ABSTRACT
IAR groundnut sheller was developed in 1985 and the design was based on the properties of the then groundnut variety known as Ex-Dakar. New varieties were later developed whose acceptability in practice override, this called for its modification and determination of the characteristics of new varieties.The machine size was modified resulting in the modification of all its components for pulse shelling. The machine consists of the hopper, shelling cylinder, removable concave, blower, chaffs outlet, grains delivery chute, clearance adjuster and frame. The machineperformance was comparatively evaluated using groundnut and cowpea as test crops. A combination of four cylinder speed levels; 2.59, 2.79, 2.98 and 3.18 m/s (130, 140, 150 and 160 rpm), three feed rates (8, 10, and 12 kg/min) and three concave clearances (19, 21 and 23 mm) were used for the performance evaluation of themodified shelling machine using groundnut while a combination of three speed levels; 2.39, 2.59, and 2.79 m/s (120, 130 and 140 rpm) and three feed rates (12, 15 and 18 kg/min) were used for cowpea crop. The results were analyzed statistically in a completely randomized block design. Least Significant Difference (LSD) method was employed to assess the effect of parameter levels while a t-test was used to assess the differences in the machines performance. The basic geometric, complex geometric, and some mechanical properties of four selected varieties each of groundnut and cowpea were determined. The optimum performance of the developed machine using groundnut was found at a speed of 3.18 m/s (160 rpm) with a feed rate of 8 kg/min and 21 mm concave clearance. These resulted in shelling efficiency, cleaning efficiency, scatter loss, damaged grains and output capacity of 94.90%, 97.22 %, 6.29 %, 14.00 % and 254.99 kg/h respectively. When evaluated with a cowpea, the optimum performance was found at a speed of 2.79 m/s (140 rpm) with a feed rate of 12 kg/min and 10 mm concave to cylinder vii clearance. These resulted in shelling efficiency, cleaning efficiency, scatter loss, damaged grains and output capacity of 93.24 %, 98.31 %, 0.625 %, 0.00 % and 546.18 kg/h respectively. The levels of the independent variables were found to have highly significant differences with most of the performance indices for groundnut shelling but otherwise for cowpea. Generally, the output capacity of the modified machine was superior over that of the existing machine while its performance on cowpea was superior over that of the groundnut.