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The ground is never exactly how you want it for new construction, which is why graders and scrapers prove themselves so useful. By Paul Hull |
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When I asked them, several contractors wondered if anyone still made powered scrapers. Most contractors are rarely involved in major highway construction projects and almost all of them remembered scrapers as uncomfortable machines that tossed their operators from their basic seat position as they cut and loaded the earth. That has changed. While excavators, loaders, and dozers receive far more glowing attention by designers and manufacturers (perhaps because many more of them are used), scrapers are more comfortable and easier to maneuver than ever. One common objection to the scrapers of yesteryear involved having to stop it before making changes. Now the phrase "on the go" is as significant for scrapers as for dozers. More comfortable operator stations and new designs also make them more productive. Scrapers usually cope with large projects. The City of Flagstaff, AZ, uses an auger scraper for preparation work at a landfill, preparing the ground for the new loads of solid waste that constantly arrive. "We have three scrapers and we use them for mass excavation at our landfill," says Mike Kennedy of the City of Amarillo's Public Works Department. While those are public agency applications rather than contractor projects, they demonstrate a key rule mentioned by several contractors. A scraper will be an excellent machine for mass excavation as long as you don't have to haul the load too far, certainly less than a mile, say contractors in states as far apart as New York and North Dakota, Alabama and Oregon. The consensus of experienced contractors seems to be: You can't forget that a scraper gives you the production of several machines with only one operator. It digs, loads, hauls, and dumps. You must work out the most efficient method of achieving all those assignments at the site. For short might have to look at excavators, loaders, and trucks, using three machines and drivers to do the work. There are single- and double-engine versions of scrapers, and they can also be part of a "push/pull" team. There are elevating and auger configurations and open bowls. The site conditions determine which is the best for a particular job, and you can rely on a single-engine scraper for the lowest cost and best speed when the grades are not steep and the ground is good. Helped by a pushing tractor, a single-engine scraper will load itself quickly and haul the material with a minimum of fuel and less iron than other models. "If grades are steeper than 5% on the haul and 12% when returning empty, tandem-powered scrapers are the answer," notes Mark Sprouls, who studied Caterpillar and other equipment to determine the best hauling systems for earthmoving. Under some circumstances, scrapers prove more cost-effective than loaders and trucks. "The higher horsepower-to-weight ratio allows twin-engine scrapers to climb grades as high as 35% and four-wheel drive powers such scrapers through underfoot conditions that can stop two-wheel-drive machines," adds Sprouls. "The ability to operate on poor ground conditions can ensure more workdays per year from the twin-engine scrapers, and they can cut cycle times. Acceleration is faster out of the cut and away from the fill." Calculations show that, even though higher owning and operating costs partially counter the increased production, tandem-powered scrapers might still produce the lowest cost per yard. The push/pull arrangement for scrapers has two twin-engine machines hooked up to help each other with loading. The scrapers have hydraulically operated bails and push blocks with hooks. The trailing scraper's bail snags the hook and holds the machines together during loading. A pair of scrapers can work as a team or can separate and work individually with a pusher. The push/pull technique gives high production at the lowest cost because the two scrapers can load in less time than two standard scrapers working with a pusher. Auger scrapers help load granular material, laminated rock, and mud more easily, while elevating scrapers work alone for great economy on hauls with lower rolling resistance. The elevating mechanism breaks up chunks; that facilitates the dumping and tends to enhance the compaction in the fill. It's a benefit that makes them useful for finishing and cleanup work at the site.
There is the perception that scrapers can only work on huge projects. Caterpillar introduced an open bowl scraper, designed specifically for smaller operations. Its bowl is 15 yd.3, and the engine offers net power of 265 hp. This Caterpillar 611 is a scraper that can be push-loaded by the D6R track-type tractor but may be served by a tractor as large as the D7. It can load in 30-36 seconds, travel (loaded) at speeds up to 27.6 mph, and dump and spread on the go. The manufacturer says this size would normally work on jobs requiring earthmoving of less than 300,000 yd.3 The width of cut is 111 in., with a maximum cut depth of 15.8 in. and a maximum spread depth of 20 in. It can turn 180º in an area just over 33 ft. wide. For ease of transportation, the 611 has an overall width of 10 ft., 9 in. and length of 39 ft., 5 in. An innovative feature on this scraper is that, when raising or lowering the bowl, the apron opening size does not change. This gives better material retention and eliminates the need for an apron float switch. The hydraulic, dozer-type ejector provides clean material ejection even for sticky materials. For bigger projects, the Caterpillar 621G, 623G, and 627G scrapers offer capacities of 20, 23, and 27yd.3, respectively. Perhaps most significant about this new G Series are the operator stations and electrohydraulic controls. The single lever implement control combines the traditional three implement levers into one joystick. The operator can raise and lower the bowl, actuate the apron and ejector, set the elevator speed and direction, actuate the auger, and operate the bail with the single joystick. The joystick also incorporates the transmission hold and cushion hitch switches. Today's scrapers give the operator 11% more space. The seat is comfortable with air seat suspension, air conditioning is standard, and there's even places for a lunch box and a first-aid kit. Tow-Along Scrapers Gain Momentum
Today many contractors feel that a pull-along scraper (with capacities from 12 to 18 yd.3) attached to an agricultural tractor may be a more economical procedure. "The tractor is not dedicated to just scraping," mentions Jeff Kennan of Reynolds International in McAllen, TX, manufacturer of pull-along scrapers for the world market. "It can be used for other attachments like rollers, disks, and water wagons. One of our contractors in Texas has been using this method for road construction for at least 15 years." Andrew Bonde of John Deere, which offers all kinds of scrapers, pointed out another aspect of this team of earthmoving machines. "Contractors tell us they can sell a used agricultural tractor more easily after the job. There is only one market for a dedicated scraper," observes Bonde. "We see a growing interest in scrapers as attachments pulled by tractors." Caterpillar's recent alliance with CEPCO, a manufacturer of tow-along scrapers, seems to reinforce this trend. Winsco Construction in Mayflower, AR, replaced its powered scrapers with what it calls scraper pans (from Reynolds), pulled by New Holland four-wheel-drive ag tractors. "We can now move the dirt cheaper and quicker," asserts David Winston, project manager for Winsco. "With the scraper pans and tractors, we have about one-third of the investment in machinery if you compare it to a powered scraper that could haul the same material." He also mentions that, with their good flotation, they are just as quick and more stable than powered scrapers, work the slopes more easily, and even get into places where a scraper cannot reach. "They're cheaper to operate," adds Winston. "And they are not a high-maintenance item." Jeff Kennan of Reynolds says, "Contractors who have used both types of equipment tell us that the reason they made the change from a powered scraper to a tractor and scraper was the lower cost per yard in earthmoving. With a brand-new tractor and two scrapers, you're talking about an investment of about $200,000. With a dedicated, powered scraper that could be $700,000. The powered scraper is more expensive to maintain too." Another aspect of the tractor-scraper combination contractors mention is that it works on wet or muddy terrain where the heavier powered scrapers may bog down. Prime Manufacturing Company of Mississippi, in business for 125 years, finds the demand for their Carry-All scrapers (with models of 10, 12, and 14, and - by contractor demand - 17 yd.3 in 2001) growing fast. "A contractor can pull two of those with the right tractor of, say, 360 to 400 horsepower," notes Randy Henning of Able & Sons in Welsh, LA. "Their lower cost is an obvious advantage, and they can do as much as the old-fashioned scrapers for earthmoving in road construction." Manufacturers and contractors agree that you would not use the tractor-scraper method for moving rock, but for common earthmoving applications - even with small gravel-type rocks - it's worth investigation.
Expect homework when looking for the best grader for a project. My first confession on the subject of graders must be that, like so many contractors and project engineers, I thought of them as awkward, difficult-to-control machines. They never looked as solid or streamlined as excavators or loaders! It was an easy impression to get since many grader operators are not contractors but county public works employees maintaining gravel roads rather than grading sites finely enough for paving or building. I became enlightened after watching and talking to an operator for Century Construction Company, based in Lewistown, MT, with contracts all over the west. "The operator can get down to an accuracy of about a quarter inch with that little grader," observes Brant Zabel, project superintendent for Century. Gale Price of Empire Machinery in Flagstaff, AZ, agrees: "We use bigger machines on highway projects, but repaving this truck stop forecourt is a perfect job for a small grader. It's good on parking lots and at schools and hospitals. The machine provides much of the accuracy, but a good operator takes us from very good to perfect. Today's graders are capable of extremely good accuracy, but they always benefit from having a good operator who knows how to control the machine to get its best performance. Most of the contractors in this region have graders. They are different makes and sizes, but they all work best when the operator is well trained and motivated." While most graders are self-contained units from such manufacturers as Caterpillar, John Deere, Komatsu, Volvo (Champion), and Hitachi, some grading happens by attachments pulled along by tractors or mounted on compact excavators and loaders for smaller projects. "When my contracting company began, we did landscaping. Now we do bigger dirt-moving projects," notes Theresa Vigil, owner of Diamond Back Construction in Colorado. "We do a lot of fine grading and use Bobcats with attachments." Vigil knows about scrapers too - the old kind, that is. "I operated a scraper when I first came to Denver, and the pay was fine," she adds. "An injury on a scraper caused me to end that work and direct me into my own company." Ask your contractor colleagues what they use and why. Sometimes they will tell you that a combination of machines gives the best results. Sometimes they will name a manufacturer who has developed a strictly regional grader, good for specific soils and terrain.
Road maintenance causes the public to notice graders. They make dirt roads level and, in many communities, give alleys with garages and garbage cans a once-a-year treatment. These days, with cities and counties outsourcing jobs that use equipment requiring maintenance and skilled operation, it could be a new area for expanding one's business. This work seldom requires quarter-inch accuracy, but it does fill potholes and, in places with rugged winters, pushes snow to the side of roads and streets. Among products from smaller manufacturers in this arena is the Harley Grader from Glenmac, which handles highway shoulder reclamation behind a tractor. Huber's M-850-C Maintainer compact grader can be used for grading jobs from base to finish work and for spreading asphalt, stone, fill dirt, and other materials. The Maintainer, 14 ft. long and 7 ft., 5 in. wide, offers five hydraulic attachments: scarifier, side dozer, bulldozer, front-end loader, and berm leveler. Add such attachments as scarifiers, and graders can even tear up old roadbeds. In the past, graders at construction sites achieved accuracy by making repeated passes over the ground. With today's instruments (including those from Topcon, Trimble/Spectra Precision, Leica, AGL, and Laser Alignment), the number of passes can be reduced dramatically and the grader's productivity improved because of fewer workers needed. Nobody has to give manual signals or guard stakes. In 1886, Champion produced a pull-along grader. Today the "Creep Mode" of the 700 AWD models has the moldboard pulled not pushed, so the rear wheels do not scuff the finished grade. Power and precision are the goals of this series from Champion, now part of the Volvo Construction Equipment Group. The all-wheel-drive system gives an even distribution of power through independent, variable displacement pumps and high-torque motors at each front wheel. The front-wheel speed sensors control the relative front to rear speeds. By engaging only the hydrostatic front wheels, the grader operates in the "Creep Mode" mentioned above (with speeds infinitely variable between 0 and 2 mph). The blade is the key component of any grader. In the Champion 700 Model Series VI graders, the design incorporates three blade mobility systems: the Blade Lift System for accurate blade control; the Circle Turn system; and the Movable Blade Control System (for improved mobility, reach, and stability). For precision in the tool handling, feathering is a favorite technique with these graders. Contractors nationwide mention many of the same features as important in their purchase decisions. One feature stands out as the most important of all. Whether it's fine grading for a housing development in California, street work in Illinois, secondary road improvement in Utah, or highway construction in Kansas, the operator wants to see exactly where the blade works. That is the number-one requirement. Other important features include a quiet, comfortable cab allowing the operator to work a long, productive day; controls easily reached and used; good brakes; no inching pedal, if possible; reliable diesel engine power; a moldboard with directional versatility; and all-wheel or four-wheel drive. Clearly contractors want the grader to be as easy to run as possible. This is especially true of the larger contracting companies (such as Peter Kiewit) that rely on hired help, as opposed to owners/operators who often do their own driving and maintenance. Are graders good rental items for contractors? Wyoming Machinery, in Casper, WY, offers a full range of graders for rent-to-purchase contracts. "Contractors use the graders for water line and sewer work, for housing developments, and for road construction jobs," comments Jim Pieper of Wyoming Machinery. He works with contractors from 16 counties in the state. Grader availability is the most important feature. "That doesn't just mean that we have one ready for the contractor," explains Pieper. "It means that the grader is available for constant work at the site when the customer needs it. Reliability is essential. We have service facilities to make sure that each machine on the job is in good condition. We usually rent out graders that have 8,000 hours or less on the main frame. Or it could be a model that has been overhauled and reconditioned to act like new." Renting for a period of a month or so (depending on the project) or rent-to-purchase agreements are good options for contractors who do not want an immediate purchase with all the expense. "We see more and more contractors renting equipment for their highway construction projects," comments Pat Bettise of ICM in Billings, MT. "That includes scrapers and graders. For some of them, winning a road-job contract might not be their usual business, so renting the required equipment makes sense." Paul Hull is a frequent contributor to Grading & Excavation Contractor.
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