## 3 Results and Discussion
### Vibration Analysis  
To determine the bearing vibration differences with and without a bracket, the easily accessible bearing housing of the combine harvester was selected. The measurements were performed comparing the data. The main objective of these measurements was to develop a database to determine the differences between cases with the manufactured bracket and without the bracket. These results are presented in Figure 8. At some locations where the manufactured bracket could be properly fitted to the surface. The RMS data are mostly used for bearing vibration evaluation. The measurement difference was calculated from the obtained results, and the given coefficient was used for evaluation of the threshing drum bearings. The collected data showed 17.92% increased vibration while using the bracket (Figure 8). Thus, if the metal bracket could be properly installed at some locations, the bracket can be used to assist in vibration measurements of the threshing drum bearings. Figure 7: Harmonic response of the bearing. The vibrations at the right side of the threshing drum bearings were measured and transferred to a personal computer. The FACIT-type graphs were obtained, from which the bearing status could be determined. For the bearing status determination the acceleration by fast Fourier transformation (Acc_FFT), root mean square demodulation (Demod_RMS), time-frequency demodulation (Demod_Time), fast Fourier transform demodulation (Demod_FFT), and acceleration time (Acc_Time) graph were selected. The FACIT sub-figures, provided by the ADASH vibrometer, show the extended and more detailed bearing vibration status: the bearing condition; speed (value only, no severity indication); unbalance; looseness; misalignment. As was mentioned above, each graph is composed of several alarms, coded with colors. If all values are in the green color area, it means good condition and no defects of the bearing. After performing the analysis using the vibration response spectrum, no significant changes in bearing defect frequencies were observed. This was expected, since the combined threshing drum bearings were relatively new. From the measured vibration results, the most important vibration parameters were selected and further analyzed with Excel 2010 software. A summary of these results is given in Figures 9-11. Then, from the analysis of the vibration data, it was possible to determine key parameters, which most accurately identified possible bearing defects. According to various investigators, analysis using the mean square vibration velocity in the frequency range of 10-1000 Hz cannot be used as the key parameter in the evaluation of the technical condition of slow-rotating bearings. Vibration parameters such as Vrms, g (5-16 kHz), and gr (0.5-16 kHz) do not properly describe the condition of the bearing. The most appropriate assessment of bearing conditions is by FFT spectrum analysis [26,27]. To determine the time before the bearing starts to show the first signs of wear, periodic monitoring of bearing vibrations is needed. The results from the right side of the threshing drum bearing were transferred from the Adash 4900 Vibrio vibration analyzer to a personal computer. The results in the FASIT-type graph represent the bearing vibrations data. Figure 8: Bearing vibration acceleration at 3050 min-1 speed. L1, L2, L3; accelerometer placed directly on a bearing seat. L4, L5, L6; accelerometer placed on a manufactured bracket. The obtained results indicate that the largest vibrations were at the L5 location, at a rotation speed of 1180 min\({}^{-1}\). This indicates that the largest vibrations of the bearings  
Figure 11: Bearing vibration acceleration at a speed of 1180 min\({}^{-1}\). Figure 9: Bearing vibration acceleration at a speed of 600 min\({}^{-1}\). were in the vertical direction. The lowest vibrations were measured at locations L4 and L6. After vibration data analysis, it was concluded that this bearing had no defects.