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G S. A belt-driven jack-shaft is shown schematically in the figure. The weight of each pulley is 900 N as shown in the figure. The shaft is made of AISI 4620 cold-drawn (CD) steel (a hardened steel) (yield strength is 120 MPa) and is driven by a motor at 1200 rpm The pulleys are held in place by sledrunner keys. Assume the bearings at A and C only support normal loads, no moments. All important surfaces have a ground finish (a) Shaft design, if the shaft is to be designed for a safety factor of 1.5, what is the required diameter at location B. (25 points) (b) Key design. If the allowable yield strength of key is 80 MPa, calculate the key dimensions (15 points) (c) Belt design at pint B. Input pulley diameter is 760 mm, input speed is 1200 rpm and output speed is 600 rpm. Use the center distance of 600 mm, and a 0.5 mm thick by 50 mm wide belt with a density of 1.1 g/cm3. Assume the coefficient of friction is 0.3. Determine: i. the torque at small pulley, ii. the belt length, iii. the belt tensions, and iv. maximum belt stress. (20 points) Horizontal 7200 N r = 380 mm Wp = 900 N 450 mm 4 2700 N r = 380 mm W3 = 900 N B. 450 mm Vertical 2250N С 6750 N D 225 mm