Application Tips: Brush cutter attachments

The brush cutter attachment market has exploded in the past five years, especially in coastal regions and the Midwest. This is mainly because of stricter burning laws and bans on certain chemicals, says Jerry Sechler, vice president of sales for Loftness/US Attachments.

Since these tools allow you to use a carrier machine you already have and can both cut down and chop vegetation, they are an efficient solution to land clearing jobs. Some of them can even process tree stumps and roots.

The most important factor you should think about when selecting a brush cutter is whether your jobs require you to just cut down brush or completely mulch it, says Bill Yearly, sales and technical manager for attachment products, Pro Mac Manufacturing. Many land development and subdivision applications require complete mulching, as do some road right-of-way jobs, usually for visual reasons. “People don’t want to see a bunch of ugly, chewed up brush sitting there,” Yearly says.

Bill Lang, president of Lang Tool, says it can be impractical to think you can mulch everything on a highway, shopping center or subdivision site where a lot of excavation will take place. “In most instances that’ll leave too much debris on the ground,” he says. If there will be a lot of excavation, putting trees through a chipper or using harvesting equipment to collect the trees and then haul them off might be a better option.

Remember also that your choice of carrier machine will play a significant role in your production rate, both because of how well it matches the terrain of your jobsites and because of the amount of power it supplies. A small machine such as a skid steer, for instance, is typically rated to process 4-inch-diameter trees continuously and 6-inch trees intermittently, says Mike Slattery, vice president of Fecon. If you plan on processing 8-inch trees using a skid steer attachment, your production rate will be much slower. “No one carrier does everything well, so pick the machine that does the majority of your work best and realize your operating costs may go up if you work outside of your core terrain conditions,” Slattery says. “That’s OK, just plan for it.”

If you are considering purchasing a brush cutter attachment, your field of choices is vast. They range from small flail mowers that attach to skid steers to a 10-foot-wide model designed for large bulldozers. The following descriptions can help you decide what type of brush cutter is right for your applications.

Flail mowers such as those from Loftness, which makes attachments for skid steers, are for clearing grass, weeds and light brush less than 1 inch in diameter. They are capable of mulching material to a fine particle size.

Horizontal shaft flail cutters are used in applications where resulting material needs to be a finished product that will biodegrade quickly and mix into the soil. Roadway maintenance is a primary application for these brush cutters, which state, county and municipal governments commonly use. The horizontal shaft flail cutters made by Pro Mac as excavator attachments will cut trees up to 5 inches in diameter.

Ax blade type cutters excel at land improvement jobs where clients want brush chopped finely and the site left looking groomed. The sharpened blades used by this type of unit are good at cutting grass, weeds and vines as well as trees up to 6 inches in diameter.

The drawback to these kinds of blades is that they require sharpening. With some brush cutters you can do this without removing the blades from the attachment and it takes about 30 minutes. Bill Schafer, product manager for Loftness, says contractors usually sharpen blades in the field six times and then take them to a machine shop for sharpening.

Fixed-tooth carbide cutters are popular with right-of-way clearing contractors who need an aggressive, roughcut machine that will quickly reduce foliage to ground level and aren’t concerned about producing a mulch-condition end product. These units can also penetrate the ground to process stumps and roots.

Swinging-hammer brush cutters are more forgiving in areas with a lot of rocks because the hammers retract when encountering something they can’t process, preventing a shock to the brush cutter’s drive components and the carrier machine, Lang says. This minimizes maintenance costs and downtime. The disadvantage to a swinging-hammer brush cutter is that it doesn’t cut as fast or as well as a fixed-hammer brush cutter. The hammers easily pivot back under a heavy load, which can happen when they encounter a thick tree. The operator has to give the machine time to increase its rpms before it will cut the material.

Horizontal-shaft, fixed-tooth brush cutters are used in forestry applications such as clearing the underbrush that fuels fires and creating fire breaks. They’re also used for right-of-way clearing and land development jobs. Horizontal-shaft, fixed-tooth brush cutters can cut up to 15-inch trees, depending on how long you can spend on the job, Yearly says. He notes that all brush cutter attachments are limited by their carrier machine. You can’t, for example, cut 12-inch trees with any brush cutter if you are using a small carrier machine. For the horizontal-shaft, fixed-tooth brush cutter, you’ll need at least a 30-metric-ton carrier. Users of this type of brush cutter generally leave the end product on the ground as mulch.

Rotary-shaft, mulching-disc brush cutters are typically less expensive and cost less to operate than flail mowers or horizontal-shaft brush cutters and are used when the size of the end product can be larger than ordinary mulch. Applications include forestry work and road and power line right of ways. Their disadvantage is a greater potential for throwing material.

Rotary-shaft, blade-and-disc units cut up to 6-inch trees. A lot of times material is left on site, Yearly says, but this cutter does not mulch as well as other types. Depending on job specifications, you might have to pick up the leftover debris and chip it.

Arm-and-two-blade brush cutters work well with light material, Yearly says. Like rotary-shaft, mulching-disc units, they have a greater tendency to throw material compared to other types of brush cutters. With the removal of eight bolts, you can put other attachments, such as a mulching disc, on these units.

The auxiliary-engine type brush cutter from IronWolf has a massive, 10-foot-wide, 40-inch-diameter cutter drum and a Cat C-15 power source. It attaches to large dozers or wheel loaders. Applications include clearing road and utility right of ways and building sites. It excels in rocky soil conditions because it processes trees and rocks simultaneously, crushing the rock and mulching the wood waste. Depending on the time of year, it usually leaves a larger product than a chipper does, says Jay Baker, national sales manager for IronWolf. In winter, when the sap is out of trees, it will chip finer.

With one pass, the Slasher pushes trees over and processes them. With a second it will rip into the ground up to 8 or 9 inches to process stumps, roots or rocks and work wood waste into the soil. While the machine is more productive with trees 10 inches in diameter or less, Baker says it is capable of processing 30- to 40-inch trees.

Training and safety
With any kind of brush cutting application, trees could fall on the cab and flying debris could be ejected toward the cab or bystanders.

If brush cutting isn’t a primary task for your company, you may need to outfit your carrier machine with some additional safeguards. You need an enclosed, ROPS/FOPS cab protected with steel plate or steel mesh wherever possible, Schafer says. The windshield should be made of high-grade, impact-resistant polycarbonate strong enough to repel large pieces of wood or other objects the rotor could propel. “It’s a brutal, dangerous environment out there and you really need to protect yourself from flying debris,” Sechler says.

Because the design of some carrier machines prevents their doors from opening when the lift arms are raised, operators need to know how to use the escape system provided by the manufacturer in case of fire or an overturned machine. Many times weather stripping has a rip cord that will allow you to push the windshield out.

Before operating the brush cutter, inspect the area to be cut for hidden rocks or metal that could be thrown.

In general, do not operate a brush cutter within 300 feet of people, cars or buildings. When cutting brush along a roadway that can be unavoidable, so operators must take particular care to make sure material falls away from the road.

Brush cutting can cause fine dust and leaves to build up against air intake screens of the engine compartment, openings into the engine compartment and air filters, Slattery says. If these areas aren’t cleaned at appropriate intervals, the machine will likely experience engine or hydraulic heating issues and possibly a fire. Multi-purpose machines often require customization to reduce the size of openings that let debris into the engine compartment. In some regions where material is less likely to get up in the air this isn’t an issue, Slattery says, but in others cleaning may be necessary in as little as a few hours.

Yearly says he isn’t aware of any formal training opportunities for brush cutter operators – probably because there are so many different types of them – but giving a new operator time to train himself is crucial. After he’s read the brush cutter’s operating manual and knows the unit’s limitations, allow your employee a few days to practice in a safe area without time constraints. Your dealer or factory representative could provide some training as well, Slattery says. Brush cutter operators need to develop a technique and get a feel for what direction material will fall. “In 30 years, I’ve never met a man who could just become a brush cutter operator overnight,” Yearly says.

Yearly cautions new operators not to work too quickly or think they’ll achieve their maximum productivity in the first two days. “You have to get used to the machine being an extension of your own two arms,” he says.

Stay on your toes
While the type of brush cutter you use has an effect on the size of processed material, this is also determined by the skill level of the operator and how much time he spends on the job, Yearly says. Essentially, the slower you go, the finer the cut material will be.

Make sure you and your equipment operator are familiar with your jobsites and always delineate with stakes the area to be cleared. One of the worst mistakes you can make is getting off the site. “That can lead to all kinds of difficulties,” Lang says, “because what you think of as brush may be someone else’s beautiful shrubs.”

Your operators need to know what they are processing and where it may go. Even a skid steer equipped with a mulcher is capable of felling an 80-foot-tall tree. “Respect the wind and how it may push the tree you are cutting the wrong way,” Slattery says. “Realize there may be other standing trees the falling tree could get hung up on, and don’t leave fallen trees hanging or someone else may be at risk later.”

Use the tilt or roll function of the carrier to increase productivity and put less stress on the cutting head. Most machines have this ability, but many operators fail to use it to their advantage, Slattery says.

If the operator pushes the cutter to go too fast, the power requirement can exceed the available hydraulic power, Schafer says, stalling the rotor while the engine continues to operate at full rpm. This can result in the hydraulic system overheating. To avoid this scenario, the operator should carefully monitor the pressure reading on the cutter and adjust travel speed to keep pressure at least 500 psi less than the advertised rating of the carrier unit.

An increase in vibration to the carrier machine could mean the brush cutter’s rotor is out of balance. You or your operator should shut down the machine and do a visual inspection for a loosened carbide tooth or lodged material. If you don’t fix an out-of-balance rotor, the brush cutter’s bearings will fail at an accelerated rate, Schafer says.

Complacency is a problem even with experienced operators. They do things they know they should not to do and this often leads to a safety mishap. Brush cutting is not a mind stimulating task, but you have to be alert when operating this kind of machinery. Inattention can be a problem on Friday afternoons or anytime an operator has not had adequate rest, Yearly says.