![]() ![]() ![]() Under this condition the maximum bearing load is given by: The maximum bearing load on either pulley shaft occurs when the belt is transmitting the maximum horsepower (i.e., the belt would slip if the horsepower were increased above this level). In this section we list some of the most frequently occurring mechanical configurations and the bearing loads imposed by them. The first step in sizing a suitable ball bearing for a given application is the determination of the loads which support. DeHart and is reproduced in Table 1.įor more details, which are beyond the scope of this presentation, the reader is referred to technical literature. A useful bearing-selection chart, which summarizes the principal considerations involved, has been given by A.O. DeHart, ASME Paper 59-MD-12, 1959, with the permission of the American Society of Mechanical Engineers, 345 East 17th Street, New York, NY, 10017īearing selection represents a compromise among many factors including the nature of the application, performance requirements and cost. * Reprinted from "Which Bearing and Why?" by A.O. Very large sizes of this bearing are used in gun turrets and large earth moving machinery" The thrust ball bearing, Figure 2(f), is adaptable to large thrust loads that have almost no radial component. On the other hand, load-carrying capacity is reduced due to the high contact stresses that result from the large difference in curvature between the balls and the In contrast th the previously discussed bearings, in which alignment is a very critical item, the self-aligning ball bearing, Figure 2(e) by virtue of the spherically ground outer race can tolerate considerable misalignment of shaft and housing. The preload is built into the bearing at the factory. The double-row, angular-contact bearing, Figure 2(d), is a simpler arrangement from the standpoint of the user. Preload is controlled by the length of the spacers, which determine axial location of the races, or by mounting the bearings against one another in a "back-to-back" or "face-to-face" fashion. Most high-speed and precision spindles use axially preloaded pairs of these bearings. ![]() When large thrust loads in one direction are coupled with radial loads, angular contact ball bearings,įigure 2(c), are usually superior. Radial load capacity is higher in this bearing than in the standard deep-groove construction, but high-speed performance and thrust-load capacity is impaired. More balls can be introduced into the bearing if a notch is machined into one of the races, Figure 2(b). Since balls are assembled into the bearing by eccentric displacement of the races the number of balls in this type of bearing is limited. At low speeds, no bearing separator is required at intermediate speeds, a ball control separator of steel-ribbon construction is adequate while the ultimate high-speed performance is obtained with a race controlled (or piloted), fully machined separator. When it has the proper separator, it is very good for high-speed operation. Radial loads and thrust-load capacities may be approximately equal in this bearing. The deep-groove ball bearing, Figure 2(a), is the most versatile. ![]() There are several types of ball bearings that fit specific needs. The rolling elements may take many forms - cylinders, balls, tapered rollers, barrels, or very slim rollers known as needles - and the whole bearing name is generally taken from this form. Where rotative speeds are low, the separator often is omitted. Alternatively, the separator may be piloted by the rolling elements or by the outer race ID. In this bearing, the separator serves to keep the balls from rubbing against one another as is piloted on the inner race OD. "A typical deep-groove ball bearing designed for high-speed operation is shown in Figure 1. DeHart ("Which Bearings and Why", ASME Paper 59-MD-12, 1959), from which source the following material (including Figures 1 & 2) is hereby reprinted* In the following we shall review their basic characteristics.Ĭommercially available ball bearings, which are usually made from hardened steel, involve many forms of construction. While the concept of the ball bearing dates back at least Leonardo da Vinci, their design and manufacture has become remarkably sophisticated. Ball bearings are used widely in instruments and machines in order to minimize friction and power loss. ![]()
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