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TE (MECH/PROD) EXAMINATIONTHEORY OF MACHINE - II

MAX. MARKS: 100 TIME: 3HRNote: Solve any three questions each section

Section a1.

A) Compare the involute gear and cycloidal gears. 4B) The following data relate to a pair of 20 involute gears in mesh: Module = 6 mm, Number of tee

on pinion = 17, Number of teeth on gear = 49; Addenda on pinion and gear wheel = 1 modu

Find: 1. The number of pairs of teeth in contact; 2. The angle turned through by the pinion and t

gear wheel when one pair of teeth is in contact, and 3. The ratio of sliding to rolling motion wh

the tip of a tooth on the larger wheel (i) is just making contact, (ii) is just leaving contact with

mating tooth, and (iii) is at the pitch point. 12.

A) Derive an expression for the distance of a pair of spiral gears. 4B) A drive on a machine tool is to be made by two spiral gear wheels, the spirals of which are of t

same hand and has normal pitch of 12.5 mm. The wheels are of equal diameter and the cen

distance between the axes of the shafts is approximately 134 mm. The angle between the shaft

80 and the speed ratio 1.25. Determine: 1. the spiral angle of each wheel, 2. the number of tee

on each wheel, 3. the efficiency of the drive, if the friction angle is 6, and 4. the maximu

efficiency. 13.

A) Define and Explain: Sensitiveness and Mean Equilibrium speed 4B) A governor of the Proell type has each arm 250 mm long. The pivots of the upper and lower arm

are 25 mm from the axis. The central load acting on the sleeve has a mass of 25 kg and the ea

rotating ball has a mass of 3.2 kg. When the governor sleeve is in mid-position, the extension li

of the lower arm is vertical and the radius of the path of rotation of the masses is 175 mm. Tvertical height of the governor is 200 mm. If the governor speed is 160 r.p.m. when in m

position, Find: 1. length of the extension link; and 2. tension in the upper arm.

124.

A) Explain the Turning Moment Diagram for a Four Stroke Cycle Internal Combustion Engine.B) A single cylinder, single acting, four stroke gas engine develops 20 kW at 300 r.p.m. The wo

done by the gases during the expansion stroke is three times the work done on the gases duri

the compression stroke, the work done during the suction and exhaust strokes being negligible

the total fluctuation of speed is not to exceed 2 per cent of the mean speed and the turni

moment diagram during compression and expansion is assumed to be triangular in shape, find t

moment of inertia of the flywheel. 15.

A) A plate clutch has three discs on the driving shaft and two discs on the driven shaft, providing fopairs of contact surfaces. The outside diameter of the contact surfaces is 240 mm and insi

diameter 120 mm. Assuming uniform pressure and coefficient of friction= 0.3; find the to

spring load pressing the plates together to transmit 25 kW at 1575 r.p.m. If there are 6 sprin

each of stiffness 13 kN/m and each of the contact surfaces has worn away by 1.25 mm, find t

maximum power that can be transmitted, assuming uniform wear., is required to transmit 25 k

at 3000 r.p.m. 1

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A) Which of the two assumptions-uniform intensity of pressure or uniform rate of wear, would ymake use of in designing friction clutch and why ? 6

Section b6.

A) Explain the effect of Gyroscopic Couple on a Naval Ship during Steering. 6B) The turbine rotor of a ship has a mass of 3500 kg. It has a radius of gyration of 0.45 m and a speof 3000 r.p.m. clockwise when looking from stern. Determine the gyroscopic couple and its eff

upon the ship: when the ship is steering to the left on a curve of 100 m radius at a speed of

km/h. when the ship is pitching in a simple harmonic motion, the bow falling with its maximu

velocity. The period of pitching is 40 seconds and the total angular displacement between the t

extreme positions of pitching is 12 degrees. 17.

A) Explain with neat sketch Prony Brake Dynamometer 6B) A band brake acts on the 3/4th of circumference of a drum of 450 mm diameter which is keyed

the shaft. The band brake provides a braking torque of 225 N-m. One end of the band is attach

to a fulcrum pin of the lever and the other end to a pin 100 mm from the fulcrum. If the operat

force is applied at 500 mm from the fulcrum and the coefficient of friction is 0.25, find t

operating force when the drum rotates in the (a) anticlockwise direction, and (b) clockw

direction. 18.

A) Give the classification of belt drives. 6B) Two pulleys, one 450 mm diameter and the other 200 mm diameter are on parallel shafts 1.95

apart and are connected by a crossed belt. Find the length of the belt required and the anglecontact between the belt and each pulley. What power can be transmitted by the belt when t

larger pulley rotates at 200 rev/min, if the maximum permissible tension in the belt is 1 kN, a

the coefficient of friction between the belt and pulley is 0.25? 19.

A) Explain the term dynamic magnifier. 4B) The mass of a machine is 100 kg. Its vibrations are damped by a viscous dash pot wh

diminishes amplitude of vibrations from 40 mm to 10 mm in three complete oscillations. If t

machine is mounted on four springs each of stiffness 25 kN/m, find (a) the resistance of the da

pot at unit velocity, and (b) the periodic time of the damped vibration.

6C) Discuss briefly with neat sketches the longitudinal, transverse and torsional free vibrations. 6

10.A single-cylinder engine of total mass 200 kg is to be mounted on an elastic support which perm

vibratory movement in vertical direction only. The mass of the piston is 3.5 kg and has a verti

reciprocating motion which may be assumed simple harmonic with a stroke of 150 mm. It is desir

that the maximum vibratory force transmitted through the elastic support to the foundation shall

600 N when the engine speed is 800 r.p.m. and less than this at all higher speeds. 1. Find t

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necessary stiffness of the elastic support, and the amplitude of vibration at 800 r.p.m., and 2. If t

engine speed is reduced below 800 r.p.m. at what speed will the transmitted force again becomes 6

N? 16