Abstract
A motorized legume thresher was redesigned to utilize coefficient of friction to separate grains from impurities, the thresher performance was evaluated and best combination of parameters for highest separation efficiency determined. The study was carried out using a randomized design of three batch weights (BW): 100, 150 and 200 g, four surfaces (S) mild steel, plywood, rubber carpet and rug at an angle of inclination of 25° and a height fall of 90 mm, two impurity levels (I) using cowpea (Vigna unguiculata) IT84S-2242 and soybean (Glycine max L) 1448-2E variety. Sorghum seeds at 10% of each batch weight were mixed in with each test samples as additional impurity. Data obtained was analyzed using SAS and Duncan tests. Results showed, cleaning efficiency varied between 90 and 63.28% for soybean samples, threshing efficiency varied between 87 and 97% with an average minimal damage of 0.78% from using carpet surface. For cowpea threshing and cleaning efficiencies were 97.44 and 97.16%, respectively with average loss 2.60%. Analysis of variance (ANOVA) showed that impurity level and feed rate affected cleaning efficiency at both 1 and 5% significance, type of surface affected threshing percentage and broken seeds at 5% significance. The best combination of batch weight, surface and impurity level to obtain cleaning efficiency, threshing efficiency, low grain damage and grain losses was 100 g batch weight using carpet surface. In conclusion, coefficient of friction could be utilized to increase separation efficiency of thresher, this would aid the development of appropriate technologies for legumes processing. Key words: Threshing, threshing efficiency (TE), cleaning efficiency (CE), coefficient of friction, percentage impurity.
Highlights
Agricultural mechanization involves using agricultural machinery to perform farm operations speedily and efficiently
The trough was shaped as chute; its base rectangular dimension was 25 × 75 cm and was made of a 1.5 mm thick mild steel inclined at an angle 25° from the vertical
It was assumed that friction between chaff and the rug or carpet surface will reduce the velocity of chaff compared to grains, plywood or mild steel should impart a higher rebound energy to grains as they land on the hard surface propelling them more quickly into the centrifugal fan
Summary
Agricultural mechanization involves using agricultural machinery to perform farm operations speedily and efficiently. It plays a significant economic role by reducing cost of cultivation, increasing agriculture production and in increasing productivity as well as overall returns to the farmers (Kamboj et al, 2012). Soybean is an important food source in human and animal nutrition with total worldwide production of about 180 million tons per year (Manuwa, 2011). The importance of cowpea lies in its food value as a major source of protein of high biological value, energy, vitamins and roughage, Nigeria cultivates about 40 million hectares of cowpea and produces an estimated 850,000 tons annually (Faleye et al, 2013; Olaoye, 2011)
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