TRACK FRAME ROLLERS.- Two types of track frame rollers are used on tracked equipment: those located on the lower portion of the track frame, which support the weight of the dozer, and those mounted above the track frame, which support the track, as it passes over the track frame assembly.

Figure 11-8.-Carrier rollers.

The carrier rollers are mounted on brackets that extend above the track frame (fig. 11-8). Two of these rollers are on each side of the dozer. The single flange on the rollers extends upward between the links of the track chain and keeps the chain in alignment between the drive sprocket and the front idler.

The track rollers support the weight of the dozer and ensure the track chain is in alignment with the truck frame, as it passes under the rollers (fig. 11-9). Track rollers, both single and double flanged, are installed

Figure 11-9.-Track rollers in position in track frame.

alternately. In the normal arrangement, a double-flanged roller is positioned directly in front of the rear drive sprocket, followed by a single-flanged roller. The rollers alternate forward to the front idler.

FRONT IDLER.- The front idler, as shown in figure 11-9, serves as a guiding support for the track chain. The idler is spring-loaded and mounted on slides, or guides, that allow it to move back and forth inside the track frame, as the dozer passes over uneven ground. The spring-loading effect causes the idler to maintain the desired tension regardless of operating conditions.

RECOIL SPRING.- The recoil spring is a large coil spring placed in the track frame in a way that enables the spring to absorb shock from the front idler. The spring is compressed before installation and held in place by stops or spacers. The track adjusting mechanism, by pressing against the spring stop, maintains the desired tension on the track assembly by holding the idler and yoke in the forward position. The operation of the coil spring depends on the amount of tension on the truck.

TRACK ADJUSTING MECHANISM.- The adjusting mechanism must be extended enough to remove slack between the front idler and spring. The adjustment is made either manually (fig. 11-10) or hydraulically (fig. 11-11). Older model dozers have mnaually adjustments; whereas, newer dozers are

Figure _11-10.-Manual track adjustment.

Figure 11-11.-Hydraulic track adjuster.

adjusted hydraulically with a grease gun. Grease is pumped into the yoke cylinder and extends it until enough tension is placed on the recoil spring to remove the slack from the track. Tension is relieved by loosening the vent screw located next to the adjustment fitting.

NOTE: Do NOT lubricate this fitting when performing daily operator's maintenance. The track adjuster fitting should only be greased when the tracks require adjustment.

Track Adjustment.- To determine proper track tension, position the dozer on a hard surface. Then place a straightedge over the front carrier roller and idler with all slack removed from the rest of the track. The tension is correct when the measured distance is as shown in figure 11-12.

Figure 11-12.-Checking track adjustment.

Track tension should be suitable for the type of area you arc working in, such as tighter for rock and looser for sand and snow. However, if the tracks are adjusted too tightly, there will be too much friction between the pins and bushings when the track links swivel, as they travel around the sprocket and front idler. This friction causes the pins, bushings, links, sprocket, and idler to wear rapidly. Friction in a tight track also robs the tractor of needed horsepower.

Tracks that are too loose fail to stay aligned and tend to come off when the tractor is turned. As a result, the idler flanges, roller flanges, and the sides of the sprocket teeth wear down. A loose track will whip at high speeds, damaging the carrier rollers and their supports. If loose enough, the drive sprockets will jump teeth (slide over the track bushings) when the tractor moves in reverse.

Should this happen, the sprocket and bushings will wear rapidly.

NOTE: Checking and performing track adjustments arc the opcrator's responsibility.

_Lubrication. - The track pins and bushings are hardened and require no lubrication. Many roller idlers arc equipped with lifetime seals that are filled during assembly and require no lubrication. However, track rollers, carrier rollers, and idlers equiped with grease fittings must be lubricated on a schedule based on the manufacturer's specifications.

NOTE: Fittings should be cleaned before lubricating to prevent forcing dirt and grime into the bearings.