A feller buncher is a self-propelled machine with a cutting head that is capable of holding more than one stem at a time. The cutting head is used strictly for cutting, holding, and placing the stems on the ground. Feller bunchers do not have processing capabilities.
Either wheels or tracks propel feller bunchers. Tracked machines are slower than wheeled machines, but often have the advantage of being more stable on steep slopes. Tracked feller bunchers are also capable of operating on wet and loose soils where rubber tired machines would be prevented from operating. Feller bunchers may have self-leveling cabs that extend the slope on which they can operate.
Drive to Tree
A drive to tree feller buncher is a rubber-tired machine with the cutting head mounted directly to the carrier. The whole machine drives up to each tree to cut it.
A swing boom feller buncher is a tracked machine with the cutting head mounted on a boom. The machine does not have to drive up to each tree to cut it.
Felling / Cutting Heads
Felling heads are attachments built to be mounted either to a boom or to the chassis on a base carrier. There are three categories of felling head, bunching heads, processing heads, and felling heads. Bunching heads are designed to handle multiple stems and do not have processing abilities. Processing heads are capable of felling and processing trees. Felling heads are capable of cutting and felling single stems with no processing capabilities. Read more about felling heads…
Slope: Tracked machines with self-leveling cabs are capable of operating on slopes up to 50%. Tracked machines without self-leveling cabs can operate on slopes up to 40%. Wheeled feller bunchers should be restricted to slopes below 25%. Ground and tree conditions will affect the slope at which the equipment can operate. Rough, broken ground or many ground obstructions will limit the slopes to less than the maximum. Larger trees also reduce the feasible operating slope because of the mass that can be handled safely.
Soil Conditions: Tracked machines have a lower ground pressure than wheeled equipment and are less prone to rutting and compaction. Drive to tree feller bunchers must traverse more of the stand to reach each tree to be cut. This means that more of the stand will see some affects from their operation.
Tree Size: Cutting head capacity and feller weight limit the size of trees that can be cut. Cutting trees at the limit of the machine may limit the ability to actually ‘bunch’ trees and require one tree to be felled at a time. This will usually decrease productivity and increase cost of operation. Cutting trees larger than the capacity of the machine is dangerous to the operator. Increased slope will decrease the size of trees that the equipment can safely handle.
Feller bunchers can be highly productive felling machines. They can work well in both thinnings and clearcuts. Their ability to control the felling of the trees can reduce residual stand damage in comparison with manual felling. Since the feller buncher does not have processing capabilities, the whole tree is usually extracted to the landing. If there is a desire to leave the slash in the woods, then a separate limbing and topping operation must be carried out prior to extraction. Feller bunchers are a good option where removal of biomass is desirable and stems to be removed fall within the suitable range of the bunching head.
The type of treatment, thinning or clearcutting, will affect the size of feller buncher that can be used. The ability to maneuver within the stand without damaging the residual is an important consideration. If the spacing is too tight for a large machine but the trees being felled are too big for a small machine, then either the treatment or equipment needs to be reconsidered.
Feller bunchers are built with Rollover Protective Structures (ROPS) and Falling Object Protective Structures (FOPS) to protect the operator. Care must still be taken when operating on slopes. Whether on flat ground or steep slopes, a large tree is heavy and tall and has the capability to tip a feller buncher. Moving with a load of trees increases the possibility of a rollover. Rough, broken ground can exacerbate the danger of tipping.
One particular safety concern with feller bunchers running hotsaw heads are broken cutter teeth. These heads spin at very high speeds, and broken teeth may be thrown very far, very fast. Those working on the ground around feller bunchers should take care.
Feller bunchers excel at felling trees and placing them in a convenient position for the extraction process. Since they do not process the tree, processing must be done manually or with another piece of equipment. The capability of feller bunchers to build and place bunches makes them a good companion to grapple skidders, clam bunk skidders, and shovel operations. The most common system combines a feller buncher with a grapple skidder and some form of processor at the landing.
The following is a selection of representative research studies and reports done on harvest systems that include feller bunchers. These reports may be used to get an idea of productivity and impacts of different systems and uses of feller bunchers as well as some of their limitations. When reading these reports, keep in mind that they describe specific systems and stand treatments. Trying to apply the lessons learned from these reports to systems and treatments outside of the studies’ scope may have unintended or unforeseen consequences.
This is not a complete listing of research on feller bunchers. Additional information can be found at the U.S. Forest Service Treesearch website. This site provides reports for research performed by Forest Service Research and Development scientists and their collaborators.
- Title: Felling small trees with a drive-to-tree feller-buncher
Author: Mitchell, Dana
Description: Conventional forestry equipment is often used to harvest small-diameter trees. The typical ground-based logging operation is highly mechanized, with the most common using feller-bunchers, grapple skidders, and a chipper or grinder. But these machines may not be economical when used in pre-commercial or unmerchantable thinning operations in which the number of trees to be removed per acre is high but volume per tree is low. Published studies commonly find that feller-buncher productivity (tons/productive machine hour) is directly proportional to tree diameter. As tree diameters increase, the tons produced per hour increase, resulting in a lower cost per unit of wood produced.
- Title: Production and cost analysis of a feller-buncher in central Appalachian hardwood forest
Author: Long, Charlie; Wang, Jingxin; McNeel, Joe; Baumgras, John
Description: A time study was conducted to evaluate the productivity and cost of a feller-buncher operating in a Central Appalachian hardwood forest. The sites harvested during observation consisted of primarily red maple and black cherry. Trees felled in the study had an average diameter at breast height (DBH) of 16.1 in. and a total merchantable height of 16 ft. A Timbco 445C Hydro-buncher was used in conjunction with manual topping and delimbing with a Husqvarna 55 chain saw. Hourly productivity ranged from 428.9 to 2267.7 ft3 per productive machine hour (PMH) for the feller-buncher and 178 to 2186 ft3/PMH for the top/delimber. Hourly costs were estimated to be $99.68/PMH for the feller-buncher and $28.23/PMH for the top/delimber. Estimated average costs of $0.08/ft3 for the feller-buncher and $0.04/ft3 for the top/delimber were derived, based on these production estimates.
- Title: Cost and productivity of new technology for harvesting and in-woods processing small-diameter trees
Author: Lambert, Michael B; Howard, James O.
Description: A study was conducted on the productivity and cost of an integrated harvesting and processing system operating in small-diameter timber (western hemlock-type) on the Olympic Peninsula of western Washington. The system uses a new steep-slope feller buncher, a clam-bunk grapple-skidder (forwarder), a prototype chain-flail debarker delimber, a chipper, a conveyor system, and a prototype shredder. The study showed that the system harvested and processed trees at a combined-system cost of $7.80 per green ton at a production rate of 455 green tons per day. The delivered product mix was 53 percent chips, 21 percent saw logs, and 26 percent hogged fuel by weight. The productivity and machine rate of each piece of harvesting and processing equipment and other data are given.
- Title: Overview of approaches to sustain forest productivity during forest road development and timber harvesting activities
Author: Blinn, Charles R.; Dahlamn, Rick; Mattson, James A.; Thompson, Michael A.
Description: Various approaches are available to minimize impacts on forest productivity during forest road building and timber harvesting activities. These approaches include a variety of practices and technologies. They include practices such as reducing road and trail development, using designated trails, and leaving slash at the stump on nutrient deficient sites. Technology options include low ground pressure machinery, tracked swing-to-tree feller-bunchers, small-scale equipment, and portable wetlands and stream crossing structures. Increased application of these approaches will require additional research, training for foresters and loggers, and support for loggers.
- Title: Development and Analysis of SRIC Harvesting Systems
Author: Stokes, Bryce J.; Hartsough, Bruce R.
Description: This paper reviews several machine combinations for harvesting short-rotation, intensive-culture (SRIC) plantations. Productivity and cost information for individual machines was obtained from published sources. Three felling and skidding systems were analyzed for two stands, a 7.6-cm (3-in) average d.b.h. sycamore and a 15.2-cm (6-in) average d.b.h. eucalyptus. The analyses assumed that whole trees were chipped at roadside.
Costs and production were summarized for each system. The systems were: (1) Continuous-travel feller-buncher, skidder, and chipper; (2) 3-wheel feller-buncher, skidder, and chipper; (3) chainsaw, skidder, and chipper. In the 7.6-cm stand, system productivities were 9.9, 7.3, and 7.5 BDLT/SMH, and costs were $20.9, $20.8, and $18.0 per BDLT for the three systems, respectively. System production rates for the 15.2-cm stand were 24.3, 10.2, and 12.5 BDLT/SMH, and costs were $8.7, $10.9, and $13.2 for systems 1, 2, and 3, respectively.
Products and Markets
Since feller bunchers do not have processing capabilities, the whole tree is often brought to the landing. This means that utilization of the material is determined by the processing capabilities present at the landing. It also means that they are very versatile machines, since they can be used efficiently in both biomass and timber markets.