When it comes to right-of-way and land clearing, few machines offer the versatility, performance, and safety of power take-off (PTO)-driven horizontal drum mulchers. With the right cutting teeth and drive system, they can be pushed or pulled behind a tractor to mulch thick grass, brush, and trees to about 10 inches in diameter.
Pick your teeth
The material you will be mulching dictates whether to use swinging-hammer or fixed cutting teeth. (See photos below). Each requires a different rotor configuration.
Swinging hammer teeth are like heavy-duty flails; they swing freely on the rotor and use centrifugal force to produce a powerful cutting action. One frustration with this design is maintenance. On early models, each row of hammers rotated on a single shaft. Therefore, if one hammer needed to be replaced, all hammers in that row had to be removed. Also, the shaft was often almost impossible to remove because of rust, damage, or wear.
Individually replaceable hammers are the answer to this problem. One manufacturer, Loftness, developed a system that doesn’t significantly increase price. Each hammer can be taken on and off in a matter of minutes so replacement can be done easily in the field.
Major benefit: the design’s forgiveness; if one hammer suddenly strikes a rock or large tree, it will buckle rather than staying rigid and stopping the rotor. This forgiveness makes swinging hammers suited for less-experienced operators.
Recommended tractor size: Ideal for less than 105 horsepower because small tractors don’t have the power needed to keep a rigid-tooth rotor spinning through tough material such as thick trees.
Recommended application: trees and brush less than 6 inches in diameter. Although they are capable of mulching larger trees, the process may take longer because the hammers are likely to give way under the heavy load rather than maintain the ideal cutting angle.
Fixed teeth are made of standard carbide or hardened steel so, unlike swinging hammers, they have no give. They always stay at the optimum cutting angle, and there are no moving parts to wear.
Recommended tractor size: 105 horsepower or more.
Recommended application: trees and brush 6 to 10 inches in diameter.
Benefits of standard carbide teeth: durability and cost efficiency, based on longer life. They are made to withstand moderate rock contact without breaking, and they don’t require sharpening. The downside of the standard tooth is its chisel point with rounded top prevents it from working as quickly as teeth with sharper edges.
Benefits of hardened steel: a sharp edge, allowing them to mulch trees and brush more effectively than other types of cutting teeth. They require less power and leave a finer finished product. The blades are reversible, but they require routine grinding to enjoy the advantages of a sharp tool.
For those who want the combination of a sharp edge and low maintenance, check out planer carbide tips. They aren’t as sharp as hardened steel or as durable as standard carbide teeth, but they can be extremely effective in loamy soils with few rocks present.
Cutting chamber components
Counter teeth, which are welded inside the housing to enhance the grinding performance, are the norm, but some units are available with a shear bar.
For example, the Loftness Tree Hammer offers a shear bar that covers the counter teeth and acts similar to the chipping anvil on a wood chipper. It’s efficient and provides a cutting edge to help reduce particle size. It also minimizes wedging from root balls or other debris in the tapered chamber.
Other options are a push bar and hydraulic mulching door. The push bar is typically offered with either manual or hydraulic adjustment, and it is used to push standing trees away from the tractor as they are being mulched. The mulching door is usually offered with manual or hydraulic adjustment.
The final options for selecting horizontal drum mulchers revolve around the drive system. Although PTO drives are known for reliability, some features can further reduce maintenance. For instance, an automatic belt tensioner eliminates the need to routinely adjust tension as the belt wears. The automatic tensioner uses a spring-loaded system to ensure smooth, consistent power transfer and maximize belt life.
Also, the mulchers come standard with a single belt drive but usually have a second drive as an option. The second drive is reserved for tractors with at least 125 horsepower.
PTO-driven horizontal drum mulchers offer safety features such as a discharge trajectory that is more controlled than on alternative mulching equipment. The operator can better control where the material will be discharged, rather than risk having debris fly into unwanted areas.
Bill Schafer is product manager for Loftness, Hector, Minn. E-mail firstname.lastname@example.org; visit www.vm-logix.com. This article originally was published in the 2013 Public Works Manual.