Development of a Cowpea Threshing Machine

The transmission system of the thresher was developed to suit the process of threshing cowpea seeds. The developed thresher included substantial modifications to the threshing concaves, threshing fan, and threshing drum. The speed of the threshing sieve, suction, and fan were increased while the drum speed was decreased. Concave hole diameters of 20, 24, and 28 mm; drum speeds of 17, 23, and 29 m s-1; and feed rates of 360, 540, and 720 kg h-1 were studied. Threshing efficiency, seed damage, losses of seed, and power requirements were computed. The main findings revealed that increasing the diameter of the concave holes increased threshing efficiency and seed losses while decreasing seed damage and power requirements. Increasing drum speed increases threshing efficiency, reduced seed damage, and lower power requirements while decreasing seed losses. The maximum threshing efficiency reached was 96.75%, while the seed loss was 4.25%, with a minimum seed damage of 1.18%. The power requirement was 7.38 kWh ton-1 at a moisture content of 14.6%. The operating costs using the developed threshing machine were decreased to 71.33 USD ha-1 instead of the manually threshed cowpea, which costs about 111 USD ha-1.