When it comes to versatility in large earthmoving equipment, the motor grader ranks as the hands-down winner. You can use this remarkable piece of equipment to establish a rough grade, produce a precise finished grade, spread stone, mix aggregate and other materials on a new road, cast material off an existing road or bring it back for top dressing, cut or clean a ditch, clear snow, and slope a bank. Add attachments, and you can also scarify hard ground, rip up asphalt, and doze construction materials. Quite a feat for a machine that’s designed primarily for one function: to move dirt, stone, and other material sideways.Stripped to its basics, this sophisticated grading tool is nothing more or less than a self-propelled moldboard. However, that moldboard can be angled right or left and tilted up or down, simultaneously, as it is pitched forward or backward, raised or lowered, or shifted right or left. This blade is attached to a circle that is mounted on a rigid, long-wheelbase frame. The frame, in turn, features an oscillating front axle and pivoting rear tandem axles. These features give the machine stability.Dan Gillen, a motor grader specialist with Caterpillar, describes the motor grader as an averaging tool. “For example, if one front tire runs over a 2-inch bump, the front-axle pivot divides this difference in half by raising the front frame only 1 inch,” he explains. “The moldboard, which is positioned about halfway between the front axle and the pivot point of the rear tandem wheels, rises only about half an inch. As the front tire of the rear tandems rolls over the half-inch-high bump left by the moldboard, the tandem pivot reduces the rear frame reaction to only about one-fourth inch.”Wes Lee, director of marketing for heavy-range products at Case Construction Equipment North America, says motor graders must deliver on three key attributes: durability, productivity, and serviceability.
Graders must have a strong chassis and ample power to move through widely varying conditions – from overgrown ditches to drifted snow,” he says. “Keeping them on the road is critical to productivity, so ease of maintenance has become a big factor.”Several other factors also play key roles in a motor grader’s performance. The machine must have enough weight to cut through material and sufficient engine torque and horsepower to push the blade. At the same time, the front wheels can be leaned right or left (up to about 18°-20º) to offset the load of material on the blade, while the frame can be articulated (about 20º-23º) right or left to compensate for changing moldboard draft or to extend the reach of the blade.The end result is a machine that stands in a class by itself, notes Gary J. Atkinson, vice president of motor graders for Volvo Construction Equipment North America Inc. “By combining all these elements, the motor grader is able to hold a finer grade than any other piece of construction equipment.”Motor Grader BasicsJust how well any one motor grader model meets your unique job requirements depends on a number of factors, such as engine and hydraulic systems and components and performance and operating features. Some are more or less generic among different makes. Others are unique. “Many features are similar from one brand to another,” says Bob Post, motor grader product manager for Komatsu America Corporation. “The variation comes in how each particular machine performs the various functions, whether it’s transferring engine power to the wheel, visibility to the blade, or maintenance procedures.”Among the areas to consider:SizeMotor graders are available in a wide array of sizes that enable them to tackle a broad range of construction jobs, from touching up city alleys and grading residential cul-de-sacs to building freeways and pioneering roads in forests and quarries. One manufacturer, for example, currently offers 10 different models of motor graders for the North American market. The Association of Equipment Manufacturers classifies motor graders by eight different categories in terms of net engine horsepower – from 45 hp to 250 hp and more.The smaller graders, including compact models, offer about 80-110 hp or less and weigh about 10,000-15,000 lb. Typically equipped with 8- or 10-ft.-wide moldboards, they generally are used by town or city public works departments for street and park maintenance or by contractors on smaller jobs, such as driveways, small parking lots, sports fields, and landscaping projects, where the ability to maneuver in tight areas is more important than muscle.“In many cases, you could do this type of work with a tractor or skid-steer loader equipped with a box blade or even with a larger motor grader, although it would be harder to maneuver the bigger grader,” says Atkinson. “However, for a contractor who specializes in site preparation on the smaller jobs, compact machines can provide a good economic payoff over time.”In fact, Volvo makes three 85-hp motor grader models with a 16.5-ft. turning radius. Atkinson reports that the compacts represent a small segment of the total motor grader market and account for no more than about 10% of the industry’s annual sales.“It’s an area that could grow because not every contractor who could benefit from this size realizes it,” he says. “Also, the popularity of small and compact motor graders varies by region. For example, they’re used much more in the Southeast than in other parts of the country.”The largest graders might weigh 45,000 lb. or more. These machines offer the power and blade length to move a lot of material quickly to get a site down to grade. They also have the capacity and speed needed for clearing snow from streets and roads in a timely fashion. The largest of these heavyweights, including Caterpillar’s 500-hp, 137,000-lb. 24H with a 24-ft.-wide blade, provide the mass and horsepower to cut through hard-packed material, such as mine haul roads carrying trucks weighing as much as 690 tons when loaded.“Those trucks, traveling about 30 to 40 miles per hour, can really tear up a haul road and pack it as hard as concrete,” says Atkinson. “So you need a very big grader to keep the road smooth and in shape.”The midsize machines – those in the 145- to 170-hp classes – represent the largest part of the market in terms of choices and unit sales. With price tags of a $250,000 or more, they generally weigh between about 30,000 and 36,000 lb. and include such models as the Case 865, Caterpillar 140H or 143H, John Deere 670 or 672, Volvo 710 or 720, and Komatsu GD655 Laterra.“Traditionally, midsize machines have the weight and power that operators like for working on construction sites,” says Post. “They are a good match for the variety of jobs many grading contractors do, including fine grading and applications that require more power, such as spreading stone for a road base or digging ditches along roadsides. They’re also easier to transport than larger machines.”Regardless of size, the front axle should carry about 30% of the machine’s weight, with the rear tandems bearing the remaining 70%, according to Gillen. “This weight distribution helps maintain good steering control while providing good traction at the tandems,” he says.Contractor Dave Roaden’s company, Roadco in Simpsonville, SC, does grading and excavating work on commercial and industrial projects, such as building pads, parking lots, and roads. Machine weight is a critical factor in selecting a motor grader for his type of work. “All the horsepower in the world won’t do you much good if you don’t have the weight you need to move a pile of stones or make a hard cut,” he says.On most jobs, he uses graders in the 32,000-lb.-or-so range. “This size is big enough to carry heavier loads and small enough to move around town on a lowboy and allows us to do fine grading, which is very important for preparing sites for building slabs,” he says. “Smaller machines don’t have enough weight and horsepower to accomplish the work in an expeditious manner. On the other hand, bigger machines are too difficult to maneuver in areas like parking lots.”The graders are equipped with 12-ft.-wide moldboards. “This allows us to make a 10-foot pass that moves material beyond the rear tires, and you can angle it to fit on an 8-foot-wide lowboy trailer without hanging over the sides.”He reports that the largest motor grader he has owned, a 55,000-lb. machine with a 16-ft. moldboard, proved too heavy and too costly to own and maintain for the type of work he does.“The large graders pay off when you have a lot of dirt to move or smooth quickly,” Roaden says. “Because it’s subject to heavier use, the machine’s parts tend to wear more quickly. That’s not so important for haul roads. But worn components make it more difficult to hold a fine grade. Also, the extra weight of bigger machines can create ruts and tracks if the subgrade is a little soft.”He once used a compact grader with flotation tires to spread wet topsoil over soft ground without leaving ruts on the surface. However, he prefers to use his small dozer for that type of work.Autry Grading Inc. in Fayetteville, NC, does grading and utility excavating on residential, commercial, and municipal projects using five 32,000- to 36,000-lb. motor graders, including an all-wheel-drive model. “We do a lot of commercial projects, like shopping centers and parking lots, which aren’t big enough to handle the bigger machines,” says owner Kenneth Autry. “We use 12-foot blades because they are easier to handle in corners than 14- or 16-foot blades.”MoldboardThe ability to adjust the moldboard to fit a variety of grading jobs is the key to the motor grader’s versatility. The blade is attached to the circle that is connected to the frame of the motor grader. Two hydraulic cylinders lift the circle, while a third cylinder shifts the circle from side to side. A gear-drive system rotates the blade 360°.These features allow you to extend the moldboard right or left and to swing the blade up as much as 90° and tilt either end down 20° or more to increase your blade position choices for cutting or cleaning ditches or shaping a bank. You can also lower the edge as much as 32 in. below the surface, depending on manufacture. This range of movements gives you more options for angling and tilting the blades. So does the ability to raise the blade above ground level.A longer wheelbase permits a more aggressive moldboard angle for a given blade length than a shorter wheelbase does. Moving the toe of the blade (the end toward the front of the machine) closer to the centerline of the machine allows material to roll more freely, which in turn reduces power requirements.Jim Reynolds, a consultant to Komatsu America Corporation, notes some of the considerations in selecting a blade width: “A wider blade can be angled for best cutting action and still move material out beyond the rear tires. A shorter blade is better for working in narrower ways. It’s also better for rocky surfaces, because it doesn’t put as much leverage on the circle gears, reducing wear on the gears.”The pitch of the blade fore or aft can also be changed to achieve the desired consistency of dirt, stone, or other material being cut. Moving the pitch forward increases the rolling and mixing action of the material and stability of the motor grader.The degree and type of curvature in the blade also affect the rolling action. The less curve in the blade, the more it tends to carry material. Think of a dozer blade: The more the blade is curved, however, the better the material rolls to the side.Adequate clearance between the top of the moldboard and the bottom of the circle is another consideration. Otherwise material can be forced into the circle, reducing rolling action and increasing power requirements.The ability to shift the blade right and left comes in handy for slope and ditch work and for grading roads and parking lots. For most midsize machines, the right or left edge of the blade can be extended up to about 6.5 ft. beyond the outside rear tires.Two manufacturers offer circles with slip clutches. This feature is designed to protect the drawbar, circle, and moldboard from shock loads should the blade hit an immovable object. One of the manufacturers provides the same protection with a unique hydraulic overload relief valve.A float blade feature relies on the weight of the blade and circle to move material. It can be useful for snow removal and removing debris from haul roads at quarries and mines because it follows the shape of the road surface.Power TrainVolvo’s Atkinson points out some important differences between motor graders and other earthmoving machines when it comes to converting engine power to tractive effort and work output. “The motor grader has the highest usable speed range of any piece of construction equipment used for cutting grades,” he says. “At the same time, it is traction-limited at low speeds and horsepower-limited at high speeds.”Add too much power when cutting a grade in the first few lower gears, Atkinson notes, and a motor grader will spin its tires. The only way to move more material is to add more weight. In the upper gears, typically used in snow removal, performance is limited by the amount of torque developed by the engine. In that case, the only option for increasing production is to increase engine power.Most midsize graders feature direct-drive power-shift transmissions with inching capability and six to eight forward-speed ranges and four to six reverse-speed ranges. Komatsu offers two drive modes at the flip of a switch: a conventional direct-drive clutch system or a torque converter, both of which are oil-driven.Some motor grader models are also available with variable-horsepower engines that automatically provide more power at higher speed ranges. This can increase productivity when working at higher speeds. In lower gears, where traction is limited, engine horsepower is reduced to lower fuel consumption and minimize tire slippage. For the Caterpillar 140H motor grader, the VHP Plus option provides a power range of 165 hp in first through third gear, 185 hp in fourth through sixth gear, and 205 hp in seventh and eighth gear. Case’s 865 VHP runs at 168 hp in gears one through three and 190 hp in gears four through eight.All-wheel drive, in which hydrostatics drive the front wheels, is another feature that can increase tractive effort while improving steering and side-draft control. The Volvo 746 is one such machine. The all-wheel-drive system provides up to 8,500 lb. more blade pull than similar-size tandem-drive units, reports Atkinson. “Also, you can switch to hydrostatic, front-wheel-drive creep mode for low-speed, fine-grading applications,” he adds. “This puts power where you need it for fine grading and lets you navigate around tight corners without the rear wheels scuffing the finished grade.”The advantages of all-wheel drive stem from the relationship between the weight and traction of a motor grader, points out Maurice Nesbitt, product sales manager of motor graders for John Deere Construction and Forestry Equipment Company.Weight determines rim pull or the ability of the motor grader to push material, he explains. The heavier the machine, the more material it can move – if that weight is properly matched with engine horsepower to prevent loss of traction. At the same time, too much weight can lead to rutting of a soft surface or base material.“A heavy motor grader can be a detriment,” Nesbitt says. “But if you can achieve the rim pull of a heavier machine with a lighter motor grader, you can have the best of both worlds – power and traction.”That’s where all-wheel drive (the two front and the four rear tandems) comes in. “All-wheel or six-wheel drive does more than just improve traction in mud and snow,” he explains. “It also allows a smaller motor grader to do the work of a bigger, heavier unit. If you’re grading with a tandem-drive machine and you’re running out of traction, you’ll raise the blade to lighten the load and prevent the tires from spinning. However, now you’re taking a small cut, so you’ll have to come back a second time to finish the cut. With the increased traction of a six-wheel drive, you may be able to do it all in one pass.”The following table compares the rim pull of tandem and all-wheel-drive motor graders. It assumes that 70% of the machine’s total weight rides on the rear tandem wheels and 30% on the front wheels. Thus, with a tandem-drive motor grader, 70% of the machine’s total weight rests on the driver wheels, while 100% of the weight rides on the six drive wheels of an all-wheel-drive machine. Also, the table assumes a 75% coefficient of traction, about the most you can expect with a motor grader.How Weight and Traction Affect the Ability of Motor Graders to Move MaterialWeight of Machine/
Type of DriveWeight on Drive WheelsXCoefficient of Traction=Rim Pull32,000 lb.Tandem22,400 lb.0.7516,8000 lb.All-Wheel32,000 lb.0.7524,000 lb.40,000 lb.Tandem 28,000 lb.0.7521,000 lb.All-Wheel 40,000 lb.0.7530,000 lb.55,000 lb. Tandem 38,500 lb.0.7528,875 lb.All-Wheel 55,000 lb.0.7541,250 lb.“This table shows that a six-wheel-drive motor grader in one size class develops more rim pull than a four-wheel-drive machine in the next bigger size class,” Nesbitt says. “Another way to view it is that a 40,000-pound model can out-rip a 55,000-pound unit.”ArticulationThe articulating frame lets you control side-draft without decreasing the load on the moldboard. It allows you to make tighter turns than a rigid frame of the same length, and it’s useful for shaping ditches and sloping banks. You can extend your reach by positioning the front frame in the ditch or on the bank while keeping the tandem-drive wheels on the road for better traction.Location of the cab – either on the front or rear frame – might be a consideration too. “When the cab is mounted on the front frame, your view of the moldboard remains the same because the drawbar/circle/moldboard assembly moves with the cab as the machine is articulated,” says Gillen. “When you look back and steer the leading end of the machine in reverse by using articulation, you can know the position of the front frame because you are sitting on it. You can see the degree of articulation by comparing the rear-window angle to that of the hood covering the rear of the machine.“When the cab is mounted on the rear frame, your view of the moldboard changes constantly as the machine articulates. In some articulated positions, the mainframe blocks your view to the moldboard. Also, when backing up and using articulation, you can’t see the degree of articulation unless you look forward.”“With the cab mounted in the rear, you get a better view of the full moldboard in all positions,” Lee from Case points out. “Your eye does have to move with the frame, but there’s much less chance of the mainframe blocking your view of the moldboard. Even with the moldboard at a 45º angle, you can see the edge and avoid cutting the tires. And with other features, such as a sloping rear hood, the result is outstanding all-around visibility.”Contractor Roaden’s crews frequently take advantage of articulation. “It allows us to work around the tight radius of a cul-de-sac and to work in the corners of parking lots,” he says.Responsiveness of ControlsProducing a final grade to a tolerance of a quarter-inch or less requires hydraulics that respond easily and precisely to a given movement of the various control levers. This is affected by the hydraulic valve itself – how the spools move and the amount of hydraulic pressure and flow required – and the linkage between the control and the valve. The more direct this linkage, the better the response.“Most manufacturers use a variable-displacement hydraulic pump system,” explains Post. “That’s the same type of hydraulics used with excavators. If you’re not using a particular function, then the pump is not drawing power from the engine. But once you activate the control, the hydraulic flow comes up immediately to produce an excellent response.”VisibilityIdeally the operator should have a clear view of the moldboard toe and heel as well as the area around the machine. “You need good visibility to the whole moldboard so that you can see how it’s responding to your various control pressures and to make required adjustments,” says Post.Such features as floor-to-ceiling cab glass, position of the cab on the machine, a sloping rear hold, and side breakaway mirrors enhance visibility, notes Lee.ComfortIn addition to heating; air conditioning; easy access to gauges, switches, and controls; and high- or low-profile rollover protective system cabs, a number of other feature can add to operator comfort, convenience, and productivity. They include a full suspension seat with adjustable armrests, a steering pedestal that adjusts to fit different operators, electronic throttle control, single-lever transmission control, and electronic monitoring of engine and machine operation.ServicingManufacturers are making routine inspection and servicing of motor graders faster and easier to help reduce downtime and operating costs. Look for such features as quick, simple access to service and check points for the engine, transmission, and other systems; spin-on oil, fuel, and coolant filters; remote lubrication points; and convenient radiator clean-out, fuel-fill, and diagnostic test ports.“The industry is moving toward increasing the ease of doing routine maintenance,” says Lee. “Features like ground-level fuel fill, easily accessible fluid sight gauges, and check-and-fill dipsticks make regular maintenance easy and enhance uptime.”Case, for example, offers a one-piece, nonmetallic sloping hood that flips up and locks to access filters and daily service points. Flip-down panels along the bottom of the hood provide more access. The company’s graders are rated best in the industry on the SAE J817 serviceability index, based on the location, access, operation, and frequency of service.A Buying Checklist Here’s some advice from the experts on what to look for when comparing the many choices available in today’s motor grader market.Machine PerformanceOne way to gauge how well a particular motor grader fits your needs is to put it through its paces. “The new motor graders available in North America are all quality products,” says Atkinson. “The differences between them can be subtle. Require a demonstration of the machine. Ask questions. Compare the different brands. Run the machine. The responsiveness and your ability to almost feel the ground through the machine are key factors. A good, seasoned operator who doesn’t have that feel in a machine will get out of it almost immediately and the demonstration is over about as fast as it started.”Dealer PerformanceContractor Roaden puts dealer service and support at the top of his checklist when shopping for motor graders. “I don’t buy the brand, I buy the dealer,” he says. “A good dealer can be hard to find. But that dealer is the life link between you and the manufacturer, because you’ll never get to talk to the people who make the machine.”
Type of DriveWeight on Drive WheelsXCoefficient of Traction=Rim Pull32,000 lb.Tandem22,400 lb.0.7516,8000 lb.All-Wheel32,000 lb.0.7524,000 lb.40,000 lb.Tandem 28,000 lb.0.7521,000 lb.All-Wheel 40,000 lb.0.7530,000 lb.55,000 lb. Tandem 38,500 lb.0.7528,875 lb.All-Wheel 55,000 lb.0.7541,250 lb.“This table shows that a six-wheel-drive motor grader in one size class develops more rim pull than a four-wheel-drive machine in the next bigger size class,” Nesbitt says. “Another way to view it is that a 40,000-pound model can out-rip a 55,000-pound unit.”ArticulationThe articulating frame lets you control side-draft without decreasing the load on the moldboard. It allows you to make tighter turns than a rigid frame of the same length, and it’s useful for shaping ditches and sloping banks. You can extend your reach by positioning the front frame in the ditch or on the bank while keeping the tandem-drive wheels on the road for better traction.Location of the cab – either on the front or rear frame – might be a consideration too. “When the cab is mounted on the front frame, your view of the moldboard remains the same because the drawbar/circle/moldboard assembly moves with the cab as the machine is articulated,” says Gillen. “When you look back and steer the leading end of the machine in reverse by using articulation, you can know the position of the front frame because you are sitting on it. You can see the degree of articulation by comparing the rear-window angle to that of the hood covering the rear of the machine.“When the cab is mounted on the rear frame, your view of the moldboard changes constantly as the machine articulates. In some articulated positions, the mainframe blocks your view to the moldboard. Also, when backing up and using articulation, you can’t see the degree of articulation unless you look forward.”“With the cab mounted in the rear, you get a better view of the full moldboard in all positions,” Lee from Case points out. “Your eye does have to move with the frame, but there’s much less chance of the mainframe blocking your view of the moldboard. Even with the moldboard at a 45º angle, you can see the edge and avoid cutting the tires. And with other features, such as a sloping rear hood, the result is outstanding all-around visibility.”Contractor Roaden’s crews frequently take advantage of articulation. “It allows us to work around the tight radius of a cul-de-sac and to work in the corners of parking lots,” he says.Responsiveness of ControlsProducing a final grade to a tolerance of a quarter-inch or less requires hydraulics that respond easily and precisely to a given movement of the various control levers. This is affected by the hydraulic valve itself – how the spools move and the amount of hydraulic pressure and flow required – and the linkage between the control and the valve. The more direct this linkage, the better the response.“Most manufacturers use a variable-displacement hydraulic pump system,” explains Post. “That’s the same type of hydraulics used with excavators. If you’re not using a particular function, then the pump is not drawing power from the engine. But once you activate the control, the hydraulic flow comes up immediately to produce an excellent response.”VisibilityIdeally the operator should have a clear view of the moldboard toe and heel as well as the area around the machine. “You need good visibility to the whole moldboard so that you can see how it’s responding to your various control pressures and to make required adjustments,” says Post.Such features as floor-to-ceiling cab glass, position of the cab on the machine, a sloping rear hold, and side breakaway mirrors enhance visibility, notes Lee.ComfortIn addition to heating; air conditioning; easy access to gauges, switches, and controls; and high- or low-profile rollover protective system cabs, a number of other feature can add to operator comfort, convenience, and productivity. They include a full suspension seat with adjustable armrests, a steering pedestal that adjusts to fit different operators, electronic throttle control, single-lever transmission control, and electronic monitoring of engine and machine operation.ServicingManufacturers are making routine inspection and servicing of motor graders faster and easier to help reduce downtime and operating costs. Look for such features as quick, simple access to service and check points for the engine, transmission, and other systems; spin-on oil, fuel, and coolant filters; remote lubrication points; and convenient radiator clean-out, fuel-fill, and diagnostic test ports.“The industry is moving toward increasing the ease of doing routine maintenance,” says Lee. “Features like ground-level fuel fill, easily accessible fluid sight gauges, and check-and-fill dipsticks make regular maintenance easy and enhance uptime.”Case, for example, offers a one-piece, nonmetallic sloping hood that flips up and locks to access filters and daily service points. Flip-down panels along the bottom of the hood provide more access. The company’s graders are rated best in the industry on the SAE J817 serviceability index, based on the location, access, operation, and frequency of service.A Buying Checklist Here’s some advice from the experts on what to look for when comparing the many choices available in today’s motor grader market.Machine PerformanceOne way to gauge how well a particular motor grader fits your needs is to put it through its paces. “The new motor graders available in North America are all quality products,” says Atkinson. “The differences between them can be subtle. Require a demonstration of the machine. Ask questions. Compare the different brands. Run the machine. The responsiveness and your ability to almost feel the ground through the machine are key factors. A good, seasoned operator who doesn’t have that feel in a machine will get out of it almost immediately and the demonstration is over about as fast as it started.”Dealer PerformanceContractor Roaden puts dealer service and support at the top of his checklist when shopping for motor graders. “I don’t buy the brand, I buy the dealer,” he says. “A good dealer can be hard to find. But that dealer is the life link between you and the manufacturer, because you’ll never get to talk to the people who make the machine.”
