Graders and Scrapers

Sept. 1, 2001

Naturally, if you’re looking to buy a motor grader or two these days, you want to be sure that the machine’s basics, such as its power, weight, and transmission, are right for you. But it will also pay dividends to look at the finer points. In recent years, manufacturers have “sweated the details” to produce motor graders that are more productive and easier to run than ever.

Graders: Getting More for Less

Caterpillar has one of the broadest motor-grader lines in the industry, offering 10 models ranging from the 125-hp 120H to the massive 24H, which boasts 500 hp. The most popular grader in the line is the 140H, which has 165 hp and up to 185 hp with a variable-horsepower option.

“One of our distinguishing features is that we have a very large displacement engine,” says Dan Gillen, Cat’s marketing supervisor for motor graders. The 140H, for example, packs a Caterpillar 3306 engine, which has 638 in.3 of displacement. With an increase in the size of pistons, flywheel, crankshaft and other engine components, the 140H–and other Cat graders powered by a 3306–can produce more inertia and “lugability” to get through the tough spots, says Gillen. Graders in the H-series have eight forward speeds and six reverse speeds, so operators can always find the right gear for the job.

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Of particular note is the hydraulic system that Cat designed specifically for its H-series of graders. Gillen says it’s a true load-sensing hydraulic system that differentiates Cat graders from other machines. “Our hydraulic valves are proportional priority pressure-compensated [PPPC] valves,” says Gillen. With PPPC valves, when an operator performs multiple hydraulic functions at once and hydraulic demand exceeds capacity, all hydraulic circuits slow down at the same rate. “If your demand is 10% more than capacity, then all hydraulic functions will slow down by 10%,” says Gillen. “That way the relative speed of all hydraulic functions stays the same.” The result: predictable rates of hydraulic response from the blade, steering, circle, and other components.

What’s more, Gillen says, “With the H-series, we redesigned our entire blade linkage system to improve blade positioning. We also moved the blade forward to give the operator better visibility of the blade. That allows him to carry a more aggressive blade angle without interfering with the front tires or rear tandem tires.

“An aggressive blade angle allows material to move more freely across the blade. And the more freely material moves, the less horsepower and fuel the machine uses.”

Deere offers six models of motor graders in two series: the 600 series and the 700 series. The 600 series includes the 140-net-hp 670C; the 670CH, which has variable net horsepower from 140 to 155; and the 672CH, an all-wheel-drive machine with variable net horsepower from 145 to 160.

The 700 series includes the 770C, with 155 net hp; the 770CH, with variable net horsepower from 155 to 185; and the 772CH, an all-wheel-drive model that features 185-205 net hp with the front-wheel drive turned on.

With the C-series, Deere introduced variable-horsepower engines in the 600 series; previously they had only been available in the 700 series, says Marty Ruhter, program manager for motor graders. Electronic fuel injection gives the 600 series the variable-horsepower capability. And with Deere’s PowerTech engines, the company introduced air-to-air aftercooling and a waste-gate turbocharger that provides more air at low engine speed for increased power and lugging.

In addition, the C-series has improved transmissions that feature eight speeds in both forward and reverse through all six models. Previously, B-series transmissions had only four speeds in reverse. Now all six Deere motor graders can move at 2.2—25.8 mph in both forward and reverse directions, says Bob Herman, Deere’s business analysis manager for road construction. And gear spacing in C-series transmissions was redesigned to provide smooth shifts through the full range of gears, says Herman.

Another improvement in the C-series: Deere designed separate hydraulic systems for the axle, transmission, and main hydraulics. In the B-series, those three systems were combined. “The advantage to separate systems is that you isolate each system for better cooling and filtration,” says Ruhter. “The result is better reliability, less downtime, and improved durability of components, because you’ve got separate filtration and cooling on each circuit.”

And Deere took steps to reduce noise on the C-series: The engine, transmission, hydraulic pumps, and cooling package are all isolation-mounted with rubber mounts to reduce noise and vibration for the operator and bystanders. “We moved the cooling package to the rear of the machine, increased the fan size, and slowed it down,” says Ruhter. “Now it’s quieter and farther from the operator for reduced noise levels.”

The 772CH and 672CH models feature speed-sensing hydrostatic front-wheel drive. “It provides similar performance characteristics as a mechanical front-wheel drive,” observes Ruhter. “We’ve got a control system that matches the speed of the front wheels to the speed of the rear wheels. It’s important that both front and rear wheels turn at the same speed. With other front-wheel-drive systems, the front wheels can lose traction and spin out of control.”

New Holland Construction builds and sells six models of motor graders, ranging from the RG80, at 76 hp, to the RG200, which features 205 hp. With the RG170, New Holland offers a variable-horsepower option that goes from 170 to 190 hp. The series features a strong mainframe with a moldboard that easily rolls material away, points out Sam Wyant, product manager for motor graders.

“The largest three models–the RG140, the RG170, and the RG200–all have 69-inch circles,” says Wyant. “That’s pretty large by industry standards. And the teeth are on the outside of the circle. With a larger circle you can get more torque to the blade while the blade is under load while grading material.”

For its blade frame, New Holland attaches the grader’s circle to a horizontal A-frame. “The A-frame provides excellent support for the circle, as opposed to using a T-shape frame design,” notes Wyant. “Our A-section gives you four points of contact with the circle, whereas a T-section gives you three points of contact. The A-section provides more contact, more stability, and more durability in the blade frame.

“And if you step back and talk about the power train, we’ve got a high-tech direct-drive power-shift transmission,” says Wyant. “It’s controlled by a bump-shift, single-lever control. On-the-go shifting through the eight forward and four reverse speeds is pretty smooth and effortless.” The transmission is monitored by an electronic control unit that provides self-diagnostics for any problems that might develop.

For the RG170 and RG200 models, New Holland motor graders use a variable-flow piston pump in their hydraulic systems. The RG80, RG100, and RG140 use gear pumps for their hydraulics.

New Features Improve Productivity and Safety

Visibility on their motor graders is an important feature for all manufacturers, and New Holland is no exception. The cab on its graders is trapezoidal in shape–narrower at the bottom and wider at the top. “That gives you excellent visibility down to the blade and out to the rear of the machine,” points out Wyant.

All blade controls are short-throw levers mounted off the steering column; the single-lever, bump-style transmission shifter is to the right of the operator’s seat. “And we do have an electronic data monitor to monitor the critical functions of the machine,” says Wyant. “The operator would be warned by a visible fault code, or a light, or an audible alarm.”

In addition, New Holland offers two axle options: a limited-slip type called the Super-Max-Trac axle and a Lock-Unlock Differential. With the limited-slip axle, the tandem that is slipping will transfer up to 65% of its torque to the tandem that has traction.

The Lock-Unlock Differential simply will lock up the rear differential to turn all of the wheels at the same time. “If you’re snowplowing or working in sloppy material, you might lock up the differential,” says Wyant. “It gives you the same amount of wheel torque to both tandems.”

Volvo Motor Graders Ltd. offers an extensive line of machines–17 models in all. You might recall that, in 1997, Volvo bought Champion Road Machinery and in that way acquired the line of motor graders. “Our strategy was that it gave Volvo an entry into the governmental business–that 70% of motor graders are sold to a government agency,” states John Marshall, product manager for Volvo Motor Graders. The 17 models range from the smallest at 80 hp and 11,000 lb., up to a 235-hp model that weighs in at 42,700 lb.

“We spend time on three areas of the graders,” explains Marshall. “First is basic productivity, the ability to cut and move material. Second is mobility–to make the machine as nimble as possible. We have excellent blade mobility, steering arc, and articulation angle. The third area is the operator environment. We’ve made the machines as quiet, clean, roomy, and comfortable as possible–with maximum visibility.

“A lot of productivity comes from positioning the power-train components over the drive wheels to get maximum pushing capability,” continues Marshall. “And we position the blade as close as possible to the rear of the machine to take advantage of the rear weight of the machine without sacrificing front-end stability.

“We’ve got the right gear speeds for all applications–from fine grading at 1 mile per hour to snowplowing at 18 miles per hour. We use eight forward and four reverse speeds in all the large models, from 30,000 pounds and up. The smaller models have hydrostatic drives.”

Attachments go a long way to augment a motor grader’s productivity these days, maintains Marshall. “They’re asking these machines to do more and more jobs. They want them to be year-round machines. So available attachments include snowplows, dozer blades, rippers, scarifiers, and windrow eliminators.” The windrow eliminator comes behind the machine to lay the windrow back down.

“We use a circle-turn system with the teeth cut on the outside of the circle,” explains Marshall. “The circle is turned by two hydraulic cylinders that are 90° out of phase. That gives us hydraulic power directly to the circle. We don’t have to use hydraulic motors or worm gear reduction drives. So we have fewer moving parts to turn the circle. As soon as you hit the circle-turn valve you get 100% startup torque immediately. Whatever the machine can push, our circle-turn system will allow the operator to cycle or redirect.”

In addition to making the operator’s cab as quiet, roomy, and comfortable as possible, Marshall says Volvo has put a lot of effort into visibility. “We want the best 360° visibility that you can possibly have,” he says. “The biggest safety feature on a motor grader is the operator’s ability to see. Because motor graders often function on or near the public roads, the operator’s ability to see is really, really important. And that’s what we focus on: his ability to see to the front axle, down to the moldboard and circle, and over the rear of the machine.”

Volvo introduced its most recent round of motor-grader upgrades in October 1999. Improvements made then included:

  • better hydraulic control for fine grading.
  • a much-improved all-wheel-drive system. Volvo offers three all-wheel-drive models: a 716, a 726, and a 736. “We really improved that all-wheel-drive system in terms of its power and ability to pull,” claims Marshall.
  • the addition of a low-speed creep mode that allows fine grading by using front-wheel drive only. “So you get the very slow speed that is required for fine grading,” explains Marshall.

New Directions in Scrapers

A recent and ongoing trend in earthmoving is the relatively rapid increase in the sales and use of scrapers pulled by four-wheel-drive agricultural tractors. In 1998, John Deere bought Cameco Industries, a manufacturer of pull-type scrapers and other equipment based in Thibodaux, LA. Since the purchase, sales of Cameco’s pull-type scrapers have increased tenfold, reports Rick Ayers, a scraper marketing specialist with John Deere. “We see the overall tractor-scraper machine population going up at 5 to 10% per year.”

The main reason for the increase: reduced costs compared with self-propelled scrapers. “We have customers who tell us they have saved 10 cents to 30 cents per cubic yard with a tractor/pull-type scraper unit versus a self-propelled scraper,” says Ayers. “Most scraper dirt is calculated at $1.00 to $1.25 per cubic yard, when hauled a quarter to a half mile. So if you’ve saved 25 cents a yard on several million yards, you’ve saved a lot of money.”

John Deere currently offers four models of pull-type, “carry-all” scrapers: one with a capacity of 13 yd.3, one with 15 yd.3, and two with 18 yd.3 The 18-yd.3 models come with either a 12-ft.-wide cut or a 14-ft. cut. The carry-all scrapers empty when the front apron opens and the bowl pivots forward to dump the load.

Three new models of pull-type scrapers, with capacities from 14.5 to 18 yd.3, were introduced this past August, Ayers reports. They are ejector models that can meter soil out of the bowl more precisely than the carry-all models do. To eject the soil, the apron opens in front and an ejector wall in back of the bowl moves forward hydraulically to push the material out of the bowl.

Ayers says the 13- and 14-yd.3 scrapers, and sometimes the 15-yd.3 models, are pulled with 200- to 250-hp ag tractors–often either a John Deere 8400 with 225 hp or a Deere 8410 with 235 hp. For the 18-yd.3 scraper, it takes more wallop–the 425-hp John Deere 9400.

“One key advantage to the new ejector line is that they’re more of a construction-grade machine–they’re heavier,” says Ayers. Secondly, the ejector scrapers will have a fixed blade. The blade will move down to scrape soil and up to carry, but it will not pivot with the bowl, as the blade does on a carry-all scraper.

“Laser controls can enhance the performance of these scrapers,” says Ayers. Typically a receiving unit is mounted on the scraper, and a transmitter is mounted on a tall tripod set on the job site. The transmitter puts out a laser beam that the receiver follows in setting grade for its respective scraper.

“The beam can be flat, or it can have a single slope or a dual slope programmed into it,” says Ayers. To do a dual grade, the laser can set a slope in two directions. A grade might be high on the south, low on the north, and at the same time slope downward from east to west.

In addition, scrapers are often pulled in tandem, one behind the other. Laser systems can be set up with dual controls, with one receiver on the front scraper and one on the rear scraper. Says Ayers, “You can put several different tractor-scraper units in the same area, and they can all work from one transmitter.”

Caterpillar recently completed introducing five new scrapers with 20- to 30-yd.3 capacity. All have been significantly upgraded from their predecessors. All five scrapers–the 631G, 637G, 621G, 623G, and 627G–feature a new operator station and electrohydraulic controls for improved productivity and operator comfort. On all five models, the new controls include a single joystick in place of three implement control levers.

The scrapers include three arrangements: open bowls, self-loaders (auger or elevator), and twin engines. Caterpillar says it offers the range to meet a wide variety of material appetites, user needs, and applications. Rather than just being a flat-haul machine, a Caterpillar scraper can handle steep grades with four-wheel drive. And self-loading machines are offered for different types of material.

The new joystick hydraulic control, which replaces three levers and up to four other buttons or switches, controls all hydraulic functions, including bowl lift or lower, apron up or down, ejector forward or back, the elevator if it applies, and more, explains Jim Czuprynski, Cat’s commercial manager for construction products.

“That one lever simplifies the operation of the scraper, which does two things,” describes Czuprynski. “It helps young operators become more skilled more quickly, and it maintains efficiency during the longer or second half of the shift, when fatigue comes into play. The single lever helps combat fatigue.”

Similarly, the new electrohydraulic controls also help make operating a scraper easier. “The electronics replace the mechanical control system, so we no longer have the links and levers we used to have,” says Czuprynski. “With the new control system, you reduce the throw of the levers by 50% and the effort by 30%.

“The other major efficiency change with the machine is that we’ve gone to an electronic power train,” he continues. The engine now features an electronic control module [ECM] that controls fuel-injection timing and pressure. The ECM monitors a series of inputs, such as atmospheric pressure, intake-manifold temperature, and exhaust-manifold temperature. That ensures precise fuel-injection timing and pressure for maximum combined efficiency.

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What’s more, the transmission also has an electronic controller, or computer. “In the G-series of scrapers, we’re able to hook those two computers together and they can communicate with each other,” says Czuprynski. “The transmission and engine are now hooked together with a cable we call a Caterpillar Data Link. And there is a main computer in the cab itself that coordinates the actuation between these two components in the drive train.”

Czuprynski gives an example of how the electronic power train functions. “We have something called a ‘control throttle shift.’” Prior to a shift, when the transmission is getting ready to shift, the system will send a signal to the main computer in the cab. That computer in turn relays a signal to the engine and tells it to decelerate. The engine reduces speed and the transmission shifts; when it completes its shift, the transmission sends another signal to the engine to go back up to rated speed again. “That all happens in about a quarter of a second,” notes Czuprynski.

“The benefits of that technology to the end user are that you reduce peak torque loads in the drive train by 30% and you reduce clutch power loads by 50%. You’re going to increase transmission life, but really you increase the life of all the power train downstream also–in the final drives and so forth–because you’re putting less peak load through the power train.

“As for the biggest feature of a scraper, I’d say it’s low cost per yard to move material. The scraper loads, hauls, and spreads material,” says Czuprynski. And in many situations today, compaction is a very important element of the job. Scrapers have the advantage of being able to lay down very thin lifts, resulting in better compaction. In some cases the scraper can meet compaction specifications by itself, eliminating the need for specialized equipment. Most other systems require a loading tool, a hauling machine, and several machines in the fill to spread and compact material. All that can often be done by one machine, in the case of a self-loading scraper. Based on the various applications, customers can gain greater efficiency by applying these scraper concepts.

Terex, a third manufacturer of scrapers, recently announced its S17E, an elevating scraper. Heaped capacity is 17 yd.3, and the machine has 285 net hp. The scraper features an electronically managed engine for increased power and torque; an eight-speed electronically controlled transmission with sequential bump shifts for smooth, low-effort gear changes; and a two-speed, reversible elevator with a general dirt-moving mode and a finish dirt-moving mode for increased versatility.

So for graders and scrapers alike, we think you’ll agree that the manufacturers have put extra effort into the details of their machines, and the benefits show–in extra ease of operation, longer machine life, and improved productivity.