Mechanics of Paddy plant for direct ear-head threshing and optimization of grain losses

This study investigates the mechanical characteristics of paddy plant, and effect of different cylinder speeds and throughput rates on different grain losses were tested in the laboratory using the direct ear-head paddy thresher developed considering the mechanics of the paddy plant to optimize the grain losses. In the developed thresher, grain bearing portion of standing plants is placed over the threshing cylinder. On this portion, upward tensile force is exerted by the threshing elements of the rotating cylinder. Consequently, grains and panicles get detached from the plant. The breakage of straw or uprooting of entire plants may also occur depending on the magnitude of force transmitted and strength of the plant straw and root grip. The panicle breaking, straw breaking, and plant uprooting forces were determined, and the average panicle breaking, straw breaking, and plant uprooting forces was found to be 68.4, 134 and 509 N, respectively. The average height of the panicle base was 620 mm, and accordingly, the height of cylinder axis was fixed at 600 mm to minimize the grain losses. The shattering, broken, and un-threshed grain losses were 3.61, 0.11, and 1.07%, respectively, at optimized speeds of cylinder (V_P) and plant feeding (V_F) of 18.94 m. s⁻¹ and 0.8 km.h⁻¹. There was a significant effect of V_P and V_F on the grain loss. The threshing of only ear-heads minimizes the power requirements. It was found to vary from 0.14 to 0.35 kW when the grain throughput rate was increased from 49 to 196 kg h⁻¹.