14_ch 17 Mechanical Design budynas_SM_ch17

14_ch 17 Mechanical Design budynas_SM_ch17 - could be...

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Chapter 17 433 The details will not be presented here, but the table is provided as a means of learning. Five groups of students could each be assigned a belt thickness. You can form a table from their results or use the table below t ,in 0.002 0.003 0.005 0.008 0.010 b 4.000 3.500 4.000 1.500 1.500 CD 20.300 20.300 20.300 18.700 20.200 a 109.700 131.900 110.900 194.900 221.800 d 3.000 3.000 3.000 5.000 6.000 D 9.000 9.000 9.000 15.000 18.000 F i 310.600 333.300 315.200 215.300 268.500 F 1 439.000 461.700 443.600 292.300 332.700 F 2 182.200 209.000 186.800 138.200 204.300 n fs 1.100 1.100 1.100 1.100 1.100 L 60.000 60.000 60.000 70.000 80.000 f ± 0.309 0.285 0.304 0.288 0.192 F i 301.200 301.200 301.200 195.700 166.600 F 1 429.600 429.600 429.600 272.700 230.800 F 2 172.800 172.800 172.800 118.700 102.400 f 0.320 0.320 0.320 0.320 0.320 The first three thicknesses result in the same adjusted F i , F 1 and F 2 (why?). We have no figure of merit, but the costs of the belt and the pulleys is about the same for these three thicknesses. Since the same power is transmitted and the belts are widening, belt forces are lessening. 17-17 This is a design task. The decision variables would be belt length and belt section, which
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Unformatted text preview: could be combined into one, such as B90. The number of belts is not an issue. We have no gure of merit, which is not practical in a text for this application. I sug-gest you gather sheave dimensions and costs and V-belt costs from a principal vendor and construct a gure of merit based on the costs. Here is one trial. Preliminaries : For a single V-belt drive with H nom = 3 hp, n = 3100 rev/min, D = 12 in, and d = 6 . 2 in, choose a B90 belt, K s = 1 . 3 and n d = 1. L p = 90 + 1 . 8 = 91 . 8 in Eq. (17-16 b ): C = . 25 91 . 8 2 (12 + 6 . 2) + 91 . 8 2 (12 + 6 . 2) 2 2(12 6 . 2) 2 = 31 . 47 in d = 2 sin 1 12 6 . 2 2(31 . 47) = 2 . 9570 rad exp( f d ) = exp[0 . 5123(2 . 9570)] = 4 . 5489 V = dn 12 = (6 . 2)(3100) 12 = 5031 . 8 ft/min...
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This note was uploaded on 12/13/2011 for the course EML 3013 taught by Professor Shingley during the Fall '11 term at UNF.

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