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By Greg Northcutt
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Stranded with a flat tire or disabled by a broken track is no way to make money in the dirt moving business. That’s why manufacturers—backed by sophisticated design techniques and continuing technological advances—continue to push the performance and durability of tires and tracks to new heights. From motor graders, scrapers, and bottom dumps to dozers, compact loaders, and excavators, your choice of tires or tracks has a direct impact on profits. Choose right and you’ll enjoy top productivity from your machine. Choose wrong and you risk wasting precious dollars and costly delays. Understanding differences in designs, materials, and methods used to build tires and tracks can help you select the ones best suited to keeping your machines mobile and your projects rolling. Tire Components In a bias tire, plies of fabric, which give the tire its strength and cross-sectional shape, run diagonally from bead to bead and diagonally to the direction of motion. Steel belts, also running diagonally from side to side, help protect the layer of fabric from punctures and give the tread stability. In a radial tire, a single layer of steel cord runs radially from bead to bead, and laterally to the direction of motion. Steel belts, running diagonally to the direction of motion, increase the rigidity of the tread, which reduces cutting and growth of any cuts. “The radial design is better for long-haul distances because it produces less heat buildup,” says Cara Junkins, OTR (off the road) field engineering manager, Continental Tire North America. “Also, because it has a flatter footprint, it provides better traction. On the other hand, bias tires have a thicker sidewall, so they provide more stability on loaders when lifting heavy loads. Bias tires also provide an advantage in applications with a high risk of sidewall damage due to their sidewall cut resistance and repairability.” Whether bias or radial, the tire fabric is secured to the rim of the wheel by the bead, a strand of wires on each side of the tire. The ability of a tire to resist wear, heat, and abrasion is based on the types and amount of rubber and oil compounds used in making it. “It’s like mixing a cake,” explains Ken Brodbeck, manager of original equipment and export sales engineering for Firestone. “You use different ingredients to give the tire different features.” Flat tires are an expensive—and annoying—part of maintaining a fleet. Goodyear Tire & Rubber Co.’s new DuraSeal Technology, the first built-in sealant for commercial truck tires, aims to make them a hassle of the past. The heart of DuraSeal is a gel-like compound that instantly seals punctures in the tread area up to a quarter-inch in diameter. That means drivers don’t have to stop for repairs, which saves money, downtime, and aggravation. Goodyear says its DuraSeal tires—initially available in the new Unisteel G287 MSA and G288 MSA mixed-service lines—will last up to six times longer than conventional tires. Tread Styles David Ashby, construction tire product manager for Firestone Industrial Tires, notes some of the considerations involved in designing tires for skid-steer loaders: A standard skid-steer loader tire is designed with a high rubber-to-void ratio. The idea is to provide as much rubber on the ground as possible to better withstand wear from constant skidding. The lugs are angled over much of the tire surface to provide more tractive effort for digging or pushing into piles of dirt. These lugs converge in a bar across the center of the tread to improve wear and riding comfort. Increasing the lug depth adds to tire durability and puncture resistance. Tread depths on his company’s skid-steer tires range from twenty-two thirty-seconds for a standard 12 x 16.5 tire to forty-six thirty-seconds for the same size tire with extra deep lugs. To withstand the increased torque loading and risk of puncture by striking debris when skidding sideways, skid-steer tires also feature thicker sidewalls than tires designed for other types of similar-size machines. Firestone’s premium skid-steer loader tires, for example, are designed with extra sidewall and wheel rim protection. “These tires have a thicker area of rubber that extends over the rim,” Ashby says. “This prevents trash and debris from getting between the rim and tire and causing a leak, and protects the tire and rim when driving over curbs or other obstructions.” More information is available online at www.firestoneag.com Sorting Through Some
Choices When it comes to equipping end dumps, articulated dumps, and scrapers with Continental or General tires, your choices include rib, traction, rock, and flotation designs available with shallow, regular, or deep tread thickness, depending on a particular tread design. For motor graders, you can choose either traction or rock design tires. It’s a similar story when buying wheel loader or wheel dozer tires.
In addition to traction and rock tire designs, the selection includes three that feature an extra deep tread 2.5 times as thick as a regular tread. Junkins notes the advantages of each: The rock design provides excellent traction while still providing rock damage resistance. The super smooth tire with a massive tread offers the ultimate in resisting rock damage and penetration. The half-rock/half-smooth design features a smooth tread on the outboard side of the loader’s front position to resist cuts and tears, while the inboard lugged-rock design equalizes tread wear across the surface of the tread and provides additional traction. Dual-use tires, suitable for both hauling and loader applications, offer still more choices. More information is available online at www.continentaltire.com In marketing tire products to the earthmoving industry, Firestone is promoting a new application for its forestry flotation tires—to equip four-wheel drive farm tractors as large as 500 horsepower for pulling two or three 18-cubic-yard pull-type scrapers as a more economical alternative to self-propelled scrapers. More information is available online at www.firestoneag.com In the case of truck tires, retreads offer a more economical alternative to buying new tires. They’re a popular choice. In 2001, truck fleets bought about 15.8 million new replacement tires. That’s less than the 17.1 million retreads purchased that year. Retreads represent about 50% of the total tire market and about 60% of the construction tire market. Market acceptance of retreads reflects several factors. “Retreads cost about one-third the price of a new tire with comparable performance,” says Don Schauer, communications manager with Bandag. “Bandag retreads are designed and tested to compete with best-in-class new and retread tires. With continuous advances in casing inspection technology, the quality of retreads has improved dramatically over the past five years.” Retreads also offer advantages for the environment. In addition to reducing the number of tires sent to landfill, they also reduce the demand for petroleum products. It takes 22 gallons of oil to manufacture one new truck tire. Most of that is found in the casing of the tire, which is re-used in the retreading process. Manufacturing a retread requires only seven gallons of oil for a net savings of 15 gallons. More information is available online at www.bandag.com In some applications, such as sites strewn with construction debris, pneumatic tires may not be the best choice. One alternative when using skid-steer loaders in such a situation is a flat-proof tire like the all-terrain Nu-Air tire made by McLaren Industries. It features three rows of cushioning holes in the sidewall, a deep lug tread pattern, and sidewalls engineered to prevent cuts and snags. “This tire combines the strength and stability of a solid tire with the smooth, cushioned ride of a pneumatic tire,” says George Zafirov, the company’s marketing manager. “It can be used safely with over-the-tire tracks, and tests show it has three to five times the life expectancy of a pneumatic tire. It offers a much smoother ride than a solid or foam-filled tire and it contains more rubber than a foam-filled tire for more durability. Even if you cut a piece out of it while working on a job site, the tire can still be used, so there is no machine downtime. More information is available online at www.mclarenindustries.com The Case for Rubber
Tracks Steel tracks, a continuous loop of ground-gripping metal bars alternating with debris-shedding open spaces, provide the ultimate in traction and durability, especially in hard-packed or harsh, abrasive surface conditions, such as rocky sites or land-clearing projects. At one time, all tracks were metal. They remain the only practical option for dozers and large excavators, in part because of the high cost of making large tracks from rubber. However, rubber tracks own the compact track loader and mini-excavator markets for several reasons. “A rubber track is solid all the way across its surface,” explains Mike Giordano, national track department manager for Solideal Rubber Tracks. “By keeping debris out of the undercarriage, rubber tracks extend the life of rollers, drive sprockets, idler arms and other components. Unlike steel tracks, rubber tracks do little, if any, damage to sensitive surfaces, like turf, concrete, or asphalt. Also, they are much quieter and produce much less vibration for a smooth ride.” Rubber tracks are also used with transporters, dumpers, and other construction equipment, including personnel carriers and over-the-tire applications to improve traction and flotation of skid-steer loaders. “Had manufacturers not made the advances in rubber tracks as they have, I don’t see how these tracks would enjoy the success they do now,” says Giordano. “Five years ago, the only tread design for compact track loaders was a straight-across bar. It didn’t provide enough protection for internal components of the track. Since then, manufacturers have improved rubber tracks to provide the needed traction while reducing vibration and increasing service life significantly. “In most cases, today’s compact track loader rubber tracks are a real bargain. They offer two to three times the traction of just a few years ago for the same price.” Making Tracks Like tires, rubber tracks are available with various tread designs. As Giordano points out, a smooth, lug-less design would offer the smoothest ride but little, if any, traction. “The goal is to provide the perfect mix between a lot of void space for the most traction and as much rubber in contact with the ground for the least vibration to match the job requirements,” he says. Tread designs for rubber tracks include an aggressive pattern with deep, narrow lugs placed straight across the track. It provides maximum traction along with the most vibration. An angled lug design provides less traction but a smoother ride. An offset design, used with excavators, features a lug on one side of the track directly opposite a corresponding void on the other side. Lug and void positions alternate from one side of the track to the other along the length of track loop to provide a smooth ride. For compact track loaders, Giordano likes his company’s B design. Deep, sharp-edged lugs are arranged in different directions. “Far and away, it’s the best long-life traction design we’ve found,” he says. In addition to tread design, the riding comfort of a rubber track depends on pitch, the distance between the centers of two metal pieces embedded in the track. In a track with long pitch, the lug bars on the metal pieces contact every other tooth of the drive sprocket. “This is how steel tracks were made for years,” Giordano says. “It’s also simpler and less expensive to make than a short pitch track, because it has half the metal pieces. But, the short pitch track provides a much smoother ride.” With the short pitch design, every tooth of the drive sprocket grabs each lug bar of the metal pieces. “This produces half the vibration for a much more comfortable ride,” says Giordano. “The difference in noise, vibration, and operator comfort is huge.” The main reason for failure of rubber tracks is damage to the steel cords, he adds. Deep cuts in the track can expose the cords to moisture, causing them to rust and eventually to break. High impacts, such as running tracks over curbs and other sharp objects can also damage the cords. The better the rubber quality, the better it resists cuts. “Natural rubber has more rebound than synthetic rubber which makes it more resistant to the impact of rocks, curbs, and other sharp objects,” he says. In addition, although forged metal pieces are more expensive than cast pieces, they’re also stronger and more durable. Among the choices in rubber tracks is the V-Track System. It’s the latest line from Solideal and is designed for machines weighing from 0.5 to 2 tons. Named after the layout of the metal pieces, the design features a longer distance between the metal pieces. This offers several advantages, Giordano notes. “It increases longitudinal flexibility of the track,” he says. “This requires less energy, leaving more power for other machine functions. The bigger gap reduces bending stresses for a lower risk of transverse cracks in the track and, by improving evacuation of foreign materials, like stones, reduces wear and accidental damage to the track, sprocket, idler wheels and guiding rollers. This design also increases axial stiffness to reduce de-tracking, and it provides continuous contact between the guiding roller and two consecutive metal pieces, resulting in far less vibration.” More information is available online at www.solideal.com Steel Track Variations Evertire Inc. makes a line of one-piece rubber pads, called Everpads, for excavators and other steel-track machines. “The pads are made of industrial-grade rubber specifically formulated and geometrically designed to compliment the operational stress dynamics and vibration of tracked equipment for optimum machine performance and reduced replacement costs,” says Nick Abeyta, a company sales representative. “This results in longer-lasting pads, better traction, and increased life of expensive undercarriage components.” The smooth-faced pads bolt onto the grouser from behind using four nuts. “There are no bolt holes to clog with debris, so it’s easy to replace the pads,” he says. “You can install them on a set of tracks in about two or three hours compared to several days with other types of pads.” More information is available on line at www.evertire.com Quality is important when buying rubber track pads. “Poor quality pads can cost you more in the long run,” Abeyta says. “Many operators don’t realize that less expensive, inferior quality pads can cause a lot of undercarriage vibration. Over time, this vibration can damage track drives, pins, sprockets, idler arms, and components.” Tracks for Tires They’re also designed to run loose, allowing objects to pass between the steel track pad and tire without damaging the machine. “If the track is installed too tight and a rock or brick tried to pass through, the tire wouldn’t be able to cushion this mass, and you’d probably break an axle or other drive component rather than simple damage to the tire,” he says. Grouser Products offers three different track styles. All three feature Grouser’s patented open side plate. “It allows for excellent clean-out in the pivot area for field adjusting,” Luther says. “On a cold, rainy worksite, the importance of this unique feature cannot be overstated. Grouser tracks also feature large 1.25-inch hardened, replaceable bushings and utilize the run loose design.” The Bar Track is a heavy-duty contractor-grade set of tracks. “It is approved by all the major OEM skid steer manufacturers because of its self-cleaning cross bar style,” he says. “The standard in over-the-tire metal tracks, it is designed for soft, muddy, and loose ground conditions where tires lose traction the most.” The Soft Track utilizes a bolt-on replaceable surface-sensitive insert that minimizes any damage to concrete and other hard surfaces. Similar in concept, the Grouser’s Hard Track uses a replaceable steel shoe. Fitting the track to the machine the first time can take up to an hour or so, Luther reports. “After that, the track can be installed in 20 minutes and removed in 10 minutes” he says. “A skid steer owner should look at tracks as an essential tool for increasing productivity,” Luther says. “You should do your homework on the different brands and styles of tracks that are available. Talk to your dealer about the tracks that are recommended by the skid steer manufacturer and what track is best for your application.” More information is available online at www.grouser.com The Protrac line of over-the-tire tracks, made by McLaren Industries, includes two full-flotation tracks made of manganese-enriched steel alloy with different shoe types. The Protrac Rubber track has heavy duty rubber pads, while the Protrac Magnum has steel with steel plates. The two shoe types are interchangeable. “You can rebuild each type of track by replacing any worn out part,” says marketing manager George Zafirov. A third Protrac product, the Diamond track, features unique, diamond-shaped crossbars. “They’re designed to keep the machine from sliding sideways when maneuvering on a slope or in wet or icy conditions,” he adds. More information is available online at www.mclarenindustries.com A pin-together design makes installation and removal of Solideal over-the-tire rubber tracks quick and easy, says Giordano. He contrasts them to a tension-based system, which may require several hours of pushing, prying, and other work to mount or dismount. “Our system combines the best of steel and rubber tracks,” he says. “To install them, you drive onto the tracks, bring them together with a ratchet strap, adjust for proper sag, pin the track ends together, remove the ratchet strap, and you’re done. You can install both tracks in about 15 minutes or less.” More information is available online at www.solideal.com Tire-Track Swapping
Tracks for Trucks The independent tracks can be used with trucks ranging in size from 0.5-ton to heavy-duty trucks, like the Ford F550 and GMC GM5500. One type of tracks, designed for 0.75-ton to 1.5-ton trucks, measures up to 16 inches wide and produces only about 1.5 to 3 psi ground pressure, depending on the particular truck model and weight, reports Del Wright, the company’s marketing manager. He tells of his experience driving a truck equipped with a set of these tracks in deep snow. “The truck sat only about 4 inches down in the snow, while I sank down to me knees when I tried to walk in it.” The one-piece, composite-reinforced tracks are made of a rubber compound, formulated to remain flexible in extremely cold weather and to withstand unusually hot weather. They do not affect the vehicle’s normal turning radius, Wright says. For trucks up to 1.5 tons, the track system attaches to the wheels using the existing lug bolts. The original installation, which typically requires adding an adapter to the truck’s steering arm and leaf spring, can be done in less than an hour, he reports. After that, installation is faster. An internal suspension system oscillates to follow uneven terrain to maintain traction and provide a smooth ride, he notes. “Optional steering assist allows you to steer while sitting still for easier maneuvering in tight areas,” he says. The 200 Series model track system, which requires a slightly more involved installation, can be used with a maximum gross vehicle weight of 20,500 pounds, Wright adds. “The tracks are capable of speeds up to 40 mph, but we don’t recommend traveling a long distance at that speed,” he says. More information is available online at www.mattracks.com Greg Northcutt writes frequently on construction and business issues. GEC - March/April 2005 |
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