Chapter Two

Dozers
 2.1 Introduction
• A bulldozers have a crawler (continuous tracked
tractor) or large tire equipped with a substantial metal
plate (known as a blade) used to push large quantities
of soil, sand, rubble, or other such material during
construction or conversion work and typically equipped
at the rear with a claw-like device (known as a ripper )
to loosen densely compacted materials.
• The term "bulldozer" is often used wrongly to
mean any heavy equipment (sometimes a loader
and sometimes an excavator), but precisely, the
term refers only to a tractor (usually tracked)
fitted with a dozer blade.
 Dozers are machines designed primarily for cutting
and pushing the material over relatively short
distance.
 They consist of a tractor equipped with a front–
mounted earthmoving blade controlled by hydraulic
cylinders to vary the depth of cut.

 A dozer moves earth by lowering the blade and

cutting until a full blade load of materials is obtained.
It then pushes the material across the ground surface
to the required location.
 Contd.
• Bulldozers can be found on a wide range of sites,
mines and quarries, military bases, heavy industry
factories, engineering projects and farms.
 2.2 TYPE OF DOZERS
1. Based on the arrangement of track chain:
a) low track dozers, and
b) high track dozers
2. Based on running gear
a) Crawler (track laying) dozer
b) Wheel type dozer
3. Based on the control
a) Cable controlled
b) Hydraulically controlled
4. Based on the Position of blades
a) Bull dozers in which the blade perpendicular to the
direction of movement
b) Angle dozers in which the blade is set at an angle with
the direction of movement
By the arrangement of track chain: low and high
Low track dozers: commonly used for grading
High track dozers: has an elevated drive
sprocket usually used for pushing in muddy
conditions.
 CONTD.
Advantages of delta drive
• due to elevated engine and drive risk of
getting dust (mud) inside is less
• longer operation (life) time
• increased bulk clearance
Disadvantages of delta drive
• higher costs of manufacturing
• more components, longer crawler belt
Types of dozers based on running gear
CRAWLER DOZERS
• It has chain type truck
• It is equipped with special clearing blades
which are excellent machine for clearing.
• Heavy ripping of rock is accomplished by
crawler dozers with use of rippers which are
mounted rear of dozers.
 Crawler-type dozer

Wheel-type dozer
 ADVANTAGES OF CRAWLER MOUNTED DOZER
• It delivers greater a tractive effort especially
when operating soft grounds as loose or
muddy soil.
• Capacity to travel over muddy surface.
• Work on different type of soil.
• Greater flotation due to the lower pressure
under the track.
• Good for short distance jobs.
• Greater use in different type of jobs.
• Can push large blade loads.
• Speed is slow about 8 to 16 km/h.
WHEEL TRACTOR MOUNTED
BULLDOZERS
 ADVANTAGES OF WHEEL MOUNTED DOZER
• Provide higher travel speed from 13 to 42 km/h
on the job or from one job to another job.
• Eliminates the necessity of hauling equipment
• Less fatigue to operator.
• It is good for long distance.
• It can travel on paved highways without
damaging the surface.
• It is best for handling loose soil.
• It can push moderate blade load.
Comparison between crawler and
wheeled tractors
 2.3 Purpose of dozers
Typical project applications are:
o Land clearing
o Dozing (pushing material)
o Ripping
o Towing(pulling) other pieces of construction equipment's
o Assisting scrapers in loading
o Excavate the material and haul in between 100 meters
distance
o Prepare roads on hilly areas as well as hard ground
o Backfilling trenches
o Maintaining haul roads
o For opening up pilot roads through mountainous and
rocky terrains
PUSHING MATERIALS
 2.4 DESCRIPTION

• Bulldozers have excellent ground hold and a

torque divider designed to convert the engine's
power into improved dragging ability.
• Some dozers can easily tow tanks that weigh
more than 70 tons. Because of these attributes,
bulldozers are used to clear areas of obstacles,
shrubbery, burnt vehicles, and remains of
structures
 SIZE & OUTPUT OF BULLDOZER
• Size of bulldozer indicated by the dimensions
of blade & its output depends upon its
operating condition.
• Each blade has a capacity of hauling a
particular type of earth & knowing the number
of turns a bulldozer can be estimated.
• Output of all the earth moving machinery
depends on given factors.
 FACTORS AFFECT OUTPUT OF
MACHINERY
a) Efficiency of operator

b) Nature of soil

c) Topography of area

d) Type of equipment

e) Weather
THE MAIN COMPONENTS BULLDOZER
 A. BLADES
• The bulldozer blade is a heavy metal plate on
the front of the tractor, used to push objects,
and shoving sand, soil and debris.
• A dozer blade consists of a moldboard with
replaceable cutting edges and side bits.
• Push arms and tilt cylinders or a C-frame
connect the blade to the dozer
• Blades can be fitted straight across the
frame, or at an angle, sometimes using
additional 'tilt cylinders' to vary the angle
while moving.
 DOZER BLADES USUALLY COME IN
FOUR VARIETIES
• A straight blade ("S blade") which is short and
has no lateral curve and no side wings and can
be used for fine grading.
 Contd.
• A universal blade ("U blade") which is tall
and very curved, and has large side wings to
carry more material.
 CONTD.
• An "S-U" combination blade which is shorter,
has less curvature, and smaller side wings.
This blade is typically used for pushing piles
of large rocks, such as at a quarry.
 CUSHION DOZER BLADES
• Cushion Dozers are used to push load scrapers or
track.
• The heavy duty design includes a wear-resistant center
liner plate and a reinforced cutting edge section.
• Narrow width increases maneuverability when lining
up for the next pass.
 CONTD.
• Blades can be fitted straight across the frame, or
at an angle, sometimes using additional 'tilt
cylinders' to vary the angle while moving.

• The bottom edge of the blade can be

sharpened, e.g. to cut tree stumps
 Dozer pushing performance
• A bull dozer pushing performance is
measured by two standard ratios.
Horse power per length of cutting edge which
provides the ability of the blade to penetrate and
obtain a load. The higher this ratio the more
aggressive the blade.
Horse power per cubic meter of material
retained in front of the blade which measure the
ability to push a load. A higher ratio means that the
bull dozer can push a load at a greater speed.
 Blade adjustment

Tilt
• The vertical movement of the blade ends is
known as tilt. This movement is with in the
vertical plane of the blade.
• Tilting permits concentration of tractor driving
power on limited length of blade.
 Blade Adjustments
• TILTING
 Blade Adjustments

Pitch
• The control which allows the operators to vary
the angle of attacks of the blade cutting edge
with the ground is a pitch.
• It is the movement of the top of the blade
toward or away from the tractor.
Blade Adjustments
 Blade Adjustments
Angling
• Turning the blade so that it is not
perpendicular to the direction of the tractor’s
travel is an angling.
• This causes the pushed material to roll of the
trailing end of the blade. Rolling material off
one end of the blade is called side casting.
 Blade Adjustments
Angle
 B. RIPPER
• The ripper is the long claw like device on the
back of the bulldozer. Rippers can come as a
single shank/giant ripper) or in groups of two
or more (multi shank rippers).
• Usually, a single shank is preferred for heavy
ripping. The ripper shank is fitted with a
replaceable tungsten steel alloy tip.
• Ripping rock breaks the ground surface rock or
pavement into small rubble easy to handle and
transport, which can then be removed so grading
can take place.
RIPPER (CONTD.)
 C. OPERATORS CAB
• Mounted behind the engine, which is the
central location of most instruments and
controls.
• Provides the operators, instruments, controls
protection against harsh weather.
 D. Undercarriage unit
• Undercarriage units consist of two crawler units
mounted on the frames
• The driving sprockets is fitted at the rear end
while the idler wheel is fitted at the front end of
the frame
• An endless chain passes over the driving
sprockets and the idler wheel and is supported in
between by carriers rollers and track rollers
• Shoes are fitted on the endless chain through out
the length
• The tensioning arrangements is fitted between the
crawler frame and the idler wheel to adjust the
chain sag
 E. Track assembly
• The track assembly consists of a continuous chain
surrounding the track frame and drive sprockets.
• The link of the chain provide a flat surface for the
track rollers to pass over, as the roller support the
equipment.
• Track shoes are bolted to the outside of the chain
links and distribute the weight of equipment over
a large surface.
• A track assembly provides all type terrain
versatility due to the low ground pressure at the
track.
• This lower ground pressure has a distinct flotation
advantage over the ground pressure of rubber
tired equipment.
 a) Track chain
• As the dozer operates, the drive sprocket
teeth contacts the track pin and propel the
dozer along the track assembly.
• The pin and bushings wear much faster
than other parts of the track because of
their constant pivoting as the track rotates
around the track frame.
 b) Track shoes
• The track shoes are available in two configurations: the
grouser shoe and extreme service shoe.
• The grouser shoe is the most common type of track
shoe. It is standard on crawler mounted dozers.
• The extreme service track shoe, on dozers operate
primarily on rocky locations

Types of track shoe

 c) Track frame
• The track frame serves as a frame work and
support for track assembly, rollers, front idlers,
recoil spring, and adjusting mechanisms.
 d) Truck frame rollers
• Two types of track frame rollers are used on
tracked equipment. Carrier and track rollers
• The carrier rollers are mounted on brackets
that extend above the track frame. They support
the track as it passes over the track frame
assembly.
• The track rollers are mounted on the lower
portion of track frame. They support the weight
of the dozers and ensure the track chain
alignment with the track frame as the track
passes under the rollers.
 e) Front idlers
• The front idlers 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 forth and back
inside the track frame, as the dozer passes
over uneven roads.
• The spring loading effect causes the idler
to maintain the desired tension regardless
of operating conditions.
 f) Recoil spring
• The recoil spring is a large coil spring placed
on track frame in a way that enables to the
spring to absorb shock from the front idlers.
• The spring is compressed before installation
and held in place by stopper or spacers.
• The track adjusting mechanism, by pressing the
spring stop, maintains the desired tension on the
track assembly by holding the idler and yoke in
the forward direction.
• The operation of the coil spring depends on the
amount of tension on the track.
 g) Track adjusting mechanisms
• The adjusting mechanisms must be extended
enough to remove the slack between the front
idler and spring.
• The adjustment is made either manually or
hydraulically by grease gun.
• Grease is pumped into yoke cylinder and
extend it until enough tension is placed on the
coil spring to remove the slack from the track.
• Tension is relieved by loosening the vent
screw located next to the adjustment fitting.
 F. Controls
• Control configurations depending on the dozer
model and make. Some dozers have a set of
levers to control the vehicle movement and
blade and attachment operations.
• The engine speed is controlled by the
governors, decelerators and brake pedals.
• The movement of tracked dozer is controlled
by a transmission control, a right and left
steering clutch, and a brake control.
• Other controls include blade lift and tilt
control and a ripper height control.
 G. Power transmission
• Power delivered from the engine is distributed
for the travelling of the machine and for the
engine is delivered to the main gear box through
the main clutch and usually mounted on the
outside track frame, there are some designs'
where the frames are fixed on the inside of the
track frame intermediate brake.
• The gear box has two output shafts one is power
take off shaft to drive the cable control unit and
other drives a bevel gear shaft, which in turn
drives two sprockets through steering clutch and
reduction gear box
 H. Hydraulic system
A dozer blade controlled hydraulically
• The oil is sent to control valve from the gear
pump installed in the hydraulic tank.
• Here the oil pressure is developed for operation
the blade in four position
1. Raise
2. Hold
3. Lower
4. float
• The safety valve is designed to control an
abnormal pressure rise beyond limit and to
release the oil into the tank
 Contd.
• The hydraulic tank is located in front of the
radiator, with in the tank are the gear pump and
control valves
• The oil filter is fitted at the top and the oil drain
plug is fitted at the lower part for draining
purposes.
• The oil strainer is installed with in the oil filter to
prevent entry of dust and dirt into the tank when
the tank is replenished with oil
• The oil level in tank can be checked by the oil
level gauge installed in the oil filter
 Specification
To prepare the bulldozer specification
• Engine rated power and torque
• Operating weight (Including Semi-U tilt dozer, giant
ripper, steel cab, operator, standard equipment, rated
capacity of lubricant, coolant, and full fuel tank)
• Drawbar pull
• Ground pressure
• Ground clearance
• Transmission type
• Control system
• Forward and reverse speed
• Blade type and capacity
 Preventive Maintenance
Daily Maintenance Checks for Bulldozers
1. Check fluid levels (check the engine oil, hydraulic fluid,
coolant, etc.).

2. Inspect tracks for wear, damage, or misalignment.

3. Monitor blade condition and adjust if necessary.

4. Clean air filters and remove debris from radiator grills.

5. Test all lights, signals, and alarms.

 Preventive Maintenance
• Every 1,000 hours: Check the fan belt tension,
look for loose mount bolts and examine the
turbocharger tightening parts.

• Every 2,000 hours: Clean the turbocharger,

check the vibration damper and adjust the
engine valve clearance.

• Every 4,000 hours: Check the water pump.

 7 Dozer Maintenance Tips You Should Follow

i. Follow the Dozer Operation & Maintenance

Manual. ...
ii. Clean Out the Undercarriage. ...
iii. Inspect the Undercarriage for Wear or
Damage. ...
iv. Check the Track Tension. ...
v. Inspect Fluid Levels and Filters. ...
vi. Check the Dozer Blade Cutting Edge. ...
vii. Inspect the Electrical System and Battery.
Thank you!
Major components