Usage:
120H (6TM, 5FM, 9FN, 4MK, 2AN, 6NM, 9YR),
135H (7MM, 8WN, 3YK, 7PM),
12H (5ZM, 4ER, 4XM, 8MN, 2WR, 2LR, 2GS),
140H (8JM, 5HM, 2ZK, 9TN, 9ZN, 8KM, 3AS),
143H (1AL),
160H (9JM, 2FM, 9EJ, 3GM, 6WM, 2HS),
163H (5AK),
14H (7WJ),
16H (6ZJ) Motor Graders
Reference: Service Magazine, March 10, 1997, Page 4, "New Wear Strips Used on Circle Drawbar Improve Performance".
Reference: Service Magazine, August 3, 1998, Page 2, "New Wear Strips for the Circle and Drawbar Assembly Improves Performance".
Reference: SENR9179-01; Specifications, 120H and 135H Motor Graders Hydraulic and Steering System, "Drawbar".
Reference: SENR9178-02; Specifications, 12H, 140H, 143H, 160H, and 163H Motor Graders Hydraulic and Steering System, "Drawbar".
Reference: SENR9187-02; Specifications, 14H and 16H Motor Graders Hydraulic and Steering System, "Drawbar".
Maintaining the proper circle drive pinion adjustment and lubrication maximizes the pinion service life. The service life of the pinion will vary widely based on application. When a lot of circle rotation is required, the service life of the pinion will be reduced.
The "H" Series Motor Graders, when compared to the "G" Series Motor Graders, have seen performance improvements made to the circle drive system. With the removal of an orifice in the lock check circuit and the addition of larger supply hoses, line losses have been reduced. The reduction in line losses, in turn, decreases heat. These changes increase flow to the circle drive resulting in increased horsepower at the circle pinion. Because of these enhancements, maintenance to the "H" Series Motor Grader's circle system is important to achieve optimum pinion life.
Additionally, the "H" Series Motor Graders have increased rim pull and an optional 27 inch (685.8 mm) blade, which carries bigger blade loads. The result is more dynamic loading on the circle drive pinion while loaded.
The pinion, in use on Motor Graders since 1986, is designed to be a replaceable wear item. Made of austempered ductile iron (ADI), the pinion is softer then the opposing circle teeth. If the pinion were as hard or harder than the circle teeth, damage would occur resulting in frequent segmenting of the circle teeth. Even though the pinion is made of a softer material, it will "work harden" with use.
NOTE: It is critical to keep the circle adjusted to slow the wear rate. Slowing the wear rate allows the process of "work hardening" of the ADI pinion to occur.
Typical wear expected with proper circle adjustment is shown in Illustration 1.
NOTE: Do not adjust the circle if this wear pattern is present. If the circle is loose, check the circle shoe wear strips.
The wear pattern on the pinion should start at the major diameter of the tooth progressing to and including the pitch. When the circle is properly adjusted, the pitch diameter of the pinion should contact the pitch diameter of the circle teeth. Improper wear pattern starting at the major diameter progressing through the pitch diameter to the root, as shown in Illustration 2, is caused from improper circle adjustment.
Illustration 1.
Typical pinion wear pattern expected with proper circle adjustment. Refer to Table 1 for callout identification.
Illustration 2.
Typical improper pinion wear pattern. Refer to Table 1 for callout identification.
Circle adjustment is made, as needed, based on application. If the circle is frequently cycled under load, the circle shoe wear strips will wear at a faster rate. Therefore, the need to adjust the circle will be more frequent.
NOTE: It is important to keep the circle shoes in contact with the circle at all times.
Work environment and experience should be considered when choosing a lubricant. There are examples of successful use of grease, dry film lubricant or nothing at all. If frequently cycling under load, grease is the preferred lubricant. Caterpillar recommends a lubricant be used every 10 hours or daily. Before clean lubricant is applied, the circle drive pinion teeth should be cleaned of dirt and old lubricant.
With the exception of the 24H Motor Graders, Caterpillar now uses nonmetallic wear strips in production of all of the Motor Grader's circle assemblies. With the use of the nonmetallic material, the circle may be adjusted tighter and turn easier. Both metallic and nonmetallic wear strips are serviced. Refer to Service Magazine articles dated March 10, 1997 and August 3,1998 that are referenced above
Circle Adjustment Procedure:
It is now recommended that all of the circle shoes (front, side and rear) are set to contact the circle. This will remove the 0.76 to 2.00 mm (.030 to .079 inch) clearance between the circle shoes and the circle.
1. Refer to Table 2 to set the circle (Item 5) and pinion (Item 6) to dimension (A) shown in Illustration 3.
2. Holding the dimension between the circle and pinion, place the front shoes in contact with the circle and adjust the set screws.
3. Tighten the nuts while holding the set screws.
4. While the front shoes are in contact with the circle, adjust the set screws on the remaining shoes to contact the circle.
5. Tighten the remaining nuts while holding the set screws.
6. Refer to the appropriate Specifications referenced above for the proper torque.
Illustration 3.
Typical circle (Item 5) and pinion (Item 6). Refer to Table 2 for Dimension (A).
