Motor grader design is keeping pace with user demands for increased productivity, fuel efficiency, versatility, and of critical importance, the need for a machine with a shorter learning curve for less-experienced operators.
Key Insights for Buyers
Manufacturers are focusing on evolving controls to help less-experienced operators attain proficiency in a shorter time.
Grade-control tech range from “2D” technology that provides guidance to the operator (via an in-cab display) —to automated systems using “3D” technology that allows the site plan (including design surfaces, grades, and alignments) to be placed in the cab’s computer and to automatically control the hydraulic functions that translate the digital design into actual grades and contours on the site.
Motor grader utility is expanding with a growing list of attachments, including snow wings, plows, front dozer blades, scarifiers, rippers, front counterweights, rear pull hooks, moldboard extensions, hydraulically powered rear attachments (such as compactors), and on some models, a lift group with hydraulic lines for controlling powered, front-mounted tools.
Overview of the motor grader market
Motor graders have been part of the North American construction and road-maintenance scene for decades, and the design of these machines has steadily evolved to meet the changing needs of users. Today, the choice of available models can satisfy the requirements of a wide range of buyers, from small paving contractors doing site-prep work, to large mines needing a fast, powerful machine to keep haul roads free of rocks and debris.
At the small end of the spectrum are the compact models. The Mauldin M413XT Maintainer, for example, weighs in at around 13,000 pounds, has a 118-horsepower engine, and is driven hydrostatically. The machine is equipped with a front bucket that has a lift height of 10 feet, as well as with quick couplers front and rear. Another compact, the 130-horsepower LeeBoy 685D, also hydrostatically propelled, has a 16,000-pound operating weight and features an articulated frame.
Moving up the motor-grader size spectrum are such models as the Case 836C, with an operating weight of 26,000 pounds; the 218-horsepower Komatsu GD655-6, weighing nearly 40,000 pounds and featuring the company’s Dual Mode transmission, which employs both a torque converter and a direct-drive clutch; the John Deere 872G/GP, with 300 horsepower and weighing nearly 47,000 pounds; and the Cat 24 with 535 horsepower and an operating weight approaching 162,000 pounds.
Few would disagree that the motor grader operator generally is among the most experienced and skilled equipment operators on the job site.
“A good grader operator has always been said to be worth his/her weight in gold,” says Craig McGinnis, product marketing manager, Komatsu America Corp. “As experienced operators begin to retire, though, it can be difficult to find good replacements. GPS control, along with simplified cab controls, can help cut down that learning time. Customers value this, because a more efficient motor grader—and operator—mean a job done quickly and accurately.”
Caterpillar product application specialist, Eric Kohout, is in agreement.
“Customers are asking for availability of factory-installed, embedded technologies that are scalable,” says Kohout. “Customers want to select the machine controls of their choice, and then be able to configure the machine for their job site and application. That ability becomes increasingly important as customers are now often faced with a shortage of skilled operators.”
Sometimes heard about motor-grader operators is that they need a pilot’s license to run one of these complicated units. That’s said in jest, of course, but there’s a certain ring of truth in the statement, given the number of machine functions that operators must be adept at manipulating, sometimes simultaneously, when running these units.
Time was, when nearly all motor graders had a bank of control levers on either side of the steering wheel, some systems having as many as 15 total levers. (Some referred to the system as an “antler rack.”) The levers were connected to the hydraulic control valves with mechanical linkage. Nothing wrong with this control system; some operators still prefer this arrangement, saying that the mechanical link to the valves provides the best “feel” for precisely executing the machine’s various functions.
Case, for example, uses a multi-lever system on its C-Series graders with a specially designed hydraulic block, which, says the company, is “directly controlled and reduces any lever free play over the entire grader life.” The operator “benefits from a direct feed-back of the hydraulic system, increasing working accuracy.” Case also offers an optional “machine-control” configuration, which provides consolidated switches for grade-control systems conveniently mounted within fingertip reach of the conventional levers.
As both Caterpillar’s Kohout and Komatsu’s McGinnis noted, however, motor grader controls are changing. Control changes are being moved along to a significant degree, as the two product managers observed, by the user’s need to have machines that assist less-experienced operators attain proficiency in a shorter time, compared with mastering conventional controls. But, manufacturers can’t forget about experienced, skilled operators who might have a different preference.
About a decade ago, Caterpillar took the equipment industry by surprise when the company introduced the M-Series motor graders with two, electro-hydraulic, three-axis joysticks replacing all the conventional levers and the steering wheel. The company reasoned that the new control system would make the motor grader easier to learn and less fatiguing to operate, a boon to both less-experienced and experienced operators alike. Ergonomic studies, said the company, showed that operator hand and arm movement could be reduced as much as 78 percent with the joystick system.
With the recent release of the new Cat 140 and 120 motor graders, however, buyers are offered choices. The 140 is designed with a refined version of conventional, multi-lever controls, along with a steering-wheel; the 120 is available with that system—or the joystick system, which now has integrated, fingertip controls for grade-control systems and attachments. The 120, in fact, has two cab designs, each configured to best accommodate the control system selected.
John Deere has three control systems available for its G/GP Series models. “G” models use conventional, multi-lever, mechanical controls. “GP” (Grade Pro) models are fitted with a “fingertip-control” system, which uses eight small, armrest-mounted levers (including a steering lever) arranged in an industry-standard pattern. The system is designed with “knob-integrated” push buttons for grade-control. An option for GP models is the company’s dual-joystick system. All three control systems include a conventional steering wheel.
Complementing the various approaches for controlling the motor grader is a wide range of technology that assists the operator in actually attaining the results (or grades) specified in the site plans. These “grade-control” systems range from those using “2D” technology that provides guidance to the operator (via an in-cab display) about the position of the blade relative to the finished grade—to automated systems using “3D” technology that allows the site plan (including design surfaces, grades, and alignments) to be placed in the cab’s computer and to automatically control the hydraulic functions that translate the digital design into actual grades and contours on the site.
Grade-control systems, available from such suppliers as Leica, Topcon, and Trimble, can employ a myriad of technologies, ranging from sonic tracers, lasers, universal total stations, and GNSS (Global Navigation Satellite Systems, such as GPS—Global Positioning System—and the Russia-developed GLONASS system), to systems that might combine technologies, such as Topcon’s Millimeter GPS, which supplements GNSS positioning technology with “zone-beam” laser technology.
“Overall, the industry is moving toward increased automation,” says Komatsu’s McGinnis. “Motor graders are no exception. All OEMs work with GPS control companies to better integrate machine control into their graders. As the work force ages toward retirement, customers require younger operators to be up to speed more quickly. GPS control helps to shorten the learning curve for newer operators. The younger workforce often adapts more quickly to the new technology and control styles appearing on many graders.”
In many instances, grade-control technology is “scalable,” that is, allowing simpler systems to be “upgraded” to more sophisticated systems. Motor-grader users wanting to initiate some form of grade control might get started, for example, with a sonic tracer to follow a string line, previous pass, or the curb for finish-grading operation. Or, a single-laser, along with a laser receiver on the machine, might be selected, allowing the user to measure the lift and tilt of the blade, or by adding another laser receiver or a slope sensor, measure the slope of the blade.
These simpler systems are sometime “indicate-only” types, meaning that the operator receives in-cab guidance, via digital display, about the blade’s position relative to the finish grade. At the other end of the grade-control-technology spectrum are those systems employing GNSS or universal-total-station technology that takes control of the machine in terms of automatically positioning the blade to conform to the site plan at every location on the job.
Caterpillar’s Kohout sums up the grade-control choices available for the new 120.
“Scalable Cat GRADE technologies provide grade-control options for customers with different application requirements and budgets—but all aimed at allowing operators to work faster and more accurately,” he says. “Cat GRADE technologies include Cross Slope, Cross Slope Indicate, Digital Blade Slope Meter, and the Attachment-Ready Option, which provides the machine with connections that enable adding on future Caterpillar or other grade-control systems. In addition, the optional Stable Blade system automatically slows the machine if the grade will be adversely affected by machine bounce.”
A recent grade-control advancement for John Deere is the company’s SmartGrade system, which Deere says is a “mast-less, 3D, integrated grade control [system] from the factory, arriving at the job site ready to work.” The SmartGrade system uses no external masts or cables (the GNSS receivers are tucked into the roof), and according to Deere, the system allows “virtually unlimited range of grade-control and hydraulic functions.”
Overall design refinement
Engines for motor graders, as with all types of construction equipment, have been refined in the recent past to comply with Tier 4 emissions regulations, incorporating high-pressure/common-rail fuel-injection systems and emissions-controls strategies that vary from manufacturer to manufacturer, and perhaps from model to model, depending on which strategy most effectively (and simply) brings the engine into compliance. Case, for example, uses only a selective catalytic reduction system as exhaust aftertreatment to satisfy Tier 4-File standards.
“Eco” operating modes are frequently designed into machines, with the intent of balancing engine output and hydraulic demands as operating conditions change and saving a significant amount of fuel in the process. Also, the variable-horsepower system is a standard feature on some models, designed to enhance performance and overall efficiency by adjusting horsepower output in certain gear ranges to optimize traction, speed, and rimpull.
Six-wheel drive, that is, powering the motor grader’s front wheels, also is a feature preferred by an increasing number of buyers to enhance the overall capability of the machine with added traction (especially in rough terrain) and front-end control. John Deere, for example, uses an independent drive system for each front wheel, incorporating a variable-displacement pump and an axial-piston wheel motor. An “aggressiveness control” allows the operator to select among 15 settings to provide the required amount of front-wheel assist.
Case all-wheel-drive models feature a “creep mode” that powers only the front wheels, and does so independently from engine speed. Creep mode, says Case, allows the rear tandems to remain in neutral and rotate independently of each other to eliminate tire scuffing in tight turns during finish grading.
Also expanding the motor grader’s utility is a growing list of attachments, which might include snow wings, plows, front dozer blades, scarifiers, rippers, front counterweights, rear pull hooks, moldboard extensions, hydraulically powered rear attachments (such as compactors), and on some models, a lift group with hydraulic lines for controlling powered, front-mounted tools.
The motor grader’s serviceability also continues to be a design focus, with simplified systems for maintaining the moldboard’s tightness, for example, as well as significantly extended service intervals for fluids and filters. In addition, other design features are aimed at reducing wear and tear on the machine’s working structures—for example, a slip clutch that protects the drawbar, circle, and moldboard from shock if the blade hits a stubborn object—or blade-lift accumulators that help to absorb impact if the moldboard is forced abruptly upward.
In the motor grader cab, operator convenience, comfort, and safety are being continually enhanced. For example, overall visibility is expanded by larger glass areas and available rearview cameras; operator-presence systems disable hydraulics and set the parking brake; secondary steering systems take over if hydraulic pressure is lost; steering systems are proportional (becoming less sensitive as speed increases); high-capacity HVAC systems automatically control the in-cab climate; and seat options provide air-suspension as well as heating and cooling.
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