FRICTIONAL RESISTANCE TO THE MOTION OF THE CHAIN IN AIR OR LUBRICAN...
4. Frictional resistance to the motion of the chain in air or lubricant.
The correct sequence of descending order of power loss due to these
sources is
(a) 1,2,3,4
(b) 1,2,4,3
(c) 2,1,3,4
(d) 2,1,4,3
IES-49.Ans. (a) Power loss in descending order takes place as 1, 2 3 and 4.
IES-50. Given that P = chain pitch, c = centre distance,
[IES-1994]
N, n = number of teeth on large and small sprocket respectively
the length of chain in terms of pitches can be approximated by
2
c
) / 2
(a)
2c
N
n
P
(b)
P
+ +
Design of Friction Drives
S K Mondal’s
Chapter 2
(c)
2
c
[(
) / 2 ]
2
P
N
n
P
N
n
P
N
n
P
P
+
−
c
(d)
2
c
(
) / 2
[(
) / 2 ]
2
P
P
+
+
+
−
c
IES-50Ans. (d)
IES-51.
For roller chain drive with sprocket having 10 teeth, the velocity of the driven
shaft with respect to that of drive will be approximately
[IES-2008]
(a) same
(b) 5% above
(c) 5% below
(d) 5% above to 5% below
IES-51Ans. (d)
V
V
1 cos
180
(
−
)
α
⎡
⎢
−
⎛
⎜
⎞
⎟
⎤
⎥
max
min
z
⎝
⎠
⎣
⎦
In order to reduce the variation in chain speed, the number of teeth on the sprocket
should be increased. It has been observed that the speed variation is 4% for a
sprocket with 11 teeth, 1.6% fro a sprocket with 24 teeth.
For smooth operation at moderate and high speeds, it is considered a good practice
to use a driving sprocket with at least 17 teeth. For durability and noise
considerations, the minimum number of teeth on the driving sprocket should be 19
or 21.
Rope driveIES-52. In a 6
×
20 wire rope, No.6 indicates the
[IES- 2001; 2003; 2007]
(a) diameter of the wire rope in mm
(b) Number of strands in the wire rope
(c)
Number
of
wires
(d) Gauge number of the wire
IES-52Ans. (b) 6
×
20 wire rope: 6 indicates number of strands in the wire rope and 20
indicates no of wire in a strand.
IES-53. Consider the following types of stresses in respect of a hoisting rope
during acceleration of load:
[IES-2000]