Speed Limit Evaluations For Belt Drive Hardware

Rotational speed limitations for belt drive hardware is based on material composition and balancing standards.  The traditional industry accepted speed limitations for gray cast iron material and static balancing is 6500 ft/min.  For speeds higher than this, materials such as ductile iron, steel and aluminum may be considered, but are typically available on a made-to-order basis at higher cost.  Dynamic balancing is also recommended for operating speeds above the 6500 ft/min limit to prevent excessive vibrations.

In more recent years, the Mechanical Power Transmission Association (MPTA) published the MPTA-B2C - Standard Practice For Sheave/Pulley Balancing Standard based on International Standards Organization (ISO) and American Gear Manufacturing Association (AGMA) balancing standards.  This MPTA standard provides a more accurate and objective evaluation of whether static or dynamic balancing is required. 

The MPTA-B2C balancing standard includes a simple maximum static balancing speed calculation based on diameter and face width.  When operating speeds are not known, static and dynamic balancing recommendations are also provided based on material and hardware weight.

Gates Design Flex Pro drive selection software utilizes the MPTA-B2C balancing calculation.  This may prevent the selection of some drive combinations that would otherwise operate below the traditional 6500 ft/min limit for gray cast iron and static balancing.  Warning notes indicating a need for dynamic balancing at operating speeds below 6500 ft/min may also appear due to this.

In summary, while the traditional industry accepted 6500 ft/min limit for gray cast iron materials and static balancing is a reasonable guide, the MPTA-B2C balancing standard provides a more accurate and objective evaluation of the need for dynamic balancing based on diameter and width.  This calculation is utilized in Gates Design Flex Pro software and may limit drive selections that would otherwise appear to be acceptable.

For questions or additional information, feel free to contact Product Application Engineering at (303) 744-5800 or ptpasupport@gates.com.

Minimum Pulley Diameters: How small is too small

As technology advances and systems get smaller and smaller so too does the desire for smaller drive pulleys.  Though size can be decreased, it is important to ensure that none of the drive pulleys fall below the minimum recommended diameters given this can result in shortened belt life, premature belt wear, and overall poor drive performance. Below are the minimum pulley sizes for both V-belt sheaves and Synchronous sprockets.

It is still important however to check with the motor or gearbox manufacturers to ensure that these small pulley sizes do not result in excessive shaft load or fall below any NEMA (National Electric Motor Association) standards which could prove to be detrimental to the drive components. For any additional questions feel free to contact us at ptpasupport@gates.com or 303-744-5800.