Machine Design - 2 - Dec 2013

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) Difference in worm and worm Gear and other three types of gears.(5 marks) 1 (b) Basic static and dynamic load rating of ball bearing.(5 marks) 1 (c) Desirable properties of sliding contact bearing materials.(5 marks) 1 (d) Factors affecting size of radial cam.(5 marks) 1 (e) Number of bends in multifall system(5 marks) 2 (a) Find suitable module for Bevel gear pair for following specification, using Barth factor and wear considerations
Power Transmitted -40kW
Input Speed-360 RPM
Reduction Ratio -3
Angle Between shafts- 90°
Application- Agitator(10 marks) 2 (b) Derive Lewis equation for strength of gear tooth.(10 marks) 3 Decide suitable layout and Completely design the centrifugal pump for following specification
Total Head - 15m
Discharge - 800lpm
Operating Speed - 1440 RPM(20 marks) 4 (a) Select suitable Spherical roller bearing subjected to radial load of 4kN, axial load of 1.2kN, running at 900 RPM, operating at 125°C, for life of 6000 hours with 93% probability of survival.(8 marks) 4 (b) Design helical gear pair with strength and wear considerations.
Power transmitted - 16kW
Pinion Speed - 1440 RPM
Velocity Ratio - 3
Check for Buckingham Dynamic load; 7 4(4 marks) 5 Following specifications are for Snatch Block of EOT crane.
Load to be lifted - 90kN
Hoisting Speed - 8 m/min
Application - Class 2
(i) Select suitable rope and find its life.
(ii) Design crane hook for critical,section
(iii) Design shackle plates, cross-piece and Axle with bearings for pulleys(20 marks) 6 A 360° hydro-dynamically lubricated full journal bearing is subjected to radial load of 9KN at 800 RPM having diameter of 75mm. Select suitable fit and with average clearance find operating parameters like
i) Coefficient of friction
ii) Oil Temperature Rise
iii) Inlet pressure
iv) Oil quantity Flow
Check the working of bearing for minimum clearance and comment(20 marks) 7 A Rotary Radial Disc cam and Central Roller Follower has following Motion .
i) Forward stroke of 22mm in 120° cam rotation with SHM
ii) Dwell for 45°
iii) Return in 90° with Parabolic Motion
iv) Remaining dwell
Mass of follower is 1.2kg. Cam operating speed is 500 RPM. Maximum pressure angle during forward stroke is 20°. The external force is varying from 50N to 1250N linearly while rise and constant of 50N during fall
Design
(a) cam
(b) Follower with Roller and Pin
(c) Spring
(d) Shaft(20 marks)