Title by Author: Shear Energy by Jason Wittig
Abstract/Artists Statement: Efficiency, function, and weight of fruit-tree pruning devices are scrutinized very closely by the purchasing end user. Efficiency, being the most valuable quality to focus on; an efficient cutting device can lead to smaller batteries and lighter materials on the tree pruner. The objective of this project was to produce a cutting head that surpassed the benchmark device by 10% in four categories: Axial cutting “green-wood,” Axial cutting “dry-wood,” Axial opening force, and Handle twisting torque. The benchmark’s use of the “scissor-type” design was changed to a double bypass anvil design, to eliminate blade clearance issues. The parabolic profile and varied rake angles of the blade concentrated on minimized cutting force. The jaw-to-blade relationship was manipulated to locate the axis of the wood tangent to the handle axis, thus addressing rotating force. A jig was built as part of the project and able to be fitted with both the benchmark cutting head and the new design head. The Tinnius–Olsen tensile testing machine in Hogue 127 was used to measure positive and negative axial force measurements. The force needed to close the device, due to blade design, was reduced from 525 lbs. to 475 lbs. in green fruitwood. The dry fruitwood test gave a similar ratio as a result. The force needed to open the cutter has been reduced from 25 lbs. to less than 1 lbs. The measured torque was reduced from 15 in-lbs. to 7.5 in-lbs. The results were clearly better than the benchmark.
Keywords: Efficiency, Energy, Rake angle