What is Belt Drive ? | Types of Belt Drives and Belt - News4u95

Breaking

Saturday, 30 January 2021

What is Belt Drive ? | Types of Belt Drives and Belt

Belt Drive

The belt drives are used to transmit power from one shaft to another shaft by using pulleys which rotate at the same speed or at different speed.

A belt drive consists of following three elements:

  1. Driving pulley or head pulley
  2. Driven pulley or tail pulley
  3. Endless belt

The power is transmitted from driving pulley to driven pulley because of frictional grip between the belt and pulley surface.


Belt Drive
Belt Drive


Speed Ratio of Belt Drive

Speed ratio or velocity ratio is defined as the ratio between the speed of the driver and the driven shaft.
Generally, speed ratio is given by

Speed ratio =   Speed of driving pulley/Speed of driven pulley

Let, d and D = Diameters of driving (small) and driven (big) pulley in mm,

n and N = Speed of driving (small) and driven (big) pulley in r.p.m.,

t = Thickness of belt in mm

Speed ratio = n/N = D/d

If thickness of belt is considered then, Speed ratio = n/N = D+t/d+t

 

Types of Belts

There are many types of belts used in variety of applications in industrial and automotive sector.

1. Flat belt

  • The flat belts have rectangular cross section.
  • The width of the belt is substantially higher compared to its thickness.
  • They are used where moderate amount of power is to be transmitted from one pulley to another, when the two pulleys are not more than 8 meters apart.
  • To avoid running out of the belt from the pulleys the pulleys are provided with proper crowning.
  • Such pulleys are called "crown pulleys". 


Advantages of flat belt

  • Flat belts are easy to produce hence have low cost.
  • Flat belts require low maintenance in regards to periodic adjustment of center distance between shafts to compensate wear.
  • Flat belts with stepped pulley can be used to obtain multiple speed ratios.
  • They are simple to design and manufacture.
  • They have relatively higher efficiency.
  • They can be used for long center distance between shafts.
  • They can be operated in dusty and abrasive atmosphere.


Disadvantages of flat belt

  • Flat belts have limited frictional contact and hence lower power transmitting capacity.
  • Flat belts are used for limited speed reduction up to 4 : 1.
  • They are used for long center distance and hence bigger size of drive.
  • They are restricted to single belt usage.
  • They are more noisy at higher operating speeds.
  • They are used for applications with two shafts being connected in horizontal plane.

 

 

2. V-belt

  • The V-belts have trapezoidal cross section.
  • They are used where great amount of power is to be transmitted from one pulley to another, when the two pulleys are very near to each other.
  • To have higher surface contact between the belt and pulley, the pulleys are provided with a groove.
  • Such pulleys are called "grooved pulleys".


Advantages of V-belt

  • V-belts have higher frictional contact and hence higher power transmitting capacity.
  • V-bell can be used for high speed reduction up to 7 : 1.
  • They are used for short centre distance which result in compact size of drive.
  • Multiple V-belts can be accommodated in the same pulley for increased power transmission.
  • They are relatively smooth and quiet at low and high operating speeds.
  • They can be used in applications with shafts being connected in horizontal or vertical plane.


Disadvantages of V-belt

  • V-belt are made of reinforcement material and cords, hence higher cost.
  • V-belt require precise alignment of shaft and pulley to ensure long life of the belt.
  • V-belts cannot be used with stepped pulley and hence it is not possible to obtain multiple speed ratios.
  • They are relatively complex to design and manufacture.
  • They have lower efficiency.
  • They are suitable for short to medium center distance between shafts.
  • They need closed environment, which is free from dust.

 

3. Circular Belt

  • The circular belts have circular cross section.
  • They are used where great amount of power is to be transmitted from one pulley to another, when the two pulleys are more than 8 meters apart.
  • To avoid running out of the circular belt from the pulley, the pulleys are provided with a groove.

 

Types of Belt Drives


1. Open belt drive

  • It is used when both, the driving and driven shaft are arranged in parallel and rotating in the same direction
  • Normally, the tight side of the belt should be the lower one, especially when the distance between the two shafts Is large.


2. Crossed belt drive Driver

  • It is used when both the driving and driven shaft are arranged in parallel, but rotating In opposite direction.
  • This arrangement provides increased frictional contact between the belt and pulley.
  • It is prone to excessive wear at a point where the belt crosses and rubs against each other.
  • It is used for low speed applications.


3. Open belt with idler pulley drive

  • It consists of an open belt drive with an idler pulley.
  • The idler pulley causes increase in frictional contact between the belt and driving pulley.
  • It is used to obtain high velocity ratio and high belt tension.
  • The position of Idler pulley can be changed to increase the belt tension.


4. Compound belt drive

  • It is used when power is transmitted from one shaft to another through a number of intermediate pulleys.
  • It provides high reduction ratio.

 

Advantages of Belt Drives

  • Belt drives can be used for long centre distances.
  • As belts are flexible, they possess a capacity to absorb shocks and vibrations.
  • For belt drive, lubrication is not required.
  • Belt drives are not affected to dust and dirt.
  • Belt drives do not require precise alignment of shaft and pulley.
  • Belt drives are relatively cheap and easy to maintain.

 

Disadvantages of Belt Drives

  • Some of the belts have low power transmitting capacity.
  • Belt drives cannot be used at extremely high speeds.
  • As compared to gear drives, belt drives have shorter life.
  • As compared to gear drives, belt drives occupy more space.
  • Belt drive is not a positive drive.

 

 Read More Articles: Brakes: Types of Brakes | Disc Brake: Construction, Working, Advantages and Disadvantages

No comments:

Post a comment