Analysis and test of power consumption in paddy threshing using flexible and rigid teeth

The study and use of flexible threshing teeth are of interest to researchers in agricultural mechanization because flexible teeth appear to damage grain less than rigid teeth. For a flexible threshing tooth, consisting of an elastic beam fixed on one end, a differential equation of its deformation curve was created, the deformation of which was calculated by numerical methods, which provided necessary condition for dynamic analysis. The corresponding formulation of calculating power consumption was deduced based on theoretic analysis in this paper. The hypothesis was as follows: the threshing roller was regarded as rigid body, the threshing teeth as elastic bodies, and threshing as the impact between threshing teeth and paddy rice. The differences in impulse moment and beating force for paddy grain between the rigid threshing tooth and the flexible one were analyzed and compared, and their respective power-consumption models were established in this paper. By analyzing the loss of kinetic energy and impact momentum for the threshing processing using the rigid threshing tooth and the flexible one, we concluded that the loss of kinetic energy of flexible threshing was less than that of rigid threshing; likewise, power consumption by flexible-tooth threshing is less than that by rigid-tooth threshing if the feed rates and the rotary speed are equal.Meanwhile, the theoretical analysis results show that the beating force of the flexible tooth was less than that of the rigid tooth, which was confirmed experimentally. Experimental data showed that the threshing roller has to have a sufficiently high moment of inertia, and the engine enough power, to preserve the stability of the threshing process. We fabricated a number of experimental devices including a transducer for measuring torque, an apparatus to measure angular velocity, and a feeding test-bed. Experiments were conducted by measuring torsion and angular velocity, enabling us to compute the brake power of flexible-tooth and rigid-tooth threshing, respectively. There is an optimal value of tooth length that minimizes power consumption but that is unique for each kind of tooth.