Slide 8 of 61

Notes:

BEARING SELECTION - To select the right bearing for an application one must first determine the requirements such as loads, both radial (perpendicular to the axis) and lateral or thrust (parallel to the axis), speed, and environmental conditions. The physical limitations on where the bearing can fit must next be accessed. Finally, the cost must be considered in light of the requirements and carefully weighed against the desired life and reliability.

Each general bearing type has its own advantages and disadvantages.

Friction Bearing - Inexpensive, good for high speeds and high loads under hydrodynamic lubrication. Rapid wear at low speeds.

Ball Bearing - Inexpensive, low load capacity due to point contact.

Cylindrical (Roller)Bearing - Moderate to low cost, high radial load capacity due to line contact, low lateral (thrust) capacity.

Needle Bearing - High cost, small size, high radial load capacity.

Tapered Roller Bearing - Moderate cost, high radial load capacity, moderate lateral (thrust) capacity. Balanced design for railroad application.

Spherical Bearing - Very high cost, good radial load capacity, moderate lateral (thrust) capacity. Can handle high misalignment.

The high radial load capacity and moderate lateral load capacity combined with the moderate cost to make the tapered roller bearing the bearing of choice for the railroad journal application. Cylindrical bearings are popular in some non-US areas. The use of spherical bearings is declining due to its high cost.