MAXIMUM TENSION IN THE BELT IS ALWAYS THREE TIMES THE CENTRIFUGAL T...

3. Maximum tension in the belt is always three times the centrifugal

tension.

Which of the statements given above is/are correct?

Design of Friction Drives

S K Mondal’s

Chapter 2

(a) 1, 2 and 3

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1 only

IES-36Ans. (b)

IES-37. In case of belt drives, the effect of the centrifugal tension is to: [IES-2006]

(a) Cause the belt to leave the pulley and increase the power to be transmitted

(b) Cause the belts to stay on the pulley and increase the power to be transmitted

(c) Reduce the driving power of the belt

(d) Stretch the belt in longitudinal direction

IES-37Ans. (d) Centrifugal tension has no effect on the power to be transmitted.

Condition for maximum power

IES-38. In a flat belt drive the belt can be subjected to a maximum tension T and

centrifugal tension T

c

. What is the condition for transmission of maximum

power?

[IES-2008]

(a)

T=T

c

(b)

T=

3

T

c

(c)

T=2T

c

(d)

T=3T

c

IES-38Ans. (d)

Condition for maximum power transmission:-

(

)

=

−

P

T

T v

1

2

T

e

μθ

=

1

T

2

⎛

⎞

P

T

T

1

1

v

⇒

=

−

⎜

⎝

−

⎟

⎠

max

c

e

( )

P

T

v mv 1

1

max

3

⇒

=

−

−

dP

T

3mv

0

⇒

=

−

=

max

dv

mv

T

2

max

⇒

=

3

T

T

c

max

∴

=

T

3T

IES-39. Which one of the following statements with regard to belt drives is NOT

correct?

[IES-2000]

(a) Increase in the angle of wrap of the belt enables more power transmission

(b) Maximum power is transmitted when the centrifugal tension is three times the

tight side tension

(c) Wide and thin belt is preferable for better life than a thick and narrow one

(d) Crown is provided on the pulley to make the belt run centrally on the pulley

IES-39.Ans. (b)

IES-40. When a belt drive is transmitting maximum power

[IES-1996]

(a) Effective tension is equal to centrifugal tension.

(b) Effective tension is half of centrifugal tension.

(c) Driving tension on slack side is equal to the centrifugal tension.

(d) Driving tension on tight side is twice the centrifugal tension.

IES-40Ans. (d)

IES-41. The power transmitted by a belt is dependent on the centrifugal effect in

the belt. The maximum power can be transmitted when the centrifugal

tension is

[IES-2002]

(a) 1/3 of tension (T

1

) on the tight side

(b) 1/3 of total tension (T

t

) on the tight side

(c) 1/3 of tension (T

2

) on the slack side

(d) 1/3 of sum of tensions T

1

and T

2

i.e. 1/3 (T

1

+ T

2

)

IES-41Ans. (b)

Selection of V-belt drive

IES-42. Assertion

(A): For similar materials having the same maximum permissible

tension V-belt transmits more power than flat belt with same velocity ratio and

centre distance.

[IES-2001]

Reason

(R): As two sides of V-belt are in contact with side faces of pulley groove,

larger contact area gives greater effective frictional force.

(a) Both A and R are individually true and R is the correct explanation of A

(b) Both A and R are individually true but R is not the correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

IES-42Ans. (a)

IES-43. In a multiple V belt drive, when a single belt is damaged, it is preferable to

change the complete set to

[IES-1993]

(a) Reduce vibration

(b) reduce slip

(c) Ensure uniform loading

(d) ensure proper alignment

IES-43Ans. (c) If a single belt breaks, all belts arc replaced to ensure uniform loading.

IES-44. Consider

the

following:

V-belts are specified by their

[IES-2008]