Popularized in the 1920s and used heavily ever since, the bulldozer, commonly termed a dozer, is a clear offspring of the crawler tractor. Used in conjunction with other earthmoving vehicles, the bulldozer is a powerful and necessary tool utilized in almost every construction site in the world.

Primarily manufactured in the United States by Caterpillar, John Deere, and Case Tractor Company, the bulldozer provides for many industrial applications such as construction, waste management, and farming.

Raw Materials

Bulldozers and crawlers, characterized for their immense blade and versatile track, are comprised of many structural, hydraulic, and engine assemblies. The core body of the bulldozer, consisting of the mainframe and undercarriage, is primarily fabricated from low carbon structural steel plates and a giant casting. The cab contains many glass, rubber, and plastic components which enhance the ergonomic feel of the machine. Supplying the power for the dozer and its various systems, the engine contains many high strength steel parts, which endure high operating temperatures. The other necessary components, the blade, power train, and various systems components, are formed from structural and high carbon steel. The track, which is fashioned from many standard grade steel links, adds to the already tremendous weight of this mostly steel machine. Once the dozer is filled with fuel, hydraulic fluid, coolant, oil, and other types of fluids, its weight increases by several hundred pounds. Decorative trim, decals, and paint complete the dozer's aesthetics and add distinctive appeal.


Two distinct features characterize the bulldozer, the long, vertical steel blade in the front of the vehicle and the rotating twin tracks, which facilitate the bulldozer movement. The blade, which can weigh up to 16,000 lb (7,264 kg), is useful for pushing material from one spot to another. Perpendicular to the ground, the curved blade is attached to the frame by a long lever arm that can tilt and move up and down under hydraulic power.

The familiar flexible track of a bulldozer is widely utilized in industrial machinery equipment and military tanks. In fact, some farming tractors are considered to be cousins to the bulldozer, since they also utilize the flexible track instead of standard wheels. Steel links, sometimes more than 2 ft (61 cm) in length, are connected with lubricated pins to provide for fluid motion and stability. Moreover, many bulldozers have incorporated an elevated sprocket design which suspends the power train, and thereby, improves its reactivity to the terrain. The diesel engine of the bulldozer can generate anywhere from 50-700 horsepower, so rough terrain and steep slopes are not a problem for this machine.

Mounted above the flexible track, the operator cabin contains the complex hydraulic mechanisms, which power the blade in a limited vertical range. The cabin design has seen many improvements in operator comfort and ergonomics and has provided for many improved automotive features, such as air conditioning, AM/FM radio, automatic seat adjustments, electronic controls, and systems-monitoring equipment. In these areas of dozer design, the engineering and research that precedes the manufacturing mimic the automotive industry in many ways.

The power train includes the transmission, differential, and gears that rotate the track. Coupled to the engine crankshaft, the power train will transmit power from the engine to the elevated sprocket gear. Many new bulldozers have independent steering, which allows each sprocket to rotate at full power even while one is rotating slower as the dozer is in a turn. Other innovations in recent years include differential steering, hydraulic power, and planetary gear transmissions.

The Manufacturing

The bulldozer, a seemingly endless network of bulky steel components, complex systems, and intricate assemblies, begins its manufacturing process on an assembly line. Prior to final assembly, much machining, fabrication, and sub-assembly must take place. Manufacturing begins with engineering prints and drawings taken from a computer-aided drafting (CAD) program that outlines the method of construction for each component part. Some of these programs can be used to set up machines for which most of the manufacturing will take place, that is, in fabrication cells, large machining centers, and sub-assembly lines. This is called computer-aided manufacturing (CAM) and is used to produce the components and assemblies that join together on the main line. Some of these components will then undergo heat treating, annealing, or painting after their respective fabrication cell, sub-assembly line, or machining center step. An overhead conveyor system will then transport the pieces through the rough paint or powder coating operation and lift them to the main assembly line, where they arrive in time to be assembled. These pieces may also be transported by lift truck, hand cart, or floor conveyor to arrive at the staging area before they are assembled to the bulldozer.

Mainframe core

Diesel engine and transmission

Radiator and additional assemblies

Large component assembly

As the entire assembly of the frame, engine, transmission, and line groups move along the main production line, larger assemblies and components are brought in by overhead cranes, overhead conveyors, automatic guided vehicles (AGV), or lift trucks. These components include the cab, larger hydraulic cylinders, undercarriage components, and the front blade.

Final assemblies




Waste produced by the manufacturing operations may include machining coolants, oils, parts-cleaning detergents, paint, and diesel fuel. The United States Environmental Protection Agency (EPA) places strict regulations on manufacturers to mandate that these potentially harmful liquids are disposed of in a proper manner. Companies contract a waste removal firm to recycle most of the liquid waste. Metal chips and shavings are recycled and sold to scrap dealers in an effort to reduce waste.

The Future

Bulldozers consistently undergo component design modernization efforts, and innovations appear inevitable. Improvements in cab comfort and diesel engine efficiency will probably be the driving force for many of these changes, while design and operational changes will be limited to individual components. In spite of the fact these enhancements in both the manufacturing process and streamlining of material flow will probably not change the face of bulldozers, costs may improve. Therefore, as a useful member of any earth-moving team, the bulldozer will continue to serve a unique purpose in building construction, waste management, and many industries.

Where to Learn More


D7R Track-Type Tractor Specifications. Caterpillar, 1996.

D9R Track-Type Tractor Specifications. Caterpillar, 1995.

DllR Track-Type Tractor Specifications. Caterpillar, 1996.

Jason Rude

Also read article about Bulldozer from Wikipedia

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