Machine Design 1 - Dec 2013

Mechanical Engineering (Semester 6)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) State the various types of keys used with shaft for torque transmission and describe their special features.(5 marks) 1 (b) Explain Soderberg and Goodman design criterion.(5 marks) 1 (c) State the various consideration in design of castings.(5 marks) 1 (d) Explain aesthetic consideration in design with suitable examples.(5 marks) 1 (e) What is factor of safety? Discuss various factors to be considered while selecting the factor of safety.(5 marks) 2 (a) Design socket and spigot cotter joint for load of 80kN, which varies from tension to compression. Select suitable material, Factor of safety. Draw neat dimensional sketch.(14 marks) 2 (b) What is the Surge in spring? How will you avoid it in spring?(6 marks) 3 (a) Design a turnbuckle to connect two tie rods. The pull in the tie rod is 60kN. Select suitable materials and design the turnbuckle.(10 marks) 3 (b) A welded connection, as shown in figure is subjected to an eccentric force of 10kN, in the plane of the welds. Determine the size of the welds, if the permissible shear stress for the weld is 100N/mm². Assume static conditions. (10 marks) 4 A screw press is to be designed to exert an axial force 45kN.i) Select suitable material and design the screw and nut. Assume the height of the screw press to be 200mm.ii) Select giving reasons suitable material for the frame. Assume giving reasons a suitable section for the frame. Design the horizontal section at the frame if the centre line of the screw is at a distance of 250mm from the inner edge of the frame.(20 marks) 5 (a) A chain drive is required to transmit 5kW power from a shaft running at 500rpm with reduction ratio of 2.6. The drive operates for 10-12 hours/day with heavy shocks and is provided with drop lubrication. Select standard chain and determine the sprocket diameters.(10 marks) 5 (b) A steel plate subjected to a force of 8kN and fixed to a channel by means of three identical bolts as shown in fig.2. The bolts are made from plain carbon steels 35C8 and factor of safety is 3, specify the size of the bolts.(10 marks) 6 A shaft is housed in two bearings 2.6m apart. It carries a pulley of diameter 300mm at 200mm to the right of left hand bearing. It also carries another pulley of 500mm diameter at a distance of 1.2m to the left of right hand bearing. The 300mm diameter pulley receives 25kW power from a motor kept below it with the help of flat belt drive. The 500mm pulley delivers power with the help of horizontal flat belt drive. The coefficient of friction and angle of contact for both the pulleys are 0.28° and 170°. Design the solid shaft. Assume the weights of both pulleys are 1.5kN each and shaft is made of C-45. The assembly rotates with 400rpm in clockwise direction when viewed from left to right.(20 marks) 7 (a) The leaf spring has 12 nos. of leaves, two of which are full length. Spring supports are 1.1m apart and central band is 90mm wide. The central load is 6kN with permissible stress of 280MPa. The ratio of total depth to the total width is 3
i) Thickness and width of leaves
ii) Recommend camber of the spring(8 marks) 7 (b) A v-belt drive is required to transmit 40kW power from an electric motor rotating at 960rpm to a machine with reduction ratio at 4.2. The drive operates for 12-14hours/day and expected life of 'v' belts is two years. Select standard section and determine.
i) Size of input and output pulleys
ii) Size and number of 'v' belts required(12 marks)