Rolling element bearings (Section 4.6) are analogous to the layout of a balanced planetary geartrain (Figure P8.32, see on page 406). The rotations of the rollers, separator, inner race, and outer race are similar to those of the planets, carrier, sun gear, and ring gear, respectively, in a planetary geartrain. The outer race of the straight roller bearing shown is held by a pillow-block mount. The inner race supports a shaft that rotates at 1800 rpm. The radii of the inner and outer races are R_i = 0.625 in. and R_o = 0.875 in. In the units of ms, how long does it take for roller 1 to orbit the shaft and return to the topmost position in the bearing? Does the roller orbit in a clockwise or counterclockwise direction?

Figure P8.32

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1800 rpm Roller 1 R. R;