Dozers

What are these ?

&

What they does ?

Preliminary question

• Preliminary question for the Dozer

• What are relative advantages & application area of CI engines over other types?

• Why Transmission System is needed ? & What are their Basic Types ?

A Wheel Dozer

A track Dozer

What are These ?

• Tractor Power Unit

• Blade Attached at the Front

• HAS NO SET VOLUMETRIC CAPACITY

• To push Earth less than 100 meters

What are These ?

• To provide Tractive Power for Draw Bar Pull

• Low centre of Gravity Machines – For Work ?

• Line of force Transmission from the Machine TO line of Resisting Force

• Dozing, Land Clearing, Ripping, Towing, Assisting Scrapper in Loading

Attachments

• Rear mounted Winch

• Rear mounted Ripper

Types

• Crawler ( Track Laying Type)

• Wheel Type

– Constructional difference is mainly types of Traction acquired to perform work.

Crawler Dozer

• Have a continuous TRACK of linked shoes that moves in the horizontal plane across the rollers

• Track passes over a vertically mounted SPROCKEK DRIVE WHEEL at rear

• Sprocket forces the track• Track passes over a vertically mounted IDLER

WHEEL at front.• - Connected to recoil device ( Mostly Recoil

Spring) having adjusting tension• -Enables to Absorb the shocks

Part of Track Chain

Crawler Dozer….

• Breaking & Steering Actions are combined

• Steering by Reducing the force hence the speed of ONE SPROCKET

• Breaking by Reducing the force hence the speed of BOTH SPROCKET

Wheel Dozer

• Have all powered four Wheel

• Wheels used for Breaking as in Vehicle

• Steering achieved by Articulation between Front and Rear portion of the Equipment

Useful Force for Work

• As discussed in “Machine Power”

• Useful Force for Work is often limited by Traction, dependent on

• 1. Coefficient of Traction of the Surface being Traversed

• 2. Weight carried by the drive wheels

Traction or Floatation

– By proper selection of Undercarriage or Tire

• Undercarriage:

• Standard: for rock to moderately soft ground ( 6 to 9 psi)

• LGP (Low Ground Pressure): for soft ground ( 3 to 4 psi)

• XL ( Extra long ): for finish work

Traction or Floatation….

• Wheel :

• For Tyre Ballast - Mixture of Calcium Chloride & Water

• Wider Tyre increase Floatation

• Rimpull Chart based on Standard Equipment, including tyres

• Wheel Dozers exerts high ground pressure : 25 to 35 psi

Track vs. Wheel Dozers

• Track type for High Tractive Force

• Wheel type for Higher Speed up 40 Kmph

• But it sacrifice Pulling Effort for Higher Speed

• Has low Coefficient of Traction between Rubber tyres and some ground Surfaces

• It may slip before developing full pulling Effort

Versatility of Crawler Dozer

• Mainly designed for High Tractive Force

• It is the Most versatile equipment for Requirement of Power, Traction and Flotation in Varieties of Working Conditions.

• It Can operate steep slope up to 45 degree

Specification of Dozer

– Dozers are Rated by

• Flywheel Horsepower ( HP) &• Operating Weight ( Ton)

– Which include all fluids, ROPS & Operator– – Operating Weight is Important Because

• Maximum Tractive effort: Wt. x Coff. of Traction– Regardless of power supplied by the Engine

Power Plant for the Dozer

• Mostly CI Engines are used

• Why CI Engines are used ?

• SI engines are rarely used in some small Dozers

• Even Electric and air powered dozers are used for Tunnel Work

Transmission Systemsfor the Dozer

• Why Transmission Systems is needed ?• What are their Basic Types ?

– Basic Types

• Hydrostatic Power Trains

• Direct Drive systems

• Torque Converter with Power Shift Transmissions

Hydrostatic Power Trains

• For small less than 100 hp dozers

• Confined oil under pressure

• Infinitely variable speed range with constant power to both the tracks

• Better Machine Control

• Better Operational Efficiency

Direct Drive systems

• Power Transmitted straight through the Transmission ( as Single shaft)

• Good for constant load conditions

• More useful for always full blade load for long distances

Torque Converter with Power Shift Transmissions

• Transmissions that can be shifted while transmitting full engine power are known as POWER SHIFT.

• These are coupled with Torque Converter

• Which absorb Drive Train Shock Loads

• Efficient flow of Power: Engine to Tracks

• Good for Variable load Applications

• Being used for most Wheel Dozers

Performance of Track Dozer having Power Shift Transmissions

Performance of Track Dozer….

– To be noted

• For First Gear Operation – Speed Range is 0 to 2.3 Kmph

• Draw Bar Pull varies • from 67000 lb at 0 Kmph to 0 lb 2.3 Kmph• For Third Gear Operation

– Speed Range is 0 to 11 Kmph

• Draw Bar Pull varies • from 23000 lb at 0 Kmph to 0 lb 11 Kmph• The Graph is not Linear

Performance of Wheel Dozer having Power Shift Transmissions

Performance of Wheel Dozer….– To be noted

• For First Gear Operation – Speed Range is 0 to 6 Kmph

• Rim Pull varies • from 24000 lb at 0 Kmph to 0 lb 6 Kmph• For Forth Gear Operation

– Speed Range is 0 to 33 Kmph

• Rim Pull varies • from 400 lb at 0 Kmph to 0 lb 33 Kmph• The Graph is not Linear

Comparison of Performance

• Usable pull depend on the

• Weight and Traction of the Dozer

• All of the Pull of the Engine may not be available to do the work

• E. g. for Dry Clay Loam

• Coefficient of Traction for Tyres: 0.5 to 0.7

• Coefficient of Traction for Track: 0.9

Comparison of Performance..• For 45560 lb Track Dozer The usable draw

bar pull • 45560 lb x 0.9 = 41004 lb• For 45370 lb Wheel Dozer The usable rim

pull • 45370 lb x 0.6 = 27222 lb

• Because of effect of Traction, The Track Dozer can supply one and half times USABLE POWER then Wheel Type

Traction Problem for Wheel Dozer

• As in example for most types of soil

• The Coefficient of Traction for Wheels is Lesser than Tracks

• Hence for Given amount of Usable Power Wheel Dozer should be considerably larger (≈ 50 % higher) than the Crawler Dozer of Same Weight.

BLADES of the Dozer

The main working TOOL

Introduction of BLADE

• Attached to the Machines Front

• Used to PUSH, SHEAR, CUT & ROLL material ahead of the dozer

• Blade operation of dozer used both for

• 1. Production Machines &

• 2. Support Machines

BLADE Features

– Blade consists of

• MOULD BOARD, replaceable CUTTING EDGES & SIDE BITS

• Blade is connected with the Dozer either of one• 1. PUSH ARMS & TILT CYLINDERS• 2. C – FRAME

• Cutting Edges & Side Bits are made of Hardened steel to face Abrasion & Wear

BLADE Operations - Tilting• Either end of the Blade is raised or lowered

in the Vertical Plane of the Dozer

• Enables the concentration of dozer driving power on the limited portion of the blade’s length

• Tilting for Increasing Penetration for Cutting or Decreasing Penetration for Backdregging

Tilting

BLADE Operations - Pitching• The top of the blade can be pitched forward or

backward

• Which varies the angle of attack of the cutting edge.

• It is the pivotal movement about the point of connection between the dozer and the blade

• The ability to pitch means that the operator can set the cutting edge to dig hard material

• Or move the edge’s plane of attack to ease the drifting of light materials.

Pitching

BLADE Operations - Angling• Turning the blade so that it is not

perpendicular to the direction of the dozer’s travel

• Normally it is perpendicular to …..• Angling causes the pushed material to roll

of the TRAILING END of the blade.• This procedure is called SIDE CASTING

operation• Any TWO of the above features are

incorporated in one dozer

Angling

Blade Performance

• The dozer’s PUSHING POTENTIALS are measured by two standard ratios

• 1. Horsepower per Meter of Cutting Edge. ( HP/ m)

• 2. Horsepower per loose Cubic Meter of Material retained in front of the blade.

Blade Performance…• 1. Horsepower per Meter of Cutting Edge. ( HP/

m)• Indicates the ability of the blade TO PENETRATE

& OBTAIN A LOAD.• Higher the Ratio more Aggressive the blade

• 2. Horsepower per loose Cubic Meter of Material retained in front of the blade.

• Measures the blade’s ability to push a load• Higher ratio means, the dozer can push a load at

greater speed.

Basic Operation & Basic Shape of Blade

• Blade is raised & lowered by Hyd. Rams

• Hence A Positive Downward Force can be exerted

• Basic Earth Moving Blades are curved in the Vertical Plane in the shape of the FLATTENED C

The use of FLATTENED CShape

• When the Blade is Pushed Down, the Edge Cuts into the Earth.

• As the Dozer Moves Forward, the Cut Material is Pushed Up the Face of the Blade.

• The Upper Part of Flattened C Rolls this Material Forward.

• The total effect is to BOIL the Pushed Material Over and Over in front of the Blade.

• The Flattened C Shape provides the necessary Cutting Angle for the Edge

Effect of the Weight of the Cut Material

• At the Beginning of the Pass, this Wt. is on the Lower Half of the flattened C

• Helps to achieve EDGE PENETRATION.

• As the push progress, this Wt. passes the Mid Point of the C & begins to Exert an Upward force on the Blade.

• This FLOATS the blade reducing the Penetration of the Cutting Edge.

• Which is Required to Limit the Load

The Dozing Operations

The Dozing Operations…

Types of Blades• Many different Special Application Blades

• Basically FIVE Blades are Common to Earth work

• 1. The Straight Blade ( S Blade )

• 2. The Angle Blade ( A Blade )

• 3. The Universal Blade ( U Blade )

• 4. The Semi Universal Blade ( SU Blade )

• 5. The Cushion Blade ( C Blade )

1. The Straight Blade ( S Blade )

• For Short & Medium Distance Passes like• Backfilling, Grading and Spreading fill Material• Have no Curvature in their length• Are mounted in a fixed Position perpendicular to

the Dozer’s line of Travel.• Generally it is Heavy duty.• Normally can be tilted 10 Deg. Arch.• May be equipped to Pitch.

( S Blade )

2. The Angle Blade ( A Blade )

• Wider by 1-2 feet than S blade• Can be angled 25 deg. Left or Right• Can be used as S blade too• It can be tilted• But can not be Pitched. Reason ?• It is attached to the Dozer by C frame not by

Push Arms• Very Effective for side casting materials like• Backfilling or• Making Sidehill Cuts

( A Blade )

3. The Universal Blade ( U Blade )

• Wider than S blade• Outside edges are Canted forward 25 deg.• Which controls spillage sidewise, Hence• Good for – Large Volume loads over Long

Distances and Where Penetration is not Prime Objective, Material is Light. So

• HP/ft. of U blade is lower than S blade• HP/l. cubic m. is also lower than S• Mostly used for stockpiles

( U Blade )

4. The Semi Universal Blade ( SU Blade )

• This combines the Characteristics of S & U blades mainly

• Large load of U &

• Penetration Capacity of S

• Has increased capacity by the addition of short wings

5. The Cushion Blade ( C Blade )

• Mostly large dozers are used to push the PUSH LOADING SCRAPPERS

• Either Pusher Block or C Blade is used in such dozers to Push.

• By Use of C blades

• The same dozer can clean up the Area Cut by Scrapper

• Thus increases the Total Fleet Production

The Cushion Blade ( C Blade )…

• C Blade Shorter than S blade for two benefits• 1.To avoid cutting of rear tyres of scrapper• 2. Ease of Maneuvering of dozer behind the

scrapper• There are rubber Cushions & springs in the

Mountings• Enables to Absorb shock by Push Block of

Scrapper• C Blade CANNOT BE Tilted, Pitched or Angled• Hence should not be used for Normal Production

Dozing

( C Blade )

Dozer Operations

The Methods of Dozer Production

Basic Dozer Operations

• Some of the Basic Dozer Operations are

• Stripping• Sidehill Cuts• Ditching• Backfilling• Dozing Rocks or Frozen Grounds• Spreading• Slot Dozing• Blade to Blade Dozing

Dozer Operations - Stripping

• Most often used Operation• Removal of Thin Layer of Materials generally

TOP SOIL of Earth• As in most of the Cases Push Distances has to

be Minimized• Economical Push Distance is ≤ 100 m• Cohesive material ( Clay content) easy to push• Granular material ( Sand content) difficult to push• For Distance is ≥ 100 m, Scrapper to be Used

with Dozer as Support Machine

Dozer Operations - Sidehill Cuts

• For steep ground working, • Excavated materials is pushed over the

side of the hill to develop working table• First passes are made perpendicular to the

long direction of the project• Initial passes of small load with short

distance to be utilized to crate bench. Than……

• Situations to be created to take advantage of the Gravity

Dozer Operations - Ditching

• Only for rough ditch sections

• Dozer pushes material out of the cut by working perpendicular to the line of the ditch

• Small shallow ditches are cut by Grader

• Large deep ditches are cut by Excavator

• Scrappers are also used

Dozer Operations - Backfilling

• Done by drifting materials sideways with an Angle Blade during Forward Motion parallel to the excavation.

• For S blade, the dozer will approach excavation at an angle, at the end of the pass, turn in toward the excavation.

• Caution: Passes across pipes and culverts to be made with min. 12 in material cover

Dozer Operations – Dozing Rocks or Frozen Grounds

• The blade must be worked under the material to be moved by Tilting the corner of the blade

• To maximize the driving force of the blade, hook only the tilted end

• Blade may be used as pry bar to lift the rock – Once blade in contact beneath the rock, Dozer driven forward with blade slowly lifted

• A track machine can often crush soft materials by running over it like soft rocks and sand stone

Dozer Operations - Spreading• Common Dozer Task• Density requirement & proposed compaction

equipment need to control the LIFT thickness & Uniformity

• It is done by keeping the Blade Straight and at the desired height above the previously placed fill surface.

• The dumped material is forced directly under the blades cutting edge

• For semi skill, cross passes can be made• Nowadays, laser blade controls are available

Spreading

Dozer Operations - Slot Dozing

• A Technique to increase production• Blade end spillage from the First Pass is

used to hold material in front of the dozer blade on subsequent passes ( sidewalls from the previous cut too)

• Leave a narrow UNCUT section between slots

• Prevents spillage at each end of the blade• Increases prod. by about 20 %

Dozer Operations – Blade to Blade Dozing

• Also referred as SIDE BY SIDE Dozing• During the Pushing Phase, two machines

maneuver so that their blades are right next to each other

• Reduces the side spillages by 50 %• But extra time needed to position machines• Hence not effective for pushes less than 50 feet• In general trade of between Less Spillage & More

maneuver time results in 15 to 25 % increase in production

Blade to Blade Dozing

Dozer Production Estimating

How much it Yields ?

Dozer Production Estimating

• Dozer has no set volumetric Capacity

• There is no hopper of bowl to load

• Production is the Quantity that will remain in front of the blade

Factors controlling Dozer Production

• The factors that control dozer production rates are

• Blade type

• Type & Condition of Materials

• Cycle Time

Effect of Blade Typein Dozer Production

• S blades roll material in front of the blade• U & SU blades controls the side spillage by

forcing the materials to move to the centre, hence there is greater Swelling.

• This makes difference in conversion factor bcu. m to lcu m

• Same type of blade comes in diff sizes to suit the type of materials

• Blade capacity is function of Blade Type & Physical Size.

• Manufacturers spec sheet give blade dimension

Effect of Type & Condition of Materials

in Dozer Production

• The Type & Condition of material affects THE SHAPE of the pushed mass in front of the blade

• Cohesive materials (Clays) will BOIL & Heap• Materials that exhibit Slippery quality ( or with

high Mica) will ride over the ground & Swell• Cohesionless materials (sand) known as

DEAD materials neither Heap nor Swell

Effect of Cycle Time in Dozer Production

• Sum of the time required to PUSH, BACKTRACK & MANEUVER into position to push represents the complete DOZER CYCLE

• Generally Dozing at slow speed 2 to 4 Kmph, lower figure for Cohesive materials

• Return speed is usually the maximum that can be attained in the distance available

• Longer the distance higher will be the speed, second gear will not be used for less then 100 ft

• Maneuver time for power shift dozer ≈ 0.05 min

Calculation of Blade Load

• The load a blade will carry can be estimated by several methods e. g.

• 1. Manufacturer’s Blade Rating.– Formula as per SAE Practice J1265

• 2. Previous Experience– (Similar material, equipment & work condition)

• 3. Field Measurements.

Field Measurements for Calculation of Blade Load

• This is Commonly used method• 1. Obtain a Normal Blade Load.

– A. Push a normal blade load into a Level Area– B. Stop the dozer’s forward motion. While rising the move forward

slightly to create a Symmetrical Pile.– C. Reverse and move away from the pile.

• 2. Make Measurements– D. Measure the height (H) of the pile at the inside edge of each

track.– E. Measure the width (W) of the pile at the inside edge of each

track.– F. Measure the greatest length of the pile. This will not necessarily

be at the centre

• 3. Make Calculations

Blade Load Measurements

Dozer Production Calculation

• Once Blade Load & Cycle Time is Known• Production in Loose Cubic meter per hour

• 60 min. x Blade Load• = -----------------------------• push time + return time + maneuver time • Blade Load in Loose Cubic meter • Times in Minutes

Production Curves

• Production Curves are for estimating the amount of materials dozer can push.

• These are published in PERFORMANCE HANBOOK of dozer mfg. Company

• A PRODUCTION NUMBER taken from the Performance Curve is a Maximum Value in Loose Cubic Meter per Hour based on a set of IDEAL CONDITIONS as follows

IDEAL CONDITIONS forProduction Curves

• 1. A 60- min hour ( 100% efficiency)• 2. Power shift machines with 0.05- min fixed

time• 3. The machine cuts for 50 ft. then drifts the

blade load to dump over a high wall• 4. A soil density of 2300 lb per lcy• 5. Coefficient of Traction:

– Track Machines -0.5 or better– Wheel Machines -0.4 or better

• 6. The use of Hydraulic Controlled blade

Use of Production Curves• Production Curves are used to Calculate

Field Production Rates• For this, the curve values must be adjusted

by the Correction Factors for EXPECTED JOB CONDITIONS.

• Correction Factors from Mfg.’s List

• Production• = (Maximum Production from the curve) x

( Product of Correction Factors)

Production Estimating Curves for Dozers Equipped with S Blade

Production Estimating Curves for Dozers Equipped with U Blade

Grade vs. Dozing Factor

RIPPING ROCK

One Common Use of Dozer

Ripper

• Ripper –a new narrow profile implement• It penetrates the earth and pulled to loosen and

split hard ground weak rock or old pavement and bases

• Heavy ripping- by crawler dozer with rear mounted ripper– Because of high power and Tractive force

• Light duty ripping graders equipped with rippers (commonly called scarifier in Nepal)

• Alternate to ripping-drilling, and blasting.

Determining the Rippability of Rock

• For selection of method of excavating and hauling rock

• Question- can be ripped or should be drilled and blast.

• Involves study of rock type and a determination of rocks density.

• Why this needed for Mech. Engineers ?• Ripper production calculation based on

type of rock indicated by seismic velocity.

Rippability of Rock by Types

• Igneous rocks ( granites and basaltic types) -cannot be ripped

• Sedimentary rocks have a layered structure and can be ripped.

• Metamorphic rocks (Igneous, quartzite, schist and slate- changed form of igneous of sedimentary)

• Vary in Rippability with their degree of lamination or cleavage.

Rippability Characteristics

• Physical Characteristics that favor ripping are.• Fractures, faults and joints all act as planes of

weakness facilitating ripping.• Weathering, the greater the degree of

weathering the more easily the rock is ripped • Brittleness and Crystalline structure • High degree of Stratification or Lamination in

rock.• Large grain size, coarse grained rocks

Rippability Indicator

• Rippability of most types of rocks is related to the speed at which sound waves travel through it.

• Refraction Seismographic methods is used for determination this

• Rocks that propagate sound waves at low velocities(<7000 ft/sec) are rippable.

• For >10,000 ft/sec not rippable• For between 7000-10000ft/sec are marginal.

Ripper Performance Chart

• Fig 6.19 indicates Rippability for specific size Dozer based on Sound Velocity ranges for various types of soil and socks.

• Information should be supplemented with other data such as boring logs or core samples.– Decision to rip or not to rip rock based on.

• 1. The relative cost of excavating using the methods under consideration.

• 2. Equipment available.

Ripper as Attachment

• Rippers are generally rear mounted.

• The mounting types are – Fixed radial – Fixed parallelogram– Parallelogram linkage with hydraulically

variable pitch.

Main parts of Ripper

• Shank and

• Tip

• Shank - the vertical piece that is forced down into the material to be ripped

• Ripper Tip (a tooth, point or tap)- fixed to the lower cutting end of the shank

Ripper Tip

• Ripper Tip (a tooth, point or tap)- fixed to the lower cutting end of the shank

• Is high wear surface of ripper

• Hence made detachable for easy replacement

• Service life may vary 0.5 to 1000 hr

• Hence needs care to note the Factors of High Wear

Shank• Shank are pinned into position on the ripper frame

for – Ease of removal for material and project requirementsShank types

• Straight Shank• Curved shank

• Straight Shank – for massive or blocky formations

• Curved Shank – for bedded or laminated rocks or for pavements– It’s lifting action will help shatter the material

Ripper Types

• Fixed Radial Ripper

• Parallelogram Type Ripper

Fixed Radial Ripper

• With this the beam of the ripper pivots on link arms about it’s point of attachment to the dozer

• The angle of tip attack varies with the depth the shank is depressed

• May make it difficult to achieve penetration in tough materials.

• This may also tend to Dig Itself In

Parallelogram Type Ripper

• Maintains the shank in vertical position and keeps the tip at a constant angle

• Adjustable type enable tip angle to be controlled by the operator hydraulically

No of Shank in Ripper

• Single Shank or Multi Shank• Number of shanks used depends upon size of

the dozer, the depth of penetration required the resistance of the material being ripped and the degree of breakage of the material desired.

• Up to 5 shank for smaller dozer up to 3 shank for large dozer

• For heavy work (high seismic velocity material) single center-mounted shank will maximize production. But rolls individual oversized pieces to the side.

No of Shank in Ripper…

• Two shanks can be effective in softer easily fractured materials that are to be scrapper loaded.

• Three shanks for very easy to rip material like hardpan or some shales.

• Multiple shank will produce more uniform breakage of Rock

Effectiveness of a Ripper

• The effectiveness of a ripper depends on

• 1 Down pressure at the ripper tip

• 2. The dozer’s usable power to advance the tip – Which is a function of – Power available, Dozer weight and Coefficient

of Traction.

• 3. Properties of material being ripped, laminated faulted, weathered and so on

Dozer size for ripping

• Sizing the dozer for ripping operation-rule of thumb

• 1 hp per 100 lb of down pressure

• 3 lb of machine weight per lb of down pressure -this is to ensure adequate traction

Ripping Production Estimates

• Generally excavating rock by ripping and scraper loading is less expensive then drilling, blasting, excavator loading and truck hauling.

• If possible estimating should be done by working a test section and conducting a study of the operational methods and determining production by weight of ripper material.

• If not possible, initial estimates can be made based on equipment manufacturer’s Ripping Production Charts.

Quick Method - Ripping Production Estimates

• An average cycle time is determined by the timed cycles

• The quantity (volume) of ripped Volume is taken ( L x B x H)

• Since such method gives about 20% more volume then accurately cross-sectioned study

• Ripper Production (bcm/hr)• = (measured volume in bcm)/ (1.2 x average

time in hr)

Seismic-Velocity Method – Ripping Performance Charts

• Relationship developed between Seismic Wave velocities and Rippability.

• These Ripping Performance Charts of particular Equipment enable to make an initial determination of suitable equipment to be used

• It is mainly based on General Rock type classifications.

• After that production rates for the particular machines are calculated from Production Charts of particular Equipment

Ripping Production Charts

• Are developed for Particular Model Equipment.• Developed from field tests conducted in a variety

of materials.• Because of extreme variations of materials

subjective judgment is needed while using these• To reflect to actual field Conditions of the Project• Increase in O&O cost due to ripping• Ripping may increase 30 to 40% of normal O &

O costs due to heavy ripping work

Ripper Operation Techniques

• Ripping should be done at the maximum penetration depth that traction will allow.

• Uniform depth to be maintained during ripping.

• For economy ripping to be performed at low gear and low speed.(1to 1.5 mph)

• Even slight increase in speed may increase the operation cost dramatically due to very fast Ripper Tip Wear

Ripper Operation Techniques…

• When removing the ripped material 4 to 6 in Cushion Material Should be left

• That will create better underfoot conditions for dozing and reduce Track Wear during subsequent Passes of Dozer.

• Downhill ripping will take advantage of gravity.• Cross Ripping will increase scrapper tyre wear• Cross Ripping is preferred to break up hard

spots or material that comes loose in large slabs.

SUMMARY – DOZER

• Dozers are used for• dozing (pushing materials), • land clearing, • ripping, • assisting scrappers in loading and • towing other pieces of construction equipment.• The factors that control dozer production rates are (1)

blade types (2) type and condition of materials (3) cycle time. Manufactures provide production curves for estimating the amount of material their dozer can push. The curves provide a maximum value in lcy/ lcm per hour based on a set of ideal conditions

SUMMARY – Dozing Operation

• The factors that control dozer production rates are

• (1) blade types • (2) type and condition of materials• (3) cycle time. • Manufactures provide production curves for

estimating the amount of material their dozer can push.

• The curves provide a maximum value in lcy/ lcm per hour based on a set of ideal conditions

SUMMARY – Ripping Operation

• Heavy ripping of rock is accomplished by crawler dozers

• equipped with rear mounted rippers

• because of the power and Tractive force available .

SUMMARY- Rippability &Ripper Production

• A refraction seismograph can be used to determine the thickness and degree of consolidation of rock layers at or near the ground surface

• Manufactures have developed relationship between seismic wave velocities and Rippability

• Additionally, there are manufacture ripping production charts that have been developed from field tests.

Learning Objectives- Dozer

• Critical learning objectives related to Dozer are

• 1. An ability to calculate dozer pushing production

• 2. An ability to calculate dozer Production for ripping operations.

Thank you