A solid circular shaft and a tubular shaft, both with the same outer radius of c=co = 0.550 in , are being considered for a particular design. The tubular shaft has an inner radius of ci = 0.300 in The shafts are to be powered by a motor operating at a frequency of f = 2.70 Hz and are to handle an attached load. Assume the cross sections are uniform throughout the lengths of the shafts and that the materials have an allowable shear stress of τallow = 14.5 ksi .

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Answer:

The power for circular shaft is 7.315 hp and tubular shaft is 6.667 hp

Explanation:

Polar moment of Inertia

[tex](I_p)s = \frac{\pi(0.55)4}2[/tex]

      = 0.14374 in 4

Maximum sustainable torque on the solid circular shaft

[tex]T_{max} = T_{allow} \frac{I_p}{r}[/tex]

         =[tex](14 \times 10^3) \times (\frac{0.14374}{0.55})[/tex]

         = 3658.836 lb.in

         = [tex]\frac{3658.836}{12}[/tex] lb.ft

        = 304.9 lb.ft

Maximum sustainable torque on the tubular shaft

[tex]T_{max} = T_{allow}( \frac{Ip}{r})[/tex]

          = [tex](14 \times10^3) \times ( \frac{0.13101}{0.55})[/tex]

          = 3334.8 lb.in

          = [tex](\frac{3334.8}{12} )[/tex] lb.ft

          = 277.9 lb.ft

Maximum sustainable power in the solid circular shaft

[tex]P_{max} = 2 \pi f_T[/tex]

          = [tex]2\pi(2.1) \times 304.9[/tex]

          = 4023.061 lb. ft/s

          = [tex](\frac{4023.061}{550})[/tex] hp

          = 7.315 hp

Maximum sustainable power in the tubular shaft

[tex]P _{max,t} = 2\pi f_T[/tex]

            = [tex]2\pi(2.1) \times 277.9[/tex]

            = 3666.804 lb.ft /s

            = [tex](\frac{3666.804}{550})[/tex]hp

            = 6.667 hp