Belt Drive - Definition, Types, Advantages and Disadvantages

By Mohit Uniyal|Updated : August 20th, 2022

The belt drive is an important part of the spinning wheel's invention. In 15 BC, the Han Dynasty philosopher, poet, and politician Yang Xiong (53–18 BC) first referenced the mechanical belt drive, which was used for a quilling machine that coiled silk threads onto bobbins for weavers' shuttles, in his manuscript, the Dictionary of Local Expressions. The belt drive was not only utilized in textile technologies, but it was also used in the 1st century AD hydraulic-powered bellows.

Before we detail belt drives, let's first learn what belts are. A belt is a flexible material loop that is used to mechanically connect two or more rotating shafts, typically in parallel. Belts can be used to provide motion, efficiently transmit power, or track relative movement. Belts are wrapped around pulleys with a twist between them, and the shafts do not have to be parallel. In a two-pulley arrangement, the belt can drive the pulleys normally in one direction (the same if the shafts are parallel), or it can be crossed, reversing the direction of the driven shaft (the opposite direction to the driver if on parallel shafts).

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What is Belt Drive?

A belt drive is a frictional drive that uses pulleys and an elastic belt to transmit power between two or more shafts. It is usually driven by friction, although it can also be a positive drive. It can function at various ranges of speed and power needs. It's also really effective. When it comes to cost, a belt drive is substantially cheaper than gear and chain drives. It is less expensive to install and maintain. When compared to chain-drive sprockets, belt drive sheaves or pulleys are less likely to wear out over time.

Power is transmitted from the driver pulley to the belt and from the belt to the driven pulley with the help of friction. The power transmitted by belt drive depends upon friction between the belt and pulley surface. Once the limiting value is exceeded, slipping of the belt occurs.

Types of Belts

Belt designs, like belt drives, have been customized for specific needs. In different scenarios, each of them has an advantage over the others. The following five are the most common belt types used in belt drives.

  • Round belt
  • Flat belt
  • V-belt
  • Toothed belt
  • Link-belt

Round Belt Drive

Round belts have a circular cross-section and are designed to fit into U or V-shaped pulley grooves. round belts are ideal for applications where belts are expected to twist and turn a lot while contacting several pulleys. These belts may transmit power and provide friction from any region of their round surface by their very nature. Other advantages of round belts include:

  • Available in different sizes, colors, and textures
  • There is no fraying.
  • Economical
  • Strong and long-lasting
  • Cleaning is simple.
  • Fit different pulley shapes
  • Non-marking
  • Can be strengthened for added durability
  • Abrasion resistance and UV resistance can be enhanced as necessary.

Flat Belt Drive

One of the most prevalent types of industrial belts are flat belts. The rectangular cross-section of these belts allows them to operate by resting on top of flat pulleys. Depending on the design, they transmit power from one or both sides. Flat belts were the first application of a leather belt. However, as new materials such as rubber and synthetic polymers have been discovered, leather belts have decreased.

Flat belts have the following advantages:

  • At high belt speeds, a flat belt can deliver significant power.
  • Operation with minimal noise
  • High efficiency (up to 98%)
  • Because of the narrow bending cross-section, there is less bending loss.
  • High flexibility
  • No need for groove
  • long service life due to their ability to handle dust and filth.
  • It can be reinforced for increased strength.

V-belt Drive

Flat belts aren't ideal for applications with short distances between pulleys. V-belts have mainly taken their place in these applications. V-belts are, in fact, the most popular belt type nowadays. The cross-section of a V belt is trapezoidal (V-shaped), and it fits into a corresponding groove on pulleys and sheaves. V-belt drives can transmit more power for the same dimensions because they have a wider contact surface between the pulley and the belt section (bottom + 2 sides).

The following are some key characteristics of V belts:

  • Available in a broad range of sizes, strengths, and materials,
  • high power transmission capacity.
  • Low cost
  • Installation is simple and inexpensive.
  • The arrangement is compact.
  • Due to the wedging effect with pulleys, flat belts have a lower efficiency than flat belts.

Toothed Belt Drive

Although flat, round, and V belts are excellent at transferring motion, they do have some drawbacks. Belt slip, for example, can not be eliminated in any of them. We must employ toothed belts in instances where there is no room for slippage. A toothed belt is a positive transfer belt that transfers power without friction. It delivers forces through teeth in the same way that chain or gear drives do, but with far less noise and no need for excessive lubrication. As a result, these belts are often referred to as synchronous belts or timing belts. They are often used to power camshafts in vehicles and motorcycle engines.

A link belt is a form of a belt that is made up of several individual links. To adjust the length of the belt, these links can be attached and detached as needed. Polyurethane linkages are commonly used, with a multilayer woven polyester fabric for reinforcement. Link belts are similar to endless belts in that they do not require special pulleys to operate. They have the same power and speed ratings as endless belts of similar size. Because the machine does not need to be disassembled, it is simple and quick to install.

Link belts are more expensive than other options, limiting their use in budget-conscious situations. However, they do have superior vibration dampening properties and are far more resistant to external variables than rubber belts.

Advantages and Disadvantages of Belt Drives

Advantages of Belt Drives

Belt drives offer the following advantages compared with other types of drives:

(i) They can be used for power transmission between the axes of driving and driven shafts having considerable distances between them.

(ii) The belt drive operation is smooth and silent.

(iii) Simple design and low initial cost.

Disadvantages of Belt Drives

(i) Have large dimensions and thus occupy space.

(ii) The velocity ratio is not constant due to belt slip.

(iii) They impose heavy loads on shafts and bearings.

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FAQs on Belt Drive

  • Power transmitted by belt drive is because of friction only. The belt drive system can be employed for shafts with a long center-to-center distance. Friction between the pulley surface and the belt surface should be as high as possible for optimal transmission.

  • Power transmitted by belt drives is due to friction between belt and pulley. 

    The condition for Maximum power transmitted by the belt is

    T = 3Tc

    Where,

    T = Tension in the belt

    Tc = Centrifugal tension

  • Creep in belt drive is due to the belt's elastic properties, whereas conventional slip is caused by a lack of frictional grip between the belt and the pulley. However, both creep and slip have the effect of reducing the speed ratio and hence power transmission. Creep in belt drive is due to the following factors-

    • Material of the pulley
    • Material of the belt
    • Larger driver pulley
    • Inconsistent contractions and extensions.
  • A belt drive is a pair of pulleys connected by an encircling flexible belt (band) that can transmit and alter rotary motion from one shaft to the other in machinery. Most belt drives are made out of flat leather, rubber, or fabric belts that run on cylindrical pulleys or V-shaped cross-section belts that run on grooved pulleys.

  • A belt's main purpose is to transfer power (rotary energy) from one source to another. When transferring rotational motion, a pulley with a groove around its diameter allows a belt to pass smoothly through it.

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