## 3 Results and Discussion
### Double Threshing Drums Dynamic Balance Test Verification  
As shown in Figure 5, the double threshing drums dynamic balance verification was tested with the Word Dragon's double threshing drums combine harvester. The transmission of threshing drum I and threshing drum II were driven by the Engine, which fit the transmission mode of this paper. The double threshing drums dynamic balance test firstly balanced threshing drum I with a balance speed of 810 rpm, and the transmission path was shown in Figure 4(a). The single drum mode was selected in the portable dynamic balancer system. The initial unbalance amount of threshing drum I was 1.96 mm and the phase was 9.6\({}^{\circ}\). It was recommended to add a weight of 68 g when the phase was 194\({}^{\circ}\). There were 65.4 g of weight actually added in the direction of 180\({}^{\circ}\). The remaining unbalance was 0.42 mm, the phase was 14\({}^{\circ}\), and the amplitude was reduced by 79.5%. The original dynamic balance axis trajectory of the single threshing drum I and the axis trajectory after weighting were plotted as shown in Figure 13.  
Figure 12: Schematic diagram of double threshing drums dynamic balance method. Figure 13: Axial trajectory of single threshing drum I. As shown in Figure 13, the original dynamic balance axis trajectories of the single threshing drum I was similar to round cake. The horizontal and vertical amplitudes of the axis trajectory were 1.70 mm and 1.34 mm, respectively. However, the axial trajectory of single threshing drum I was reduced after increasing the weight. The horizontal and vertical amplitudes coordinate values of the axis trajectory were significantly reduced, which are 0.38 mm and 0.39 mm, respectively. The amplitude of the axis trajectory was similar to the vibration amplitude. In the portable dynamic balancer system, the double threshing drums mode was selected. The unbalance mass of the threshing drum I was measured. The initial unbalance mass (the remaining unbalanced mass after the first balance) was 0.42 mm in amplitude and 13.4\({}^{\circ}\) in phase. Enter the coordinates of the equivalent unbalance of the chain drive, and calculate the total unbalance amount as the amplitude of 2.36 mm and the phase of 28.2\({}^{\circ}\). The amplitude was significantly increased, that was the chain drive exacerbated the dynamic unbalance of the drum. After this test, it was recommended to add a weight of 103 g whose phase was 184.9\({}^{\circ}\). Actually, added a 107.5 g of weight in the direction of 180\({}^{\circ}\). The residual unbalance was 0.2 mm. The phase was 32.8\({}^{\circ}\), and the amplitude was reduced by 91.5%. Then, threshing drum II was dynamically balanced, and its equilibrium rotation speed was 810 rpm. The unbalance mass of threshing drum II was measured in the single drum mode of the portable dynamic balancer system. The initial unbalance amount was 3.86 mm in amplitude and 36\({}^{\circ}\) in phase. It was recommended to add a weight of 137.7 g whose phase was 258\({}^{\circ}\). Actually, 270 g of weight was added in the direction of 141\({}^{\circ}\). The residual unbalance was 1.18 mm, the phase was 34\({}^{\circ}\), and the amplitude was reduced by 69.2%. The original dynamic balance axis trajectory of single threshing drum II and the axis trajectory after weighting were plotted as shown in Figure 14.  
As shown in Figure 14, the horizontal and vertical amplitudes of the axis trajectory were 3.71 mm and 2.42 mm, respectively. However, the axial trajectory of double threshing drum II was reduced after increasing the weight. The horizontal and vertical amplitudes coordinate values of the axis trajectory were significantly reduced, which were 2.02 mm and 1.63 mm, respectively. It can be seen from the above that the test results of the whole combine machine on the spot were remarkable, and the unbalanced amplitude of the drum can be reduced by 69%-91% after dynamic balancing.