Crosscut shearing is a fast productive method of tree harvesting, while offering advantages in safety, lower capital and maintenance costs than saw cutting heads. However, existing shearing equipment falls far short of wood industry requirements due to excessive wood fiber damage caused by the pinching type action of thick blades which compress the wood fibers ahead of the cut, thereby pulling and fracturing the fibers from above and below the cut. Extensive efforts have been made to improve crosscut shearing, but have largely failed for a variety of reasons. Wood Tech Engineering has demonstrated preliminary feasibility for a novel shear that incorporates three major changes that improve upon previous efforts: 1) reduced blade thickness, 2) lateral slicing motion to the blade, and 3) pretensioning of the blade for increased blade stability. While early test work has demonstrated that the novel shear dramatically reduces fiber damage by as much as 98% from conventional shears, a blade failure occurred due to a design error which caused inadequate pretensioning. This advanced feasibility assessment will incorporate earlier changes and test three additional modifications to the novel shear: 4) downward tilted blades, 5) blade taper on only the bottom side of the blade, and 6) increased amount of pretensioning.Applications:The innovative crosscut tree shear will be marketed with a trademark name, Stem Shear, and will enter the marketplace by providing a safer and more economical method of timber felling. Preliminary market research indicates there is substantial interest from wood product mills in a shear which does not cause fiber damage, achieve higher yield of wood harvested and which can operate more economically than saw cutting heads.
