V belt drive definition, types, design, advantage, disadvantage

The V belt is used where a greater amount of power is required from one pulley to another and the distance between these two pulleys is very less. This belt is made of trapezoidal shape. This belt is made of fabric and cords moulded in rubber. Which is covered with fabric and rubber cover from outside. 

The included angle under these belts is kept from 30 degree to 40 degree. This belt uses high force of friction to pull the pulley. This force of friction depends on the included angle under the belt. The force of friction is high when the angle is less, which causes wear and tear problem. Therefore a right included angle is required. There is always some clearance in these belts and pulleys.

Types of V belt :-

According to Indian standards (IS: 2494–1974), there are five types of V belt.

1) Type A            

2) Type B          

3) Type C           

4) Type D            

5)Type  E

These five types are divided according to the power range. 

Length of V belt :-

According to IS: 2494–1974, we describe V belt is in its type and nominal inside length. For example, if a V belt is of type A and its inside length is 1295 mm, then we will call it A1295 - IS: 2494. The length of this belt is always standard. We take its length unit in mm.

To take pitch length, we deposit in inside length such as 36 mm in type A, 43 mm in type B, 56 mm in type C, 79 mm in tpe D and 92 mm in type E.

Pulleys for V belt :-

The Pulley is used for this belt is made of cast iron or pressed steel. Grooves are cut in V pulley.

Face width (B) = (n-1) e + 2f

Advantages of V belt drive :-

1. This belt has long life.
2. These belts have greater shock tolerance when a machine is started.
3. This drive is positive because there is negligible slip between the grooves of the belt and the pulley.
4. This drive also works at higher Velocity ratio (Max. 10).
5. The center line of the pulley of this belt drive can be horizontal, vertical or inclined.
6. This belt is without any joint.

 Disadvantage of V belt drive :-

1. These belts are not more durable than flat belts.
2. In this belt drive the construction of the pulley is more difficult, than the construction of the pulley of the flat belt drive.
3. We mostly face creep problems in this belt. So this is why we do not use this belt with constant speed like synchronous machine etc.
4. This drive is not used for long center distance because the weight per unit length increases due to the length.

Velocity Ratio :-

        Let        d₁     =   Pitch diameter in metre of driver Pulley

                    d₂     =   Pitch diameter in metre of driven Pulley

                   N₁     =   Speed of driver Pulley

                   N₂     =   Speed of driven Pulley

                             N₁/ N₂        =    d₁ / d₂         

Power transmitted per belt :-

 Let              T₁     =   Tension in belt on tight side (N)

                    T₂     =  Tension in belt on slack side (N)

                     v      =   Speed of driver Pulley (m/s)

           

                    v  =  ∏d N / 60       

     Power transmitted per belt = (  T_{1 -} T₂  ) v     in Kw

No. of V belts :-

No. of V belt = Total power transmitted / Power transmitted per belt

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Ishan Kumar