Design, fabrication, and testing of a hand operated grain amaranth thresher

Abstract

Iowa State University-Uganda Program (ISU-UP) supports the growth of grain amaranth because of its high nutritional potential to be used as a malnutrition mitigation measure in Kamuli district. Although its support has increased amaranth production in the district though the threshing methods being used are still traditional. These traditional methods are time-consuming, labor-intensive and result in increased post-harvest losses. To mitigate the stated problems, a hand-operated grain amaranth thresher was designed, fabricated and tested. The machine uses impact and rubbing actions to separating the grains from the straws within the threshing cylinder. The power is transferred from the operator to threshing drum through a gear assembly and the flywheel helps to maintain the angular velocity. Testing was carried out using farmers of different weight (50, 57 and 65kg), different machine feed (1, 1.5 and 2kg) and the traditional method of threshing (hand rubbing) was used as the control. Results showed that at the machine feed of 1kg, threshing capacity and efficiency were 76.11kg/hr and 89.90%, 79.42kg/hr and 90.16%, 90.67 kg/hr and 92.87% for a 50kg, 57kg, and 65kg operators respectively. At a machine feed of 1.5kg, the threshing capacity and efficiency were 65.3kg/hr and 84.27%, 71.06kg/hr and 84.27%, 74.98kg and 90.5% respectively for the same operators. At a machine feed of 2kg, the threshing capacity and efficiency 43.66 kg/hr and 79.04%, 46.17 kg/hr and 82.09%, 52.52kg/hr and 85.84%. Hand threshing showed an average threshing capacity of 14kg/hr. The ease of operation of the machine also showed the average of all the operators ranged from 66.67% to 37.50% at a machine feed of 1kg, to 2kg and negligible grain damage. In conclusion, the best threshing capacity and efficiency were achieved at a machine feed of 1kg and machine threshing can thresh 6.5 times hand threshing can do. Therefore, the designed machine will be able to thresh the grain amaranth at a machine feed of 1kg efficiently and in a short time