Bulldozer (crawler dozer)

01

Choose the size class

Caterpillar groups its dozers into small, medium and large classes. Its archived specification pages for three models show the spread in power, weight and blade size. [1] [2] [3]

Editorial calculation: the D10 is about 4.2 times the operating weight of the D6N (70,256 ÷ 16,757) and has about 3.6 times the net power (449 ÷ 124).

The US Army field manual FM 5-434, Earthmoving Operations (June 2000), defines a dozer as a tracklaying crawler or wheel tractor fitted with a blade, built for high drawbar pull and tractive effort, and fitted as needed with a rear-mounted winch or ripper. It places military dozers in a light class of about 16,000 lb operating weight and a medium class of 15,000 to 45,000 lb. It advises moving dozers between projects on heavy trailers, because travelling under their own power increases track wear and shortens machine life. [5]

Give the supplier the work (bulk pushing, ripping, grading, land clearing, landfill), the material and ground conditions, the target size class or power, the blade type and capacity, the ripper requirement, the undercarriage (standard, XL or LGP), the emission stage, the cab and guarding requirements, and the dealer and parts support needed.

02

Choose the blade and ripper for the work

FM 5-434 describes a dozer blade as a moldboard with bolted-on, replaceable hardened-steel cutting edges and side bits, which wear quickly. The blade connects to the tractor through push arms and tilt cylinders or through a C-frame. A blade can be tilted (one edge raised or lowered), pitched (top forward or back to change the cutting angle) or, on a C-frame, angled from the direction of travel, and any two of these may be combined in one mount. [5]

The manual gives three blade groups. A straight blade is fixed perpendicular to travel for pushing material and cutting ditches, and can be tilted and pitched within a 10° arc. An angle blade is 1 to 2 ft wider than a straight blade and can be angled up to 25° either side, for side-casting when backfilling, sidehill cuts, rough grading and windrowing; when angled it can be tilted but not pitched. Special-purpose clearing blades such as the Rome K/G cut brush and trees at or just above ground level and are not for earthmoving. [5]

For ripping, the manual recommends first gear and, for one-shank ripping, the centre shank. It suggests three shanks in packed soil, hardpan, shale and cemented gravel, two in fractured rock that breaks into small pieces, and one in solid rock, granite or material that breaks into large slabs. It warns that turning with the rippers in the ground damages the dozer. Its ripping-performance chart for a 300 hp dozer relates rippability to the seismic velocity of the material, and states that tooth penetration is the key to ripping success. [5]

Its production curves for straight and universal blades assume a 60-minute working hour, a 50 ft cut and drift, soil at 2,300 lb per loose cubic yard, and a traction coefficient of 0.5 or better for crawlers. Material factors for crawlers include 1.2 for loose stockpile, 0.8 for hard-to-cut frozen material with a tilt cylinder (0.7 without) and 0.6 to 0.8 for ripped or blasted rock. [5]

Editorial calculation: with the manual's material factors, the same dozer pushing ripped rock at 0.6 to 0.8 achieves half to two-thirds of its output on a loose stockpile (0.6 ÷ 1.2 to 0.8 ÷ 1.2), before grade, weight and operator corrections. [5]

Give the supplier the material (soil, rock, clearing), push distance and grade, required production, blade type (straight, angle, universal or special) with tilt, pitch and angle functions, ripper (shank count) or winch, undercarriage (standard or LGP), emission stage, safety equipment and service support.

03

Match undercarriage to ground, and meet safety rules

Low-ground-pressure (LGP) undercarriages spread the machine's weight over a larger track area. Caterpillar lists a ground contact area of 3.56 m² and a ground pressure of 46.1 kPa (6.7 psi) for the D6N XL, against 5.76 m² for the LGP version. [1]

Editorial calculation: the LGP's contact area is about 1.6 times that of the XL (5.76 ÷ 3.56), so at a similar weight the ground pressure falls roughly in proportion.

In the United States, OSHA 29 CFR 1926.602 lists bulldozers among the earthmoving equipment it covers. It requires seat belts meeting SAE J386, and for bidirectional machines such as bulldozers a horn distinguishable from surrounding noise, operated as needed when the machine moves in either direction. Equipment with an obstructed rear view may not be used in reverse unless it has a reverse signal alarm distinguishable from the surrounding noise, or an employee signals that it is safe. [4]

04

How Caterpillar, FM 5-434 and OSHA figures fill a dozer offer

Treat the production row with care: FM 5-434's curves rest on a 60-minute hour and soil at 2,300 lb per loose cubic yard, so ask the supplier to correct any production figure for your material and grade. [5]

05

Send the job, ground and configuration data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Work: [pushing; ripping; grading; landfill]
Ground: [material; bearing capacity]
Size: [power; operating weight]
Blade: [type; capacity]
Ripper: [single/multi-shank; none]
Undercarriage: [standard; XL; LGP]
Compliance: [emission stage; ROPS/FOPS; alarms]

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