CHAPTER 10 GRADERS AND SCRAPERS

In the Naval Construction Force (NCF), graders and scrapers are essential tools used in the construction of airfields, ammo supply points (ASPs), roads, and site work. The primary purpose of the grader is to cut and move material with the blade for final shaping and finishing. The scraper is a large earthmover with the capability of digging, loading, hauling, dumping, and _{spreading material.} This chapter covers the characteristics and basic principles of graders and scrapers operations.

GRADERS

Graders are multipurpose machines used primarily for general construction and maintenance of roads and runways, moving large amounts of materials laterally by side casting. Additionally, the grader can be used for crowning and leveling roads, mixing and spreading materials, ditching and bank sloping, blade mixing asphalt materials, snow removal, and scarifying.

The grader is a rubber-tired hydraulically operated,- single-engine unit. The single engine provides power for all grader functions. The steering system, moldboard, and scarifier are hydraulically controlled.

Although the grader, at times, must be hauled to and from jobsites, the grader has an advantage over other heavy equipment because of its capability to travel over the road under its own power.

NOTE: When hauling a grader with a tractortrailer, ensure the height of the grader cab clears all overhead obstacles.

A variety of makes and models of graders are used in the NCF. Each operator is responsible for reading the operator's manual to obtain detailed information about each make and model.

GRADER COMPONENTS

The basic grader consists of a prime mover and a grader mechanism. The principal parts of a grader are shown in figure 10-1.

Figure 10-1.-Principal parts of a motor grader.

Prime Mover

The prime mover is a rubber-tired tractor, power-driven by a four- or six-cylinder diesel engine mounted at the rear. The prime mover has four-rear mounted single tires driven in tandem drive through gears and chains and a single-steering axle.

TANDEM DRIVE.- The tandem drive of the grader allows climbing over rocks, logs, or humps, and permits passing through depressions or ditches one wheel at a time. Having the capability to operate in this manner, one rear wheel can raise or lower, while the other remains on the same level with the front wheels thereby holding the grader on a level terrain (fig. 10-2). This is a very important feature. If the rest of the grader does not rise and fall when working uneven terrain, the grader blade does not vary its elevation, as the grader passes over its work.

ARTICULATED FRAME STEERING.- Some graders have frames that are hinged just forward of the

Figure 10-2.-Tandem drive.

Figure 10-3.-Articulated grader.

Figure 10-4.-Grader frame.

_{Figure 10-5.}-Front axle.

engine with articulating controlled by a pair of hydraulic cylinders. The articulated frame steering allows for an increase in productivity and stability. The articulated frame has a shorter turning radius than the conventional grader (fig. 10-3). This allows for easier maneuvering in close quarters and quick turnaround at the end of a pass and enables the grader to carry a full blade of material around a curve. Crab steering helps compensate for side drift when turning a windrow, keeps tandems on a firm footing when clearing ditches, and increases stability on side slope work.

NOTE: Before articulating the grader, be aware of the position of the grader blade. With the blade angled in an acute position, articulating the grader sharply can position the rear tires to run into the blade.

Frame

The frame connected to the front axle extends the full length of the grader (fig. 10-4) and is high enough to allow space for carrying and manipulating the grading mechanism.

The front axle is compound. The lower section carries the weight of the grader, oscillates on a center pin, and is hinged to the bottom of the wheel spindle. The upper section of the axle is hinged to the top of the spindle, allowing the front wheels to lean as well as turn (fig. 10-5).