The Importance of Bearing Engineering
A bearing is simply a part used to reduce friction between the rotation of an axle or shaft within a housing. Most commonly ball bearings are used because they are less expensive to manufacture. Bearings are found in most mechanical parts where there is rotation involved. This can be anything from medical equipment to tractor parts to advanced aerospace machinery. During World War II, German factories that produced ball bearings were often considered highly sought-after bombing targets by allied forces. That was how important of a role ball bearings played in the German war effort.
Understanding Radial and Axial Loads
It's important to understand radial and axial loads when examining bearings. The design and selection of bearings depends on the conditions of these loads.
A radial load is one that is perpendicular to the axle. Think of the weight of a cart. More often than not, the most force is produced perpendicularly to the axle and passes through the diameter of the bearing.
An axial load is one where the majority of the force is along the axle. Most commonly, that means the center of the axle is aligned with the force of gravity. Another example would be that of an electric drill. The most force generally passes through the length of the drill bit, and the bearings must be able to handle a mostly axial load.
Situations where both radial and axial loads are present often require custom bearing engineering. Oil drilling is a good example. Sometimes, it's necessary to drill against the surface of the earth at angles where the force is not parallel to the force of gravity. In that case, specifically engineered bearings are often needed for the unique angle and forces involved.
Types of Bearings for Different Load Conditions
There are three basic designs of bearings based on the three loads they bear. The three aforementioned loads were radial, axial, and a combination of both. For uses that handle mostly radial loads, the bearings design is called deep-groove ball bearings. In situations where there will be mostly axial loads, axial or thrust ball bearings should be used. When both axial and radial loads are present, then specially designed bearings must be used called angular contact ball bearings.
It's important to note that load factors both axially and radially are always present. The degree to which each type of load is present influences more detailed facets of the bearing design. Aspects such as lifespan, failure modes, lubrication, fit, torsion, and others are then determined based on the basic expected forces that will be present under operating conditions.
To summarize, there are three basic types of loads; axial, radial, and a combination of both. They work either perpendicular or along the axle. Therefore, three different designs of bearings are made based on the load conditions present. Although both types of loads are always present in some degree, one is typically minimal while the other is significant. The degree to which one force or the other is present determines many of the other factors involved.