Chainsaw

Description

A chainsaw is a gas, hydraulic, or electric powered saw with a loop of chain that is pulled around a bar at a high speed. The chain contains cutting teeth that are capable of slicing through wood. A chainsaw can be used to fell and process trees.

Mechanical Configurations

A chainsaw consists of the powerhead, bar, and chain. The powerhead has two integrated handles for handling the saw.

The bar is a made of flat steel with grooves cut in the edges within which the chain runs. They may have a sprocket mounted in the tip or a solid tip. A sprocket increases the efficiency and decreases wear on the bar and chain. The diameter of the bar tip affects the possibility of kickback. Kickback is a condition where the chain catches on the material and forces the tip of the bar up, rotating the chainsaw around the handle. This dangerous condition can seriously injure the operator. A smaller tip diameter decreases the likelihood of kickback.

All modern chainsaws have a chain brake capable of stopping the chain instantaneously in the event of kickback. The brake is actuated by a bar that runs across the front of the top handle of the chainsaw. When the saw rotates back toward the operator, it forces the chain brake bar against the arm of the operator, actuating the chain brake and disengaging the chain before the chain can strike the operator.

Chains come in a variety of pitches, the distance between three rivets in the chain, gauges, the width of the drive link, and cutter teeth. Some chains are referred to as safety chain and contain special links and design features that decrease the likelihood of kickback.

Some chainsaws are sold for cold weather applications and include warmers built into the handles for operator comfort and safety.

Operational Considerations

Physical Limitations

Chainsaws come in a range of power sizes that correspond to available bar lengths. The length of the bar determines the size of material that can be effectively cut. Material larger in diameter than the length of the bar can be cut, but doing so affects productivity and safety to the operator. The larger, heavier saws may fatigue the operator and affect safety. It is important to size the chainsaw properly for the material being cut. Some operators prefer a longer bar than is necessary to cut through material when delimbing or bucking logs lying on the ground to minimize the amount of operator bending.

Chainsaw felling is generally not limited by slope or soil conditions. In cases where either condition prevents chainsaw felling, there is often no other alternative to accessing the site for treatment.

Treatment Options

Chainsaw felling and processing is generally considered feasible for any type of treatment. Its major disadvantage is the decreased productivity compared to mechanical options. This decreased productivity may translate into increased treatment costs.

Safety Concerns

The inherent dangers of working unprotected, other than by a helmet and chaps, are the main concerns with chainsaw operations. Areas susceptible to windthrow, due to shallow rooting or numerous snags, and burned areas tend to present greater danger to the operator.

Steep slopes with uneven or unstable ground also present hazards to chainsaw operators.

Chainsaws produce high frequency vibrations that are capable of fatiguing the operator. Most chainsaws contain vibration-mitigating measures to decrease the affects of vibration.

Two stroke gasoline engines power most chainsaws used in the woods. These engines operate at high RPMs and produce loud noises. Operators should always wear hearing protection while operating chainsaws.

Chainsaw operators are in danger from falling objects and fatigue. Fatigue can be caused by the vibration and noise produced by the chainsaw as well as constantly walking and working in rough terrain. Falling objects include not only the tree itself, but also limbs and small trees knocked down by the falling tree. Operating in windy conditions increases this danger to the operator.

System Interactions

Because chainsaw felling and processing leaves material scattered through the stand, it is generally not used in conjunction with grapple skidders or forwarders. Other than those extraction methods, it works well with animals, cable skidders, cable, and helicopter extraction.

The number of chainsaw operators should be matched to the productivity of the extraction method to avoid slowing the productivity of that stage in the process. High productivity extraction like helicopters will require a greater number of fallers working days in advance of the extraction process. For lower productivity extraction like animals or grapple skidders, the number of fallers can be decreased and may be able to work within the same unit that extraction is taking place.

Research

The following is a selection of representative research studies and reports done on harvest systems that include chainsaw felling. These reports may be used to get an idea of productivity and impacts of different systems and uses of chainsaw felling 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 chainsaw felling. 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 and skidding productivity and harvesting cost in southern pine forests
  Author: Kluender, R.A.; Stokes, B.J.
  Date: 1996
  Description: Sixteen stands were harvested at various levels of basal area removed (intensity). Chainsaw felling productivity was more sensitive to stem diameter than harvest intensity. Skidding productivity was highest when removing large trees at high intensity. Harvesting cost was more sensitive to stem size than harvest intensity, although harvest intensity was a very important factor in cost of removing small stems.
• Title: Productivity and cost of manual felling and cable skidding in central Appalachian hardwood forests
  Author: Wang, Jingxin; Long, Charlie; McNeel, Joe; Baumgras, John
  Date: 2004
  Description: A field production study was conducted for a manual harvesting system using a chainsaw and cable skidder in a central Appalachian hardwood forest site. A partial cut was performed on a 50-acre tract with an average slope of 25 percent. Felling time pre tree was most affected by diameter at breast height and the distance between harvested trees while skidding cycle time was mainly affected by turn payload size and skidding distance.
• Title: Development and Analysis of SRIC Harvesting Systems
  Author: Stokes, Bryce J.; Hartsough, Bruce R.
  Date: 1993
  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

Chainsaws are capable of producing virtually any product for transport, from tree length stems to cut to length bolts. This versatility means that they can produce almost any product that the market demands.