Wheeled platform material handlers are gaining in popularity among recyclers with paved scrap yards.

The merits of wheeled and tracked platform scrap handlers are well known. The strength and stability of a tracked machine vs. the mobility and versatility of its wheeled counterpart--each model has traditionally had its own niche in which to shine. However, as more scrap processors pave their yards, the trend has been turning increasingly toward the wheeled variety in recent years. In fact, wheeled machines have been gaining on, and even overtaking, tracked models.

"You've seen an increase; you saw very few a decade ago," says Scott Sutherland, excavator product manager at LBX Co., the Lexington, Ky.-based maker of Link-Belt equipment, which makes tracked material handlers.

The European market is leading the trend. Julian Marceglia, CEO of Colmar USA, Wheatfield, N.Y., says the ratio of wheeled to tracked machines in Europe is already about 80 percent to 20 percent. Following that trend, Sutherland estimates that, today, rubber tired machines make up roughly half to 60 percent of units sold in the United States.

"There are machines that move and machines that don't. If it's your rover, your odd-job machine, the rubber tire [handler] has a distinct advantage," Sutherland says.

OFF TRACK. Tracked and wheeled machines have their advantages and disadvantages, but "ground conditions are the primary driver of the tracked vs. wheeled debate," Sutherland says.

While most wheeled material handlers have four-wheel drive and are capable of operating when the ground is soft and wet, that environment is usually left to crawlers, says Paul Hill, products manager at Liebherr America Inc., Newport News, Va.

Neil LeBlanc, senior marketing consultant for Caterpillar Inc., Peoria, Ill., agrees. "Typically, tracked undercarriage machines are utilized when the ground conditions are rough, irregular or wet and muddy," he says. "Wheeled material handlers are better suited to work on smooth, paved surfaces that will provide a stable base from which to operate the machine. As more processors pave their facilities, the trend is to purchase wheeled material handlers in hopes of minimizing damage to the improved operating surfaces."

A number of factors, including general economic prosperity, are driving scrap processors to pave their yards in increasing numbers. But regulatory agencies also play a role, encouraging (or requiring) owners to pave their yards for environmental reasons, according to Hill. The U.S. Environmental Protection Agency and local authorities have led a move toward concreted yards because paving helps prevent oil and other dangerous runoff from scrap stored outside and exposed to rain from leaching into the ground and possibly contaminating groundwater, Hill says.

Another factor driving the popularity of wheeled handlers is simply general improvement in the equipment, according to Marceglia. "Today, wheeled [machines] have the same performance, reliability and capabilities, but they are faster and easier to operate," he says.

They may not be able to climb mountains of scrap, but wheeled material handlers offer many advantages to scrap processors, Marceglia says. In addition to the ease of moving over paved surfaces, versatility is another factor that gives wheeled platform machines the edge over tracked, LeBlanc says.

Traditionally, a scrap handler has one job on a scrap yard that it sticks to, often a more stationary job like loading a shredder or rail cars. However, as the industry evolves, an increasing number of scrap processors want to get more out of each machine rather than buying and maintaining a machine for each specialized job on a yard, which is where wheeled machines also come in handy, LeBlanc says.

Wheeled machines offer moderate travel speeds of about 10 to 12 mph--about three or four times faster than a tracked model. The speed allows the wheeled material handler to move quickly from operation to operation, which increases their versatility, LeBlanc says.

Another attractive feature to some scrap processors is the cab on a wheeled machine, which tends to be higher, even at its minimum height, than the cab on a tracked machine, says Marceglia.

REINVENTING THE WHEEL. While maintenance intervals don't vary much between wheeled and tracked machines, the kind of maintenance the two machines require differs. Hill says because wheeled machines have less ground-engaging parts than crawler models, they typically require less maintenance. "Provided oil levels in the transfer case and axles are regularly monitored, the owner of a wheeled machine needs to consider only the replacement of tires," Hill says.

However, LeBlanc points out rubber-tired machines are typically more susceptible to damage on a rough jobsite than tracked machines. He says that in addition to tires, structural frames, the transmission, drive shafts and bearings require frequent inspection.

A set of tires can be expected to last anywhere from 6,000 to 12,000 hours, LeBlanc says. By limiting travel over sharp steel scrap, an operator can increase the life of his tires and drive components dramatically, he says.

Carrier weight can also determine a tire's lifespan. Buck Hill, president and owner of SETCO Solid Tire & Rim, Idabel, Okla., which manufactures a solid tire and wheel assembly designed for scrap operations, says smaller machines with dual tires can get between 20,000 and 30,000 hours out of their tires. Larger machines vary widely--some operators can get 20,000 hours, while others get only 7,500, he says. Hill points out that nonferrous operators tend to run over more material, resulting in lower life spans.

Manufacturers say two types of tires are available for use with wheeled scrap handlers--pneumatic or solid. Pneumatic tires can be operated when filled with air, or more often, foam. But the most common tire used in scrap applications is the solid tire, says LeBlanc.

Marceglia says Colmar only uses solid tires for scrap handlers because they are stronger and more puncture-resistant. "You cannot afford punctures and other damage to the tires," he says.

Whether filled with air or foam, pneumatic tires aren't always advisable for scrap applications, says Sharon Birdsong, also of SETCO. "Even a foam-filled tire can be destroyed at a wrong turn," she says.

In addition to opting for solid tires, manufacturers say keeping the yard as clean as possible limits the exposure of vulnerable parts to sharp steel scrap and is the best way to prevent tire and undercarriage damage to wheeled handlers.

Birdsong also recommends keeping the boom retracted when moving the material handler from one area to another. "An extended boom when the machine is mobile puts excessive weight and pressure on the front tires and, if continued, could cause premature tire failure," she says. "An operator's performance and cooperation in running the machine within the limits of its capacity is paramount to achieving maximum tire life."

WHEELING AND DEALING. While the wheeled material handler may be gaining in popularity, many manufacturers don't see it overtaking tracked models entirely. "I don't think we're ever going to have the yards completely paved," Sutherland says. "There will always be a need for tracked machines."

Still many manufacturers say they see the recent gains made by wheeled handlers as earning the machines a permanent and important place in modern scrap operations, even if it's in partnership with tracked models.

"Most yards still have both and probably will always have both," says Sutherland.

The author is assistant editor of Recycling Today and can be contacted via e-mail at [e-mail].