1. Bulldozer
   • Examples

Bulldozer

Usually called bulldozer whether blade is straight or angle.

Basically a tractor with a blade accessory added. The blade may tilt, pitch, angle or be cushioned to push-load scrapers (see pgs 107 & 108, textbook)

Classifications (pgs 107-108, textbook):

~ bull (straight) or angle blade

~ cable or hydraulically controlled blade

~ crawler or wheel tractor (see comparison in Table 5-1, pg. 98, textbook)

~ horsepower/ft cutting edge - measure of hard soil penetration

~ horsepower/lcy - indication of a loaded blade’s push capabiliity

Uses:

~ land clearing (pgs. 118-132, textbook)

~ striping top soil (not suitable for fill)

~ pioneering cuts or trails

~ moving earth short distances ( < 300 ft)

~ spreading earth to rough grade

~ backfilling

~ rough ditching

~ "pusher duty" for loading scrapers

Production estimating considerations:

~ material type

~ blade load capacity (avg. load on blade)

~ manufacturer’s rating or data on blade

~ estimating blade capacity (assuming 2:1 slope)

~ cycle time:

1) fixed time (avg. shifting time)

-power shift: 0.05 min (automatic)

-direct drive: 0.10 min (manual)

2) variable time:

- dozing: 120-220 fpm (feet per minute)

-return (reverse): 220-400 fpm

~ working efficiency: 50 min/hr operating factor, etc.

Examples

Example: Bulldozer production

~ material: loose soil

~ haul distance: 75 ft

~ crawler tractor: with power shift & straight blade

~ blade capacity: 8 lcy

~ haul: 2nd gear, 2.0 mph

~ return: 2nd gear, 3.5 mph

Production in lcy/60 min working hr (ideal)

~ fixed cycle time: = 0.05 min

~ haul time - 75 ft/(88 fpm/mph x 2.0 mph): = 0.43 min

~ return time - 75 ft/(88 fpm/mph x 3.5 mph): = 0.24 min

~ total cycle time: = 0.72 min

Expected production in bcy/hr

~ swell: 25%, calculate load factor

~ load factor (lf): = 1/(1 + swell) = 1/(1 + .25) = 0.80

~ operating factor: 50 min work/60 min = 0.83

~ production: = 667 lcy/hr × 0.8 bcy/lcy × 0.83 = 443 bcy/hr

Unit cost of dozing

~ O & O costs: w/operator = $31/hr

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