ABSTRACT
The existing IAR multicrop thresher was evaluated and found to have low feed rate and output with millet and soybean crops. The machine was modified and reconstructed to increase its threshing performance. Its components were increased in size and a shredder was added below the feed hopper to cut stems of crops that entangle the threshing cylinder and stop its motion. The beaters were tilted and arranged spirally on the threshing cylinder to facilitate the flow of threshed grains, chaff and unthreshed materials. Performance tuning was done and the machine?s performance was evaluated. With millet as the test crop the machine gave feed rate, threshing efficiency, cleaning efficiency, scatter loss, grain damage and output capacity of 14 kg/min, 99.98 %, 99.71 %, 12.18 %, 0.62 %, and 520.6 kg/hr as against 3 kg/min, 92 %, 80 %, 2.4 %, 3.5 %, and 81 kg/hr respectively for the existing IAR multicrop thresher. With soybean the machine gave 12 kg/min, 100 %, 97.26 %, 7.25 %, 6 %, and 205 kg/hr as against 1.7 kg/min, 80 %, 70 %, 2 %, 1.94 %, and 23 kg/hr respectively for the existing IAR soybean thresher. Therefore, feed rate was increased from 3 to 14 kg/min and from 1.7 to 12 kg/min; output was increased from 81 to 520 kg/hr and from 23 to 205 kg/hr for millet and soybean respectively. Threshing and cleaning efficiencies for both crops were also increased. The ANOVA indicates that the effect of all the factors evaluated and their interactions were significant at 1 % probability level. Further analysis using Duncan multiple range test shows that there was significant difference between the means at 1 % level of significance. A good linear relationship was achieved between the measured and predicted data with r2 equals 0.73. Hence the threshing efficiency model was accurate as the calculated t-value (0.101) was less than the tabular value (1.96) at 1 % level of significance. Optimum feed rate, threshing efficiency, cleaning efficiency, scatter grain loss, grain damage, output capacity of 12 kg/min, 99.7 %, 97.4 %, 11.2 %, 0.02 %, 420 kg/hr and of 10 kg/min, 100 %, 92.5 %, 4.7 %, 0.3 %, 163 kg/hr were attained for millet and soybean at a cylinder speed of 18.7 m/s and crop moisture content of 11.9 % and 12.2 % respectively.