Belt drives – toothed belts, V-belts and belt pulleys

Belt drives are used for power transmission between two or more shafts. Via belt drives, step-up and step-down gear ratios can be achieved by means of different pulley diameters.

Operating principle

For belt drives, a principal distinction is made between form-fit drives which use toothed belts and friction-fit drives which use V-belts and ribbed V-belts.

Toothed belts – form-fit belt drives

The drive power and motion is transmitted via the teeth of the belt interlocking in a form-fit manner with the gaps between the teeth of the toothed lock washer. Toothed belt drives ensure a form-fit, absolutely synchronous and slip-free power transmission. Toothed belt drives are maintenance-free. Their efficiency is around 98%.

Structure of toothed belts

The cords are crucial for the transmission of power by the toothed belts.

Depending on the type and application, different types of cords are available:

  • Steel and/or reinforced steel
  • Fibreglass / Aramid
  • Highly flexible
  • Stainless steel
  • Carbon

The cords are generally sheathed in polychloroprene or polyurethane (PU). Depending on the belt type, the material is sheathed in different fabrics or coatings. This makes the belt more robust, modifies its operating characteristics, or reduces the friction factor.

Depending on the application, different tooth shapes are available. For belt drives in linear applications and/or for transport applications, belts with flat teeth (T-profile, AT-profile) are usually used.

For rotating belts for power transmission, round teeth are usually used. These teeth mesh optimally with the toothed belt pulley and provide for reliable power transmission.

V-belts and ribbed V-belts – friction-fit belt drives

V-belt and ribbed V-belt drives transmit the torque in a friction-fit manner with an efficiency of approximately 95%. In order to ensure a friction fit, a higher preloading is required compared to the toothed belts. This means higher radial forces and hence a greater load on the motor bearing. This is to be taken into account during the dimensioning.

When selecting a suitable toothed belt, not only must the physical performance data (power to be transmitted, mass to be transported, speeds, accelerations etc.) be taken into account, but also the ambient conditions, the installation situation (minimum pulley diameter, guide pulleys) and many other factors.


Our specialists would be glad to assist you with the dimensioning of your belt drive.

Lenze Selection Austria