Efficient linear or rotational movement usually relies on some type of bearings. In fact, most of the machines built today incorporate bearings—and without them, maintenance technicians would face the frustration of constantly replacing parts that wore out due to friction.
The basic concept behind a bearing is that things roll more easily than they slide. This could be explained by the fact that when surfaces slide, the friction between the two objects generates a force that slows them down. However, friction can be significantly reduced if the two surfaces are able to roll over each other.
Bearings minimize friction by providing smooth rollers or metal balls, as well as a smooth outer and inner metal surface that the balls can roll against. These rollers or balls “bear” the load, enabling the device to spin smoothly.
Bearings normally deal with two types of loading, thrust and radial. Depending on what type of application they are used in, bearings may experience all thrust loading, all radial loading, or both.
For instance, the bearings in an electric motor and a pulley face radial load only. This is because the load originates from the tension of the belt that connects the two pulleys. The bearing in a barstool is loaded primarily on thrust, as the load is attributed to the weight of the individual sitting on the stool. Meanwhile, the bearing in the hub of a tractor wheel supports both a thrust and radial load. The weight of the tractor provides the radial load, while the cornering forces produced when the operator makes a turn present the thrust load.
There are many types of bearings, each of which is used for varying purposes in different applications.
A roller bearing, which is a weight distribution-oriented bearing, is any spherical or cylindrical object that helps an object larger than the bearing itself move. It uses various contact points between a circular housing containing internal rolling elements. These bearing systems use the reduced rolling resistance to increase the moving object’s efficiency.
Roller bearings commonly help two or more items reduce the amount of friction between them. An example of this is a simple wheel and axle. The roller bearings allow the wheel to freely spin on the axle without being limited by friction. They also reduce the force of drag on the spinning wheel, enabling the wheel to be easily pushed by any power source, such as an engine or a person pushing a vehicle.
There are numerous types and designs of roller bearing systems that may be used in various applications.
Cylindrical roller bearings, for instance, comprise a metal collar containing a smaller, toothed wheel inside. A ball bearing lies in between each of the wheel’s teeth, while the toothed wheel holds it in place. Thus, the wheel turns as the load travels, but the load’s weight remains directly fixed over the spherical ball bearings within the cylinder, enabling the easy movement of the load.
Roller thrust bearings usually support large thrust loads and are often found in gearsets such as vehicle transmissions between gears, rotating shafts and the housing, while tapered roller bearings are a kind of bearing that can support large thrust load and large radial load. They are used in car hubs and often mounted in pairs facing opposite directions, allowing them to handle thrust in both directions.
Meanwhile, ball bearings or anti-friction bearings are used to minimize friction between axles and shafts in numerous applications. Comprised of small ceramic or metallic spheres, ball bearings are commonly used in a series, absorbing the weight placed on the moving part. Most ball bearings are developed to meet very demanding standards of roundness and any deformation may cause the unexpected failure of the moving parts.
Spherical bearings are generally used in pivoting, high-load applications where angular misalignment is required. They allow angular rotation around a central point and often support a rotating shaft that is rotating at an angle. They may be employed in steering linkage suspensions on vehicles, articulated joints on heavy equipment, hydraulic cylinder rod ends, and other similar severe-duty uses.
Linear motion bearings are specifically designed to allow motion in one direction, such as on a linear slide. With these bearings, the rolling contact is provided by hardened and ground balls. A linear ball slide is a compact form of linear bearing with a small form factor and a similarly short stroke. Stroke can be a maximum of about one-third of the slide length, but the form factor justifies the stroke.
Magnetic bearings are used in some very high-speed devices, such as advanced flywheel energy storage systems. These bearings enable the flywheel to rapidly rotate on a magnetic field produced by the bearing.
Content provided by Design World.