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##### 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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