DEVELOPMENT AND PERFORMANCE EVALUATION OF A MULTI-GRAIN THRESHER

Abstract

Agriculture still remains a major support of the Nigerian economy and the role of agriculture still remains significant in the Nigerian economy despite the strategic importance of the oil sector. The vast majority of farmers have limited access to modern input, processing implements and other productive resources and despite the amount of energy and efforts of researchers in the development of multi-grain threshers, the available multi-grain threshers are found to be non-adaptive for the crops grown in Nigeria. Also, most machines are cumbersome in structure therefore not suitable for rural farmers that don’t cultivate very large hectares of crops and such machines are found to be complex in their system of operations therefore not adaptive for non-learned farmers. Therefore, in this research, a multi-grain thresher that is simple in structure, locally available and affordable is designed, fabricated and evaluated using cowpea and pigeonpea. The machine was designed to thresh selected multiple crops e.g soybean, wheat, sorghum, cowpea and millet effectively. The major components of the machine include; the hopper, the threshing chamber (consisting of the cylinder mounted on the shaft, the rubber spikes and the concave), the screen, the fan/blower, blower speed control, chute and frame. Materials used for fabrication were locally sourced for and appropriate materials were used where they were required. Materials ranged from stainless to galvanised steel and mild steel. Total cost of production sums up to ₦105,000.00. The thresher was evaluated for performance by introducing stalks of cowpea (at 10, 12 and 14% moisture content dry basis) and pigeon pea (at 12, 15 and 18% moisture content dry basis) into the hopper and data were collected as the threshing took place. The process was repeated at three selected speeds of (615, 876 and 1402 rpm) and three feed rates (17, 32 and 40kg/hr) each. After each threshing session, quantity of threshed grains and threshing duration were noted and recorded. All broken,chipped and cracked grains were categorized as damaged grains. The last phase was the analysis stage. The obtained results from the experiments were computed using Microsoft excel version 2016 and further analyzed using multiple linear regression and analysis of Variance (ANOVA) on Minitab statistical software version 2017 and the F- calculated value was compared with the F-tabulated in order to determine the level of significance between the variables. The optimal operational condition was determined using response surface methodology on Design expert version 11 (Stat-ease. Inc.). From the optimization process, a degree of desirability of 0.801 and 0.879 was obtained for cowpea and pigeon pea respectively. For cowpea, the best conditions for its threshing were 11.88% moisture content, fed into the machine at a feed rate of 30.16kg/hr and at a threshing speed of 615 rpm which gave a T.E of 97%, T.C of 18kg/hr, C.E of 94%, M.L of 4% and M.D of 11%. For the threshing of pigeon pea, the best conditions were 12.23% moisture content, at a feed rate of 14kg/hr with a threshing speed of 785rpm which gave a T.E of 99%, T.C of 11kg/hr, C.E of 97%, M.L of 2% and M.D of 6%.