Optimization of On-Farm Machine Design Parameters for

Abstract

This study compared performance of three timber sawing systems; chain, bench and pit saws determined the optimal design parameters of the chainsaw system using polynomial functions. Results showed significant differences among the sawing systems at p=0.05. Chainsaw system recorded higher timber production rate of 0.23m3/man-hour than 0.17and 0.08m3/man-hour for bench and pit saws, respectively. However, chainsaw’s recovery rate was significantly lower at 30% compared to 39.8% and 35.9% for pit and bench saws respectively. Timber sawn with chain saw had significantly higher dimensional variability (±5.53mm), than that sawn with pit and bench saws at ±2.64mm and ±3.55mm respectively. Application of empirical approach successfully determined the optimal chainsaw design parameters as3.02m/min for sawing speed, 6.87lt/m3 for fuel consumption and ±1.25mm for dimensional variability. These values were obtainable at a cutter angle of about 25o and depth gauge clearance of 0.650mm. The optimized chain, attached to a framed chainsaw, recorded timber recovery of 52.3% which was significantly higher than that for freehand chainsaw(30.2%).The optimized system achieved lower dimensional variability and surface roughness of when compared with the freehand chainsaw system. The system reduced the operator exposure to vibration and noise, and also lead to reduced solid wastes released to the environment. The framed chainsaw system istherefore recommended as appropriate for timber sawyers operating on the farms, where trees are few, scattered and small in diameter.