Roller and needle bearings - Calculations

This article presents the calculation of roller bearings: static load capacity, expected service life, and friction torque. Needle bearings are included, as the needle is simply a small-diameter cylindrical roller. Needles and cylindrical rollers are calculated in the same way.

The distinctive feature of roller bearings is that the roller/track contact is linear, which gives them a high load capacity but also high friction torque, especially when an axial load is applied. This results in properties that are opposite to those of the point contact between the ball and raceway in ball bearings, which offer moderate load capacity and low friction torque. The calculation of ball bearings is discussed in the articles [BM 5 372] and [BM 5 373] .

There are three types of rollers: cylindrical rollers, tapered rollers, and spherical rollers. In the case of cylindrical or tapered rollers, the force must be evenly distributed along the length of the roller, which requires careful alignment of less than 1 mrad between the shaft and the housing. Spherical rollers are only found in spherical roller bearings, which allow for misalignment of ± 1.5 to 3.5 degrees depending on the series offered in the catalog, but only ± 0.5 for sealed versions.

Conical roller:

Of the three types of rollers, only tapered rollers can be preloaded to eliminate backlash. Tapered roller bearings are used in gearbox shafts, heavy truck wheels, high-speed train axle boxes, truck and car rear axles, and bevel gear angle drives.

Cylindrical roller:

With high axial expansion freedom, cylindrical roller bearings are used in large electric motors, railway axle boxes, pressure rollers, and rolling mill cylinders. Needle roller bearings are used in applications where low radial clearance is required: cardan joints and planetary gear trains. The catalogs also offer a version without an inner ring, allowing it to be mounted directly on the shaft.

Spherical roller:

The spherical roller bearing is the most sophisticated and expensive type of bearing. It offers high load capacity, long...