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Choosing the right Transmission Belt

Belts are mechanical elements used for power transmission without phase shift. They are loops of flexible materials used to mechanically connect several rotating shafts, most often parallel. Belts can be used as a transmission element, to efficiently transmit power or movement.

  • How to choose a transmission belt?

    In order to make the right choice, you will need to know the type of section and the belt dimensions. In this guide you will find the different sections available on the market, with their advantages and disadvantages.

    The type of belt you should use depends on the type of application:

    • torque to be transmitted

    • rotational speed

    • center distance

    • reduction ratio

    • temperature and lubrication conditions

Why choose a V-belt?

These are the most commonly used belts for power transmission. At the same level of tension, they transmit higher power than flat belts. They are used, for example, in variable-speed drives. They offer the best combinations of traction, speed, bearing load and service life.


The V-shaped section of the belt follows a groove in the pulley, which prevents the belt from slipping and improves torque transmission.

It is less wide than a flat belt and therefore takes up less space.

It doesn’t need to be as taut.

The optimal speed range is between 300 and 2,130 m/min.

For high power requirements, two or more V-belts can be assembled side by side in an arrangement called a “multiple belt drive.”

V-belts, also called trapezoidal belts, can be made of rubber or polymer without reinforcement, or they can have fibers incorporated into the rubber or polymer to increase strength. These fibres can be made of textile material (such as cotton), polyamide (such as nylon), polyester or, for greater strength, steel or aramid (such as Kevlar).

When a seamless belt does not meet the requirements of the application, articulated V-belts can be used. Most models offer the same power and speed as endless belts of the same size and do not require special pulleys to operate. They are easy to install and have a higher environmental resistance than rubber belts. They are also adjustable in length if you choose to remove the links.

V-Belt Construction

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An entire v-belt can be regarded as a composite material composed of different types of rubber and reinforcements. In its usual application, a v-belt is subjected to combined tensile and compressive stresses. The top side of a v-belt is subjected to a tensile force directed longitudinally, while the bottom side is compressed due to the compression against the grooves and bending as a belt segment passes the pulley. Moreover, a different type of material is also needed at the surface of the belt. Ideal material for the surface must have a high coefficient of friction and increased wear resistance.


V-belts are generally composed of the following parts.

Fabric Cover: This part of the v-belt has higher abrasion and contamination resistance. The cover protects the internals of the v-belt from harmful external effects such as a chemical attack, corrosion, and temperature. The materials used for covers are patented by different manufacturers. An example of these materials is aramid or Kevlar fiber.

Tension Cord or Member: Tension cords are embedded into the rubber compound creating a composite structure. The tension cord or member is the main power transmitting component. The cords are positioned at the pitch diameter of the belt cross-section to increase its tensile strength. The tension cord is usually made of polyester, steel, or aramid fibers. In some v-belt constructions, the tension cord is bonded into the core by an adhesion rubber.

Elastomer Core: The elastomer core holds the components together and gives the v-belt its trapezium cross-section. This is usually made from an elastomer with good shock resistance, high flexural strength, and excellent temperature stability. Common elastomers used are neoprene, EPDM, and polyurethane. In some designs, the elastomer core is divided into two sections separated by the tension cord. Above the tension cord is the top cushion rubber while below is the compression rubber. These two sections are made from different types of rubber because of the distinct type of stresses experienced.

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