Researchers have shed more light on the performance of felling machines in steep slopes.
Machines designed and adapted for sleep slope harvesting are becoming increasingly common. This is due to the safety and productivity concerns regarding the use of manual felling on this terrain. One of the main new techniques developed involve the use of cable-assisted, or “tethered,” feller-bunchers, which use tension in a wire rope which is anchored on the upslope to assist with traction and gradeability. Even though this technique has become relatively common, there has been little research carried out to examine the relationship between tether tension, stability, ground pressures, and slip, especially in the context of machine specifications and site operative conditions. Researchers set out to examine these machines and try and provide information on this subject. The research presented a theoretical framework that uses a moment equilibrium approach to evaluate the relationship between equipment dimensions and specifications and soil and site conditions to identify allowable slopes of operation and associated ground pressures. This analysis highlighted that deeper grousers, higher cable tensions, wider tracks, and uphill boom orientation all increase gradeability and stability during operation. However, effective track length touching the ground and stability are decreased from grappling of heavier trees, operation on weaker soils, fully extended boom operation in the downhill direction, and increasing slope. Increasing soil pressure, increasing slope, and decreasing stability may increase soil disturbance. The researchers indicated that these last-mentioned factors would need to be confirmed with future, planned field tests. The research was published in Forest Science, Volume 63, Number 2. The authors are J Sessions, B Leshchinsky, W Chung, K Boston and J Wimer. Source