Figure Q3 shows a gear train of straighttooth spur gears from input Gear 2 to output Gear 8. Gear 2 is run by a 1 hp and rotates at 1800 rpm. Gear 8 rotates at 900 rpm. The gears have diametral pitch P = 8 and a full-depth pressure angle 20. Face width b is 1 in. All the gears are made of steel heat-treated to 350 Bhn. Teeth are cut with a top quality hobbing operation. The design life corresponds to 5 years of 60hours/week and 28 weeks/year operation. Sharing load is assumed for all gears. 3 4. b 5 15T 18T 25T 33T 44T 18T Figure Q3 Multi-gear set 8 48T For Gear 7 and Gear 8, answer the following questions: (i) Which gear is more critical? Why? 5Marks PO1 (ii) Using reliability of 99% and a safety factor of 2.0, estimate the maximum horsepower that can be transmitted, based on bending analysis. 12Marks PO1 (iii) Using reliability of 99% and a safety factor of 2.0, estimate the maximum horsepower that can be transmitted, based on surface 13Marks PO1 fatigue analysis. (iv) To what value could the gear hardness be reduced, without making 5Marks PO2 the Gear 8 weaker than Gear 7 teeth based on surface fatigue?