Design and construction of an improved motorized sorghum thresher.

Abstract

Sorghum is one of the most important and second cereal grown in Uganda just after maize. Despite the high level of production of sorghum in Uganda, its threshing and cleaning operations remain among the major challenges especially to farmers in the Eastern and Northern region of the country. To overcome those challenges, locally made sorghum thresher were designed and fabricated but still they are associated with many problems like low capacity of production, high scatter losses, contamination of cleaned grain with chaff (chaff outlet and clean grain outlet face the same direction) and mechanical grain damage. To solve the problems, I developed an improved motorized sorghum thresher to thresh, separate and clean Sorghum. The major components of the machine include the hopper, threshing rotor (central shaft, feeder conveyor, L- beaters on a cylindrical pipe), concave sieve, frame, driving mechanism, top cover, blower, shaking mechanism (four rubber hinges and cleaning sieve). The threshing action is achieved by parallel L-type round beaters arranged in helical form striping the sorghum from the stalks as it passes between the revolving rotor and a concave sieve and this is based on a combination of impact, compression and shear force created in the threshing chamber. The grains are further separated by the blower fan which blows a column of air horizontally past the grains that drop vertically on a shaking sieve and force the chaff through the chaff- discharge outlet. The machine was designed to be powered by a 4hp electric motor. Performance tests were further done, achieving average threshing, cleaning efficiencies and mechanical grain damage of 79.9%, 57.8% and 8.3% respectively at average feed rate of 0.006Kg/h and moisture content of 14% dry basis. The machine throughput capacity was also computed and found to be 101Kg/h. It was observed the Moisture content, federate and speed are highly significant on throughput capacity, mechanical grain damage and scatter losses. Therefore, the designed and constructed improved motorized sorghum thresher increased the sorghum output, reduced contamination of the grain and drudgeries which led to production of good quality sorghum that can easily be stored for long and fetch high prices.

Keywords: Sorghum, moisture content, grain, chaff, efficiency, improved.