CH-3 -MOTOR Grader

MOTOR Grader

1. CHAPTER-3 MOTOR GRADER By: Debas D. 1 Heavy duty and Construction Equipment MEng5383 Ambo University Department of Mechanical engineering

2. Motor grader The motor grader is one of the most versatile earthmoving machines in use today. It is a construction machine with a long blade used to create a flat surface . The blade (moldboard) of motor grader is mounted underneath which can be lifted an lowered with a hydraulic system. 2

3. A pplication of Motor grader The blade is used to push dirt straight ahead or to the side at a desired level. The grader can be used for Light surface excavation leveling, Spreading grading shaping bank sloping ditching mixing side casting road and runway maintenance 3

4. Motor grader components 4

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6. POWER TRAIN A rear engine and rear drive wheel system is the most popular for motor grader. A power train composed of engine, clutch, transmission and reduction gears is mounted as a unit on rear side. The speed of rotation of transmission output shaft has reduce in the reduction gear unit. The tandem drive, a unique device employed on most motor graders, minimizes pitching. This unit also acts as the reduction gears.

7. FINAL DRIVE The final drive connects the transmission to right and left tandem drive. Unlike ordinary vehicles, motor grader have no differential. To assure straight forward traveling of motor graders which are mainly operated in bumpy roads, they are not provided with differential. This makes motor graders difficult to turn along sharp curves.

8. TANDEM DRIVE It receives driving power from the final drive and delivers to the rear wheels to rotate them at a reduce speed. It minimized vertical movement of the blade when the grader travels on rough ground so that ground surface is leveled flat. The tandem drive is designed so that is able to swing on rear axle . It allows all rear wheels to keep proper ground contact even when any wheels fall in to a hole.

9. Structure of Tandem drive Out of four rear wheel, two mounted side by side on right tandem and two mounted on the left tandem drive case. Each tandem drive case includes its own gearing which transmit rotation of rear axle to each wheel. The tandem case is supported at its centre bearing on the end surface of rear axle case. Rotation of rear axle is transmitted to each wheel through two stage reduction gearing.

10. WHEELS Motor graders are provided with rear wheel for driving and the front wheel for steering. Low pressure tires of 2.0 to 4.0 kg/sq.cm.air pressure are commonly used for motor graders.This will provide large tractive force with minimum slippage. Tires are provided with traction type tread pattern which is optimum for suspending the machine on muddy ground and producing large tractive force.

11. BRAKE Function of Brake Motor grader are provided with two individually controlled brake systems : Service brake ( or foot brake ) and parking brake ( or hand brake ). Brake pedal is connected to the master cylinder piston through the push rod. When the pedal depressed the oil from master cylinder will press the piston of wheel cylinder. Each wheel cylinder acts to expand brake shoes inside the drum. The brake drum mounted on each of four rear wheels includes internal expanding type brake shoes which cause friction force to brake the drum rotation.

12. Dual Braking Circuit The service brake system uses the dual braking circuits ( or dual brake oil piping structure ) for ensuring independent operation of service brake of each side of machine. If either service brake oil pipe for left or right rear wheel is damaged,the safety valve will stop feeding oil to the leaky pipe. This feature will help to supply oil to the other circuit of wheel cylinders on the opposite of the machine. The brake lamp switch provided in the master cylinder outlet port turns on the brake lamp with increase of oil pressure resulting from depression of brake pedal.

13. Parking Brake The parking is used when a motor grader is left parked or when starting on an upgrade. It is applied by pulling the hand brake lever towards the operator’s seat

14. STEERING SYSTEM The front wheel axle is fitted to the frame with a pin at the center of axle. No chassis spring is provided. The leaning mechanism is provided for preventing the front wheels from slipping sideward and for minimize the turning radius .

15. Leaning Mechanism Leaning mechanism is used for tilting the front wheels to right and left to prevents wheels for sleeping and keeps machine in straight travel. When a motor grader is operated for road leveling, its blade is usually angled from the machine centre line which causes a slide slip force on the wheel. Under this circumstances, the front wheel which supports only the light weights of the front frame, are liable to slip. It will cause the machine to turn from the straight forward traveling motion.

16. Leaning Mechanism Contd….. Leaning of the front wheel is necessary to prevent the front wheel from slipping. Sideslip force (A) caused by angling of the blade is cancelled by the opposite force(B) resulting from leaning of the front wheel. The leaning mechanism allows the machine to turn in a reduce turning radius.

17. Leaning Mechanism Construction Contd…. A hydraulic leaning cylinder is installed on the front axle. This cylinder is controlled by the leaning controlled lever in the operator’s compartment. When the leaning cylinder piston rod is extended, the right wheel knuckle bracket connected to the piston end and the left wheel knuckle bucket linked to the right knuckle through the leaning rod are leaned to the right. When the cylinder rod is retracted, both right and left wheels are leaned to the left which causes both right and left wheels to tilt to the right.

18. Work equipment of motor grader Blade The blade which is the main work equipment of motor grader is mounted under the frame at the middle of the wheel of the wheel base between front and rear axle. The blade system consists of drawbar,circle and blade. Several types of blade control mechanism are there for different blade application.

19. T he blade is supported and held in position by a pair of heavy curved brackets, called circle knees. They are attached to the underside of rotatable ring, called a circle. 19

20. The blade is having capability for the following movements: Up and down movement Sideways movement Rotational motion 20

21. Blade Lifting Mechanism The blade is fitted to the drawbar through the circle. The drawbar fitted to the frame through the ball stud at the front end of the drawbar and through two blade lift cylinders and a circle side shift cylinder at the rear end. Ground cutting depth is adjusted equally extending or retracting two lift cylinders rod. Blade rotating mechanism consists of hydraulic motor and circle reverse gear.

22. Circle reverse gear Rotation obtained by the hydraulic motor, which is driven by oil is too high in speed and too low in torque. This is compensated by the circle reverse gear mounted on the drawbar. Rotation of the hydraulic motor is reduce by the worm gear in the circle reverse gear . Rotation of the worm wheel is transmitted to the circle through pin roller.

23. Blade side shift mechanism The blade side shift cylinder horizontally mounted on the back of blade is controlled by the control lever in the operator’s cabin. Retracting or expanding the blade side shift cylinder rod causes the blade to move sidewise, so that any desire protrusion, right or left of the blade from the circle can be obtained.

24. Circle side shift mechanism The circle side shift cylinder located behind the blade lift cylinders is fitted to the frame through the slide block. The piston rod end of this slanting cylinder is joined to the rear end of the drawbar to move the drawbar sideward with retraction or extension of piston rod. The circle fitted to the drawbar follows the movement of drawbar.

25. Circle The circle is a large sized internal ring gear made of cast steel. It is suspended from the drawbar and is turned with rotation of the pin roller of the circle reverse gear.

26. Scarifier The scarifier is used for breaking hard ground prior to cutting of ground surface with the blade. The scarifier lifting cylinder is mounted on the front side of the frame. When the cylinder piston rod is retracted, movement is transmitted through the arm shaft and arms to the right and left lifting links and the scarifier is lifted. When the cylinder piston is extended the scarifier is lowered.

27. Frame Articulation Articulated Frame is a jointed frame in which the machines can pivot in the middle of machine for better traction and handling . Articulated mode reduce the need for additional equipment at the job site. Articulation helps the motor grader quickly and easily do jobs a rigid frame unit could not do or would have difficulty doing . Articulation can prevent a machine from getting stuck and helps remove it should this occur. 27

28. Frame Articulation There are three Modes of Operation of frame a motor grader. Straight Frame, Articulated Frame, Crab Mode Figure: Modes of Operation Caterpillar M-series motor graders Modes of Operation 1. Straight Frame, 2. Articulated Frame, 3. Crab Mode 28

29. Straight Frame Only front steering is used. Front steer angle is 50 degrees left or right for maximum productivity even when articulated frame is not used Normally used for long straight blading passes, most finishing, ditch cutting and ripping work. 29

30. Articulated Frame Use front steering and frame steering as required. Articulated frame gives the shortest turn radius for close quarter work, cul-de-sacs or corners. Improves maneuverability in all applications. Used to counter side draft from large windrows blade loads , to change cutting width of the moldboard and reduce blade loads without use of the circle. Allows steering the leading end when reversing or in tight quarters for more control and safety. 30

31. Crab Steer Front wheels and rear frame travel in same direction. Used to level truck dumped material without running front of machine over pile. Keeps the entire machine on a smooth surface allowing faster finishing of the area. Used for large windrows. 31

32. Linkbar The center shift link bar is designed to increase moldboard positioning and reach from the centerline of the machine. Repositioning the link bar will increase the motor grader’s productivity when ditching , back sloping and moving large windrows. Cutting/cleaning ditches and back slopes when using the link bar gives the ability to keep the mainframe running on a level surface at the top of the ditch or base of the slope while the moldboard cuts a slope beside the machine. When moving large windrows with the linkbar repositioned either side of center, it is possible to run extremely steep moldboard angles and maintain adequate clearance between the moldboard and front tandem tires. This position also helps visibility to the toe and heel when operating with steep moldboard angles. 32

33. There three linkbar adjustment positions. First and Second Hole From Center Center Hole Third Hole From Center Figure : Modes of Operation 33

34. Center Hole • This position is used for long straight blading passes, most finishing, and light to medium windrows. 34

35. First and Second Hole From Center • This position is used for cleaning shallow ditches . • Processing and moving large windrows. • Used with articulation to build narrow flat bottom ditches and backfill curb radiuses . 35

36. Third Hole From Center • This position is used for cutting ditch back slopes and high bank slopes. • Cleaning deep ditches. • Grading and dressing fill slopes. • Disposing of sod and oversize rock on backslopes . • Use with articulation to grade on steep slopes 36

37. Controls Most motor graders have control levers which change the position of the moldboard. Most motor graders will have six or more control levers in addition to the usual brake, clutch, transmission and fuel controls . For specific application to any given machine, refer to the operators manual, but generally a grader will have the following controls: Figure: Caterpillar 135H Controls 37

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42. Moldboard positions 1) pitch: the angle for the cutting edge in relation to the road. 2) sharp blade: a blade angle in relation to a line at right angles to the machine, and will be an angle greater than 30°. Toe is near the front wheel, heel is near the back of the tandems. 3) square blade: the blade is straight across (making a 90 degree angle with a frame) or the blade angle is 30° or less from the right angle. 4) loose blade: setting the blade so it just touches the surface with the weight of the blade supported by the machine. 5) tight blade : setting the blade so that it puts some down pressure on the surface 42

43. The rigid frame grader can accomplish virtually all grading operations . A grader equipped with articulation can accomplish the same operations, but some with greater ease . Straight frame operation is usually used for long passes such as road maintenance and snow removal . With an articulated frame grader you can reduce your turning radius, counteract side thrust when grading wet ditches or during ditching applications and have the tandem wheels on solid ground for maximum traction while achieving maximum blade reach. Moldboard positioning is very important when grading. The moldboard is usually angled 15 to 75 degrees from the center line of the frame. The greater the moldboard angle, the more material is carried across the moldboard allowing for deeper cuts and heavier grading. 43

44. The earth moved by the moldboard creates a side thrust on the grader. The operator can counteract this side thrust by leaning the front wheels in the direction the material is moving along the moldboard. Moldboard pitch is also important. For normal grading , the moldboard should be tilted slightly forward from the vertical position. Tilting the moldboard forward allows material to roll for spreading or compacting. Tilting the moldboard backward increases the cutting ability and reduces the rolling action of the material. Important terms Moldboard Toe -The point of the moldboard closest to the front wheels. Moldboard Heel- The point of the moldboard farthest away from the front wheels. Moldboard Angle -The angle of the moldboard as measured from the moldboard toe to the center line of the front frame of the grader . 44

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46. Avoid unnecessary speed, particularly on rough ground. Do not spin the wheels as this is hard on the machine and tires and also makes the surface rough. Start out slowly and do not jerk the machine. Drive the machine in a straight line by watching ahead, lining up with some object, and driving toward it. Front wheel lean can usually be used to steer the motor grader on level ground. Wheel lean also helps to keep the motor grader straight when pulling a load by counter acting load pull. Operating speed affects the quality of work. When ditching or blading, do not hurry. Higher speeds could cause the grader to bounce and gouge the surface rather than smooth it. In extreme cases, bouncing could cause the operator to lose control of the grader, producing a potential accident situation. Wheel lean can help counter side-draft created by the pull of the blade when it is loaded. When working on a slope, the wheels are leaned up slope to help hold the machine in a straight line. Remember that leaning the front wheels will lower the blade slightly. When moving material left, lean wheels opposite for traction on the front end. 46

47. Motor grader operation common terms: Articulated : jointed, articulated machines will pivot in the middle of machine for better traction and handling . Blade angle : refers to angle of blade in relationship to mainframe. The frame represents a 180 degree or a straight line. The moldboard will form a angles with the frame. (Figure 3.1) Circle: circular part of motor grader located under the frame. Moldboard with cutting blade is attached to the circle. Crown: build up middle of road bed so that water will flow to sides. Cutting edge: blade. Heel of the blade : following end of the blade. Ice blades: Serrated or saw tooth cutting edges. 47

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49. Lugging: trying to move forward in a gear that is too high for the work load or the terrain. Moldboard : attached to the circle and is pulled by a draw bar fastened in the center of the front wheels. The blade is attached to it. Scarify : to loosen the road surface. Tandem drive : all four rear wheels are driving and have constant traction. Toe of the blade : leading end of the blade. Wheel lean : lean of front wheels to the left or right, used to stabilize the grader and assist in turning. Windrow: a ridge of loose material, also known as a berm. 49

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