The study evaluated the performance of the multi-crop motorized stationary thresher acquired by the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), Nigeria. The performance indices used were threshing efficiency, cleaning efficiency, output capacity, scatter loss and breakages. The independent variables used were the concave cylinder speed, revolution per minute (rpm) and feed rate, kg/min. The work was conducted using a factorial experiment in a completely randomized design (CRD). Data obtained were subjected to Analysis of Variance (ANOVA) using GENSTAT 17.1version statistical software and least significant difference (LSD) was adopted in separating the means. The mean performance values of IK00007 machine for sorghum crop ranges from 102.71 – 157.33 kg/h, 72.36 – 93.30 % , 64.52 – 79.49 %, 17.33 – 27.80 %, and 0.12 – 0.67 %; for millet crop it ranges from 34.10 – 78.12 kg/h, 57.77 – 92.07 % , 41.76 – 64.55 %, 13.35 – 27.99 %, and 0.23 – 0.38 %; while for maize crop it ranges from 298.23 – 580.00 kg/h, 70.26 – 100.00 %, 61.20 – 91.60%, 22.74 – 43.06 %, and 0.70 – 1.27 % for output capacity, threshing efficiency, cleaning efficiency, scatter loss, and breakages, respectively. Machine IK00007 can be best used in threshing maize at a combination of feed rate of 40 kg/min and a speed of 950 rpm. With this, the mean values for output capacity, threshing efficiency, cleaning efficiency, scatter loss and grain breakages are 580.60 kg/h, 100.00%, 86.22%, 39.43% and 1.06% respectively. The best combination for threshing of sorghum with the machine (IK00007) is at the feed rate of 12 kg/min and a speed of 950 rpm. With this, the mean values for output capacity, threshing efficiency, cleaning efficiency, scatter loss and grain breakages are 157.33 kg/h, 86.20%, 76.07%, 22.39% and 0.47%, respectively. The best combination for threshing of millet with the machine (IK00007) is at the feed rate of 8 kg/min and a speed of 950 rpm. With this, the mean values for output capacity, threshing efficiency, cleaning efficiency, scatter loss and grain breakages are 78.12 kg/h, 77.68%, 56.20%, 25.04% and 0.27% respectively. The mean annual operational cost for IK00007 machine was found to be N 118,936.3, N 116,637.4 and N 117,313.9 for the threshing of sorghum, millet and maize respectively. It is concluded that all independent factors have significant effects on the dependent performance indices. Specifications for the combination of operational machine parameters to give best performance have been obtained. The assessment of the operational cost of the thresher was conducted.
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