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.
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3. Application 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
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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. • The 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.
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20. The blade is having capability for the following
movements:
Up and down movement
Sideways movement
Rotational motion
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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.
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28. Frame Articulation
There are three Modes of Operation of frame a motor grader.
1. Straight Frame,
2. Articulated Frame,
3. Crab Mode
Figure: Modes of Operation Caterpillar M-series motor graders Modes of Operation
1. Straight Frame, 2. Articulated Frame, 3. Crab Mode
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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.
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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.
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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.
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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.
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33. • There three linkbar adjustment positions.
i. First and Second Hole From Center
ii. Center Hole
iii. Third Hole From Center
Figure: Modes of Operation
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34. Center Hole
• This position is used for long straight blading
passes, most finishing, and light to medium
windrows.
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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.
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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
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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
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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
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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.
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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
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.
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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.
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