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Nov Dec 2017.pdf-Total No. of Questions : 10]

Nov_Dec_2017.pdf-Total No. of Questions : 10]

Nov Dec 2017.pdf-Total No. of Quest...

Nov_Dec_2017.pdf-Total No. of Questions : 10]

##### Page 1

Total No. of Questions : 10]

[5254]-533

B.E. (Mechanical)

DYNAMICS OF MACHINERY

(2012 Pattern)

Time : 2½ Hours]

[Max. Marks : 70

Instructions to the candidates:

1)

Neat diagrams must be drawn wherever necessary.

2)

Figure to the right indicate full marks.

3)

Use of electronic calculator is allowed.

4)

Assume suitable data, if necessary.

P2138

P.T.O.

[Total No. of Pages : 4

SEAT No. :

Q1)

a)

A four cylinder vertical engine has cranks 150 mm long. The cylinders

are spaced 200 mm apart. Mass of reciprocating parts of I

st

, 2

nd

and 4

th

cylinders are 50 kg, 60 kg and 50 kg respectively. Find the reciprocating

mass of the 3

rd

cylinder and relative angular positions of the cranks to

achieve complete primary balance.

[6]

b)

Determine the expression for natural frequency of the system shown in

Fig. 1

[4]

OR

Q2)

a)

A shock absorber is to be designed so that its overshoot is 10% of the

initial displacement when released. Determine the damping factor. Also

find the overshoot if the damping factor is reduced to 50%.

[6]

b)

Explain the terms Static Balancing and Dynamic Balancing.

[4]

CEGP013091

49.248.216.238 04/12/2017 14:18:24

CEGP013091

49.248.216.238 04/12/2017 14:18:24

CEGP013091

49.248.216.238 04/12/2017 14:18:24

##### Page 2

[5254]-533

2

Q3)

a)

A single cylinder vertical petrol engine of total mass 320 kg is mounted

on a steel chassis and causes a vertical static deflection of 2 mm. The

reciprocating parts of the engine have a mass of 24 kg and move through

a vertical stroke of 150mm with SHM. A dashpot attached to the system

offers a resistance of 490 N at a velocity of 0.3 m/s. Determine :

[6]

i)

the speed of driving shaft at resonance

ii)

the amplitude of steady state vibrations when the driving shaft of the

engine rotates at 480 rpm.

b)

Define the following terms :

[4]

i)

Damping coefficient

ii)

Critical damping coefficient

iii)

Damping factor

iv)

Logarithmic decrement

OR

Q4)

a)

A horizontal spring mass system with coulomb damping has a mass of 5

kg attached to a spring of stiffness 980 N/m. If the coefficient of friction is

0.25, calculate :

[6]

i)

the frequency of free oscillations

ii)

the number of cycles corresponding to 50% reduction in amplitude

if the initial amplitude is 5 cm

iii)

time taken to achieve this 50% reduction

b)

Write a short note on Forced vibrations due to reciprocating unbalance.

[4]

Q5)

a)

Find the natural frequencies of the system shown in Fig. 2.

[12]

m

1

= 10 kg, m

2

= 12 kg

r

1

= 0.10 m, r

2

= 0.11 m

k

1

= 40 × 10

3

N/m

k

2

= 50 × 10

3

N/m

k

3

= 60 × 10

3

N/m.

CEGP013091

49.248.216.238 04/12/2017 14:18:24

CEGP013091

49.248.216.238 04/12/2017 14:18:24

CEGP013091

49.248.216.238 04/12/2017 14:18:24

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