SERVICE TIP

Realigning Procedures For McCracken Conventional Packerhead and Bidirectional Machines

1. With crosshead in the low or down position, hang two plumb bobs at 90 degrees from top of packershaft. Now measure the distance from packershaft to string at top and then again at bottom. Note these measurements.
   
   
2. Now raise crosshead to top of stroke. Steady plumb bobs. Now measure again. You will need only to take measurement at bottom of packershaft. Note this measurement.
   
   
3. The measurement from top of packershaft to bottom of packershaft should read the same. For conventional machines only - not BiDi.
   
   
4. If there is a difference in these measurements, would suggest rotating the packershaft at a very slow speed to determine if the packershaft is rotating true.
   
   
5. Should the packershaft not be rotating true, it can be corrected by shimming at the top of the packershaft between the flanges or flange and gearbox.
   
   
6. Now with the packershaft rotating true, take another measurement as stated before in Paragraphs #1 and #2.
   
   
7. There should not be a variance of more than 1/8".
   
   
8. With the difference being at the bottom of the stroke, one can make the adjustment by moving the guide tubes at the bottom. Loosen the bolts (1") at bottom of guide tubes. First raise crosshead to top of lift. This will aid in moving guide tubes. With adjusting screws supplied, move guide tubes making very minor adjustments. 
   
   Lower crosshead and take another measurement. Repeat this procedure until packershaft is tracking true throughout stroke.
   
   
9. Now that the packershaft is plumb, remove plumb bobs. Lower crosshead until packershaft is within one of the holes in the table. With table in correct position with stop bar in locked position, measure from packershaft to I.D. of hole in table in four 90-degree locations. Do this with all four holes before doing any adjustment. Note all measurements.
   
   
10. At this time , make sure table centering ring is against the four cam followers that are bolted to the front post.
    
    
11. If the measurement from the packershaft to the I.D. of table hole is off in the direction of between the two front posts, then it is a matter of adjusting cam followers out. 
    
    The table can be moved in our out by adjusting the cam followers in the direction required. During all adjustments, the table should be rotated as this will help in moving table. After table has been returned to correct position, make sure all bolts and set screws have been secured properly.
    
    
12. With McCracken packershafts, you will find 5/8" NC threaded holes in bottom of packershaft. Also in center of McCracken top vibrating plate on bell down unit, there is also a ½" NC threaded hole.
    
    
13. If the bell down unit is not level, it should be done now. Once leveled then check for being centered.
    
    
14. For centering bell down unit, it will be necessary to loosen mounting bolts on some machines and moving the complete unit until centered. On larger machines using guide tubes, it is a matter of loosening the bolts holding the guide tubes at the top and moving the upper portion of guides until centered. 
    
    Now that the packershaft is plumb from bottom to top of stroke, the hopper or mud pan can be centered with packershaft. 
    
    Should your McCracken machine be equipped with hopper guide tubes, it is a matter of moving guide tubes. 
    
    Loosen the bolts at bottom of guide tubes. Move hopper until centered. Lightly tighten guide tubes. 
    
    Raise hopper to the top of stroke. Repeat same procedure to center as was done at bottom of guide tubes. Lightly tighten guide tubes. 
    
    Lower hopper to bottom of stroke. Re-measure, and if necessary, make adjustments as required. Tighten guide tubes securely. Raise hopper to top of stroke again. Measure and make adjustment as required. Tighten guide tubes securely. 
    
    Should your machine have the guide rollers that track along both front post, it will be necessary to work all four guide brackets, two brackets on each side. 
    
    
    Should it be necessary to move mud hopper sideways, between front post, shims can be added to one side for shifting mud hopper in the direction required. With bolts loosened, the mud hopper may be shifted front or backward as required. 
    
    When the hopper has been centered at bottom of stroke, raise hopper to top of stroke and re-measure. Make minor adjustment as required and then tighten all bolts. 
    
    With mud hopper centered and all bolts tightened, it would be advisable at this time to tack weld the hopper brackets. 
    
    Also on these type of hopper guide brackets, there are threaded rerods that can be adjusted to hold the hopper guide brackets together. This will help to stop guide brackets from spreading.
    
    
15. Once each components have been centered, it would be advisable to tack weld to assure that the components stay in place and then should any one of the components misalign in the future, one can visually check and if welds are broken, it then can be brought back to the original position.

Posted 2 January 2001