position and pull the drum con-
exactly 1-3/4 inches through the adjustment of nut
trol levers to the "raise" position momentarily to disen-
"B". This applies to both pawls.
gage the pawls from the drum teeth.
5. With the boom hoist control lever in the neutral posi-
4. Check both pawls for complete release from the drum
tion, the boom hoist planetary pawl should clear the ratchet
ratchet teeth.
teeth by a minimum of 1/8 inch. Adjust to this dimension by
means of the adjusting nut "A", if necessary. See the note
5. If the pawls do not operate properly, proceed as follows.
in step 4 if any adjustment was made.
A. Repeat steps 1 and 2.
6. Slowly push the boom hoist lever forward, to the boom
B. The length of pawl spring (A) should be 5-7/8" and the
lowering position. Make certain the planetary pawl is fully
pawls must be fully engaged in the drum ratchet teeth.
engaged in the ratchet teeth and the length of the pawl
spring "A" is approximately 2-1/16 inches. Adjust to this
C. If the spring IS not the dimension given in step B, adjust
dimension by means of adjusting nut "A", if necessary. See
to 5-7/8" using jam nuts (B).
the note in step 4 if any adjustment was made.
D. The pawls should be disengaged from the drum teeth by
7. With the boom hoist control lever forward, in the boom
a minimum of 1/4" when the pawl IS disengaged. If
lowering position, the boom hoist pawl should clear the
necessary, adjust clevis (C) and jam nut (D) to get the
ratchet teeth by a minimum of 1/8 inch. Adjust to this di-
pawl to disengage from the drum teeth.
mension by means of the adjusting nut "A". if necessary.
Again, refer to the note in step 4 if any adjustment was
6. As a final check, repeat steps 1 through 4.
made.
CHECK BOOM HOIST PAWLS
8. Check that all jam nuts on cables and yokes are tight-
Two safety pawls are provided to prevent the possibility of a
ened securely.
"live" boom when the boom is being raised or lowered.
LUBRICATE U-JOINTS
These pawls engage the ratchets on the boom hoist drum
Lack of adequate or proper lubrication is among the most
assembly. One pawl prevents the boom from falling if the
common causes of U-joint and drive shaft failure. Proper
planetary brake band should slip while the boom is being
lowered; the other pawl is normally engaged and prevents
servicing of the drive shaft is an essential part of mainte-
nance and should not be overlooked in routine preventive
the boom from falling while it is being raised or when it is in
maintenance
the raised position.
5-9
