Dozer types and uses

First of all, let’s answer this question: What is a bulldozer? Despite the general public’s perception, dozers are not the machines you see with buckets mounted on sticks digging dirt (they’re called excavators) or rigs equipped with a front end loader (those are called wheel loaders).

Bulldozers are, specifically, tractors equipped with a heavy, front-mounted blade on tracks or wheels.

Despite their relatively simple design, bulldozers – more commonly known simply as 'dozers' in Australia – can be put to a number of tasks across industries such as earthmoving, construction, mining, road building, forestry and agriculture.

To understand what they can do, it is important to know, first and foremost, the types of bulldozers available out there.

By far the most commonly used and seen dozer types are crawler dozers, which use tracks to grip the ground, distribute the machines' weight and help them power through most types of terrain.

As tracks help reduce pressure to the ground, they help dozers stay afloat instead of sinking into softer materials like sand and mud.

Crawler dozers range in size from smaller models for lighter work, medium ones for general grunt-work and larger ones for moving massive amounts of material. The size and power of the models vary between manufacturers, but a general guide is:

As the name suggests, 'swampies' are dozers made or modified to work in swampy, boggy or wet conditions.

Generally, this will involve the provision of extra-wide swamp tracks or LGP (low ground pressure) tracks with triangular or arc-style shoes which further distribute the dozer’s weight and create buoyancy.

Other modifications for use in the wet can include long track frames, a wider machine gauge and the use of waterproof connectors, new relays and injection-moulded instruments.

In situations where you need some speed and manoeuvrability, wheeled dozers will come in handy.

Wheeled dozers can travel up to three times faster than tracked units and are generally more manoeuvrable. However, because the weight is distributed at four points, the machine loses the power conversion and pushing power provided by tracks and won't perform as well on softer surfaces.

These are bulldozers built for serious work in war zones – something that has been going since World War Two.

Among the features on military dozers are armoured cabs, rifle brackets, winches, emergency egress hatches in the roof, and fresh-water fording kits up to 1.5 metres. Some also have foldable blades and removable cabs for easy air transportation and quick deployment.

The blades can be replaced with military-spec work tools such as mine rakes, ploughs and rollers.

Cat has developed a remote-control retrofit for its D7R-II medium dozer which allows combat engineers to operate the machine from 400 metres away (line of sight) while staying safe from enemy fire, improvised explosive devices and the like.

Now that we have covered the different types of dozers, let’s get straight to the main topic - what can we use them for?

Want to push something out of the way? Get a bulldozer.

A dozer's primary function is to perform rough work in applications such as mining, site development and road construction. For this application, dozers are usually equipped with heavy metal blades that are strong enough to move mounds of dirt or other material; tracks that give excellent grip in all conditions; powerful engines as well as a torque divider to convert the engine's power into dragging ability.

Many bulldozers have a long, claw-like device called a ripper on the rear that is used to break up the ground so it can be pushed or scooped away, leaving the ground clear for grading or ploughing.

Rippers can consist of a single shank – or blade – or in a multi-shank configuration of two or more.

It's generally agreed that the easiest way to clear land for agriculture is to use a large bulldozer.

Some ways this can be achieved are: simply pushing over smaller trees; pushing and scooping larger trees with well-established root systems; using chains to uproot stumps and boulders; and using a rake attachment to pull away and clear smaller debris and roots.

This work is often done in tandem with a tracked loader, excavator or backhoe loader. A tilted blade is often used for removing boulders and rocks.

When you want to pull rather than push with your dozer, a winch is the answer. It can be used for a variety of purposes, including load towing, wreck recovery, uprooting stumps and pulling down trees. Two types of winches can be fitted to a bulldozer:

Hydraulic winch: This is driven by the dozer's hydraulic circuit and is ideal for when you need precise line speed control.

PTO winch: If your dozer has a PTO, this will provide faster speeds and more brute force than a hydraulic one.

Bulldozer winches are designed specifically for these machines, with a higher angle of departure than those built for other equipment, and a drum set higher and closer to the dozer. This means the machine can be driven uphill or on to a trailer without scraping the winch frame.

Dozers can be used for pushloading scrapers in situations where, for example, the scraper can't gain enough traction to make a deep cut, or where sandy material causes traction loss. Companies such as Caterpillar make cushion dozer blades designed for this purpose.

Many rural fire departments around the world use bulldozers to build bushfire containment lines. These are essentially dirt paths near fires designed to stop them from spreading further.

Dozers used for this purpose are often more compact models which are able to get as close as possible to the point of origin of a fire.

While blades are often used in this application, some organisations have resorted to rakes instead, which remove vegetation to create a mineral earth control line and leave much of the soil in place. This allows for faster post-fire rehabilitation.

Landfill management is possibly the toughest job a bulldozer can take on, so the machine needs a higher level of protection than normal.

Among the extra features on a landfill dozer are: guards for the radiator, engine compartment, crankcase and tilt cylinder lines; self-cleaning track shoes and protective guarding to prevent refuse from clogging up the undercarriage; blade trash racks; and an additional counterweight with drawbar.

The tracks are matched to site conditions to strike a balance between compaction and flotation.

There are a number of forestry tasks for which dozers are ideally suited, including towing logs, heavy cutting and pushing, and loosening densely compacted materials.

Special features of forestry dozers include: cyclonic air filtration, reversible cooling fans, fire suppression systems, high capacity fuel tanks, protective guarding, winches and auxiliary hydraulics.

Bulldozers are well suited to the spreading of aggregate and preparation of road beds.

Cat recommends the use of a medium dozer equipped with a VPAT (Variable Pitch Angle Tilt) blade, which allow the equipment to move material laterally in a rolling action. "This keeps granular material (such as CA-6) from segregating, providing optimum cohesion and compaction," Cat said.

The company added the VPAT blade is also useful in helping the dozer pull material from the edge of the roadbed or around other obstacles.

While dozers have traditionally been used for bulk work in Australia, with finish-grade or final-trim work being undertaken by graders, the use of 3D machine control technology is now extending the usefulness of bulldozers.

While they still can't handle extremely tight tolerances such as those in applications such as highway construction, dozers equipped with 3D machine control are more than capable of taking on jobs with 20mm-30mm tolerances such as batter slopes and sports fields.

A few years ago, Komatsu released the D375Ai-8 “intelligent” mining dozer. Komatsu Australia Mining Product Manager, Michael Hall, said the iMC version of the earthmover "can carry out both bulk and final trim dozing in fully automatic mode from start to finish, delivering final grade performance and accuracy”.