FORMAT OF I A TEST QUESTION PAPER (CIE) | MODEL QUESTION BANK | MODEL QUESTION PAPER | APPLICATION | ANALYZE THE EFFECT OF FRICTION ON MACHINE ELEMENTS| Diploma



APPLICATION                                                                                                                

 

1.         An engine, running at 150 r.p.m., drives a line shaft by means of a belt. The engine pulley is 750 mm diameter and the pulley on the line shaft being 450 mm. A 900 mm diameter pulley on the line shaft drives a 150 mm diameter pulley keyed to a dynamo shaft. Calculate the speed of the dynamo shaft, when

1.  There is no slip, and 2. There is a slip of 2% at each drive.

2.       The power is transmitted from a pulley 1 m diameter running at 200 r.p.m. to a pulley 2.25 m diameter by means of a belt. Calculate the speed lost by the driven pulley as a result of creep, if the stress on  the tight and slack side of  the belt is 1.4 MPa and 0.5 MPa respectively. The Young’s modulus for the material of the belt is 100 MPa.

3.       Calculate the power transmitted by a belt running over a pulley of 600 mm diameter at 200 r.p.m. The coefficient of friction between the belt and the pulley is 0.25, angle of lap is 160° and maximum tension in the belt is 2500 N.

4.       Two pulleys, one 450 mm diameter and the other 200 mm diameter are on parallel shafts 1.95 m apart and are connected by a crossed belt. Calculate the length of the 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 1 kN, and the coefficient of friction between the belt and pulley is 0.25 ?

5.       A shaft rotating at 200 r.p.m. drives another shaft at 300 r.p.m. and transmits 6 kW through a belt. The belt is 100 mm wide and 10 mm thick. The distance between the shafts is 4m.The smaller pulley is 0.5 m in diameter. Calculate the stress in the belt, if it is an open belt drive, Take μ = 0.3.

6.       A leather belt is required to transmit 7.5 kW from a pulley 1.2 m in diameter, running at 250 r.p.m. The angle embraced is 165° and the coefficient of friction between the belt and the pulley is 0.3. If the safe working stress for the leather belt is 1.5 MPa, density of leather 1 Mg/m3and thickness of belt 10 mm, determine the width of the belt taking centrifugal tension into account.

7.       Determine the width of a 9.75 mm thick leather belt required to transmit 15 kW from a motor running at 900 r.p.m. The diameter of the driving pulley of the motor is 300 mm. The driven pulley runs at 300 r.p.m. and the distance between the centres of two pulleys is 3 metres. The density of the leather is1000 kg/m3. The maximum allowable stress in the leather is 2.5 MPa. The co-efficient of friction between the leather and pulley is 0.3. Assume open belt drive and neglect the sag and slip of the belt.

8.       A pulley is driven by a flat belt, the angle of lap being 120°. The belt is 100 mm wide by 6 mm thick and density1000 kg/m3. If the coefficient of friction is 0.3 and the maximum stress in the belt is not to exceed 2 MPa, Calculate the greatest power which the belt can transmit and the corresponding speed of the belt.

9.       In a flat belt drive the initial tension is 2000 N. The coefficient of friction between the belt and the pulley is 0.3 and the angle of lap on the smaller pulley is 150°. The smaller pulley has a radius of 200 mm and rotates at 500 r.p.m. Calculate the power in kW transmitted by the belt.

10.    Two parallel shafts, whose centre lines are 4.8 m apart, are connected by open belt drive. The diameter of the larger pulley is 1.5 m and that of smaller pulley 1 m. The initial tension in the belt when stationary is 3 kN. The mass of the belt is 1.5 kg / m length. The coefficient of friction between the    belt    and the pulley is 0.3. Taking centrifugal tension into account, calculate the power transmitted, when the smaller pulley rotates at 400 r.p.m.


11.    An open belt running over two pulleys 240 mm and 600 mm diameter  connects two parallel shafts 3 metres apart and transmits 4 kW from the smaller pulley that rotates at 300 r.p.m. Co-efficient of friction between the belt and the pulley is 0.3 and the safe working tension  is10N   per   mm  width. Determine: 1. Minimum width of the belt, 2. Initial belt tension and 3. Length of the belt required.

12.    Power is transmitted using a V-belt drive. The included angle of V-groove is 30°. The belt is 20 mm deep and maximum width is 20 mm. If the mass of the belt is 0.35 kg per meter length and maximum allowable stress is 1.4 MPa, determine the maximum power transmitted when the angle of lap is 140°. μ = 0.15.

13.    A compressor, requiring 90 kW is to run at about 250 r.p.m. The drive is by V- belts from an electric motor running at 750 r.p.m. The diameter of the pulley on the compressor shaft must not be greater than 1 metre while the centre distance between the pulleys is limited to 1.75 metre. The belt speed should not exceed 1600 m/min. Determine the number of V-belts required to transmit the power if each belt has a cross-sectional area of 375 mm2, density 1000 kg/m3 and an allowable tensile stress of 2.5MPa. The groove angle of the pulley is 35°. The coefficient of friction between the belt and the pulley is 0.25.Calculate also the length required of each belt.

14.    A rope drive transmits 600 kW from a pulley of effective diameter 4 m, which runs at a speed of 90 r.p.m. The angle of lap is 160° ; the angle of groove 45° ; the coefficient of friction 0.28 ; the mass of rope 1.5 kg / m and the allowable tension in each rope 2400 N. Calculate the number of ropes required.

15.    A pulley used to transmit power by means of ropes has a diameter of 3.6 metres and has 15 grooves of 45° angle. The angle of contact is 170° and the coefficient of friction between the ropes and the groove sides is 0.28. The maximum possible tension in the ropes is 960 N and the mass of the rope is 1.5 kg per metre length. Calculate the speed of pulley in r.p.m. and the power transmitted if the condition of maximum power prevail

16.    Two parallel shafts, about 600 mm apart are to be connected by spur gears. One shaft is to run at 360 r.p.m. and the other at 120 r.p.m. Develop the gears, if the circular pitch isto be 25 mm.

17.    Two parallel shafts are to be connected by spur gearing. The approximate distance between the shafts is 600 mm. If one shaft runs at 120 r.p.m. and the other at 360 r.p.m. Calculate the number of teeth on each wheel, if the module is 8 mm. Also determine the exact distance apart of the shafts.

18.    A flat belt is required to transmit 35 kW from a pulley of 1.5 m effective diameter running at 300 r.p.m. The angle of contact is spread over 11/24 of the circumference and the coefficient of friction between belt and pulley surface is

0.3. Determine, taking centrifugal tension into account, width of the belt required. It is given that the belt thickness is 9.5 mm, density of its material is

1.1 Mg/m3 and the related permissible working stress is 2.5 MPa.

 

CO3: ANALYZE THE EFFECT OF FRICTION ON MACHINE ELEMENTS                                                                                                    

 

 

UNDERSTANDING                                                                                                                

 

1.     Explain the following terms:

(i).Angle of response (ii).Angle of friction

2.     Explain limiting angle of friction.


3.     Explain coefficient of friction.

4.     Explain with neat diagram limiting angle of friction.

5.     Explain with neat diagram coefficient of friction.

6.     Explain with neat diagram friction in a journal bearing.

 

 

APPLICATION                                                                                                                

 

1.           A 60 mm diameter shaft running in a bearing carries a load of 2000 N. If the coefficient of friction between the shaft and bearing is 0.03, Calculate the power transmitted when it runs at 1440 r.p.m.

2.           Explain with neat sketch different types of pivot bearings.

3.           Explain with neat sketch single and multiple flat collar bearing.

4.           A vertical shaft 150 mm in diameter rotating at 100 r.p.m. rests on a flat end footstep bearing. The shaft carries a vertical load of 20 kN. Assuming uniform pressure distribution and coefficient of friction equal to 0.05, Calculate power lost in friction.

5.           A conical pivot supports a load of 20 kN, the cone angle is 120º and the intensity of normal pressure is not to exceed 0.3 N/mm2. The external diameter is twice the internal diameter. Calculate the outer and inner radii of the bearing surface. If the shaft rotates at 200 r.p.m. and the coefficient of friction is 0.1, Calculate the power absorbed in friction. Assume uniform pressure.

6.           A conical pivot bearing supports a vertical shaft of 200 mm diameter. It is subjected to a load of 30 kN. The angle of the cone is 120º and the coefficient of friction is 0.025. Calculate the power lost in friction when the speed is 140 r.p.m., assuming uniform pressure.

7.           A thrust shaft of a ship has 6 collars of 600 mm external diameter and 300 mm internal diameter. The total thrust from the propeller is 100 kN. If the coefficient of friction is 0.12 and speed of the engine90 r.p.m., Calculate the power absorbed in friction at the thrust block, assuming l. uniform pressure only

8.           A shaft has a number of a collars integral with it. The external diameter of the collars is 400 mm and the shaft diameter is 250 mm. If the intensity of pressure is 0.35 N/mm2 (uniform) and the coefficient of friction is 0.05, Calculate:1. Power absorbed when the shaft runs at 105 r.p.m. carrying a load of 150 kN ; and 2. Number of collars required.

9.           Explain with a neat sketch single plate or disc clutch.

10.       Explain with a neat sketch multi plate clutch.

11.       A single plate clutch, with both sides effective, has outer and inner diameters 300 mm and 200 mm respectively. The maximum intensity of pressure at any point in the contact surface is not to exceed 0.1 N/mm2. If the coefficient of friction is 0.3, determine the power transmitted by a clutch at a speed 2500rpm.

12.       A multiple disc clutch has five plates having four pairs of active friction surfaces. If the intensity of pressure is not to exceed 0.127 N/mm2, Calculate the power transmitted at 500 r.p.m. The outer and inner radii of friction surfaces are 125 mm and 75 mm respectively. Assume uniform wear and take coefficient of friction = 0.3.

13.       Explain with a neat sketch internal expanding brake.


CO4:APPRECIATE THE ESSENTIALITY OF BALANCING IN ROTATING PARTS..                                                                                                    

 

 UNDERSTANDING                                                                                             

 

1.       Explain the balancing of rotating parts necessary for high speed engines

2.       Explain clearly the terms ‘static balancing’ and ‘dynamic balancing’.

3.       Discuss how a single revolving mass is balanced by a single mass revolving in same planes.

4.       Explain the method of balancing of different masses revolving in the same plane.

 APPLICATION                                                                                             

 

1.                       Four masses m1, m2, m3 and m4 are 200 kg, 300 kg, 240 kg and 260 kg respectively. The corresponding radii of rotation are 0.2 m, 0.15 m, 0.25 m and

0.3               m respectively and the angles between successive masses are 45°, 75° and 135°. Calculate the position and magnitude of the balance mass required, if its radius of rotation is 0.2 m.(Analytical method)

2.                       Four masses m1, m2, m3 and m4 are 250 kg, 350 kg, 290 kg and 310 kg respectively. The corresponding radii of rotation are 0.25 m, 0.20 m, 0.35 m and

0.4               m respectively and the angles between successive masses are 45°, 75° and 135°. Calculate the position and magnitude of the balance mass required, if its radius of rotation is 0.25 m. (Graphical method)

3.                       Four masses A, B, C and D are attached to a shaft and revolve in the same plane. The masses are 12kg, 10 kg, 18 kg and 15 kg respectively and their radii of rotations are 40 mm, 50 mm, 60 mm and30 mm. The angular position of the masses B, C and D are 60°, 135° and 270° from the mass A. Calculate the

magnitude and position of the balancing mass at a radius of 100 mm.

4.                       Five masses A, B, C,D and E are attached to a shaft and revolve in the same plane. The masses of A is 200N, B is 100N, C is 160 N respectively and their radii of rotations are equal.  The angular position of       the  masses  B, C  , D and E are 60°, 135°, 2100 and 270° from the mass A. Calculate the magnitude of D and E                  for complete balance. Solve graphically.

5.                       Five masses A, B, C,D and E are attached to a shaft and revolve in the same plane. The masses of A is                           250N, B is 160 N, C is 210N respectively and their radii of rotations are equal.  The angular position of the masses B, C , D and E are 60°, 135°, 2100 and 270° from the mass A. Calculate the magnitude of D and E            for complete balance. Solve by Analytical method.

6.                       Four masses m1, m2, m3 and m4 are 100 N, 150 N, 120 N and 130 N respectively. The corresponding radii of                                                                  rotation are 0.225 m, 0.175 m,

0.25 m and 0.3 m respectively and the angles measured from A                                                are                                               45°, 1200 and 255°. Calculate the position and magnitude of the balance mass

required, if its radius of    rotation is 0.3 m.( Analytical method)

7.                       Four masses A, B, C and D are attached to a shaft and revolve in the same plane. The masses are 16kg,                                14 kg, 22kg and 20 kg respectively and their radii of rotations are 40 mm, 50 mm, 60 mm and 30 mm. The angular position of


the masses B, C and D are 60°, 135° and 270° from the mass A. Calculate the magnitude and                                 position of the balancing mass at a radius of 50 mm

CO5: CONSTRUCT CAM PROFILE FOR THE SPECIFIC FOLLOWER MOTION                                                                                                    

 

 

 REMEMBERING                                                                                                                

1.     Define the following terms.

(a)     Base circle, (b) Pitch circle, (c) Pressure angle, and (d) Stroke of the follower.(e)Trace point

 

UNDERSTANDING                                                                                                                

1.     Explain cam and follower

2.     Classify different types of cams

3.     Describe the types of follower.

4.     Classify different types of followers.

5.     Explain prime circle and pitch circle related to cam profile

6.     Explain base circle and pitch point to cam profile

7.     Explain pressure angle and lift or stroke related to cam profile

8.     Interpret why a roller follower is preferred to that of a knife-edged follower.

9.     Illustrate the different types of motion with which a follower can move.

 

APPLICATION                                                                                                                

 

1.     Construct the displacement diagram for uniform velocity and S.H.M motion of the follower

2.     Construct the displacement and velocity diagram S.H.M motion of the follower

3.     Construct the displacement and velocity diagram for uniform velocity motion of the follower

4.     Construct the displacement and velocity diagram for uniform acceleration and retardation motion of the follower.

5.     Explain with sketches the different types of cams and followers.

 

6.     Construct a disc cam to give uniform motion to a knife edge follower during out stroke of 50 mm during the first half of the cam revolution. The follower again returns to its original position with uniform motion during the next half of the revolution. The minimum radius of the cam is 50 mm and the diameter of the cam shaft is 35 mm. Draw the profile of the cam when the axis of follower passes through the axis of cam shaft.

7.       Construct a cam operating a knife-edged follower, has the following data :

(a)            Follower moves outwards through 40 mm during 60° of cam rotation.

(b)            Follower dwells for the next 45°.

(c)            Follower returns to its original position during next 90°.

(d)            Follower dwells for the rest of the rotation.

(e)            The displacement of the follower is to take place with simple harmonic motion during both the outward and return strokes. The least radius of the


cam is 50 mm. Draw the profile of the cam when the axis of the follower is offset 20mm towards right from the cam axis.

8.   Construct a disc cam rotating in a clockwise direction is used to move a reciprocating roller with simple harmonic motion in a radial path for the details given below:

a)       Outstroke with maximum displacement of 25 mm during 120° of cam rotation,

b)      Dwell for 60° of cam rotation,

c)       iii) Return stroke with maximum displacement of 25 mm during 90° of cam rotation, and

d)      Dwell during remaining 90° of cam rotation.

e)       The line of reciprocation of follower passes through the camshaft axis. The maximum radius of camis30 mm. The roller diameter is 8 mm. Draw the profile of the cam when the line of reciprocation of the follower is offset by 20 mm towards right from the cam shaft axis.

9.   Construct a cam profile to raise a valve with simple harmonic motion through 50 mm in 1/3 of a revolution, keep if fully raised through 1/12 revolution and to lower it with harmonic motion in 1/6 revolution. The valve remains closed during the rest of the revolution. The diameter of the roller is 20 mm and the minimum radius of the cam is 25 mm. The diameter of the camshaft is 25 mm. The axis of the valve rod passes through the axis of the camshaft.

10. Construct a cam rotating clockwise with a uniform speed is to give the roller follower of 20 mm diameter with the following motion:

i.     Follower to move outwards through a distance of 30 mm during 120° of cam rotation ;

ii.     Follower to dwell for 60° of cam rotation ;

iii.     Follower to return to its initial position during 90° of cam rotation ; and

iv.     Follower to dwell for the remaining 90° of cam rotation.

The minimum radius of the cam is 30 mm and the line of stroke of the follower is offset 15 mm from the axis of the cam and the displacement of  the follower is to take place with simple harmonic motion on both the outward and return strokes. Draw the cam profile.

11.   Construct the profile of cam rotating clockwise at a uniform speed of 100

r.p.m. is required to give motion to knife-edge                                          follower as below, Follower to move outwards through 40 mm during 120° of cam rotation,

(f)   Follower to dwell for the next 60° of cam rotation,

(g)  Follower to return to its starting position during next 90° of cam rotation, and

(h)  Follower to dwell for the rest of the cam rotation.

(i)    The minimum radius of the cam is 30 mm and the line of stroke of the follower passes through the axis of the cam shaft. If the displacement of the follower takes place with uniform and equal acceleration and retardation on both the outward and return strokes.

12.    Construct a cam profile with 30 mm as minimum diameter is rotating clockwise at a uniform speed of 1200 r.p.m. and has to give the following motion to a roller follower 10 mm in diameter:


(a)  Follower to complete outward stroke of 25 mm during 120° of cam rotation with equal uniform acceleration and retardation ;

(b)  Follower to dwell for 60° of cam rotation;

(c)  Follower to return to its initial position during 90° of cam rotation with equal uniform                      acceleration and retardation;

(d)  Follower to dwell for the remaining 90° of cam rotation.

Draw the cam profile if the axis of the roller follower passes through the axis of the cam.

13.   Construct a cam profile, rotating clockwise at a uniform speed of 200 r.p.m. is required to move an offset roller follower                             with a  uniform           and                                 equal acceleration and retardation on both the outward and return  strokes.  The angle of                            ascent, the angle of dwell (between ascent and descent) and the angle of descent is 120°, 60° and                        90° respectively. The follower dwells for the rest of cam rotation. The least radius of the cam is 50                    mm,                                           the lift of the follower is 25 mm and the diameter of the roller is 10mm. The line of stroke

of the follower is offset by 20 mm from the axis of the cam.

14.    Construct the profile of a cam to suit the following specifications:

Cam shaft diameter = 25mm; Least radius of cam = 30 mm ; Diameter of roller

= 20 mm;

Angle of lift = 120° ; Angle of fall = 150° ; Lift of the follower = 40 mm ; Number of pauses are two of equal interval between motions. During the lift,  the motion is S.H.M. During the fall the motion is uniform acceleration and deceleration. The speed of the cam shaft is uniform. The line of stroke of the

follower is off-set12.5 mm from the centre of the cam.

15.    Construct the profile of a cam to give the following motion to a knife-edged follower:

Outstroke during 60° of cam rotation: 2. Dwell for the next 30° of cam rotation; Return stroke during next 60° of cam rotation, and 4. Dwell for the remaining 210° of cam       Rotation. The stroke of the follower is 40 mm and the minimum radius of the cam is 50 mm. The                    follower                                  moves       with uniform velocity during the outstroke and return strokes. With uniform velocity. Draw the profile of the cam when the axis of the follower is offset by 20 mm from the axis of the cam shaft.

 

Text Box: CO6: UNDERSTAND THE TERMINOLOGY AND TYPES ASSOCIATED WITH VIBRATION IN MACHINE ELEMENTS

 

 

 REMEMBERING                                                                                                                

 

1.     Define free vibrations, forced vibrations.

2.     Identify the causes and effects of vibrations?

3.     Define free vibrations,. And damped vibrations.

4.     Define forced vibrations,. And damped vibrations.

 

UNDERSTANDING                                                                                                                


1.       Discuss briefly with neat sketches the longitudinal, transverse vibrations.

2.       Discuss briefly with neat sketches the transverse and torsional free vibrations.

3.       Discuss briefly with neat sketches the longitudinal, and torsional free vibrations.

4.       Explain the term ‘whirling speed’ or ‘critical speed’ of a shaft

 


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