Government College of Technology 2007 Diploma Mechanical Engineering Semester - Question Paper

SUBJECT : THEORY MACHINES
Third/Fourth semester exam November 2007

Instructions

part I

1. Fill in the blanks: 1*4=4

a) A screw and net will be self locking if efficiency is ___________.
b) The side of cam depends upon ________ circle.
c) The radial distance ranging from the pitch circle and the top of the tooth is called __________.
d) For maximum power transmission the centrifugal tension is ____________ of the maximum tension.


part II

2. a) Differentiate ranging from machine and structure. 4
b) Define the subsequent. 4
i) Kinematic link ii) Kinematic chain.
c) With a neat sketch, discuss the working of Old Hams’ coupling with a sketch. 8

3. a) With a neat sketch, discuss the subsequent. 6
i) Stepped cone pulley drive ii) Jockey pulley drive
b) A shaft rotating at 200rpm drives a different shaft at 300rpm and transmits 6KW through a belt. The belt is 100 wide & 10 thickness. The distance ranging from the shaft is 4meters. The smaller pulley is 0.5 in diameter. compute the stress in the belt if it is an open belt drive. Co-efficient of friction is 0.3. 10

4. a) What are the advantages of V-belts over flat belts? 4
b) Define slip and creep of belts. 4
c) A 100mm wide and 10mm thick belt transmits five KW ranging from 2 parallel shafts. The distance ranging from the shaft centers is 2m. the diameter of the smaller pulley is 400mm. the driving and follower shaft rotates at 60 rpm and 150 rpm respectively. obtain the stress in the belt, if the 2 pulleys are connected by an open belt drive. 8



part III

5. a) What are ‘self locking’ and ‘overhauling’ of screws? 6
b) A load of 20 KN is raised by means of a screw jack having square threaded screw of 12mm pitch and of 60mm mean diameter. If a force of 100 N is applied at the end of a lever to raised the load, what should be the length of the lever used? Take co-efficient of friction as 0.16. what is the mechanical advantage obtained? State whether the screw is self locking. 10

6. a) With a neat sketch, discuss the working of a single plate clutch. 7
b) A friction clutch is to transmit 10 KW at 3000 rpm. It is to be of single plate kind with both sides of the plate being effective. The axial pressure is limited to 0.9 bar. If the external diameter of the friction lining is 1.4 times the internal diameter, obtain the needed dimensions of the friction lining. presume uniform wear conditions and co-efficient of friction as 0.3. 9

7. a) Explain basic steps involved in balancing of several masses rotating in the identical plane (only analytical method). 6
b) Five masses m1, m2, m3, m4 and m5 are revolving in the identical plane at equal radii. The magnitudes of m1=10kg, m2=4.8kg, m3=8kg. the angular position of m2 is at 50degree from m1, m3 at 85 degree from m2, m4 at 120 degree from m1, and m5 at 150 degree from m4, all measured in the identical direction. Determine the magnitude of masses m4 and m5 in order to balance the system. 10



part IV

8. a) Define the subsequent. 6
i) Addendum ii) Module iii) Circular pitch iv) Black lash
b) Two parallel shaft are to be connected by spur gearing. The centre to centre distance ranging from the shaft is to be approximately 330mm and the module of the wheels is to be 6mm. if the desired velocity ratio is 11:5, obtain the P.C.D. of the wheels, number of teeth on the wheels and the wheels and the exact centre distance ranging from the shaft axis. 10

9. a) Give the classification of gears. 6
b) Draw the profile of a cam operating a knife edged follower having a lift of 30mm. the cam raises the follower with SHM for 150degree of its rotation followed by a period of dwell for 60degree. The follower descends for the next 100degree rotation of the cam with uniform velocity again followed by a dwell period. The cam rotates at an uniform velocity of 120 rpm and has a cast radius of 20mm. 10

10. a) Define the subsequent. 6
i) Base circle ii) Pitch circle iii) Lift or stroke iv) Pressure angle
b) What are the advantage of gear drives? 6
c) Mention the important applications of cams. 4


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Earning:   Approval pending.