Flexible-Type Couplings —

Remote-Mounted Driven Equipment

1. Droop

Mount a dial indicator on the engine flywheel housing. Mark the flywheel at points A, B, C, and D in 90° incre- ments as shown in Figure 36. The indicator tip must contact the pilot diameter of the flywheel assembly. With the dial indicator in position (A), set the reading to zero. Place a pry bar under the flywheel assembly at position (C) and, by prying against a floor mounted support, raise the fly- wheel until it is stopped by the main bearings. (Caution: Do not pry against the flywheel housing.) Record the reading of the dial indicator. This is the amount of droop in the crankshaft which results from engine bearing clearances and natural droop as a result of the overhung weight of the flywheel.

The flywheel should be raised sever- al times to get a “feel” for the bearing clearance to prevent excessive lift which means reverse bending of the crankshaft.

Figure 36

2. Flywheel Concentricity

Remove the pry bar and check to ensure that the dial indicator has re- turned to zero; if it is not, reset. Rotate the crankshaft, in the normal direc- tion only, and record the TIR when the flywheel positions (A), (B), (C), and (D) are at the top. (Refer to Page 58 for proper tolerances.)

3. Crankshaft End Play

Ensure the crankshaft-flywheel assem- bly is completely to the rearmost posi- tion of the engine assembly. Reset the dial indicator to zero. Relocate the pry bar and move crankshaft-fly- wheel assembly forward in the engine assembly. The dial indicator reading in this position is the crankshaft end play. 4. Flywheel Face Run out

Set the tip of the indicator on the face of the flywheel Figure 36. Position the crankshaft to the front of its end play and zero the indicator. Shift the crank- shaft to the rear of its end play and record the TIR. With the crankshaft at the rear of its end play, zero the indi- cator. Rotate the crankshaft and record the TIR when the flywheel posi- tions (A), (B), (C), and (D) are at the top. Remove all end play before recording each reading. Remove the flywheel housing access cover. Then place a pry bar between the rear face of the flywheel housing and the front of the flywheel assembly. Move the crank- shaft-flywheel assembly to the rear of the engine, removing all end play.

5. Mounting

The engine and the driven equipment should be mounted so that any neces- sary shimming is applied to the driven equipment. The centerline of the engine crankshaft should be lower than the centerline of the driven equipment by approximately 0.0065 in (0.165 mm) to allow for thermal expansion of the engine. The value 0.0065 in (0.165 mm) allowed for thermal expansion is for the engine only. If it is anticipated that ther- mal expansion will also affect the dri- ven equipment centerline to mounting plane distance, that value must be sub- tracted from the engine thermal expan- sion value in order to establish the total engine centerline to driven equipment centerline distance. When measuring this value, the TIR will be 0.013 in (0.330 mm) plus the droop as estab- lished in Step 1.

Shim packs under all equipment should be 0.200 in (5 mm) minimum thickness to provide for later correc- tions which might require the removal of shims.

6. Coupling

Attach the driven member of the cou- pling to the flywheel and tighten all bolts to the specified torque value. Gear-type couplings, double sets of plate-type rubber block drives, and Cat viscous-damped couplings are the only ones that can be installed prior to making the alignment check. Most couplings

are stiff enough to affect the bore align- ment and give a false reading.

7. Angular Alignment

Mount a dial indicator to read between the driven equipment input flange and the flywheel face and measure angular misalignment. Adjust position of driven equipment until TIR is within 0.008 in (0.20 mm).

8. Linear Relationship

Mount dial indicator to the driven equipment side of the flexible coupling and indicate on the outside diameter of the flywheel side of the coupling. Zero the indicator at 12 o’clock and rotate the engine in its normal direction of rotation and check the total indicator reading at every 90°. Subtract the full “droop” from the bottom reading to give the corrected alignment reading. The value of the top-to-bottom reading should be 0.008 in (0.20 mm) or less under operating temperature condi- tions, with the engine indicating low. Adjust all shims under the feet of the driven equipment the same amount to obtain this limit.

The final value of the top-to-bottom alignment should include a factor for vertical thermal growth.

Subtract one-half the “droop” from the 3 o’clock and 9 o’clock reading. This should be 0.008 in (0.20 mm) or less. Shift the driven equipment on the mounts until this limit is obtained. Note: the sum of the side “raw” reading should equal the bottom reading within 0.002 in (0.051 mm). Otherwise the mounting of the dial indicator is too weak to support the indicator weight.

Figure 37

9. The combined difference or readings at points B and D should not exceed a total of 0.008 in (0.20 mm). (See Figure 37.)

10. Crankshaft End Play

The crankshaft end play must be rechecked to ensure that the driven equipment is not positioned in a man- ner which imposes a preload on the crankshaft thrust washers. (Refer to Step 4.) Place a pry bar between the flywheel assembly and the flywheel housing. The crankshaft should move both forward and backward within the engine and, in both positions, remain fixed when pressure on the pry bar is relaxed. Any tendency of the crank- shaft to move when pry bar pressure is released indicates that the driven equipment assembly must be moved rearward on the base assembly or, if used, the number of shims between the input flange and the flexible cou- pling must be reduced.

Tolerances and Torque Values

Permissible alignment tolerances and torque values for Caterpillar standard mounting hardware are available from your Caterpillar Engine supplier and are listed in the Caterpillar service manuals for each spe- cific engine model.

CAUTION: DURING OPERATION, SHOULD A CHANGE IN THE VIBRATION OR SOUND LEVEL OCCUR, ALIGN- MENT SHOULD BE RECONFIRMED. THIS IS PARTICULARLY TRUE FOR SEMIMOBILE INSTALLATIONS AND ON ANY FIXED INSTALLATIONS WHICH ARE SUBJECT TO INFREQUENT RELO- CATION. ALIGNMENT SHOULD ALSO BE CHECKED ON A PERIODIC BASIS OR AT TIME OF MOVEMENT IF INSTAL- LATION IS ON A SUBBASE OR SKID- TYPE BASE.