Machine Design - 2 - May 2014
Mechanical Engineering (Semester 7)
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) Explain the force analysis in case of the bevel gears.(5 marks) 1 (b) Explain static and dynamic seals.(5 marks) 1 (c) Explain the concepts of the bends in case of the wire ropes. What is its significance?(5 marks) 1 (d) Define static load carrying capacity, dynamic load carrying capacity, equivalent load and cubic mean load related to rolling contact bearings.(5 marks) 2 A two stage gear box is used to transmit 10 KW power from an electric motor running at 1440 RPM to a machine with overall reduction ratio of 18. For the first stage helical gear pair,
i) Determine the module using bending failure.
ii) Check the gears for dynamic load by using both Barth velocity
factor method and Buckingham's method.
iii) Check the gears for wear strength.(20 marks) 3 (a) he SKF bearing No. 6312 is subjected to the following load cycle;
|Phase||Radial load (KN)||Axial load (XN)||Speed (RPM)||Time (Sec.)|
Determine the expected life of the bearing in hours with probability of survival 92 %. The loads are with light shock, outer race rotates and operating temperature is 140°C.(14 marks) 3 (b) What are the desirable properties of a good bearing material used in sliding contact bearings(6 marks) 4 A rotary cam: with central translatory roller follower has following motions; Forward stroke of 20 mm in 100° of cam rotation with parabolic motion, dwell for 40° return Stroke in 120° with SHM and remaining dwell to complete the cycle.
Mass of the follower is 1 kg, cam shaft speed is 600 RPM, external force during forward smoke is 500 N and during return stroke is 100 N.
ii) Follower with pin and spring
iii) Cam Shaft (20 marks) 5 (a) A worm and worm wheel drive is used to transmit 11 KW power from an electric motor running at 1440 RPM to a machine running 12-14 hours per day with reduction ratio of 15.
i) Determine the module based on wear failure.
ii) Check for dynamic load.(12 marks) 5 (b) A hydro dynamically lubricated full journal bearing is used to support a radial load of 15 KN. The speed of the journal is 1500 RPM. Use L/D ratio as 1 and bearing pressure 1.5 N / mm2 . Find the length and diameter of the bearing. Assume suitable fit and at average clearance find, minimum oil film thickness. coefficient of friction and oil flow rate.(8 marks) 6 A centrifugal pump is required to pump the water for the following Specification;
Static suction head : 4 m
Length of suction pipe : 6 m
Static delivery head : 4 m
Length of delivery pipe : 6 m
Discharge : 1000 LPM
i) Pipe diameters
ii) Impeller and impeller shaft
select the suitable motor
Draw the layout(20 marks) 7 The following specifications refers to an EOT crane:
Load to be lifted : 80 KN
Hoisting speed : 6 m/min
Application : Class-II i) Select suitable wire rope and find its life.
ii) Select standard hook and check the induced stress at the most critical section. Design a out for the hack and select suitable bearing.
iii) Design the pulley axle and select suitable bearings.
iv) Design the cross piece and shackle plates.(20 marks)