- Dozers are machines designed primarily for cutting and pushing the material over relatively short distances.
- They consists of tractors with front mounted blade, controlled by hydraulic cylinder to vary the depth of cut and rate of levelling depending on the material and applications.
- Rear mounted hydraulic scarifiers and rippers can be fitted to loosen hard material prior to dozing.
- Dozer is a frame mounted unit with a blade, curved in its section, extending in front of the tractor.
- Bulldozer is a most versatile and most important equipment in the construction projects.
- Basically its pushing units, but its widely used as multipurpose equipment and can perform large number of operations with minor changes under different names like; angle dozer, tilt dozer, tree dozer push dozer.
Angle dozer: angle dozer is used to push load at an angle of nearly 250 to the direction of travel of the dozer. This is helpful where the material is pushed down the slope on hill work or where the material to be collected in a long withdraw on one side of the line of travel of the dozer.
Tilt Dozer: used where blade is required to be tilted by rising one end upto 25cm above the other, so as to start excavating a ditch or a trench or for excavation in hard ground.
Push Dozer: used to push the scarper unit during digging or loading operation by means of a rectangular plate, called pusher plate.
Tree Dozer: used to remove the trees.
- A heavy blade is in concave profile is attachment in the front of the tractor.
- Its connected though two arms and a yoks to the tractors.
- The blade has a replaceable cutting edge and controlled by the hydraulic cylinders
- The dozer blade is also known as moldboard and are available in sizes from 2m to 7.5m wide and 0.8 m to 1.5m height.
Different types of dozer blades
U Blade: should be selected for moving large amount of materials over a long distances, and is appropriate for moving dozed materials. These blades are used for stockpile work, tapping for loaders, and land reclamation.
Straight blade: being a smaller then U blade, it is easier to manoeuver. This blade penetrates material easily. Addition of tilt cylinder increases the versatility of this blade. It can move heavy materials more easily.
Angle blade: the angle blade can be mounted straight or angled 250 to either side. It is designed to move material towards the sides of a cut, as required in road construction, backfilling or cut ditches.
Special application U blade: these blades provide the capability to move high volume of light and non-cohesive materials, such as coal, wood, chips etc
Landfill blade: These blades are specially designed to handle refuse and/or fill material. A screen mounted on top of the blade offers good visibility and protects the radiator. The curved moldboard impart a rolling motion to the material being pushed and reduced horsepower demand.
This blade is chosen, when land clearing operations is of primary importance. The blade will cut the tree, pile vegetation and cut drainage ditches.
This is used to shear trees, stumps and brushes at ground level. The two cutting edges form a sharp V and bring full machine power output to bear on the center of the blade. This means the vegetation can be cut and pushed side at a constant dozing speed.
Rake : these are used in land clearing operations. They remove vegetation, including tree, and penetrate soil well. They perform efficiently when removing smaller stumps, roots or rocks. They are generally replaceable.
- All other factors being equal, dozing performance will still vary considerably, depending on the nature of the materials to be displaced.
- The three important characteristics which influence the dozing performance are
- Moisture contents
- Particle size
- If the moisture content falls below the optimum – Particle adheres each others
- If the moisture content increases above optimum – material become heavy
- Negative effect on dozing performance
- Particle making up a specific type of materials has direct bearing on the ability of a dozer blade to penetrate and loosen material.
- Larger particle resist the penetration more then the smaller ones, requiring more dozing power.
- Rounded particles are easy to doze
- Sharp edge and irregular shaped particles are difficult to doze
- Dense materials – few voids- large number of individual particles – close contact
- Close contacts in the particles more force required
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