THEORY OF MACHINES

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Chapter 1:-

BELTS & CHAINS DRIVES

Short answer questions (1x8=8, 2x3=6, total 14 Marks)

1. Mention any three important factors required to select a suitable power drive.

2. Write the condition for maximum power transmission in the belt drive by considering the

centrifugal tension and write the expression for maximum power.

3. List any six applications of chain drive.

4. What is creep in a belt drive and what is its effect?

5. What are the most commonly used belt materials?

6. Write the advantages of V-Belts over flat belts.

7. List the different elements of chain drive.

Essay answer questions

1. Two pulleys 450 mm and 200 mm diameters are on parallel shafts 2 m apart and are connected by a crossed belt. Find the length of belt required and the angle of contact between the belt and each pulley. What power can be transmitted by the belt when the larger pulley rotates at 200 rev/min, if the maximum permissible tension in the belt is 1000 N, and the coefficient of friction between belt and pulley is 0.25. (Ans: P = 2.73KW)

2. A belt 100 mm wide and 6 mm thick is used to transmit power. The density of the belt material is 1000 kg/m3. If the angle of contact is 150°, coefficient of friction is 0.25 and the maximum permissible stress in the belt material is 1.75 MN/m². Find the greatest power which the belt can transmit and corresponding speed of the belt.

3. A 100mm wide and 10mm thick belt transmit 5kw power between two parallel shafts. Distance Between the shaft centres is 1.5m and diameter of the smaller pulley is 440mm. The driving and driven shaft rotates at 60rpm and 150 rpm respectively. Find the stress in the belt if two pulleys are connected by crossed belt drive. Take coefficient of friction mu = 0.25

4. A belt is required to transmit 15kW from a pulley of 1000 mm diameter at 420 rpm. The angle of lap is 160° and coefficient of friction is 0.3. If the safe working stress of belt material is 1.2N/mm². Find the width of belt. Take thickness of belt is 10mm. (Ans: b = 100.6mm)

Chapter 2:-

GEARS DRIVES ( 1 * 8 = 8 2 * 3 = 6 total 14 Marks)

Short answer questions

1. Define the following terms:(a) Circular pitch (b) Back lash (c) module (d) Diametral pitch.

2. State any three advantages of gear drive over belt drive.

3. List the required properties of gear materials

4. State the difference between involute profile and cycloidal profile.

5. How are the gears classified?

6. A wheel has 48 teeth and circular pitch of 20 mm. Find (a) pitch circle diameter and (b) module.

(Ans: d=305.5mm, m=6.36mm)

7. A gear having 80 teeth meshes with a pinion having 30 teeth. Calculate the centre distance between gears, if the circular pitch is 12 mm. (Ans: C = 210.08 mm)

Essay answer questions

1. Explain the reverted gear train with neat sketch.

2. Explain the following gear trains with neat sketches and state their applications:

(a) Epicyclic gear train (b) Compound gear train

3. A set of spur gear has to transmit 30kW, when the pinion rotates at 400 rpm. The gear ratio is 1:4,

the permissible stresses for the pinion and driver gear materials are 130 N/mm2 and 110N/mm²

respectively. The pinion gear has 22teeth and face width 12 times the module Compute (i) module

and (ii) face width. ( Ans / m = 6mm . b = 48mm )

4. A lathe back gear arrangement is to provide total speed reduction of about 12:1 from the cone pulley to the spindle which are coaxial. The module of high speed and low speed pairs are 4mm and 6 mm respectively. Determine the number of teeth and the exact total reduction on the different wheels. If the pinions have nearly equal teeth. The centre distance is 240mm.(Ans: 11.7:1)

Chapter 3:-

FLYWHEELS & GOVERNORS (1x8=8, 2×3=6, total 14 Marks)

Short answer questions

1. Define the following terms:

(a) Fluctuation of energy (b) Fluctuation of speed.

2. What is the function of flywheel?

3. What is the turning moment diagram? Draw a simple turning moment diagram for 4-stroke engine.

4. What is the function of governor?

5. State the differences between flywheel and governor.

6. Write classification of governor

7. Define the terms related to governor (a) sensitiveness and (b) stability.

8. Define the terms effort and power of governor.

Essay answer questions

1. Describe the working principle of porter governor with a neat sketch.

2. Describe the working principle of watt governor with a neat sketch.

3. The kinetic energy of flywheel at 150 r.p.m. is 1200 joules. If the radius of gyration is 0.5 m, what

should be its mass? (Ans: 38.9KG)

4. A flywheel rotating at 600 r.p.m. does 1950 joules of work per revolution. The coefficient of

fluctuation of energy is 0-2 and that of the speed is 0.02. Mass of the flywheel is 80 kg. Compute,

(a) Power transmitted by the shaft on which flywheel is mounted (Ans: 19.5kw)

(b) Maximum fluctuation of energy.(Ans: 409.5 J/rev)

(d) Mass moment of inertia.(Ans:5.19kg.m²)

5. The speed of the crank shaft of an engine varies from minimum of 118 rev/min to a maximum of 122 rev/min. A flywheel of mass 500 kg and radius of gyration 1.2 m is keyed to crank shaft. If the work done per cycle is 16 kJ. Calculate:

(a) The maximum fluctuation of energy in the flywheel.(Ans: 3801.17)

(b) Maximum fluctuation of energy(Ans: 409.5 J/rev)

(d) Mass moment of inertia.(Ans:5.19kg.m²)

6. The speed of the crank shaft of an engine varies from minimum of 118 rev/min to a maximum of 122 rev/min. A flywheel of mass 500 kg and radius of gyration 1.2 m is keyed to crank shaft. If the work done per cycle is 16 kJ.

Calculate:

(a) The maximum fluctuation of energy in the flywheel.(Ans: 3801.17J)

(b) The coefficient of fluctuation of speed, if the mean speed is 120 rev/min. (Ans: 0.033)

Chapter 4:-

CAMS (1x8=8, 2×3=6, total 14 Marks)

Short answer questions

1. Draw a neat sketch of cam mechanism. State its applications.

2. Define (a) Base circle; (b)Dwell (c)stroke (d)Pressure angle

3. How do you classify the cams?

4. How do you classify the followers of cams?

5. State the function of cams

Essay answer questions

1. Draw the cam profile for the Knife edge follower with uniform velocity. Out stroke 120°, Dwell 30°,return stroke 90° and dwell for remaining period of cam rotation. Stroke of the follower is 30 mm and minimum of radius of the cam is 25 mm, axis of the follower passes through the axis of the cam shaft.

2. Draw the displacement diagram and cam profile for a knife edge follower moving with uniform velocity as given below: Outward stroke 120° of cam rotation, Dwell 30°; Return stroke 90° of cam rotation, Dwell for the remaining period of cam rotation. Stroke of the follower is 30 mm. The axis of the follower passes through the axis of the cam shaft. The minimum radius of the cam is 25mm. The cam is rotating in clockwise direction.

3. Draw the cam profile to give the follower motion to a roller follower. Outward stroke through 60mm during 120° of cam rotation: Dwell 90° of cam rotation. Return stroke during 120° of Cam rotation: Dwell for the remaining part of cam rotation. The cam is rotating in clockwise direction with minimum radius of 30 mm. The line of stroke of the follower passes through the centre of the cam axis and the follower moves with uniform velocity during out stroke and return Stroke. The diameter of the roller is 20 mm.

4. A cam with a minimum radius of 35mm, rotating clockwise at a uniform speed, is required to give a knife edge follower: (a)To move outward through40mm during 120° rotation of the cam. (b) To dwell for next 60°. (c)To return its starting position.(d)To dwell for the rest period of rotation during next 90°.Draw the profile of the cam, when the line of stroke of the follower passes through the centre of the cam shaft and the follower moves during both outstroke and instroke with uniform acceleration and retardation.

Chapter 5:-

MECHANICAL VIBRATIONS (1×8=8, 2×3=6, total 14 Marks)

Short answer questions

1. Define the term SHM. Give any three examples of SHM.

2. Define (a) periodic time (b) degree of freedom & (c) resonance

3. How do you classify mechanical vibrations?

4. List the types of damping.

5. Define the terms viscous damping, coulomb damping and structural damping.

6. Define the terms viscous damping, coulomb damping and structural dam6. Find the natural frequency of a spring-mass system in Hz, if the mass is 10 kg and stiffness of the spring is 10

N/mm

7. Find the length of a simple pendulum if its time period is 3 sec and acceleration due to gravity is

9.81m/sm

Essay answer questions

1. A body moving with simple harmonic motion has amplitude of 1m and period of oscillation of 2 seconds. What will be its velocity and acceleration 0.4 second and after passing an extrem eposition?

2. Explain the sources of vibrations in mechanical systems

3. Write in brief about the methods of controlling vibrations in mechanical Systems

NOTE- 10 Marks question will be come in 1st, 2nd or 4th lesson

THEORY OF MACHINES