Stroke Boom Delimber
A stroke boom delimber is an attachment mounted on a base machine that is capable of delimbing and bucking a tree.
A stroke boom delimber consists of a boom with a grapple (referred to here as the “front” grapple) and saw mounted on it. Another grapple (referred to here as the “rear” grapple) and saw are mounted on the base machine. The boom is mounted on the machine horizontally. The boom can be tilted down and extended to pick up a tree with the forward grapple. The tree is normally grasped somewhere near the middle of the stem. The butt of the tree is placed in the rear grapple. The grapple arms function as delimbing knives just like the knives on a processor head. The boom ‘strokes’ the front grapple along the stem to remove limbs while the rear grapple holds the tree stem in position. The tree is topped and bucked into log lengths by the saw on the boom. The rear saw is often used to trim the butt end of the tree and may also be used to make bucking cuts.
There are two types of booms, monobooms, and telescoping booms. Monobooms are one piece booms that do not change in length. The whole boom slides back and forth during operation. This means that there must be tail swing clearance behind the machine. Telescoping booms, on the other hand, generally have a fixed piece mounted at the carrier with a telescoping portion extending in front and out of the fixed piece. A telescoping boom does not extend any further out the back than the fixed boom portion.
Stroke boom delimbers share the same limitations as any tracked piece of equipment on slopes or different soils. They are not often mounted on self leveling cabs, so are usually not suited for operating on slopes.
Monoboom delimbers require extra space behind them for the delimber boom to operate. The machine should be positioned so that it can operate without danger of hitting other objects. People working around stroke boom delimbers should be aware that the boom can extend over the back of the machine.
Stroke boom delimbers usually operate at a landing. They can be used in the woods provided there is clearance for the operation of the machine.
Stroke boom delimbers are generally used with a whole tree harvesting system such as a feller buncher/skidder system. This system delivers whole trees to the landing where the delimber can operate in essentially a fixed position. They are good at processing trees into sorted piles, but are not as efficient at moving piles around the landing as a dedicated loader or processor. They are not capable of loading trucks.
Products and Markets
Stroke boom delimbers can be used to produce the same merchandise as a processor. They are often used to process tree length stems, but they can also be used to process log length material.
The following is a selection of representative research studies and reports done on harvest systems that include stroke boom delimbers. These reports may be used to get an idea of productivity and impacts of different systems and uses of stroke boom delimbers 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 stroke boom delimbers. Additional information can be found at the USDA Forest Service Treesearch website. This site provides reports on research performed by Forest Service Research and Development scientists and their collaborators.
Title: Comparison of mechanized systems for thinning ponderosa pine and mixed conifer stands
Author: Hartsough, Bruce R.; McNeel, Joseph F.; Durston, Thomas A.; Stokes, Bryce J.
Source: 1994 international winter meeting sponsored by the American Society of Agricultural Engineers. ASAE Pap. 94-7513. St. Joseph, MI; American Society of Agricultural Engineers. 20 p.
Description: Three systems for thinning pine plantations and naturally-regenerated stands were studied. All three produced small sawlogs and fuel chips. The whole-tree system consisted of a feller buncher, skidder, stroke processor, loader, and chipper. The cut-to-length system included a harvester, forwarder, loader, and chipper. A hybrid system combined a feller buncher, harvester, skidders, loader, and chipper. Time-motion study data were analyzed to predict cost per unit volume. The cut-to-length system had higher costs and yielded less fuel than the other systems. In plantations, the hybrid system was least expensive, while the whole-tree system was cheaper in the natural stands. The harvesters were capable of handling larger-Trees in the natural stands, and could remove limbs from the plantation pines, up to a limit. The cut-to-length system could operate on the steep and broken terrain included in the study.
Title: Productivity of a tree length harvesting system thinning ponderosa pine in northern Arizona.
Author: Jason D Thompson