The gear-reduction unit shown has a gear that is press fit onto a cylindrical sleeve that rotates around a stationary shaft. The helical gear transmits an axial thrust load T of 250lbf as shown in the figure. Tangential and radial loads (not shown) are also transmitted through the gear, producing radial ground reaction forces at the bearings of 875lbf for bearing A and 625lbf for bearing B. The desired life for each bearing is 90kh at a speed of 150 rev/min with a 90 percent reliability. The first iteration of the shaft design indicates approximate diameters of 1 1/8 in at A and 1 in at B.

Select suitable tapered roller bearings from Fig.11€“15.

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