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.
