Machine Design - 2 : Question Paper Dec 2014 - Mechanical Engineering (Semester 7)

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Machine Design - 2 - Dec 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 different types of gear tooth failure.(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) Explain Churning effect and Cavitation in Centrifugal pump.(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 20. For the second stage spur gear pair,
i) Determine the module using bending failure.
ii) Check the gears for dynamic load by using Buckingham's method.
iii) Check the gears for wear strength.
iv) Work out constructional details of geaRs.(20 marks) 3 (a) A DGBB having SKF No. 6208 subjected to load cycle as below. Find expected life of the bearing in hours with probability for of survival 90%. Take Service factor=1.2.

Sr. No.	Radial Load (N)	Thrust Load (N)	Speed (RPM)	%
1	3000	1000	600	15
2	3500	1000	800	20
3	5000	100	900	30
4	500	2000	1500	35

(14 marks) 3 (b) What are the desirable properties of a good bearing material used in sliding contact bearings?(6 marks) 4 Rotary cam with central translatory roller follower has following motions: Forward stroke of 20 mm in 100° of cam rotation with SHM 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 500 RPM, external force during forward stroke is 500 N and during return stroke is 100 N. Design
i) Cam
ii) Follower with pin and spring
iii) Cam shaft(20 marks) 5 (a) Find the module of the bevel gear and check it for wear load for the following specification;
Power transmitted: 30 KW
Input speed: 360 RPM
Reduction ratio: 3
Angle between shaft: 90°(10 marks) 5 (b) A full journal bearing is use for supporting a load of 7 KN runs at 500 RPM for machine tool application. Select fit H9e9 and Take L/D=1. Find,
i) Bearing dimensions
ii) Sommerfeld Number
iii) Minimum oil film thickness
iv) Coefficient of friction
v) Rise in temp of oil.(10 marks) 6 A centrifugal pump is required to pump the water for the following specification;

Static suction head	:3 m
Length of suction pipe	:6 m
Static delivery head	:10 m
Length of delivery pipe	:15 m
Discharge	:1200 LPM

Design:
i) Pipe diameters
ii) Impeller and impeller shaft
iii) Casing
Select the suitable motor
Draw the layout.(20 marks) 7 The following specification refers to an EOT crane;

Application	: Class-II
Load to be lifted	: 120 KN
Hoisting speed	: 6 m/min

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 nut for the hook and select suitable bearing.
iii) Design the pulley axle and select suitable bearings.
iv) Design the cross piece and shackle plates.(20 marks)

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