DESIGN, MANUFACTURING AND PERFORMANCE EVALUATION OF FABABEAN THRESHING MACHINE

Abstract

Favabean threshing, in Ethiopia at present, is predominantly done by employing animals to trample the crop on the ground. Traditional methods of threshing favabean require high man-hours, cause fatigue to workers, have low output, and reduce seed quality. In an effort to alleviate these problems, diesel engine driven favabean thresher was designed, fabricated, tested and evaluated. The performance evaluation of the thresher was made in terms of threshing capacity, threshing efficiency, cleaning efficiency, mechanical seed damage, and fuel consumption. The performance evaluation was carried out at three levels of cylinder speeds (400, 450, and 500 rpm), concave clearances (25, 30 and 35 mm), and feed rates (8, 12 and 16 kg/min). The experimental design laid was a factorial, split–split plot design. The maximum threshing capacity of 933.64 kg/hr was obtained at a cylinder speed of 500 rpm, concave clearance of 35 mm, and feeding rate of 16 kg/min. The threshing efficiency and percentage of un-threshed grain highly depended on concave clearance rather than other factors. Maximum threshing efficiency of 96.67% was achieved at a cylinder speed of 400 rpm and a concave clearance of 25 mm. Maximum cleaning efficiency of 95.00% was achieved at a cylinder speed of 500 rpm and a concave clearance of 25 mm. Maximum mechanical damage of 6.31% was recorded at a cylinder speed of 500 rpm, and a concave clearance of 25 mm, and a feeding rate of 16 kg/min.