The air compressor crankshaft will turn while removing or tightening the drive hub retaining nut unless some provision is made to hold it. One method is to weld a modified drive coupling to a support or base which can be anchored to the mounting flange of the compressor.
A Series 71 or 92 flywheel housing cover that matches the flange of the compressor makes an ideal base for the modified coupling. When positioned, the exterior splines of the coupling mesh with the internal splines of the drive hub and the assembly is secured to the compressor housing. The shaft is then kept from rotating when the nut is loosened or tightened, by the hub and key.
To replace the air compressor drive hub, perform the following procedure. See Figure 21715 .
Flowchart for Replacement of Air Compressor Drive Hub
Precleaning is not necessary.
Refer to Section for removal of the air compressor.
To keep the shaft from rotating, perform the following:
To properly position the cover and coupling with the drive hub, four collars, 19 mm O.D. and 12.7 mm I.D., 19 mm long (3/4 in. O.D. and 1/2 in. I.D., 3/4 in. long), and two pieces of bar stock 19 mm x 19 mm x 102 mm (3/4 in. x 3/4 in. x 4 in.) must be fabricated and welded to the flywheel housing cover at the positions shown in the next illustration. See Figure 20546 .
Position the coupling into the drive hub. Lay the flywheel housing cover over the coupling, center the collars over the compressor housing bolt holes, and tack weld the cover to the coupling.
The diameter of the cover hole must be opened up to the same diameter as the coupling inside diameter to permit access to the drive hub retaining nut. Two bolts will secure the base to the compressor during the operation.
Remove the air compressor drive hub as follows:
Air Compressor Crankshaft Holding Fixture Installation
Refer to OEM guidelines to determine if the air compressor drive hub needs to be repaired or replaced.
Install the air compressor drive hub as follows:
The drive hub and nut on the Series 50 have a unique configuration. Only the correct part numbers should be used.
Air Compressor Drive Hub Assembly
Torquing Drive Hub Retaining Nut