Mechanical Design 2 Assignment 2 To be submitted on 27th

MECHANICAL DESIGN – II

ASSIGNMENT – 2

1. A compressor running at 320 rpm is driven by a 50 kW motor running at 1440 rpm through a pair of helical gears. The gears are 20⁰ full depth involute in the normal plane and the helix angle is 30⁰. The center distance between the gears is approximately 360 mm. the pinion is to be C30 steel, heat treated and the gear is to be 0.2% carbon steel, untreated. The operation is with medium shock for 8 to 10 hours/day. Design the gear by assuming width of face as 15 times the normal  module
2. A motor shaft rotating at 1400rpm has to transmit 20kW power to a shaft with transmission ratio 3.5 to1 .The teeth are 14.5° involute with 20 teeth on pinion. Both pinion and gear are made of SAE 1040 steel. Design the gears by assuming the starting torque to be 50% higher than the running torque. The pinion is surface hardened to 400H_B. Design the pinion  and the gear shaft  if the allowable shear stress in the shaft material is limited to 55MPa.The pinion and gear are mounted on overhang shafts at a distance of 100mm from the bearings. Neglect the weight of pinion and gear. Prepare a list of gear specifications.
3. Two parallel shafts are connected by helical gears with 20° full depth and helix angle of 15°. The power of 40KW is to be transmitted at 1400rpm of pinion. Design the gear with Lewis equation and check for wear and dynamic load. Determine the BHN required gear ratio of 4.5:1. Prepare a list of gear specifications.

4.               a)  A compressor, running at 250 rpm, is driven by a 15 kW, 870 rpm motor through a pair of 14 ½ ⁰ full depth gears. Estimate the module, the beam width, and number of teeth on each gear using Lewis beam equation. Use C45 steel untreated for pinion, and C40 steel untreated gear.

b) Design the gearing of Q4a. If 20⁰ full depth teeth are used. Compare the results. State the advantages if any 

5.      A pair of straight tooth bevel gears at right angles is to transmit 5 kW at 1200 rpm of the pinion. The diameter of the pinion is 80 mm and the velocity ratio is 3.5 to 1. The tooth form is 14 ½ ⁰ composite type. Both the pinion and gear are of cast iron (s_d = 55MN/m²). Design the gear and check for dynamic and wear loads.

6.       Design a worm gearing to transmit 5 kW power at 1200 rpm. The speed ratio is 30. (design should involve calculation of efficiency and thermal capacity) also find whether the system is self locking  or not.

7.      For an industrial application, a pair of spur gears is to be designed with equal strength. Speed reduction required is 5:1. Pinion transmits 30kw of power at 1600rpm 20⁰ stub involute teeth cutter is to be used for cutting gear teeth. Gears would be operating 8 hrs per day against steady loads. Design and specify the gears completely. To what hardness numbers, the gears are to be heat treated?

8.      What are the basic advantages and disadvantages of helical gears over spur gearing

9.      Give two reasons for the selection of worm gearing and also two main disadvantages

10.  What is the reason of using lubrication factor in designing of helical gears

 

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