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dozer

1. CHAPTER TWO DOZER

2. INTRODUCTION A bulldozer is a large powerful tractor , also called as crawler tractor (track type or chain type) (track laying) (continuous tracked tractor). Equipped with a substantial (large) metal plate (known as a blade) in front used to push large quantities of soil, sand, rubble, or other such material (flattens areas of ground) during construction or conversion work 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 erroneously/incorrectly/ 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.

3. Cont. Dozers (Tractors) are self contained units that are designed to provide tractive power for draw bar work. Dozers are consistent with their purpose as a unit for a draw bar work; they are low center of gravity machines. This is a prerequisite for a good machine. A dozer is a tractor unit which has a blade attached to its front. The blade is used to push, shear, cut , and roll material ahead of the tractor. The dozer is an effective and versatile earth mover.

4. Function and purpose Dozers are used as both support and production machines on many construction projects, where they may be used from start to finish of the project such as; Clearing land of timber and stumps Moving earth and rock for short haul (push) distances, up to about 300 ft. Spreading earth and rock fills Back-filling trenches Helping to load tractor-pulled scrapers Clearing the floors of borrow and quarry pits

5. Cont. Leveling Dozing

6. Cont. Ripping Land clearing

7. Main components of Dozer Main components Engine Hydraulic System Power train Final drive Cooling System Lubrication System Structures Undercarriage The hydraulic system components include: Hydraulic pump Control valves Hydraulic lines(hoses) Actuators (Pistons) Radiator Core

8. Classification of Dozer Depend on the nature of blade; Front casting Dozer Where the blade is fixed perpendicular to the direction of travel. It moves earth in forward direction.

9. Cont. Angular Dozer Where the blade is fixed at an angle with the direction of travel. It moves earth one side in the forward direction.

10. Cont. Dozer can be also classified based on wheel types. Crawler mounted dozer Wheel mounted Dozer

11. Crawler mounted dozer There is an endless chain or track in place of pneumatic wheel. They are distinguished by a large ground contact area and therefore have a good track adhesion; Such crawler tractors show a high cross-country power and can develop high pull. They are generally used in farms where soils are difficult to cultivate , such as heavy clays , or where seasons are shorter and wet conditions predominate. More power can be transmitted to the drawbar than wheeled tractors. Maintenance costs are however higher than for wheeled tractors. Also, unlike wheeled tractors, they must be transported from field to field by a low loader' . High powered, high speed tracked tractor that runs on rubber tracks and can be driven on the road are also available. This model may make the tracked tractor more popular in future. Tracked tractors have power ratings of 65-700 HP .

12. Cont. Delta drive Oval drive

13. Advantages of delta drive : Due to elevated engine and drive Risk of getting dust (mud) in is less Longer operation (life) time Increased bulk clearance Disadvantages of delta drive: Higher costs of manufacturing More components Longer crawler belt

14. Wheeled dozer Another type of bulldozer is the wheeled bulldozer , which generally has four wheels driven by a 4-wheel-drive system and has a hydraulic, articulated steering system. The blade is mounted forward of the articulation joint, and is hydraulically actuated.

15. Comparison of wheeled and crawler dozer

16. Blades of dozer Made from mold boards which having concave profile. Blades connect to dozer with the help of push arms and tilt cylinders or a C frame. Based on different type of work application the size of blade is varies. Straight Blade (S) Angle Blade (A) Cushion Blade (C) Universal Blade (U)

17. Straight blade(S) Designed and manufactured for the purpose of especially short and medium distance passes, such as backfilling, grading, and spreading fill material. Design of this type of blades have no curvature across their length and are mounted in a fixed position, perpendicular to the dozer’s line/direction of travel.

18. Angle blade (A) An angle blade is wider (face length) by 1 to 2 ft than S blade. It can be angled up to a maximum of 25° left or right of perpendicular to the tractor or held perpendicular to the dozer's line of travel. The blade can be tilted but it can’t be pitched. The angle blade is very effective for side-casting material, particularly for backfilling or making side hill cuts. not recommended for rock or hard digging surfaces.

19. Universal blade (U) Used for moving big loads over longer distances Curved shape and side and top extensions reduce the spillage of loose material Best suited for lighter materials

20. Cushion blade (C) Cushion blades are mounted on large dozers that are used primarily for push-loading scrapers. Rubber cushions and springs in the mounting enable the dozer to absorb the impact of contacting the scraper push block. By using a cushion blade instead of a "pusher block" to push scrapers, the dozer can be used to clean up the cut area and increase the total fleet production. It is a blade of limited utility in pushing material and should not be used for production dozing. It cannot be tilted, pitched, or angled.

21. Blade positions Tilt In some machines either end of the blade can be raised or lowered in the vertical plane of the blade called Tilt. The movement takes place within the vertical plane of the blade. Tilting the blade is done by lowering one end or edge of the blade and lifting the other edge up about the vertical axis of the center of the blade and is useful for ditching and breaking up frozen or crusty soils. Tilting permits concentration of tractor driving power on limited length of blade.

22. Cont. Pitching The top of the blade can pitch forward or backward varying the angle of attack of the cutting edge. It is known as pitch. It is the movement of the top of the blade toward or away from the tractor. Pitching is turning the blade up (pitching backward) or down (pitching forward) about the horizontal axis of the center of the blade and pitching the blade forward reduces blade penetration and causes the loosened material to roll in front of the blade whereas pitching the blade back ward increases penetration.

23. Cont.

24. Angling Angling is moving the blade sideways and is applied when side hill cutting, ditching and moving material laterally sideways is required. All the blades may be tilted except the U-blade, however, only the angle blade may be angled. Turning the blade so that it is not perpendicular to the direction of the tractors travel is angling. This causes the pushed material to roll off the trailing end of the blade. Rolling material off one end of the blade is called “side casting”. This features are not applicable for all blades. Turning the blade in such a way that it is not perpendicular to the direction of the travel .

25. Factor influencing productivity Operating weight. Dozer capacity. Engine model. Engine power. Total length, height and width. Track chain width and length. Travel speed. Attachment (ripper).

26. Bulldozers application Bulldozers can be found on a wide range of sites, Land excavation, road construction etc., Mines and quarries, military bases, Heavy industry factories, Engineering projects and Farms

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