This equipment is used in open cast mines for maintaining the haul roads. The grader can be used for finishing of scraped road, repairing of gravel road, removing of snow, spreading of material, ditch cutting, side bank cutting etc. This is basically a tyre mounted equipment with three axles, one in the front and two at the rear. The engine, transmission, differential, final drive and cabin are mounted over the two rear axles. There is a blade in between front and rear wheels for grading purpose. The machine can be fitted with some extra optional attachments depending on requirement like, ripper at the rear, a scarifier in front of the blade, a dozer blade in the front etc. The capacity of grader is indictaed by the blade size which may range from 2.5 metre to 7.3 metre and engine capacity which may range from 125hp to 500hp.
Blade – It is the main component of the grader and it has multiple operations so that a good surface finish can be obtained. There are two cylinders on each side for independently lifting or lowering the blade so as to maintain slope of the surface according to requirement. There is one hydraulic cylinder for shifting of the blade side ways so that the machine can run on different line and grading can be done to different line, thus remote areas/ corners can also be accessed. There is one cylinder for blade angle tilting (optional in smaller equippments), this results in better utilisation of blade according to soil conditions. The blade angle can also be rotated by means of a hydraulic motor so as to change the angle of scrapping depending on soil conditions.
Drawbar – It is a pivoted structure connected to front axle frame and blade is fixed to this structure. The drawbar contains all the blade controlling cylinders and motors. The drawbar can also be rotated about the main frame so that the blade can be made vertical for side bank cutting. The drawbar can be shifted sideways so that the blade can moved away from the line of travel, this helps in accessing further ends without exposing the grader to damages.
Main frame – The main frame of grader has special capabilities hence requires special attention. The main frame is splitted to two parts the front part and the rear part. The power train system is mounted over the rear frame. The blade is connected to front frame. The two frames are pivoted and their relative angle can also be changed by hydraulic cylinders. This operation is termed as articulation. This helps in achieving shorter turning radius and taking sharp turns. Moreover this also allows front axle and rear axle to run along different path. The front axle can run on previously graded path and rear axle will be behind the blade doing the grading work thus there will be minimum vertical vibration of the machine giving better finish.
Power Train – The power train consists of Engine, Torque convertor, Transmission, Transfer case, Differential and Tandem drive.
Tandem Drive – The tandem drive is used to drive four wheels of the rear axles from single engine output shaft. The power comes from engine to tandem drive via transmission and differential. The differential has two output for left side and right side. From this output two sprockets are driven. Each sprocket has two rows of teeth. Drive from one row of teeth goes to front side rear wheel via chain and sprocket mechanism and another row of teeth gives drive to back side rear wheel. Thus both the wheel of one side runs at same speed, hence the name of tandem drive is given.
Hydraulic System – All the operations of grader are hydraulically actuated, hence hydraulic system plays an important role. The blade is totally controlled hydraulically. Moreover steering of front wheels, frame articulation and leaning of front wheels are also done by hydraulic cylinders.