Q2. What shaft in a power shift transmission has the reverse drive gear keyed to the front of the shaft?

Q3. What components are the heart of a hydrostatic drive system?

Q4. What component in a hydrostatic drive system maintains system pressure by using oil from the reservoir?

Q5. A hydrostatic drive pump with a movable swash plate is known as what type of pump?

TRACK AND TRACK FRAMES

Learning Objective:

Identify the operational components of the track and track frame. Describe the maintenance procedures used on tracks and track frame assemblies.

The undercarriage of crawler-mounted equipment contains two major components - TRACK ASSEMBLY and TRACK FRAME. This under- carriage (fig. 6-18) is provided on equipment that must have positive traction to operate efficiently.

TRACK ASSEMBLY

The track assembly consists of a continuous chain surrounding the track frame and drive sprocket. The links of the chain provide a flat surface for the track rollers to pass over, as they support the equipment. Track shoes are bolted to the outside links of the chain and distribute the weight of the equipment over a large surface area.

Track Chain

Figure 6-19 shows a cutaway view of a section of track chain, showing the internal arrangement of the pins and bushings. As the tractor operates, the drive

Figure 6-19. - Track chain cutaway.

sprocket teeth contact the track pin bushings and propel the tractor along the track assembly.

The pins and bushings wear much faster than other parts of the track because of their constant pivoting, as the track rotates around the track frame. This pivoting results in internal wear of both the pin and the bushing. As the pins and bushings wear, the track lengthens. When it does, the track is adjusted to remove excessive slack.

Bushings that show lots of wear on the outside are good indicators of inner wear that is also nearing the maximum allowed by the manufacturer, if the track is to be rebuilt. To determine whether the track should be removed for rebuilding or replacement, measure the outside of the bushings and track "pitch" (length of the

Figure 6-18. - Side view of crawler tractor chassis.