Current issue: 56(2)
Under compilation: 56(3)
Cable yarding is a general solution for load handling on sites not accessible to ground-based machinery, and is typically associated with steep terrain. On flat terrain, such conditions can primarily be found on soft or wet soils, most frequently encountered in Central and Northern European countries. Today, changed environmental and market conditions may offer an unprecedented opportunity to the actual implementation of cable yarding on flat terrain in commercial operations. The study goal was to collect cable yarder manufacturers experience regarding the use and adaption of cable yarding technology on flat terrain. European manufacturers of cable yarding technology were interviewed about customer experience, particular challenges, adaptation potential, future potential and main hurdles for the expansion of cable yarding on flat terrain. Almost all manufacturers have received requests for flat-terrain yarding technology solutions, primarily from Germany. Temporal or permanent inaccessibility, regulatory or environmental reasons were the most frequent motivation for considering cable yarding technology. Installation was considered particularly challenging (clearance, stable anchoring). Potential adaptations included higher towers, artificial anchors, mechanized bunching before extraction and un-guyed yarder-systems. An artificial, highly mobile, self-anchoring tail spar was considered the most useful adaptation. While concerned about limited profitability and qualified labour shortage, most manufacturers demonstrated a positive or neutral view concerning the expansion of cable yarding on flat terrain. However, cable yarding is not considered to be cost-competitive wherever ground-based systems can be employed and cable yarding is not subsidized.
Early thinnings are laborious and costly. Thus forest companies are searching for cost and time efficient ways to carry out this task. The study’s purpose was to determine the productivity of the EF28 accumulating energy wood harvesting head in harvesting small-diameter hornbeam (Carpinus betulus L.) undergrowth trees and evaluate the effect of its multi-tree handling (MTH) capacity on time consumption. The harvester was a wheeled, three-axle Komatsu 911. A time study of 7.1 hours on 19 plots, with a total area of 0.76 ha was conducted. On average, the harvested tree volume was 8 dm³ and the stand density was 2666 trees/ha. The productivity was modelled with MTH conduction, mean diameter at breast height and the number of trees handled per cycle as independent variables. On average, MTH took 27% longer per cycle, increased extracted volume per cycle by 33% and consequently increased productivity with 5.0%. In 71.9% of the cycles more than one tree was handled and if so, dimensions were smaller than in single-tree handling (5.8 cm vs. 12.0 cm). Maximum felling diameter of 23 cm was about 15% smaller than in softwood (according to the manufacturer’s specifications) and the driver didn’t exploit the EF28’s theoretical potential in terms of trees handled per cycle. It can be concluded that the head could significantly improve productivity in small-diameter wood procurement.