Performance Evaluation of a Rasp Bar Type Small Rice Thresher for Small Scale Farmers

Abstract

 The parameters effecting to the working capacity of a rasp bar type small rice thresher were studied.  This machines are popularly used among the small scale farmers in the north east of Thailand.  The small rice thresher consisted of engine, rasp bar thresher, feed board, transmission system, threshing cylinder cover and cleaning fan.  The parameters used consist of number of rasp bar and threshing drum speed. Five and six rasp bar and three level of threshing drum speed (200, 300 and 400 rpm) were determined. Additionally an engineering economic analysis was determined the optimum use of the machine for small scale farmers.

                Results showed that the optimum number of rasp bar and threshing drum speed were 5 and 300 rpm, respectively.  Working capacity of the machine was 396 kg/hour with the total grain loss of 0.28%.  Fuel consumption of the machine was 0.46 litre/hour.  While economic analysis showed that the operation cost of the machine was 125.8 Baht/hour or approximately 0.32 Baht per kilogram.  Considering the contract rate of 200 Baht/hour, the break-even point of machine was 14.6 hour/year and the pay-back period of the machine was 1.3 year.