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The theoretical optimal clearance for a radial bearing under radial load is a slight pretension as this leads to an optimal load sharing between rolling elements. In case of a planet bearing with line load on two angular positions this is different because of elastic deformations due to the radial load components. One image shows the reference rating life L10rh over bearing clearance in case of an elastic or rigid outer ring. In case of the rigid outer ring the radial forces have no effect and the optimum is reached at a small pretension. In case of the elastic outer ring the optimum is at larger clearance. The load distribution is shown in another image for the elastic ring and zero clearance. The other two images provide some geometry information. A calculation with elastic bearing rings can be done within the MESYS Rolling Bearing Calculation based on elastic beam elements or within the MESYS Shaft Calculation using 3D-FEA.

The final drafts ISO/FDIS 16281 and ISO/FDIS 17956 are available for voting now. ISO/FDIS 16281 is an update of the existing ISO/TS 16281. The technical content is unchanged, but it includes some clarifications and has proper coordinate systems. Hybrid bearings are now mentioned too. ISO/FDIS 17956 defines the calculation of an effective static safety factor and requires the load distribution within the bearing to be known as in ISO 16281. The effective static safety factor is then calculated based on the rolling element load. This allows to see an influence of clearance or misalignment. As ISO 16281 extends ISO 281 by considering the actual load distribution, ISO 17956 extends ISO 76 by considering the actual load distribution.

In case of hollow shafts centrifugal forces lead to a radial expansion and an axial shortening of the shaft. This can be considered in the MESYS Shaft Calculation by using FEA based 3D-elastic parts. In this example the left bearing is fixed and the right bearing has a spring pretension. The axial movement of the left end of the shaft is -10µm and the axial movement on the right end is -20µm. Therefore the shaft is shortened by 10µm at 20'000rpm.

Track roller bearings usually have a point (or line) load to the outer ring and therefore a thicker outer ring. The MESYS Rolling Bearing Calculation allows to calculate reduced working load ratings Cw and C0w for track rollers based on a FEA-beam model for the outer ring. Maximum contact stress and minimum life are calculated when the load is applied on the position of a rolling element, while the maximum stresses in the ring occurs if loaded between two rolling elements.

A corrected version of ISO/TR 1281-1 is available. The only change is formula 52 where some exponents were missing.

See page 122-124 in latest issue of BEARING NEWS for an article about Release 06/2024 of the MESYS Software. The whole issue is available as PDF at https://lnkd.in/d4h98DJq

If two gears are connected by two intermediate gears with the same geometry in both load paths, how is the load shared between the gears? In the example below for equal backlash in both paths the upper intermediate gears transmits 64% of the power based on the stiffness in the coupled system calculation. Because of the direction of the gear forces the upper shaft is pulled into the contact which leads to reduced backlash. The lower shaft is pushed out off the contact leading to larger backlash. This results for the load sharing should not be taken for real as there are tolerances and also not all stiffnesses are considered in this model. There should be a possibility to adjust the backlash during mounting of the system. The diagram shows the load sharing in the two paths based on the backlash of the upper path. An increase of the backlash in the upper path improves the load sharing between the gears. In the design of a system with different load paths the problem with load sharing should be considered.

In case of Wolfrom type planetary gear sets, large moment loads are introduced into the planet shafts. In case of soft planet carriers this can lead to two flank contact of the gears. This not only reduces the strength but will also lead to much noise.

The reports for the gear calculation examples in ISO 6336-30 were added to the MESYS website. See https://lnkd.in/e_dUVT5i for the reports in English, https://lnkd.in/evb2vNkd for the reports in German and https://lnkd.in/e_QgW68n for the reports in Japanese language. The results match the results in the standard. The link to the reports is added to the download page on the website.

Several customers asked about contact dimensions for ball bearings, like half axes of contact ellipses or contact surface. The half axes for all contact ellipses had been available as numerical results for long time in result tables. In version 06/2024 also a diagram for contact dimensions was added to the MESYS Rolling Bearing Calculation. In addition to the half axes of the contact ellipse the contact area is also directly available. Like for all diagrams, the data values can be exported into a table for further processing.