ABSTRACT

Despite the high level of production of sorghum in Nigeria its threshing and cleaning operation remains among the major challenges to farmers especially in the northern part of the country. Efficient sorghum threshers are not available to Nigerian farmers. The prototype thresher developed at Institute for Agricultural Research (IAR) was associated with many problems such as: low out capacity, higher scatter loss and mechanical grain damage. To solve these problems a modified model was designed, constructed and evaluated. The major components modified include feed hopper, cylinder, concave and shaker. The machine performance was evaluated at various levels of moisture contents, cylinder speed and feed rates. The results showed that threshing efficiency, cleaning efficiency and throughput capacity of the modified thresher were 99.98, 99.95 % and 253.96kg/h respectively while those for scatter losses and mechanical grain damage were 5.45 and 3.70 % respectively. This indicate the percentage increase of 0.98, 6.95 and 56.96 % for threshing efficiency, cleaning efficiency and throughput capacity respectively and decrease in scatter loss and grain damage of 5.98 and 3.84 % respectively. The best combinations of the independent variables for optimum operations were 13 % moisture content, 12.67 m/s cylinder speed and 5 kg/min feed rate. The optimum performance values obtained were of 297 kg/h throughput capacity, while threshing efficiency, cleaning efficiency, scatter losses and mechanical grain damage were 99.8, 99.5, 5.09, and 3.4 % respectively.