Abstract
To improve the quality of threshed cowpea (Vigna unguiculata L.), produced by rural farmers in Ghana, and determine the best machine-crop parameters combination for optimum performance, a cowpea thresher was developed and evaluated at different moisture contents. The cowpea after harvesting was divided into five units and dried to 20.7, 18.4, 15.5, 13.5 and 12.6 % seed moisture contents. The effect of seed moisture contents on threshing quality was assessed at 735 rpm rotor speed using the white with black eye cowpea. The performance test showed that 12.6 % had the highest throughput of 77.56 kg/h with the lowest of 66.28 kg/h from the 20.7%. The seed damage ranged from 1.64 to 9.46 % and threshing efficiency from 93.11 to 99.40 %. Analyses done at 5% level of significance indicated no significant difference in the throughput and threshing efficiencies. However, seed damage had significant difference. Subsequently, analysis performed on the data for seed loss of 12.6 and 13.5 % which were the best performing moisture contents showed no significant differences. Therefore, seed moisture contents less than 13.5 % and rotor speeds less than 735 rpm are the crop- machine parameters combination for optimum thresher performance.
 
 
 
 Key words: Design; Throughput; Impact Force; Seed Loss; Simulation
 
 
Highlights
Cowpea (Vignaunguiculata L.Walp) is an annual legume crop (Yalcın, 2007) and originated from Africa
The results indicated that moisture content, feed rate, and rotor speed significantly affected the throughput selected based on calculations and the properties of materials so as to withstand stress and strain from the capacity, threshing efficiency, and grain damage
The impact force simulation results obtained with ANSYS Workbench on the rotor peg is shown in figure 2
Summary
Cowpea (Vignaunguiculata L.Walp) is an annual legume crop (Yalcın, 2007) and originated from Africa. In drawing and simulations were employed to design the another study Herbek and Bitzer (2004) reported that thresher It was developed through fabrication cylinder speeds ranging from 400 to 800 rpm were processes of machining, cutting and welding at the generally sufficient and that greater seed damages are Mechanical Engineering workshop of the Koforidua caused by higher cylinder speeds ranging from 700 to Technical University. The results indicated that moisture content, feed rate, and rotor speed significantly affected the throughput selected based on calculations and the properties of materials so as to withstand stress and strain from the capacity, threshing efficiency, and grain damage. The objectives of this paper seek to: Design a portable cowpea threshing machine for use by rural farmers in Ghana; Evaluate the effectiveness on the bases of threshing efficiency, grain damage and. This was done to determine the MCdb at which the sum of seed damage and unthreshed seeds obtained is the lowest so as to provide the best MCdb for optimal machine performance
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