Design improvement of indigenous beater wheat thresher in Pakistan

Mechanical wheat threshing has gained a spectacular popularity in Pakistan over a short span of time and so is the population of beater-wheat threshers that are being manufactured and marketed by the roadside vendors with little scientific and engineering experience. In fact, the major problems on conventional threshers have been identified as bulky weight, poor machine performance, human accidents and a high fuel consumption rate. A review of the conventional thresher suggests presence of three heavy flywheels with little scientific argument and similarly poorly designed threshing beaters and five MS rings on the beater-drum appear injudicious and unscientific. A horizontal throw of straw from the exhaust-blower takes away a noticeable amount of grains with it. Conventional threshers have witnessed terrifying accidents for the persons feeding the material without any safe crop feeding system. The local manufacturers least care about the fabrication drawings of the conventional machines and therefore their knowledge of manufacturing is restricted to the whims and wishes of "ustad-shagird" (seniors, juniors). Therefore, the present study has been planned for investigation and improvements in the prevalent design of the indigenous beater-wheat thresher to bring about durability, reduction in weight of machine and grain losses in addition to an accident free and cost effective thresher. Modified designs and fabrication drawings of various components such as flywheel, beater, beater drum, blower and feeding conveyer were prepared. Total weight of redesigned beater wheat thresher was reduced from 1600 kg to 1300 kg and the grain damage was reduced four times. The mean threshing efficiency was increased from 98% to 99%. The replacement of the three flywheels by one redesigned flywheel of required size saved 24.37 kN-m energy. The fluctuation in speed was reduced to 3.05 times and coefficient of energy 3.11 times than that of conventional thresher By redesigning and redeveloping the direction of fan blower exhaust, the mean grain cleaning efficiency improved from 97.44 to 98.18 % causing elimination of grain loss through straw blowing process. A newly designed feed conveyor uniformed the feeding rate that not only eliminated overloading of thresher but also reduced the fuel consumption by 1.3 L/hr (15 kW).