Soybean threshing efficiency and power consumption for different concave materials

Abstract

Soybean is one of the most slowly established crops in many developing countries. During recent years, greater interest has been given to the cultivation and mechanization of soybean. Particularly, soybean threshing is an important problem because of the product loss. Most of the trials for soybean threshing have been on the structure of beaters, although the type and structure of contrbeaters are as important as structure of beaters. This work designed and tested concaves made of different materials with respect to threshing efficiency, power requirement and specific power consumption at various feed rates and drum peripheral speeds. Regression equations have been established. The multiple regression technique was used to study the relationship among different variables, namely, concave type, feed rate and drum peripheral speed in relation to three dependent variables, namely, threshing efficiency, power requirement and specific power consumption. An experimental model of a soybean thresher without a cleaning and separating unit was developed. The threshing machine had a peg-tooth drum and was powered by a 4 kW electricity motor. Also, four concaves made of different materials were used for the trials. SA-88 soybean variety was used for the trials. The four concave types were PVC, rubber, chromium, and steel plate with three feed rates (360 kg/h, 720 kg/h, and 1,080 kg/h) and five beater peripheral speeds (7.95 m/s, 9.10 m/s, 10.54 m/s, 12.16 m/s, 14.66 m/s). Speed and feed rate were found to a have a significant effect (p < 0.01) on power requirement. The power requirement increased with increasing feed rate and drum peripheral speed. The specific power consumption decreased with increasing feed rate. Threshing efficiency decreased with increasing feed rate and increased drum peripheral velocity significantly improved the threshing efficiency. The highest threshing efficiency was achieved with the chromium type of contrbeater, followed by PVC, the sheet iron, and the rubber.