## 2 Materials and Methods
The bearing vibrations were measured in three perpendicular radial directions [21] to determine which location provides the most pertinent information on the bearing condition. There are many different bearing housings of the combine harvester shaft. The bearing housing can be made of cast iron or steel, with edges large enough to attach accelerometers. However, in cases where the bearing seats are made from a relatively thin metal plate, there is not enough room for accelerometer installation. In these cases, a metal bracket can be manufactured and installed at the bearing seating, to which an accelerometer is attached. In the present investigation, a bracket was constructed and installed, as shown in Figure 2a. Bracket dimensions presented in mm. The surface where the accelerometer or the bracket is attached should be clean, and preferably unpainted. In addition, the location should be flat to ensure proper bonding, and the best conditions selected so that the accelerometer measures vibrations in the direction that is normal for the shaft. The bracket was bolted onto the housing of the bearing. After loosening the bolts of the bearing holders, the bracket was inserted between the bearing holder and the mounting  
Figure 1: Bearing vibration measuring points: L1, L2, L3; accelerometer placed directly on a bearing seat. L4, L5, L6; accelerometer placed on a manufactured bracket. Figure 2: Manufactured bracket for vibration measuring points that are difficult to access: (a) dimension of the bracket; (b) accelerometer placed on the bracket (1). bolt and tightened back, to ensure a reliable and stationary connection and proper vibration measurement (Figure 2b). The amount of energy loss for a bolted joint depends on the material, surface finish, contact area, bolt tension, lubrication, and fretting corrosion. Modal analysis and harmonic response analysis were performed for the bracket and housing bearing in ANSYS software to identify and eradicate the common natural frequencies which could result in resonance. To take a genuine vibration measurement of the bearing from the added manufactured materials, it is necessary to develop a suitable design, with appropriate material selection and simulation of that material to avoid the resonance phenomenon. Before conducting vibration measurement using the added bracket, the selection of material was discussed from a material properties point of view. The bracket design aimed to avoid vibration lapse, and modal analysis was undertaken to avoid resonance due to similar natural frequencies in the associated parts. The bearing, bracket, and housing design were molded in SolidWorks, as shown in Figure 3. The material properties of the components used in the modeling are shown in Table 1. The dimensions of the bearing housing and bearing are shown in Figures A1 and A2 respectively. The load for the bearing was identified from the threshing components (flywheel, housing, shaft, threshing drum, chain and sprocket drive, and blower) mounted on the shaft. The modal analysis was performed for the system components consisting of the bearing, housing, bolt, and bracket. The frictional connection was defined with a frictional coefficient between the bearing races and housing (0.4), rollers and bearing races (0.21), and bolts and brackets (0.23). The radial load was applied as the bearing load on the inner race of the bearing in the system, and from the harmonic response analysis system oscillation at its natural frequency due to forced vibration of the bracket, maximum displacement was obtained. The natural frequencies (eigenvalues) of the bracket obtained from the modal analysis were compared