Problem 1 (8 points) (CLO: 1 100%) The motor mounted on the bracket is acted on by its 160N weight and its shaft resists a repeated thrust load of 120 N and a repeated couple of 25 N-m that are applied to it. If the motor is fixed to the bracket by four bolts and the stress concentration factors for shear stress is 2.5 and for normal and bending stresses are 2.1, determine the diameter of the bolts for a static and fatigue factor of safeties that are more than 4. Note that: ⚫ The vertical distance between the bolts and the 25Nm mm 120 N 100 mm shaft's axis is 100mm and the endurance limit is 129MPa. 200 mm 160 N • Choose the diameter of the bolts from Metric Mechanical-Property class. Problem 2 (7 points) (CLO: 3 100%) -75 mm It is desired to design a gear box as shown in the figure. Following information must be followed: • Gears type: Spur Smallest possible size gears To avoid interference, number of teeth on Input ✓ ✓ ✓ ✓ Output the smallest gear should not be less than 14 • Maintain exact speed ratio • Input and output shafts are collinear Input speed 3000 rpm Output speed 150 rpm • Module 2.5 mm Pressure angle = 20° Power = 7.5 kW Analyze the gear box and: a) Calculate the number of teeth of all gears. 30 90 30 Dimensions are in mm b) Determine the shafts center distance c, and c₂ (in mm) c) Draw FBD showing all forces on gear 3 and 4 with the countershaft at A and B. d) Calculate forces exerted by gear 2 on gear 3 and gear 5 on gear 4. e) Calculate the countershaft forces at A and B. f) What is the output torque of the shaft attached to gear 57 Neglect frictional losses.