9_ch 17 Mechanical Design budynas_SM_ch17

9_ch 17 Mechanical Design budynas_SM_ch17 - may differ, and...

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428 Solutions Manual • Instructor’s Solution Manual to Accompany Mechanical Engineering Design Now add and subtract F c ± exp( f θ ) exp( f θ ) 1 ² F 1 = F c + F c ± exp( f θ ) exp( f θ ) 1 ² + ± F ± exp( f θ ) exp( f θ ) 1 ² F c ± exp( f θ ) exp( f θ ) 1 ² F 1 = ( F c + ± F ) ± exp( f θ ) exp( f θ ) 1 ² + F c F c ± exp( f θ ) exp( f θ ) 1 ² F 1 = ( F c + ± F ) ± exp( f θ ) exp( f θ ) 1 ² F c exp( f θ ) 1 F 1 = ( F c + ± F )exp( f θ ) F c exp( f θ ) 1 Q . E . D . From Ex. 17-2: θ d = 3 . 037 rad, ± F = 664 lbf, exp( f θ ) = exp[0 . 80(3 . 037)] = 11 . 35, and F c = 73 . 4 lbf. F 1 = (73 . 4 + 664)(11 . 35 73 . 4) (11 . 35 1) = 802 lbf F 2 = F 1 ± F = 802 664 = 138 lbf F i = 802 + 138 2 73 . 4 = 396 . 6 lbf f ± = 1 θ d ln ³ F 1 F c F 2 F c ´ = 1 3 . 037 ln ³ 802 73 . 4 138 73 . 4 ´ = 0 . 80 Ans . 17-9 This is a good class project. Form four groups, each with a belt to design. Once each group agrees internally, all four should report their designs including the forces and torques on the line shaft. If you give them the pulley locations, they could design the line shaft. 17-10 If you have the students implement a computer program, the design problem selections
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Unformatted text preview: may differ, and the students will be able to explore them. For K s = 1 . 25, n d = 1 . 1, d = 14 in and D = 28 in, a polyamideA-5 belt, 8 inches wide, will do( b min = 6 . 58 in) 17-11 An efciency of less than unity lowers the output for a given input. Since the object of the drive is the output, the efciency must be incorporated such that the belts capacity is increased. The design power would thus be expressed as H d = H nom K s n d eff Ans . 17-12 Some perspective on the size of F c can be obtained from F c = w g V 60 2 = 12 bt g V 60 2...
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