Crawler v/s Tyre Tractor

Advantage by using crawler mounted tractor

  • More efficient effort, hence can be operated on loose or muddy soil
  • Can easily operate in rocky conditions, as there is no damage of tyres
  • Maintenance of haul road is difficult, it can easily travel, specially in rough terrains.
  • More compact and powerful and hence can handle difficult job
  • Greater flotation because of the lower pressure under the track

Advantage by using wheel-mounted tractor

  • Can travel a higher speed during the operation and also from one job to another.
  • Ease of operation, operator feels less fatigue
  • Can travel paved roads without damaging them
  • Can travel a long distance at its own power, whereas crawler mounted needs trailers
  • When work spread long area, these are found to be producing more output.
  • Operation, maintenance and repair costs less.
  • Initial cost in less

Dozer specification

  • Engine horse power, total operating weight, speed range in various gear positions; blade type and sizes and also the tilt position or angle position, turning radius, fuel tank capacity.
  • Wheel base, ground clearance, size of tyres

Application of dozers

  • Land Clearing: on every project, a bulldozer is the first equipment and its first task is to clear the ground for camp-site, and site for installing various plants.
    • The operation may include, removal of soil to remove unevenness of the ground, removing of trees and stumps including roots, removal of vegetation etc
  • Stripping: its is the removal of top soil that is not usable
    • Minimum distance up to 100m.
  • Sidehill cut: sidehill cut always be started from top and then downwards.
  • Backfilling: in back filling materials is pushed ahead over embankments in to ditches or against a structure.
  • Angle dozer
    • Ditching: the rough ditches can be prepared by the dozers. These are constructed with a straight blade
    • Spreading
    • Dozing rocks and frozen ground
  • Cleaning the quarry pits
  • Digging
  • Breaking pile

Output of dozers

The production of bull dozers mainly depend upon the following factors:

  • Size and condition of the bulldozer
  • Distance travelled by the bulldozer
  • Speed of operation
  • Characteristics of soil being handled
  • Surface on which bulldozer is operating
  • Efficiency
  • When dozing the materials that tend to stick together and remain in front of the blade during dozing, the efficiency is higher as compared to that when dozing loose granular earth or shattered rock. Whereas hard and cemented material needs extra efforts in preblasting or ripping.
  • Output of a dozer in bank-volume/hr.
  • S is swell factor, t= cycle time in minute (time req. per trip)

Swell factor

  • As we know that, loosening of earth causes an increase in volume, which if expressed as a % of original undisturbed volume gives the percentage of swell earth.
  • The ratio of volume of original earth to the loose earth is known as swell factor.
  • Blade factor depends upon the type of soil and generally taken between 0.4 to 1.1 depending upon difficult to easy dozing work.


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