Compare the foregoing figure with the illustration given in Fig. 98, where the contact points A, B, C, represent the three bearing circles, which differ in their circumference, and it is obvious that a ball in traveling around must slip somewhere on one or more of the paths A, B, C.
Fig. 99. Improper Alinement.
Wrong Construction.—Another sample of wrong construction is shown in Fig. 99. In this diagram the three bearing points A, B, C, also represent circles of different diameters, which are sure to wear grooves in the three paths made by the balls.
Fig. 100. Correct Raceways.
The most ideal form of bearing is shown in Fig. 100, which represents the four-point contact, and this also provides against longitudinal thrust of the shaft or axle.
Roller Bearings.—This type of bearing is ideal because of the large surface which is available. The difficulty is to keep the rollers parallel, with the shaft. Furthermore, they should not roll in contact with each other. To obviate this the rollers are put into a cage.
Fig. 101. Cage for Roller Bearing.