TURNTABLE BEARING INSPECTION PROCEDURES FOR GROVE M977, GROVE M984, AND GROVE M985 CRANES.

TB 9-2320-279-34

2-8. TURNTABLE BEARING INSPECTION PROCEDURES FOR GROVE M977, GROVE M984, AND

GROVE M985 CRANES.

2-8.1.

Initial Setup.

NOTE

Ensure that the turntable bearing is lubricated and that all the turntable mounting

bolts have been tightened to the recommended torque.

Operate the crane controls smoothly to avoid any jerking or harsh movement that

could affect the dial indicator reading.

Perform steps a. through c. for GROVE M984 cranes.

Perform steps b. and d. for GROVE M977 and M985 cranes.

Lower fairlead into operating position (Refer to TM 9-2320-279-10).

Place crane in operating position and level side to side with outriggers

(Refer to TM 9-2320-279-10).

Keeping boom level, lower mast until approximately one inch (24.4 mm) clearance is present

between the erection cylinder and the crane outrigger cover. Rotate the crane in both directions

to ensure no contact will be made with the outrigger cover by either the cylinder or the tension

links. Adjust the clearance if contact might occur.

Keeping boom level, lower mast until approximately one inch (24.4 mm) clearance is present

between the erection cylinders and the rear cargo body panel. Rotate the crane in both directions

to ensure no contact will be made with the rear cargo body panel by either cylinder. Adjust the

clearance if contact might occur.

2-8.2.

Placement of Dial Indicator.

NOTE

To obtain a true reading of bearing vertical movement, the dial indicator and

magnetic base must be positioned correctly.

Perform step e. for placement of dial indicator for M977 and M985 trucks.

Ensure that the plunger of the dial indicator is straight up and down in all directions, front to

back and side to side. It is not necessary to measure this, but try to get it as close as possible

with a visual inspection from different angles.

Ensure that the dial indicator is pre-loaded at least one turn by allowing the needle to complete

one turn around the dial before zeroing the dial.

Ensure that the magnetic base is secure at its attachment point so it will not move and

contribute to a false indicator reading.

The dial indicator must be in line with the axial centerline of the boom for all measurements.

Due to the position of the crane power/remote control junction box, it is not possible to position

the boom at exact 90 degree and 180 degree positions and have a mounting spot for the magnetic

base. Position the magnetic base first and then rotate the boom to place the boom axial

centerline over the magnetic base, then install the dial indicator.

To ensure a consistent reading, the dial indicator plunger must be as close as possible to the

outside diameter of the swing gear tooth tip, as the allowable bearing movement only applies at

the tip of the gear tooth. The indicator reading will be magnified if the plunger contact point is

off of the outer diameter of the swing gear tooth tip.

Always verify that the dial indicator reading is correct by lowering the boom from the 60 degree

boom angle to the level boom angle, then check that the dial indicator returns to the zero

position. Repeat the procedure if the dial indicator does not return to the zero position.

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