Adjusting Rotor End Play

Question: After disassembling and reassembling a motor, what is the proper method for adjusting the rotor end play?

Answer: Should a motor be disassembled for any reason, the rotor end play must be adjusted. Use one of the following procedures, depending upon the type of thrust bearing:

I. Spherical Roller Thrust Bearings and Angular Contact Bearings (With Springs)

On spherical roller or angular contact thrust bearings with springs, setting the correct end play for preload requires a controlled assembly method, due to various deflections internal to the motor and friction of locknut threads from spring force. An end play setting of .005 to .010 inches is required to allow the lower guide bearing to return to an unload position when external thrust is applied to the motor (see Figure 5). End play can be properly adjusted by the following recommended procedure:

A. Place spring retainer, without springs and lower thrust washer of bearing, into upper bracket bearing bore.

B. Using a depth micrometer, measure the distance between the top of the lower thrust washer and the faced surface on top of the bearing housing. Record this dimension to three decimal places.

C. Add .005 and .010 inches to the recorded dimension to obtain the correct minimum and maximum settings range for the unit.

D. Reassemble bearing with springs; motor is now ready to set end play.

NOTE: Certain motor builds require removal of the fabricated steel or cast aluminum oil baffle to provide access for depth micrometer measurements.

Motors built with spherical roller thrust or angular contact bearings with springs require a minimum external thrust load, sufficient to compress upper die springs and unload lower guide bearing from axial spring thrust. Refer to the motor's spring thrust plate for required minimum thrust.

NOTE: Do not run motor without load for more than fifteen minutes, as lower bearing damage may occur and improper seating of thrust bearing may cause vibration.

2. Angular Contact Ball Bearings (Without Springs)

A. No preliminary measurements are required to set end play. End play may be set by any of the following methods described in this section.

B. To correctly adjust the rotor end play setting on units with angular contact ball bearings, a dial indicator should be positioned to read the shaft axial movement. (See figure 7 for location of dial indicator.) The rotor adjusting locknut should be turned until no further upward movement of the shaft is indicated. The locknut is then loosened until .005 to .010 end play is obtained, lock the locknut with the lockwasher.

C. Motors that have two opposed angular contact bearings, locked on the mount for up and down thrust, do not require rotor end play adjustment. The shaft, however, must be set to original "AH" (shaft extension) to prevent the guide bearing in the lower bracket from taking external thrust.

End Play Adjustment Methods

Method 1 (refer to Figures 6 & 7) This method requires the user to install a bolted chain from the bearing mount back to a lifting lug, and rotate the locknut with a spanner wrench and 8 foot long bar until the dial indicator shows no movement on the end of the shaft. The locknut should then be loosened until .005 to .010 end play is obtained. Lock the locknut with the lockwasher. (See figure 7 for location of dial indicator.)

NOTE: This is the lowest cost of the three methods and requires the least amount of equipment. This method, however, may be less desirable than Method 2, as considerable locknut torque may be encountered on units with die springs.

Special equipment required includes: * Locking bolts * 3/4" chain * Spanner wrench with extension * Dial indicator * Depth micrometer

Method 2 (refer to Figure 8 - Utilized on Spring Loaded Bearings Only) This method utilizes a spreader bar and chains to wrap around lifting lugs, a hydraulic jack (five ton), and a crane to lift the spreader bar. The hydraulic jack is supported by two steel blocks of equal thickness on top of the bearing mounting, with the jack pushing against the spreader bar. On very heavy solid shaft rotors, the rotor can be lifted by placing a second jack below the motor to allow the locknut to be turned easily. After correct range (recorded earlier) is obtained, lock the locknut with the lockwasher.

NOTE: This method utilizes usual shop equipment and tools. End play settings can be checked quickly on larger vertical motor products. The locknut lifts rotor weight only.

Special equipment required includes: * Large spreader bar with chains and locking bolts * Overhead crane * Spanner wrench * Hydraulic jack (five ton) * Depth micrometer * Metal blocks * Dial indicator

Method 2

Method 3 (refer to Figure 9) This method uses a one inch thick steel disc, with center hole for shaft end bolt, and two threaded hydraulic jacks connected to a single pump. Apply load to the hydraulic jack until the dial indicator shows no movement on the end of the shaft. (See figure 7 for location of dial indicator.) Pressure from the hydraulic jack should be relieved until .005 to .010 end play is obtained. Lock the locknut with the lockwasher.

CAUTION - Excessive hydraulic pressure should not be used when setting end play, or bearing damage may occur.

NOTE: This method is directly usable on solid shaft motors, and can be utilized on some HOLLOSHAFT motors with the use of a long threaded rod and plate. It is very easy to apply and settings can be checked quickly, especially in field service. The locknut does not see rotor weight or spring force and can be turned easily.

Special equipment required includes: * Fixture with hydraulic jacks (five ton) * Dial indicator or depth micrometer * Spanner wrench

CAUTION: After setting end play by any of the above methods, run unit for fifteen minutes and recheck end play setting. If not within range, end play must be reset. All loosened or removed parts must be reassembled and tightened to original specifications. Keep all tools, chains, equipment, etc. clear of unit before energizing motor.

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