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Though the component of threshing drum is pre-balancing on the factory, the drum after assembly still has the problem of unbalanced vibration. In this study, the unbalance mechanism produced by assembly are introduced and the centroid propagation model in the series rotation system was established. The influence of the eccentricity and assembly phase on the assembly unbalance was studied. It is shown that there was a superposition effect between the initial centroid eccentricity caused by the machining error and the centroid eccentricity caused by assembly error, the unbalance amount under the in-phase assembly was larger than that of the anti-phase assembly. Moreover, the unbalance variation was experimentally investigated using in-field balancing detection on the test rig and combine harvester. The experiment results showed the excellent vibration reduction effect of in-field balancing, which showed a reduction of 83.0% and 85.8%. In order to increase the range of in-field balance detection and reduce the calculation error, the double-speed influence coefficient method was proposed. The proposed method adopted the way of first low-speed pre-balancing, and then high-speed precision balance, taking advantage of vibration information at two speeds and avoids nonlinear vibration conditions caused by high unbalanced vibration. Finally, the doublespeed influence coefficient method was verified on the test rig. The vibration reduction effect of proposed method was better than the traditional method. [ABSTRACT FROM AUTHOR]

In order to study the influence of the side drive on the balance state of the threshing drum, this paper used the side eccentric load chain drive as the power on the threshing drum dynamic balance test bench. By analyzing the influence of different radial phases, different axial distances, and spiral combinations of the threshing drum on the counterweight, this paper studies the law of the effect of side partial load chain drive on the dynamic balance of the threshing drum and finds that the side chain drive has obvious influence on the unbalance phase of the threshing drum and the change of the axial distance of unbalance has little effect on the equilibrium state of the threshing drum. And from this, a vibration balance method based on the equivalent unbalance of the chain drive is proposed, which can predict and calculate the unbalance of the threshing drum. The unbalance of the threshing drum predicted by this method is smaller than the actual measured unbalance. The maximum error is 32.64% and the minimum error is 4.6%. In the two tests, the predicted unbalance is 1.24 mm/s in amplitude and 270 degrees in phase and amplitude 1.4 mm/s and phase 120 degrees, respectively. The measured unbalance is amplitude 1.587 mm/s and phases 286 degrees. The error between prediction and actual measurement is less than 32.64%, and the unbalance amplitudes that can be reduced by one-time dynamic balance are 0.856 mm/s and 0.674 mm/s, respectively. The research results in this paper provide an effective method for the balance state of the multidrum side chain transmission. [ABSTRACT FROM AUTHOR]