Manitowoc Published 04-06-18, Control # 231-14 6-3
MLC650 VPC-MAXâ„¢ OPERATOR MANUAL MAINTENANCE
DRUM 5 BOOM HOIST
For a detailed explanation of the Drum 5 boom hoist
operation, reference the MLC650 Service/Maintenance
Manual.
Drum 5 Pawl Operation
See Figure 6-2 for the following procedure.
The Drum 5 pawl (1) is controlled by the Drum 5 park switch.
When the Drum 5 park switch is turned on, the cylinder
rod (11, View B) extends, engaging the Drum 5 pawl, thereby
disengaging the pawl (1, View B) from Drum 5 (9).
When the Drum 5 park switch is turned off, the cylinder
rod (11, View A) retracts, disengaging the Drum 5 pawl
thereby engaging the pawl (1, View A) to the drum.
When the control system is not powered, the Drum 5 pawl
engages Drum 5 by the return springs (8, View A) force.
Check the Drum 5 pawl for proper adjustment each time the
VPC-MAX and fixed mast are installed.
Adjusting the Drum 5 Limit Switch
The Drum 5 pawl limit switch (2) must be properly adjusted to
ensure proper operation of Drum 5.
See Figure 6-2
for the following procedure.
1. Loosen the set screw (3, View A) and rotate the limit
switch lever (4, View A) to a 54° angle (6).
2. Disengage the Drum 5 pawl (1, View B) by moving the
Drum 5 park switch to the unparked position. It may be
necessary to boom up slightly before the pawl will
disengage the drum.
3. Rotate the limit switch lever up and hold it so the
roller (12, View B) is against the pawl.
4. Turn the limit switch shaft (5, View B) clockwise until the
limit switch clicks open and hold.
5. Make sure the roller is against the pawl and securely
tighten the set screw (3, View B).
6. Check for proper operation by performing the following:
• Engage the Drum 5 pawl by moving the Drum 5 park
switch to the parked position and try to boom down.
The boom hoist should not be able to turn
downward.
• Disengage the boom hoist pawl by moving the Drum
5 park switch to the unparked position and try to
boom down. The boom hoist should be able to turn
downward.
7. Readjust the limit switch if required.
Adjusting the Drum 5 Return Spring
1. Loosen the jam nuts (13, View A) on the eye
bolt (7, View A).
2. Adjust the eye bolt so the return spring (8, View A) has
enough tension to fully engage and hold the Drum 5
pawl (1, View A) against Drum 5.
3. Tighten the jam nuts.
Lubricating the Drum 5 Pawl
Spray or brush an anti-seizing lubricant on the sliding surface
between the cam (10) and the pawl.
WARNING
Moving Parts Hazard!
To make adjustments, the engine must be running and the
boom hoist and the drum pawl must be operated.
Avoid injury from moving machinery. Stay clear of the
drum and the pawl while either is being operated.
Maintain constant communication between the operator
and the adjuster so the drum and pawl are not operated
while the adjuster is in contact with parts.
WARNING
Falling Boom Hazard!
Before performing the steps in this section, land the loads
and lower the boom onto blocking at ground level. There
is no positive means of holding the boom up when the
pawl is being serviced.
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