Machine Design - 2 - May 2016

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.

Attempt any four

1(a) Write the requirements of gear material(5 marks) 1(b) Write the advantages and limitations of Hydrostatic Bearing.(5 marks) 1(c) According to uniform wear theory, prove that for maximum torque capacity of plate clutch, R_i=0.577 R₀(5 marks) 1(d) explain the significance of pressure angle in cam and follower design.(5 marks) 1(e) With neat sketch explain force analysis of Helical gear.(5 marks) 2 A single stage spur gear box is used to transmit 15 kW power at 1440 rpm of pinion. The desire transmission ratio is 4:1
Assume 20 degree FD in-volute profile and material C55Mn1 for pinion and gear.
i) Find the module
ii) Check gear for Lewis Dynamic Load
iii) Check gear for wear strength
iv) Write Constructional Details.(20 marks) 3(a) Design a Bevel gear pair for following specification,
Rated power = 25KW
Input speed = 960 rpm
Output speed = 240 rpm
Shafting intersecting angle = 75 degree.(15 marks) 3(b) What are the materials commonly used for mechanical seals. Explain Stationary and Rotating Mechanical Seal with application.(5 marks) 4(a) A full journal bearing has a journal diameter of 25 mm, with a unilateral tolerance of -0.03 mm. The bushing bore has a diameter of 25.03 mm and a unilateral tolerance of 0.04 mm. The 1/d ratio is 0.5.The load is 1.2 kN and the journal runs at 1100 rev/min. If the average viscosity is 55 mPa/s, find the minimum film thickness, the power loss, and the side flow for the minimum clearance assembly.(10 marks) 4(b) Select DGBB for the shaft diameter of 60 mm which rotates at 1400 rpm with radial load of 2500N and Axial load of 1200N, Expected life of the bearing is 25000 hrs and load facor is 1.2.(10 marks) 5(a) Design a chain based on bearing failure and check for tensile failure for the following specification. (Design should include, Number of teeth on sprockets, centre distance, pitch, number of link and chain length)
Specification:
i) Rated power: 8 kW
ii) Input speed:84 rpm
iii) Output speed: 20 rpm
iv) Nature of load and duty: mild shock and 8 - 10 hrs.(10 marks) 5(b) Find the flat belt dimensions and life in hours for the following specification,
Power=25KW, Input Speed=1440 rpm, Output Speed=720 rpm, Centre distance=3m.(10 marks) 6(a) A cone Clutch is used to transmit 20KW at 1200 rpm. The coefficient of friction is 0.2, while the permissible intensity of pressure is 0.25N/mm². The semi cone angle is 15 degree, the larger diameter of the friction surface is 240mm. If the overload factor is 1.25, determine 1) The dimensions of the clutch, 2) Axial force required to engage and disengage the clutch.(10 marks) 6(b) A Rotary disc cam with central translatery roller follower has following motion.
Forward Stroke of 25mm in 120° of cam rotation with SHM motion dwell of 60° of cam rotation and return stroke of 25mm in 100° of cam rotation with SHM. Remaining dwell to complete the cycle. Mass of the follower is 1Kg and cam shaft speed is 600 rpm. The maximum pressure angle during forward stroke and return stroke is limited to 25°. The external force during forward stroke is 300N and that of return stroke is 50N.
i) Draw displacement, Velocity and Acceleration time diagram
ii) Find Prime circle radius, Base circle radius
iii) Calculate radius of curvature of pitch curve and cam profile
iv) Determine the width of the cam.(10 marks)