A gearbox is needed to provide an exact 36:1 decrease in speed, while minimizing the overall...

 

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A gearbox is needed to provide an exact 36:1 decrease in speed, while minimizing the overall gearbox size. The input and output shafts should be in-line. Specify appropriate teeth numbers. Input shaft transmits the power of 20 hp and rotates at 2000 rpm for air moving at 500 ft/min at 70 F with a = 1. The lubricant is SAE grade 20 oil. All gears are spur gears with 20° pressure angle. Gears have diametral pitch as 5 teeth/in. 1. Calculate the number of teeth for each gear without interference and then diameter of each gear. (25 points) 2. Calculate the diameter of shaft b with respect to a. stress consideration. Shaft is steel having 36.5 ksi yield strength. For shaft design factor of safety is 3. (15) b. Deflection consideration; slope under gear 3 on shaft b must be 0.005 radian. E=30x106 psi. (15 points) c. Critical speed consideration; find factor of safety. (5 points) 3. Design journal bearings for shaft "b" . (40 points) 2 Lateral surface area of sump for bearing is 80 in. The bearing has a journal diameter tolerances of + 0.000/-0.002 in, a bushing bore tolerances of +0.004/-0.000 in. 6 in 5 10 in 24 in 3 input shaft a shaft b 3 in A gearbox is needed to provide an exact 36:1 decrease in speed, while minimizing the overall gearbox size. The input and output shafts should be in-line. Specify appropriate teeth numbers. Input shaft transmits the power of 20 hp and rotates at 2000 rpm for air moving at 500 ft/min at 70 F with a = 1. The lubricant is SAE grade 20 oil. All gears are spur gears with 20° pressure angle. Gears have diametral pitch as 5 teeth/in. 1. Calculate the number of teeth for each gear without interference and then diameter of each gear. (25 points) 2. Calculate the diameter of shaft b with respect to a. stress consideration. Shaft is steel having 36.5 ksi yield strength. For shaft design factor of safety is 3. (15) b. Deflection consideration; slope under gear 3 on shaft b must be 0.005 radian. E=30x106 psi. (15 points) c. Critical speed consideration; find factor of safety. (5 points) 3. Design journal bearings for shaft "b" . (40 points) 2 Lateral surface area of sump for bearing is 80 in. The bearing has a journal diameter tolerances of + 0.000/-0.002 in, a bushing bore tolerances of +0.004/-0.000 in. 6 in 5 10 in 24 in 3 input shaft a shaft b 3 in