The importance of bearing selection for gearbox performance

Jul 26, 2023

Large reduction gearboxes deliver high torque by reducing the high input speed to the desired output speed. This is why gearboxes are widely used and are common equipment in heavy industry to drive conveyors, mills, crushers and pumps.

In operation, the gear design does not cause axial loads. In the more common helical and pinion drives, the axial load generated must be borne by the support bearing. Usually, the selection of bearings is based on load bearing capacity and theoretical bearing life, without a basic understanding of bearings and their basic design.

The bearing loads can be radial load, axial load, or a combination of both. Usually, most applications have some combination of the two. Bearings are designed to bear different loads, and most are able to bear a combination of loads. For example, a ball bearing is designed to bear the radial loads, however, it can also support some axial loads and is therefore well suited for use in an electric motor as the bearing will actively position the rotor. In this case, there will also be some heat growth of the axis. In order to eliminate the risk of bearing "cross positioning", cylindrical roller bearings can be used. This type of bearing comes in a variety of configurations. It can be used because some designs allow the axial movement of the bearing itself while still maintaining radial load bearing.

This can be beneficial in cases where there may be inaccuracies between the bearing seat and the shaft or the possibility of shaft deflection. Similar to the helical gear design, these bearings also have advantages and disadvantages. This type of bearing comes in a variety of configurations. It can be used because some configurations allow the axial movement of the bearing itself while still maintaining radial load bearing.

For spherical roller bearings, the ability to misalign while allowing rotation is excellent without affecting the load-carrying capacity. These spherical roller bearings with CC cage are excellent design for conveyor belts because it is always difficult to maintain accurate alignment and the radial loads applied are usually high. In addition, these bearings are able to position the shaft by adapting to smaller axial loads.

Bearings specifically designed to withstand a combination of radial and axial (thrust) loads, as well as load ratings that maintain minimum load requirements, can be considered. Tapered roller bearings are often a good choice if spherical roller bearings fail prematurely or do not provide a sufficient service life in gearbox applications.