Some will say their machines are just fine now, thank you—but then they’ll concede off the record that they’re working on enhancements and don’t want to tip off the competition.
Still others will acknowledge that the equipment they sell today, while greatly improved from previous models, represents a transition to even greater efficiency and cost-effective operation.
“In general, as employees become harder to find, you’ll see equipment that is more efficient and reliable, and easier to use with fewer people,” says Mike Byram, senior director of the environmental business segment at Vermeer Manufacturing Co., in Pella, IA.

“Components need to last longer, do a better job for a given amount of horsepower, and produce a better product coming out the back end. We’re always looking for materials that last longer and wear less.”

Fuel costs also will influence future C&D equipment designs. Byram anticipates the emergence of alternative fuels, including ethanol derived from wood as a substitute for gasoline, and biodiesel to replace petroleum-based diesel fuel. “Things being buried today will be burned for energy tomorrow,” he says.

Out of The Woods
For stripping vegetation from a construction site, manufacturers offer a wide range of whole-tree chippers and grinders. Chippers use sharpened knives on a disc or a drum to make a dimensional chip; grinders employ a hammer mill to pound trees into shreds.
A chipper processes woody material more rapidly than a grinder does. “A chipper can dispose of a typical 80-foot tree in less than a minute,” says Jerry Morey, president of Bandit Industries Inc., in Remus, MI, “but it won’t tolerate dirt and debris. It uses a high-tensile knife that needs to be sharp to work properly.”

Morey says that over the past 16 years, Bandit has designed better feed systems for its chippers, with in-feed trays that make collecting piled brush easier. “We’ve also developed bigger, more productive machines that allow you to take a whole tree, crush its limbs and branches, and force all the material into the chipper rather than having to cut it,” he says.

McCloskey International's 616 track trommel screener is designed for processing large amounts of topsoil, composting, or CAD waste.

Morey predicts the next decade will see “a lot of development in drum-style chippers.” Compared to the disc-style chippers that are today’s industry standard, “a drum-style chipper will be more compact but will allow for a larger-diameter opening so you can put more material in it at one time.”

Vermeer makes chippers ranging in capacity from 6–20 inches and in power from 25–250 hp. Some of the smaller ones have gas engines, but most are diesel-powered.

Byram says the future of chippers involves “increased emphasis on safety and on power density—more capacity in a smaller package.”

Horizontal vs. Tub Grinders
Freestanding grinders come in two varieties, horizontal and tub. Horizontal grinders pull the material to be processed into the hammer mill on a conveyor belt or a steel-track chain; tub grinders have an opening on top into which the material is dropped, relying on gravity to feed the hammer mill. “Tub grinders are more productive than horizontal grinders in land clearing, primarily because gravity keeps the hammer mill loaded,” says Ed Hardesty, operations manager at CW Mill Equipment Co. Inc., in Sabetha, KS.

He notes, however, that tub grinders have a tendency to throw material out of the feed bed. “In a congested area with a lot of people around, there’s no room for a safety zone with a 300-foot radius around the machine. We can put an optional anti-throw protection device like a baseball backstop on some of the machines, but if you position it to stop all material from being thrown out, you can’t feed it.” In such situations, the horizontal grinder is the machine of choice.

Hardesty says that in recent years hydraulic functions and the computer electronics that control the hammer mill and tub have improved. Today some grinders are self-propelled, roaming a work site on the same Caterpillar undercarriages used for bulldozers and excavators. “They can be operated remotely with a control range of almost 400 feet—the distance between home plate and the outfield wall in some baseball stadiums,” Morey says.

Morbark Inc., of Winn, MI, has horizontal-grinder models operated by remote control from the cab of an excavator that feeds material into the grinder. “This ‘smart feed’ computerized high-quantity feed system boosts the production level by providing a constant feed,” says Larry Burkholder, Morbark’s southeastern regional manager. “It also senses the hydraulic pressure and how much horsepower is being required to grind the material, and when necessary it will slow the feed to avoid jamming.”

In the future, grinders will be increasingly computerized, user-friendly, and productive, says Burkholder. “We’re just getting to the point at which remote controls on a machine allow the operator to scroll down and diagnose any problems. Oil pressure, temperature, hydraulic pressure, a feed jam-up—all are at his disposal in graphic form. Our machines now average 93% operating time.”

Morey also foresees advances in hydraulics and electronics that will enable a grinder to read the situation and automatically adjust its conveyor in-feed speed and other operating parameters for maximum performance and fuel economy.

Continental Biomass Industries Inc., of Newton, NH, makes the Magnum Force line of horizontal grinders, which have a patented offset helix rotor with four alternating rows of six hammers. “It’s a very efficient rotor design for processing material to uniform size,” says Aaron Benway, CBI’s East Coast regional sales manager. “The product size can range from 1-inch minus to 6-inch minus, and the machine can process up to 500 cubic yards an hour.”

Magnum Force models cost $550,000 to $650,000. Benway explains that the more expensive models have a stronger rotor, shaft bearings, and grinding chamber to accommodate the added stress of processing greenwaste contaminated with rocks and other hard debris. Other options include a hydraulically operated split-clamshell opening to the grinding chamber and a choice of wheeled or self-propelled track units. 

Torque and Teeth
“The conveyor systems have become rollers supported by ball bearings to cut down on the horsepower required to convey material, and to transfer more horsepower to the grinding mill itself,” Hardesty says. “Most of the machines now come with a torque-converter drive, a fluid connection that allows the entire power unit to be more efficient and also protects the engine from any shock being transported from the mill.”

Grinders also are undergoing a revolution in the design of the teeth that cut, split, and grind the wood. Most grinders have a cutting or splitting tool made of carbide, which fractures easily if it encounters rock or heavy pieces of metal. “Bandit has a whole new line of teeth that will increase production and tooth life,” Morey says. “We also have a new cutter body [the tool that holds the cutters] that has wear surfaces hardened with tungsten carbide. That should double or triple its life. This tougher, more robust head is a demolition-type tool with welded, impregnated carbide rather than a solid-carbide piece. It will better withstand the impact of steel or rock better, though we still don’t recommend putting any of our high-speed grinders into an application with a high level of steel and rock. You’re better off precutting the material or breaking it down with a slow-speed shredder.”

When CW Mill started making wood grinders in 1989, Hardesty recalls, it had a screen in front of the radiator. “Now we have a precleaner of perforated metal that prevents material large enough to plug the radiator from getting in. The precleaner room has grown in size. We now use it to house some auxiliary hydraulic equipment and fuel tanks that we don’t want exposed.”

Size Matters
To increase capacity and production, grinders are getting heavier, with bigger hammer mills. The largest models now approximate the size and weight of a railroad freight car and cost well over half a million dollars. “Design work is being done to make these big monster machines lighter and stronger, so they’re easier to tow and transport,” Hardesty says.

The model 3400 stump grinder from Bandit Industries features a hydrostatic system with a rotating case motor.

CW Mill’s smallest tub grinder weighs 82,000 pounds, its largest tub grinder weighs 109,000 pounds, and its horizontal grinder weighs 106,000 pounds. Lighter-weight machines are desirable but may require a sacrifice in longevity, Hardesty observes.

“Grinding wood is a severe application. As the hammer mill turns, big stumps and rocks and tramp metal get into the system,” he says. “Even though you’re using stronger alloys, if the turning hammer mill hits an unyielding object, the lighter the machine is, the more vibration will occur in the chassis and the shock will be a little more severe.

“The thickness of the steel in the frame determines how soon the machine will require welding to keep it in one piece, and how soon the metal will fatigue to the extent that the machine needs to go to the scrap heap. Extra metal means extra weight. Heavier is better—until you go to transport it. We try to tread a line between ease of transport and the longevity of the machine.”

Stump Grinders
Also available are stump grinders, specialized machines that pulverize tree stumps in place down to a specified depth as an alternative to digging them up before grinding. “If you leave the stump in the ground and grind it there, it’s an easier task than pulling the stump out of the ground,” Morey says.

Morbark's 6600 Wood Hog includes a 42-inch-by-67-inch hammer mill with 28-inch-diamter rotors.

A stump grinder may be an attachment to a hydraulic excavator, a small rubber-tired backhoe, or a skid-steer; a separate tow-behind unit; or a self-propelled machine.

Morey and Byram both note the increasing demand for larger, self-propelled stump grinders. “We’ve got a new model coming out in September with more horsepower,” Morey says.

Kelly Guthrie, marketing coordinator at Coneqtec Universal, in Wichita, KS, says the future of stump grinders for skid-steers is technology that bridges the gap between low-flow and high-flow hydraulics. “A lot of companies have one or the other,” he explains. “High flow has a lot more power, requires a bigger skid-steer, and costs more. You would choose low-flow if you don’t have enough money to get a high-flow. Our grinders will attach to anything that’s out there.”

Guthrie also expects to see more powerful skid-steers in the future. “Our attachment is only as strong as the skid-steer you attach it to,” he says.

Cutting Brush
A typical brush cutter (also called a mower by some manufacturers) is an attachment replacing the bucket on a hydraulic excavator or a small rubber-tired backhoe.
Brush cutters keep small trees and shrubbery at bay along highway and railroad rights of way and in the linear swaths of open land beneath electric-power transmission lines. Sometimes they are used for land clearing.

CW Mill's HTC-1464T Hogzilla tub grinder is often favored when it comes to clearing land.

“The smallest machines would be used with a limited flow of material in tight places they can get to. A bigger machine might do 2 acres a day, depending on the size of the material,” says Bill Yearly of Pro Mac Manufacturing Ltd., in Duncan, BC, Canada.

Pro Mac has produced brush-cutting equipment since 1980, and in that time its equipment has undergone changes in shaft and cutting-tool design. “The original machines used a two-blade arm—a flail arm system,” Yearly says. “Now the majority of our machines have a three-blade arm and mulching disc, which gives you more cuts per minute relative to the tip speed and makes the material fine enough so it can be left to biodegrade on the site. We also make a flail hammer cutter and a rotary-drum type.

“In the future,” Yearly says, “our technology will evolve into more efficient cutting tools—but I don’t know yet what they are.”
Carter Brown, sales manager at John Brown & Sons Inc., in Weare, NH, estimates that his firm’s Brown Brontosaurus Brush Mowers can clear 3–5 acres a day.

Brush-cutter technology has changed over the past 20 years, Brown says. “We used to have flail-type, free-swinging hammer mowers with a lot of wear-and-tear parts that were hard to maintain. Today all those parts are gone. You can run the machine and not have to work on it. There are only two grease fittings on the entire attachment, one for each main-shaft bearing that the drum spins on. We have maintenance down to making sure your knives are sharp and putting in four pumps of grease in the morning.”

Downsizing the Product
Today, brush cutters require an excavator the size of a Caterpillar Model 315, which weighs about 35,000 lbs. What the world needs—and eventually will get, Brown says—is a smaller excavator, weighing less than 20,000 lbs, with high-flow hydraulics to run the machine and auxiliary hydraulics of at least 30 gallons a minute to run the brush-cutter attachment. “The first company to do that is going to have a huge market for it,” he says. “You could tow such an excavator on a tag trailer behind a large truck. You wouldn’t need a low-bed to move it around.”
Brown also expects brush-cutter manufacturers to design even smaller attachments to mount on a skid-steer. Weighing 10,000–12,000 lbs, skid-steers already meet a brush cutter’s hydraulic requirements, and they can be towed behind a large pickup truck.

“You could spend $25,000 for the mower head and $40,000–$60,000 for a skid steer,” Brown says. “For under $100,000 you could be in the mowing business. Such a small one-person contracting business could get a lot of work done. The equipment would be small enough to get in and out of job sites in small areas, and it would have the appropriate hydraulics to run our attachment and many others.”

Still another refinement Brown foresees is application of variable hydraulic motors to brush cutting. “They’re out there,” he says. “It’s something we’re working toward.”