DESIGN, DEVELOPMENT AND PERFORMANCE EVALUATION OF ENGINE DRIVEN FINGER MILLET THRESHER

Abstract

Finger millet is the sixth most important cereal crop in Ethiopia in total area and production. Nonetheless, the unavailability of efficient and adequate number of threshing machine are the most serious constraints in finger millet production in Ethiopia. Traditional method of threshing is characterized as time consuming, wasteful, associated with excessive losses, and has high drudgery. Therefore, engine driven finger millet thresher was designed, fabricated, and evaluated. Physicomechanical properties of finger millet grains in were investigated to optimize the design of the thresher components. Performance tests of the fabricated finger millet thresher were conducted at three different levels of cylinder speed (600.00, 700.00, 800.00 rpm) and three levels of feeding rates (6.00, 9.00, 12.00 kg/min) at constant moisture content. The experimental design was CRD with factorial arrangement having three replications of each treatment; i.e. 3x3x3.Comparison between treatment means was made using the least significance difference (LSD) at a 5.00% level. The results indicated that the mean maximum threshing capacity of 311.95 kg/hr was observed at the feed rate 12.00 kg/min and cylinder speed of 800.00 rpm, threshing efficiency was 98.63% at feed rate of 6.00 kg/min and cylinder speed of 800.00 rpm. The cleaning efficiency was 98.13 % at feed rate of 6.00 kg/min and cylinder speed of 800.00 rpm.Threshing loss were 2.75 % at feed rate of 12.00 kg/min and cylinder speed of 800.00 rpm and the maximum fuel consumption of 63.06 ml/min was observed at a feed rate of 12 kg/min and an 800 rpm drum speed. With an increase in feed rate and cylinder speed, the threshing capacity, threshing loss, and fuel consumption tend to increase. In addition, the result showed that increased feed rate and cylinder speed affect threshing capacity, threshing efficiency, and fuel consumption, though speed only mainly affected threshing loss. Neither feed rate nor cylinder speed had significantly effects on cleaning efficiency. The analysis of variance showed that the interaction effect of feed rate and cylinder speed had significant effects on threshing capacity, threshing efficiency, and fuel consumption; they had no effect on cleaning efficiency and threshing loss