Bearings are machine elements, implemented within an assembly to limit motion to a specific movement and to mitigate friction between moving components. When equipment and systems rotate while under operation, radial and axial loads are produced which may begin to cause damage if left unchecked. To prevent inevitable failure of the assembly, bearing surfaces are provided by bearings to compensate for the friction. Antifriction bearings, also known as rolling bearings, are components that carry an assembly load on rolling elements placed between races.
Antifriction bearings are indispensable to equipment and systems, protecting parts from friction and wear with their bearing surfaces. As compared to other bearings, the antifriction bearing produces much less friction while utilizing less lubricant, allowing for more optimal operation. Antifriction bearings serve to benefit various applications due to their balance in size, weight, load carrying capacity, cost, friction, durability, and more. Nevertheless, such bearings are held back by their service life, and are typically more expensive than standard bearings. Typically, antifriction bearings are implemented within aerospace, marine, automotive, and industrial assemblies.
While bearings may come in a variety of materials depending on the application, the most commonly used materials include metals such as tin, antimony, copper, and lead. These metals may be combined to make an alloy known as a Babbitt alloy, first patented by American Inventor Isaac Babbett in 1839. Bearings may also be constructed from wood in a few applications, mostly concerning light-duty machinery. Rubber bearings are also used and benefit applications that contain abrasives in their lubricant.
When antifriction and roller bearings are used within aircraft applications, they mostly come in the form of straight roller and tapered roller bearings and are placed within pumps, engines, gearboxes, APU’s, and other locations. Straight roller bearings feature high-radial load capacity, low friction, and high speed capabilities. Such bearings are cylindrical in shape, also having their contact placed between the bearing and race. As loads are more evenly distributed across a large area, the bearing can accommodate for a greater load. As aircraft bearings, the straight roller bearing may be used within high power reciprocating engines for the crankshaft. Straight roller bearings are also present within gas turbine engines, supporting high radial loads.
Tapered roller bearings are specifically engineered to withstand radial and thrust loads, featuring shaped rings and rollers in the form of truncated cones to support loads. Depending on the angle of the axes between the roller and the bearings, the ratio of permissible loads may be changed. With a greater angle, a higher axial load may be accommodated for. While most tapered roller bearings are in between 10 to 16 degrees in angle, higher thrust load capacity bearings may feature a 30 degree contact angle. As aircraft bearings, tapered roller bearings may be found within almost all aircraft wheel assemblies due to their unmatched ability to take off radial and axial loads. They may also be found in aircraft gearboxes, providing for radial and axial loads.