14_ch 10 Mechanical Design budynas_SM_ch10

14_ch 10 Mechanical Design budynas_SM_ch10 - to 80 springs...

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274 Solutions Manual • Instructor’s Solution Manual to Accompany Mechanical Engineering Design For a clearance of 0.05 in: ID = (7 / 16) + 0 . 05 = 0 . 4875 in; OD = 0 . 4875 + 0 . 16 = 0 . 6475 in D = 0 . 4875 + 0 . 080 = 0 . 5675 in C = 0 . 5675 / 0 . 08 = 7 . 094 G = 11 . 5 Mpsi N a = d 4 G 8 kD 3 = (0 . 08) 4 (11 . 5)(10 6 ) 8(26 . 67)(0 . 5675) 3 = 12 . 0 turns N t = 12 + 2 = 14 turns, L s = dN t = 0 . 08(14) = 1 . 12 in O . K . L 0 = 1 . 875 in, y s = 1 . 875 1 . 12 = 0 . 755 in F s = ky s = 26 . 67(0 . 755) = 20 . 14 lbf K B = 4(7 . 094) + 2 4(7 . 094) 3 = 1 . 197 τ s = K B ± 8 F s D π d 3 ² = 1 . 197 ³ 8(20 . 14)(0 . 5675) π (0 . 08) 3 ´ = 68 046 psi Table 10-4: A = 140 kpsi · in m , m = 0 . 190 S sy = 0 . 45 140 (0 . 080) 0 . 190 = 101 . 8 kpsi n = 101 . 8 68 . 05 = 1 . 50 > 1 . 2 O . K . τ 1 = F 1 F s τ s = 10 20 . 14 (68 . 05) = 33 . 79 kpsi, n 1 = 101 . 8 33 . 79 = 3 . 01 > 1 . 5 O . K . There is much latitude for reducing the amount of material. Iterate on y 1 using a spread sheet. The final results are: y 1 = 0.32 in, k = 31.25 lbf/in, N a = 10.3 turns, N t = 12.3 turns, L s = 0 . 985 in, L 0 = 1 . 820 in, y s = 0 . 835 in, F s = 26 . 1 lbf, K B = 1 . 197, τ s = 88 190 kpsi, n s = 1 . 15, and n 1 = 3 . 01 . ID = 0 . 4875 in, OD = 0 . 6475 in, d = 0 . 080 in Try other sizes and/or materials. 10-21 A stock spring catalog may have over two hundred pages of compression springs with up
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Unformatted text preview: to 80 springs per page listed. Students should be aware that such catalogs exist. Many springs are selected from catalogs rather than designed. The wire size you want may not be listed. Catalogs may also be available on disk or the web through search routines. For exam-ple, disks are available from Century Spring at 1 (800) 237 5225 www.centuryspring.com It is better to familiarize yourself with vendor resources rather than invent them yourself. Sample catalog pages can be given to students for study....
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