Ball Bearings, as shown to the left, are probably the most common type of bearing. They are found in everything from inline skates to hard drives. These bearings can handle both radial and thrust loads, and are usually found in applications where the load is relatively small. In a ball bearing, the load is transmitted from the outer race to the ball, and from the ball to the inner race.
Since the ball is a sphere, it only contacts the inner and outer race at a very small point, which helps it spin very smoothly.
But it also means that there is not very much contact area holding that load, so if the bearing is overloaded, the balls can deform or squish, ruining the bearing. Roller Bearings, like the one illustrated at right, are used in applications like conveyer belt rollers, where they must hold heavy radial loads. In these bearings, the roller is a cylinder, so the contact between the inner and outer race is not a point but a line.
This spreads the load out over a larger area, allowing the bearing to handle much greater loads than a ball bearing. However, this type of bearing is not designed to handle much thrust loading. Figure 4 shows two bearings, called "thrust bearings", which support a force applied in the same direction as the shaft.
Races are used for these thrust bearings. The race on the side, into which the shaft, is inserted is called the shaft race. The race inserted, into the housing, is called the housing race. The surfaces of bearing rings races on which the rolling elements roll are made to be extremely smooth, to allow for smooth bearing rotation.
There are a variety of different rolling elements designed to suit the specific conditions of the bearings, such as the strength of the supporting force or the speed of the rotation. We will explain in Part 4 about the types of bearings, but if you are interested, please check out the link below. As shown in Figure 5, when the bearing's inner ring rotates this causes the rolling elements to roll.
When this happens, unless the bearing has a cage, the rolling elements next to each other will make contact. When their surfaces come in contact, the rolling elements' rolling direction will be inverted relative to each other, and the rolling motion of the rolling elements will be disrupted.
In order to prevent this, a cage is put in place to keep the rolling elements separated from each other. This allows them to roll smoothly. There are a variety of different types of cage designed to suit the specific conditions of the bearing, such as the strength of the supporting force or the speed of the rotation.
In this way, bearing rings races , rolling elements and cages all play a role in allowing bearings to function, and it is by combining these functions that bearings can rotate smoothly. The bearing would be unable to continually rotate stably and smoothly, however, with just these various components. We need now to introduce one more very important component of bearings.
Have you ever had a plate covered with oil slip out of your hand when you held it? You probably all understand that when there is oil between two surfaces the amount of friction is decreased.
Bearings aim for stable and smooth rotation, and to do that the friction with rolling motion needs to be reduced and the abrasion of the various components needs to be prevented. Other material types include stainless steel bearings for improved corrosion resistance and hybrid ball bearings for which ceramic balls are the moving parts of the bearing between the inner and outer races to reach high rotational speeds.
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It uses cylinders that are very small diameter rollers. This allows the bearing to fit into tight places. Ball thrust bearings are mostly used for low speed applications and cannot handle much radial load.
Swivel chairs and small hand tools use this type of bearing. Roller thrust bearings can support large thrust loads. They are often found in gearsets of car transmissions between gears and between the housing and the rotating shafts. The helical gears used in most transmissions have angled teeth. This causes a thrust load, which must be supported by a bearing. Tapered roller bearings can support large radial and thrust loads.
They are used in car hubs where they are usually mounted in pairs facing opposite directions, so they can handle thrust in both directions. Some very high-speed devices, such as advanced flywheel energy storage systems, use magnetic bearings.
These bearings allow the flywheel to float on a magnetic field created by the bearing. Some flywheels run at speeds near 50, rpm. Ball or roller bearings would melt or explode at these speeds. Magnetic bearings have no moving parts. They can handle these incredible speeds. By Marshall Brain December 1,
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