The second shaft on a parallel-shaft 25-hp foundry crane speed reducer contains a helical gear with a pitch diameter of 8.08 in. Helical gears transmit components of force in the tangential, radial, and axial directions (see Chap. 13). The components of the gear force transmitted to the second shaft are shown in Fig. 11–12, at point A. The bearing reactions at C and D, assuming simple-supports, are also shown. A ball bearing is to be selected for location C to accept the thrust, and a cylindrical roller
Figure 11–12
Forces in pounds applied to the second shaft of the helical gear speed reducer of Ex. 11–7.
Â
bearing is to be utilized at location D. The life goal of the speed reducer is 10 kh, with a reliability factor for the ensemble of all four bearings (both shafts) to equal or exceed 0.96 for the Weibull parameters. The application factor is to be 1.2.
(a) Select the roller bearing for location D.
(b) Select the ball bearing (angular contact) for location C, assuming the inner ring rotates.
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