We take it for granted that this year’s model is better, whether it is a personal car, a pickup truck, or the equipment we use in our business. Most of the latest models in construction equipment do perform better, but the reasons are not always confined to the obvious changes. New techniques–a whole new approach to the type of equipment used–are making the work not only more productive but more comfortable too. Scrapers used to be the machines on which inexperienced workers would start (and make all their mistakes) because they were perceived in much the same way as the old family car for the teenager with the new license. Spending some time training operators to run equipment efficiently will soon pay for itself in better work, believe owners of scrapers and graders.
Comfort in a rumbling, ground-grabbing machine such as a scraper does not mean that the operator sits back and lets his equipment do all the work and make all the decisions, but it does mean that he or she will not be tired by lunchtime and unproductive in the afternoon. Comfort, when we are talking about excavation and grading machines, has nothing to do with laziness. Quite the opposite is true. The comfortable operator works well for more hours, and usually the work is more accurate. The ability of the operator to concentrate on the assigned job (rather than on aches and awkward sitting positions) has great influence on getting that job done right the first time.
|This tire was developed especially for large scrapers.|
Scrapers–considered ideal machines for earthmoving jobs involving short distances, less than a mile, say–usually work on rough, unfriendly terrain. What makes the contact between a scraper and the ground it works? The tires. Which parts of a scraper can stop the machine if they malfunction? The tires. We can become so wrapped up in cubic yards of capacity and horsepower that we ignore those components of scrapers and graders. They might be so obvious that we don’t notice them. “They could be the parts you change most often,” observes Keith Mitchell, whose contracting company has worked scrapers in the Dakotas, Wyoming, and Montana. “It helps my costs if the tires last a long time.” The larger the ground-contact patch for scraper tires, the more likely they are to enjoy long life, and there are other aspects of tire design that can contribute toward better operator control and comfort. Michelin introduced a radial tire especially for large scrapers. The XMS is described as an E3 tire, available in 40.5/75 R39. Its practical goal is to provide the scraper user with good traction, superior resistance to damage, and a smooth ride.
It has been our experience that, anytime a tire manufacturer develops a tire specifically for one type of construction machine, the product is worth serious consideration. We have seen it with skid-steers, wheel loaders, and now scrapers. “It has a high lug-to-void ratio,” states the manufacturer, accounting for claims of better performance. “The staggered tread blocks help improve operator comfort, while the edges of the tread pattern offer exceptional lateral grip.” The tread on this Michelin tire has a square format to protect the shoulders and sidewalls, and there is a thick rubber bridge at the base of the tread, designed to increase the strength of the tread blocks and create strong resistance to punctures.
So much for the specs. What does a user say? Dave Coveney of Ford Construction in Lodi, CA, tells us that his 31 scrapers come across many different soil conditions. “We needed a tire to cope with all those conditions, and the XMS has proven its superiority over some other well-known brands. We are getting more than 3,500 hours off the front tires, and the Michelins have been about 20% better than any others we’ve tried. Sometimes our scrapers are traveling at more than 30 miles per hour, and the tires must be able to handle that.”
You’ll find phrases such as “enhanced productivity and operator comfort” in most manufacturers’ scraper brochures. The reason is that those two features have been requested by users. With large construction machines, manufacturers will not change the design every year because the cost is prohibitive. The G Series of scrapers from Caterpillar started arriving in 2000; nobody should expect an H Series this year. Among the new features that make the G Series better than its predecessor (the F Series) are improvements in the power train (with an electronically controlled tractor engine) and in the controls (with a single joystick replacing three implement control levers).
Filling the Scraper
|Agricultural tractors are finding plenty of work at construction sites.|
|Self-contained scrapers have a history of productive success.|
The two most popular techniques for filling a scraper have been a push-load system and one that is self-contained and independent. The Cat 627G is a good example of the latter. With a capacity of 20 yd._, plus twin engines, it can load independently or be push-loaded. The auger-scraper arrangement for this model gives it a self-loading capability and expands the capacity to 21 yd._, while the push-pull configuration has the machine working in tandem with another 627 to give high production and low cost per yard. G Series scrapers from Caterpillar have been designed to give the lowest cost per yard for road construction projects and site development where the amount of material to be moved is less than 500,000 yd._ The manufacturer expects this type of scraper to be used when the hauling distance is more than 1,000 ft. Cat D8 and D9 tractors have worked well with both the 621G and 627G.
“The biggest advantage is that self-contained scrapers really do self-load,” asserts Dennis O’Rourke, owner of Sureway Construction in Alberta, Canada. He is talking about auger scrapers, Cat models with tandem power: an engine for the tractor and another for the scraper. “They are cutting ditches, building highways, and stripping ahead,” adds Joel Yundt, project superintendent for the contractor. “They have an auger, so you can mix material while you’re loading, which makes the fill easier to manage. We don’t have to dedicate a grader or dozer to work in the fill.”
The TS14G from Terex is the heir to more than 11,000 TS14 scrapers in previous series (B, C, D, and F) that have been working worldwide. It is recommended by the manufacturer for small to medium earthmoving projects. The 340-hp machine has a heaped capacity of 20 yd._, a struck capacity of 14 yd._, and a payload of 48,000 lb. Among the benefits offered by this scraper, Terex stresses the low maintenance costs, helped by the new, extended intervals for oil changes (450 hours with the manufacturer’s filters), fuel filters (900 hours), and coolant filters (also 900 hours). Maneuverability of the scraper is important to the operator, and efficiency in this aspect of the machine’s operation can significantly improve the daily productivity. The TS14G can complete a full turn within a width of 33 ft. It has full 90° steering to the right or left, with two hydraulic cylinders (mounted low to improve stability) providing the power. The degree of rotation of the steering wheel controls the speed of the turn.
Some of the discomfort in yesterday’s scrapers was caused by the working motions of the scraper’s bowl. Terex offers a cushioned bowl suspension system, especially appreciated at higher speeds. To attain good penetration of the ground, the bowl uses positive downpressure while the semiradial, power-down apron gets down and around the load smoothly. Recognizing that all “earth” is not the same, there are reversible, interchangeable, four-piece cutting edges that can be adjusted in drop center or alternative configurations. What seems a small point, but might be most practical, is that the arms of the apron are mounted outside the bowl, so they are neither impacted by the abrasion of the load nor restricted by it.
The Third Option Continues to Win Support
|Longer service intervals for scrapers reduce operating costs.|
|Scrapers often work in tandem for greater productivity.|
There is a third method of loading: the tow-along (or pull-type) scrapers. These are really attachments, and they originated in the farm machinery sector. They are pulled by agricultural tractors, and some companies making them have been successful since the beginning of the last century. There seems to be a continuing revival of interest in these types of scrapers for construction-related projects, and some people in the industry have forecast that they will eventually take over from independent or self-contained scrapers as the preferred equipment. Miskin Scraper Works, for example, has been making dirtmoving equipment since 1917. It has introduced scrapers for construction use (with 9-, 17-, and 24-yd. capacities) that can be pulled as single units or in a train of scrapers behind a single tractor. These construction scrapers are heavier and built more ruggedly than their agricultural relatives. “The 24-yard model is the biggest scraper capacity anywhere,” says Mike McRory for Miskin in Mississippi. “Road builders like our scrapers. One reason is that there is nothing to go wrong on them–no transmission, for example. They work and work, and the user may well change his tractor before he has to change the scraper.” The tow-along scraper is a simple, tough, and reliable piece of equipment, which explains why grading and excavating contractors are finding it so interesting.
Currently the largest manufacturer of tow-along scrapers, Reynolds International in McAllen, TX, reminds us that these earthmoving machines can be pulled by either track-type or wheeled tractors–whichever is available or better for the terrain. Reynolds calls its scrapers the Carry-All range and describes them as having a basic design that involves a front gate and pivoting bucket. We counted 17 models (including some with low ground pressure for the most sensitive terrain) with heaped capacities from 5 to 18 yd._ and cutting widths up to 168 in. While the larger models require tractors with 300 hp or more for a single-unit system, the small ones can be worked by 100 hp or less. A recent model, the 17E10.5, is described as an ejector scraper with laser leveling. It has a three-piece, reversible cutting blade to fill the 17-yd._ bowl. How much does it cost to run a tow-along scraper as opposed to a self-contained unit? Reynolds has a spreadsheet available for calculation of those costs, based on the initial investment, repair costs, distance to be covered, speed required, efficiency of the system, and swell factor.
Some parts of our country had a dry summer this past summer. In South Carolina, pond levels were low or nonexistent. “This has meant that landowners have been able to clean out their ponds for the first time for years,” observes Brian Derrick of Ridge Spring, SC. “They have used tow-along scrapers to do it.” In Alabama, tow-along scrapers have been used for similar work. “We use them here to build pond dams,” says Dane Linton of Goshen, AL. “They require no maintenance, and the ones we favor [Prime Manufacturing] are well built.” Another popular site for a small tow-along scraper–a 7-yd.-capacity model, for example–is ground being prepared for building foundations.
|These tow-along scrapers are simple, rugged pieces of equipment.|
Prime Manufacturing in Poplarville, MS, is an old-time company. “Our scrapers–some of them also known as Carry-Alls–are recommended for a variety of jobs, including general land management, building ponds and roads, and the preparation of construction sites,” comments Payton Morrison of Prime. “Pull scrapers are generally not recommended for excessively rough, moist, or rocky conditions that require push assistance from a bulldozer or do not permit all of the scraper tires to remain in contact with the ground.” Morrison adds that pull-type (or tow-along) scrapers are appropriate for jobs that require the movement of less than 500,000 yd. of dirt. That amount seems to be the minimum required to provide significant profit for self-contained scrapers. Because the regular maintenance of a pull scraper will prolong its life, Prime recommends regular inspection of hydraulic lines and connections for leaks or damage, as well as a daily application of grease to all grease fittings and inspection of tire inflation, tongue and lug bolts, hubs, wheels, spindles, blades, and all pin connectors.
The consensus among contractors seems to be that a tow-along or pull-type scraper is less expensive than a self-contained unit. Users can purchase a power unit, such as a tractor, that will perform multiple tasks by using different attachments, and the wear on the scraper is significantly less costly than that of a self-contained unit. It can also be easier to transport a tractor/pan combination. Reports also indicate that the tow-along scraper is easier to trade in or resell, a point that is especially useful for those contractors who might need scraping equipment for only occasional projects. But again, tow-along scrapers are not recommended for soils that include large rocks, and hard or frozen soils might require special bits or ripping first.
Other companies offering tow-along scraper systems include John Deere and New Holland, both leaders in the manufacture of agricultural tractors. “A key reason for the success of pull-along scrapers has been the improvement in tractors,” notes Randy Rust of Ashland Industries in Ashland, WI. “Grading and excavation contractors are accepting that these powerful tractors–some of them with nearly 500 horsepower–can play an important role in construction as well as in their original market, agriculture. Some of today’s drawbar configurations transfer much of the weight to the power unit, and the flotation you can get with a tractor-plus-scraper combination means you can extend your working season to include those times at the beginning or end of the regular season when self-contained scrapers may not handle the wet or muddy ground.” With a well-designed transfer of weight, the same gross weight can handle a larger capacity. Ashland tow-along scrapers tend to be “narrow and stout” rather than wide; that might help them deal with a wider variety of soils, including clay dirt and tight clay. To put it simply, a narrow scraper lets the tractor pull more easily and deeper.
Just Fine, Thank You!
|Grader manufacturers pay special attention to blade design and control|
It amazes most people that a grader can be so accurate. I’ve met people who wonder how a “big, awkward” grader manages to go straight when it has that big blade always at an angle. Whatever the public perception, the motor grader has been one of the most frequently used machines for both public and private applications. Contractors agree that being able to see where the blade is going is a prime consideration in selecting a grader, but there is still plenty of operator skill and concentration required to make sure the work is done in as few passes as possible. Years ago, some contractors told us, the new workers would learn on the scraper and end up on the grader. The chief skill required of a grader (or scraper) operator is the ability to steer in the right direction, regardless of the bumps and slopes. Scraper drivers soon learn whether it is better to turn going down the slope or up. A feature on Komatsu’s Laterra graders is the circular geometry blade. It enables 90º bank sloping and accurate positioning while giving good ground clearance. There are three models in the Laterra series, with operating weights from 30,525 to 34,390 lb. The horsepower varies from 140 to 180, and variable horsepower is available on all models.
Fine grading is a term still used. It seems almost unnecessary to say it now, because graders are so accurate as they level the ground, whether it is for a new road, reshaping an old road, or for basic grading work at construction sites. One of the challenges for traditional self-contained graders comes from equipment such as skid-steer loaders that can do the fine grading for contractors if the right attachments are mounted. It would be a mistake, however, to imagine that a small loader will be more accurate (i.e., give a smoother result) than a self-contained motor grader.
The design and use of the blade seems to control success. Volvo says its graders (the ones we used to know as Champions) in Series VI have blades that are right for every job. The operator can set the blade angle up to 90º vertically on both sides of the machine, as well as adjust a 21º down angle for clearing and cutting ditches. The mobility of the blade allows the operator to clean ditches in a single pass while keeping the grader’s wheels up on the shoulder where the traction is usually better. Volvo also claims that the Series VI blade has the longest reach outside the tire profile to improve cycle times and enable the user to cut a 2:1 bank slope with the moldboard completely outside the tire profile. The operator can also lower the blade to some 33 in. for a deep cut, while the lift above ground means that the blade can be carried over obstacles at the job site.
All-wheel drive for a grader has obvious advantages. This kind of system distributes the power evenly to each front wheel and, if traction changes at either front wheel, gives instant power adjustment so that the best pulling power is attained. The system can be used in two-, four-, or six-wheel modes. When the all-wheel drive is disengaged, the grader will return to four-wheel tandem drive with no parasitic loss. Also consider the possibilities of the Champion Creep Mode. This lets the operator disengage the rear drive and pull the grader at low precision-grading speeds, using only the hydrostatic front-wheel drive.
Do you use your grader for roadwork? This is usually a municipal or county job, but the trend toward outsourcing or privatization for some public works makes one wonder if grading contractors could capture worthwhile contracts in that sector. There are many thousands of miles of gravel roads; they enjoy grading at least once a year. An attachment we spotted that seems worth investigating for grading where there are ditches is the Road King Sloper from Rockland Manufacturing in Bedford, PA. “It can double your grader’s productivity,” claims Bob Shaffer for Rockland. “You can use this sloper and articulate the grader at the same time, while the extra reach to the side means that the grader stays on the road and out of the ditch. It can also be used for tail grading if you get that attachment too.”