Grading and Excavation Contractor

Comment On This

Create A Link
To This Article
On Your Website

From moving earth in wide-open spaces to grading within inches of a house foundation, the current lineup of crawler dozers for construction and finish duties offers a wide range of power, comfort, and convenience features to make your job easier and the results more profitable.

Greg Northcutt

Check out the selection of new crawler dozers on the market today, and you’ll find that manufactures have focused much of their efforts to boost the performance and value of these earthmovers in three key areas—increasing machine productivity, enhancing operator comfort, and reducing the time and money needed to service and maintain these machines.

Depending on make and model, these latest machines are designed do more work in less time than ever with such features as no-shift hydrostatic transmissions, dual-track power for pushing loads while turning, and more efficient blade designs. Such advances as isolation-mounted operator platforms, ergonomically designed joystick controls, and programmable speed control mean more comfortable operation. Meanwhile, more fuel-efficient engines, self-adjusting brakes and extended service intervals help lower operating expenses.

Today’s state-of-the-art dozer technology represents manufacturers’ years of experience in designing and building dozers. That includes the newest name in the business, Dressta. This 15-year-old company is the successor to the long-established Dresser and International Harvester brands of dozers and other construction equipment.

From the operator’s seat, it’s easy to overlook the hurdles manufacturers face in engineering these machines. One of the bigger ones is meeting the desires of today’s operators.

“Creating a heavy-duty product for moving earth and rocks safely, efficiently, and comfortably that offers amenities similar to those of today’s automobiles is a formidable challenge,” says Bernie Winker, manager of marketing and engineering services for Dressta North America. “These operators wouldn’t think of shifting their car into reverse while driving at highway speeds. However, they’ll push a dozer forward under full load and instantly put the drive lever in reverse without even reducing power. Imagine designing the power train and undercarriage on a dozer to stand up to the stresses of this type of work.”

The continuing quest by profit-minded equipment owners for ever more cost-effective machines also contributes to advances in dozer performance. So have the EPA’s clean-air requirements, which have spurred innovations in the technology of engine, transmission, and cooling systems.

While dozers range in size from less than 100 horsepower for finish work in tight areas to mammoth 500-horsepower-and-greater mining machines that can make molehills out of mountains, those used in most grading and excavating applications generally are in the smaller to mid-size category. These include the smaller 70-horsepower to about 100-horsepower models typically used for residential grading and backfilling work, and larger machines up to about 200 horsepower for dozing, grading, and slope work on commercial developments and road construction projects.

Here are some of the specific features you’ll find as you size up the current models of dozers for your grading and excavating projects.

Improved Engines
To meet the EPA’s requirements for reducing hydrocarbon and nitric oxide emissions, 100-horsepower and larger diesel engines must now be Tier 3–certified. (Diesel dozer engines between 50 horsepower and 100 horsepower must be Tier 3–certified by January 2008.) To meet these requirements, manufacturers have introduced such improvements as more accurate electronic fuel-injection systems and more effective combustion. Caterpillar’s new D6K track-type tractor, for example, is equipped with a 125-horsepower engine that offers an advanced electronic controller and common-rail fuel injection for precise fuel delivery. This, in turn, improves lugging performance while lowering emissions. “Constant net horsepower ensures peak engine power is available for the drive train and implements even in high ambient temperatures,” says Paul McKneight, mid-size dozer marketing manager for Caterpillar.

Engines on many of the new dozers are also equipped with electronically controlled, hydraulically driven, engine-cooling fans that automatically speed up or slow down as needed, depending on engine coolant and hydraulic oil temperatures. This saves on power and fuel, compared to a belt-driven fan. Also, it reduces wear of the radiator core and lowers noise levels. Besides adding to operator comfort, a quieter machine makes communication on the job site easier and can help comply with any local restrictions on ambient noise levels at the job site.

Drive-Train Developments
Many of the new dozers built for construction and finish work come standard with joystick-controlled, no-shift hydrostatic transmissions. Instead of a torque converter and a gear box, they use hydraulic fluid, pumps, and motors to transmit engine power to the tracks.

The hydrostatic drive on the new Case K-series crawler dozers, for example, is controlled by a single left-hand lever. This system includes electronic straight tracking, which eliminates the need to cross-steer or ride the brakes to travel forward or reverse in a straight line. “To move forward, you push the lever forward,” says Jim Hughes, the company’s brand-marketing manager. “For reverse, you pull the lever backward. It’s an intuitive control.”

Hydrostatics are also used to control steering on both hydrostatic drive dozers and those with torque converter transmissions. The same left-hand lever used to control forward or reverse direction is also used to steer the dozer. To turn the machine, you tip the lever to one side. In the process, one track speeds up and the other slows down. That’s a big advantage over the clutch-and-brake steering system used with mechanical transmissions. In that case, power is disconnected from the inner track, leaving only the outer track with power for pushing dirt with the blade. By contrast, hydrostatic steering keeps all power going to both tracks for maximum traction and power throughout the turn.

The hydrostatic drive on Case dozers uses hydrostatic pumps and large drive components to deliver power to both tracks. “This dual-path drive is engineered to maintain a two-to-one power ratio speed when steering,” Hughes explains. “There’s no need to brake or lift the blade to lighten the load when turning. It makes the dozer easy to run, improving productivity, reducing operator fatigue, and lowering operating cost per cubic yard.”

For maximum maneuverability, you can push the steering lever of hydrostatic transmissions all the way to the right or the left to counter-rotate the two tracks and turn the dozer within its own length.

Other advantages of hydrostatic transmissions include fast response to controls, the ability to maintain a given speed under varying loads, and infinitely variable speed control throughout the machine’s speed range.

Among other functions, John Deere’s hydrostatic drive train offers automatic load sensing.

“By adjusting the speed-selection button, you can choose the highest speed that you want to work in, and the tractor automatically adjusts speed to match the load up to that speed,” says Dan Drescher, Deere’s crawler dozer marketing manager.

Caterpillar’s new hydrostatic drive system allows you to program forward and reverse speeds independently, simply by pressing a button. This allows you to quickly recall a speed to best meet specific ground and job conditions.

Komatsu’s hydrostatic drive system offers two operating modes. Performing like a three-speed transmission, the quick-shift lets you downshift to get an immediate increase in tractive effort when dozing large loads, reports Chuck Murawski, product manager for Komatsu dozers. The variable-speed mode operates like a 20-speed transmission for fine speed control while grading.

Today’s dozer represents years of design experience.

Undercarriage and Track Performance
The durability of dozer undercarriages continues to increase. The undercarriage of Caterpillar’s new D6K crawler dozer features an oscillating-track roller frame, designed to keep more of the track on the ground in uneven terrain. The result is a more stable machine, less ground shock to the operator, and a smoother, more comfortable ride, notes McKneight.

“It reduces operating costs and extends undercarriage life up to 70%,” he says. “This undercarriage has proved to outperform sealed and lubricated track and heavy-duty track across a wide range of applications and operating conditions.”

This system combines a bushing that rotates with a center-tread-idler for high-speed operation in both forward and reverse. “Because it eliminates accelerated wear on the bushings and sprockets when operating in reverse, cycle times can be reduced without sacrificing life of the undercarriage,” McKneight says.

Case offers two undercarriage choices. One is the lubricated track. The other, an optional extended-life track, features an additional floating bushing for longer wear than a standard bushing. “It’s designed for abrasive soil conditions and increases track life by one-and-a-half to two-times over the lubricated track,” reports Hughes.

Typically, you can equip the latest dozers with different track configurations to match job conditions. In addition to the standard track, for example, John Deere offers an extra-long track frame, with an additional roller, for improved grading performance; a wide track with wide pads for improved stability when working on slopes; and an even wider, lower, ground-pressure track for maximum flotation in soft conditions.

Blade Options
A choice of blade widths offers another way to match a dozer to your job. For example, a narrow blade is more efficient when working in close quarters, while a wide blade offers more productivity in open spaces.

Combining various blade widths and track configurations offers even more opportunities to customize dozer performance to your needs. Combining a wide blade with a long track frame, for instance, can enhance light grading performance.

Manufacturers are also making it easier to adjust the fore and aft pitch of straight and semi-U blades to match the angle of the cutting edge to soil conditions for optimum pushing or cutting performance. John Deere uses a screw jack or twist adjustment instead of shims to simplify pitch changes. Case eliminates the need for a separate pitch adjustment tool by using the cover of the pitch pin as an integrated tool to make infinitely adjustable pitch changes.

Unlike a straight, semi-U, or angle blade, a Power Angle Tilt blade lets you hydraulically adjust the blade six ways. In addition to raising and lowering the blade, you can pitch it forward or backward and angle it right or left for top performance.

John Deere also builds the mainframes of its J Series machines specifically to accommodate either a PAT blade or an outside-mounted straight or semi-U for best balance and grading ability. “The PAT blade is attached at different mounting points than the other two blades to produce the best weight distribution and performance for each type,” says Drescher.

Blade control is also being improved. Electronic controls allow you to adjust angle, tilt, and blade height more easily and more precisely than mechanical controls for more productive operation. Automatic blade-control systems offer even more precision. Caterpillar offers such technology as an OEM system. “It uses either laser or GPS technology to automatically and precisely control the blade for optimum-finish grade accuracy,” McKneight says.

At the same time, advances in blade design are boosting productivity. The shape of Komatsu’s new sigma dozer blade, for example, keeps material heaped in the front middle of the blade. This prevents material from flowing out and around the edges of the blade. Recently introduced on its 354-horsepower D155AX-6 dozer, this blade will be added to other models, notes Murawski. “It has low ground resistance and can carry up to 20% more material than a conventional blade,” he says.

Enhanced Comfort
Enclosed cabs continue to grow in popularity. It’s not just because a more comfortable operator is a more productive one, but also because a clean, dry, air-conditioned, or heated work space makes it easier for contractors to attract new operators in a tight labor market.

Manufacturers are making an operator’s job more attractive by designing cabs with such features as easy entry and exit, a better view of the blade and surrounding work site, easy-to-use controls, air-suspension arm chairs, and adjustable foot pedals, along with such amenities as power ports for cell phones, AM/FM radios, cassette players, coat hooks, and cup and lunchbox holders.

Most of the new dozer models designed for finish and construction work are available with a spacious hexagonal cab. In addition to positioning the door over the track for easy entry and exit, this design, with its full-length door and window glass, provides the operator a panoramic view, similar to that of an open rollover protective structure (ROPS). Improved sealing and optional pressurization and filters minimize dust inside the cabs, too.

Ergonomics, from design of the seats to the shape and placement of controls and gauges, continues to play a big role in improving operator comfort. Such advances include joysticks that require little effort to operate and short lever travel. The two joysticks on Komatsu dozers, for example, are shaped to fit the palm of the operator’s hands. “Unlike a vertical lever, which you have to grip, these unique control levers fit your palm when your hand is in a relaxed position,” Murawksi says. “You don’t have to move your hand more than a few inches to operate them, either.”

Caterpillar’s D6K features new seat-mounted electro-hydraulic controls for more comfortable and convenient operation of the blade and control of steering.

Manufacturers are improving operator comfort in other ways, as well. On Komatsu dozers, a ROPS has been incorporated into the cab rather than installed as a separate structure. This improves visibility by eliminating the posts of conventional cabs. Also, the heavier-duty material used to construct the ROPS helps insulate the interior from outside noise. This, plus other design features, results in an usually quiet cab, notes Murawski. Sound levels inside these cabs at normal engine operating speed measure about 73–75 decibels, he reports. That compares to the 50–65 decibels of normal conversation and 80 decibels of normal city traffic noise.

“The cabs are mounted on four large dampers filled with silicone oil that remove much of the shock and vibration experienced with conventional cab mounting systems,” he says.

Among the methods Case uses to make its K-series dozers quieter and smoother riding are those of connecting the engine to the hydrostatic pumps via a drive shaft instead of directly; isolating the hydrostatic pump mountings from the frame; and using helical-cut gears in the final drive assemblies.

Easier Operation
Like other pieces of construction equipment, electronic controls are making dozer operation easier, more convenient, and more precise by taking on more and more of the operator’s work load. Dressta, however, is adopting this technology in a measured manner.

“Because of the environment in which dozers work, we strive to keep them as simple to operate and maintain as possible,” says Winker. “Our goal is to design and build dozers that use electronic technology intelligently, adopting it when it will make a difference in improving performance, comfort, service, and safety.”

Operating a dozer has never been easier or more tailored to individual needs and desires of operators, thanks to a variety of features now being offered. For example, on John Deere’s J-Series dozers, you can customize machine operation and response for more flexibility and productivity. This includes the ability to adjust such functions as forward and reverse ground-speed ranges and speed ratios to your preferences. This allows you to maneuver slowly and precisely in tight quarters without sacrificing engine power or to keep working productively in open areas at higher speeds. You can also adjust how quickly the steering responds to joystick movements and how quickly the transmission shifts between forward, neutral, and reverse.

New seat-mounted, electro-hydraulic controls on Caterpillar’s D6K include buttons on the left joystick for programming independent forward and reverse operating speeds and a thumbwheel for precise on-the-go speed adjustments, notes McKneight. The right joystick, which controls the dozer blade, features a button for automatic blade shake and a thumbwheel for adjusting the blade angle.

Two bump-up–bump-down speed buttons on Case hydrostatic-drive dozers allow an operator to increase or reduce maximum travel speed in increments of 10%. “These buttons are handy for traveling faster or slower without having to constantly adjust the throttle,” Hughes says

Komatsu’s right joystick features a closed-center load-sensing system that maintains blade speed in direct proportion to lever stroke, regardless of the load and travel speed. That means even more precise controllability, Murawski notes.

Several dozer manufacturers combine control of engine deceleration, transmission braking, and service brakes in a single foot pedal. Depending on the mode selected, pressing the pedal part way down allows you to reduce ground speed by braking the transmission without reducing engine revolutions per minute or to slow both machine travel and engine speed simultaneously. Depressing the pedal fully applies the service brakes.

A clear view of the blade from the operator’s seat enhances productivity and helps prevent damage to the machine or structures when operating in tight spaces. Komatsu’s brand new 130-horsepower D51EX-22/D51PX-22 slant-nose dozer models offer operators a whole new perspective. “The radiator and oil coolers have been moved to the back of the machine, allowing engineers to lower the front of the hood and giving operators an unrivaled view of the blade,” says Murawski.

Advances in blade design are boosting productivity.

Faster, Less Costly Service and Maintenance
A number of features on the new dozers are designed to save time and money in servicing and maintaining them. On Komatsu dozers, for example, engine side doors open up like gull wings, without any tools, to nearly 180 degrees for easy access to daily service checks, such as oil levels and filters. Oil and filter service intervals on John Deere J-Series dozers have been extended to 500 hours for engines and 2,000 hours for transmissions and hydraulics, and the engine, transmission, and hydraulics use the same type of oil. Electronic monitoring systems on the Caterpillar D6K alert the operator when service is required for the engine air cleaner and fuel/water separator.

The drive train of Komatsu dozers equipped with hydrostatic transmissions is built in modules. This makes repairs less costly and improves serviceability and durability, says Murawski.

“Instead of removing individual components, like a clutch plate, bearing shaft, or gears one at a time for repairs, this system lets you remove a complete assembly without having to disassemble other parts of the drive train,” he says. “If you have a replacement on hand, you can remove a faulty module and replace it the same day to reduce downtime and cut costs.”

Manufacturers are also reducing the need for maintenance. “We’ve gone to a lot of effort to eliminate grease fittings,” says Winker. “This not only reduces time spent on daily service, but it prevents dirt from getting into bearings and bushings and accelerating wear.” The PAT blade on Dressta’s smaller dozers, for example, has just two grease fittings.

On Dressta dozers, all connections on cylinders that raise, tilt, or angle blades use sealed, permanently lubed bushings and lip seals to keep out dirt. Also, the pins are chrome-plated for added durability.

In addition to lubricated track, John Deere makes an extended-life undercarriage that increases track up to two times in abrasive conditions, Drescher reports.

A number of dozer models offer electronic monitoring systems to keep an eye on engine and machine operation to alert operators to any malfunctions and help prevent minor problems from becoming major ones. In addition to trouble shooting, many of these systems also allow technicians to keep a record of maintenance work for scheduling future service.

Some of the new dozer models can also be equipped with Web-based, wireless technology systems that allow technicians to locate the machines, check maintenance items, and monitor operating systems from the shop or their pickup trucks, using a laptop computer.

Komatsu’s system is called Komtrax. “It tells you where a machine is, what it’s doing, and how it’s doing it,” says Murawski. “It can provide a variety of maintenance information, from engine-hour meter and water temperature to average hourly fuel consumption and how frequently the hydraulics went over-relief. You can also use it to set up an electronic geofence around the machine to help spot a theft if it’s moved outside this boundary without authorization.”

More to Come
The trend in increased productivity, easier and more comfortable operation, and improved serviceability and durability of the latest dozers is expected to continue.

Look for more plug-and-play integrated grade control options from the factory, says Drescher. “The open architecture design of this option allows a customer to add the grade control components and brand of his choice in the field without invasive installation procedures. It’s now available on several of our J-Series dozers.” In addition to more enhanced onboard diagnostic systems, he expects additional component changes to be offered aimed at lowering operating costs.

“Manufacturers will continue to improve dozers by increasing engine performance and pushing power,” says Hughes. “You’ll see more precise hand controls and improved laser-guidance systems, along with more creature comforts in the cab, like better climate control and ergonomics, and such features as satellite radio and MP3 power ports.”

Komatsu’s automatic-shift transmission with lockup torque converter on the company’s new D155AX-6 is a sign of things to come on larger dozers, says Murawski. It replaces a conventional torque converter in which a thumb switch is used to manually shift gears.

“Torque converters are inherently inefficient, because in the process of multiplying torque some of the engine power is lost as heat,” he explains. “However, this new transmission will lock up the converter under certain blade-loading and ground-speed conditions, boosting efficiency by 15%. That’s a huge increase and allows you to push more dirt with less fuel.”

Greg Northcutt writes on construction and business issues.

GEC - July/August 2007

Back To Table
Of Contents