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.
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