Belts provide an efficient load transfer between shafts on a wide variety of applications. They also perform special tasks such a speed ratio variation, power transmission in more than one plane, clutching, torque limiting, and shaft synchronization.

Compared with most forms of power transmission, belts often provide the best overall combination of design flexibility, low cost and maintenance, ease of drive assembly, and space savings.

Disadvantages on some applications may include the need to retension belts periodically to avoid slippage (note: overtensioning can damage bearings on pulley system), deterioration because of severe exposure to chemicals and lubricants, and the requirement that damaged belts must be replaced, rather than repaired. Although V-shaped belts are not recommended for drives with a fixed-center distance or in low-speed, high-torque applications, synchronous belts will often solve these design considerations.

Many OEM products use commercially available belts and sheaves or pulleys. This facilitates mass-produced designs, and allows OEM customers to obtain stock replacement parts easily and quickly from local distributors.

Some OEMs have belts made especially for their use. Many times the belt is actually a stock item, with a standard construction, but with a special private brand label. In other cases, a special construction belt will be developed for unique application needs such as clutching, temperature extremes, idler use, extremely high loads, or small-diameter drives.

Advanced application methods and years of experience from reputable belt manufacturers generally assure good performance without extensive OEM field testing. This is especially true where operating characteristics are predictable and the load and speed range is rather small such as on electric motors in combination with fans, pumps, conveyors, and so on. However, suppliers recommend a field test to assure proper belt performance when speeds, loads, or both vary significantly, or when customer operating practices are not accurately predicted.

The following section describes belt types and cross sections generally available at the OEM level and in the marketplace. Most manufacturers have special belt sections or constructions which are developed for special applications, or which have higher performance characteristics. Belt manufacturers also offer special assistance to OEMs with unique applications. See the sections on Mechanical Fixed and Adjustable-Speed Drives for a complete discussion.