12_ch 07 Mechanical Design budynas_SM_ch07

# 12_ch 07 Mechanical Design budynas_SM_ch07 - Eq(6-19 k a =...

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Chapter 7 189 (g) To use a non-crowned gear, the gear slope is recommended to be less than 0.0005 rad. Since all other deﬂections are acceptable, we will target an increase in diameter only for the long section between the left bearing and the gear. Increasing this diameter from the proposed 1.56 in to 1.75 in, produces a gear slope of –0.000401 rad. All other deﬂections are improved as well. 7-8 (a) Use the distortion-energy elliptic failure locus. The torque and moment loadings on the shaft are shown in the solution to Prob. 7-7. Candidate critical locations for strength: • Pinion seat keyway • Right bearing shoulder • Coupling keyway Table A-20 for 1030 HR: S ut = 68 kpsi, S y = 37 . 5 kpsi, H B = 137 Eq. (6-8): S ± e = 0 . 5(68) = 34 . 0 kpsi
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Unformatted text preview: Eq. (6-19): k a = 2 . 70(68) − . 265 = . 883 k c = k d = k e = 1 Pinion seat keyway See Table 7-1 for keyway stress concentration factors K t = 2 . 2 K ts = 3 . ± Proﬁle keyway For an end-mill proﬁle keyway cutter of 0.010 in radius, From Fig. 6-20: q = . 50 From Fig. 6-21: q s = . 65 Eq. (6-32): K f s = 1 + q s ( K ts − 1) = 1 + . 65(3 . − 1) = 2 . 3 K f = 1 + . 50(2 . 2 − 1) = 1 . 6 Eq. (6-20): k b = ² 1 . 875 . 30 ³ − . 107 = . 822 Eq. (6-18): S e = . 883(0 . 822)(34 . 0) = 24 . 7 kpsi Eq. (7-11): 1 n = 16 π (1 . 875 3 ) ´ 4 µ 1 . 6(2178) 24 700 ¶ 2 + 3 µ 2 . 3(2500) 37 500 ¶ 2 · 1 / 2 = . 353, from which n = 2.83...
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