BHARATIYA VIDYA BHAVANSSARDAR PATEL COLLEGE OF ENGINEERING

(An Autonomous Institution Affiliated to University of Mumbai)MUNSHI NAGAR, ANDHERI (WEST), MUMBAI- 400 058

TEST - IICLASS/SEM: B.Tech.(Mech) Sem VII Total Marks: 20SUBJECT: Machine Design II Duration: 1 Hour

Date: August 2014 Attempt any TWO out of three questions.

Use of PSG data book is permitted. Assume suitable data if necessary.

1.a) A single row deep groove ball bearing is subjected to a pure radial load of 3 KN from a shaft rotates at 600 rpm. The expected life L10hr of bearing is 30000 h. The minimum acceptable diameter is 40mm. select suitable ball bearing for this application, for selected bearing designate manufacturers designation and also find life of bearing with 92.5% reliability.b) Derive relation for efficiency of worm gear drive.c) Lewis equation for bevel gear is corrected for

i) variation in PCD ii)variation in tooth thickness

iii) taking care of axial thrust iv)variation in torque acts on tooth

(6) (3) (1)

2.a) In a worm gear reducer the centre distance should not exceed 250mm, the gear ratio 12.5, the worm speed is 2500 rpm. Select suitable materials. Determine the dimension and capacity of reducer based on wear and beam strength. Also find capacity of gear drive based on heat dissipation and decide what should be input power if involute tooth system is used.b) Type of failure which occurs in ball bearing is

i) shear ii) fatigue iii) bending iv) crushingc) List main component of gear box

d) Life of ball bearing is halved if the load P changed to

i) 2P ii) 0.5P iii)1.1P iv)1.26P

(7)(1) (1)

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3.a) Design a pair of bevel gear to transmit 12KW at 600 rpm. Gear ratio is 2:1. The pinion has 24, 20o full depth involute teeth. The safe static stress is 105MPa. B = Cone length /3 ,. Find m,B, Cone length, PCDs. Check the design for dynamic load and wear using Buckinghams equation if Ce factor (Material combination factor) is 300KN/m and the mean plane of gear is 120 mm from the left hand bearing, determine the forces acting on bearings.b) The type of gear with minimum axial thrust is

i) Miter gear ii) worm gear iii) helical gear iv) herringbone gear

c) Stribecks equation defines

i) life of RCB ii) static capacity of R.C.B

iii) dynamic load capacity of DGBB iv) none of above (8)(1)

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