Pulley Design and Pulley Construction

Both Pulley Diameter and Groove Design are crucial factors in the design of mechanical cable assemblies, cable assemblies, cable lanyards, custom cable assemblies, wire rope assemblies, and pulleys.

Flexible cable constructions are typically used in the design of pulley systems. Avoid using pulleys with smaller diameters than required, or the life of the cable will be reduced.

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The Groove Design can be calculated by adding: 1.5 X Diameter Tolerance (including tolerance of bare cable or coating) plus the Maximum Cable Diameter.

Recommended Pulley Diameter to Cable Diameter ratios are listed below.

Pulley to Cable Ratio:

Results represent Pulley Thread / Root Diameter TO Nominal Bare / Coated Cable Diameter.

3x7 7x7 7x19
Preferred Minimum 50:1 42:1 24:1
Absolute Minimum 40:1 30:1 18:1

Pulley Construction:

Pulleys are most commonly made from aluminum, steel, nylon, and acetal. Some options to consider in the construction of a pulley are sintered bronze bushings, an open or closed ball, or roller bearings. The corrosion resistance and RPMs are also factors in the construction of a pulley system.

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Here is a chart describing some features and uses of common pulleys and bearings:

Pulley Construction:

Plain metallic or Thermoplastic Pulleys Metallic or Plastic Pulleys (Sintered bronze bearings) Open free turning or precision closed (Lubricated ball bearings)
Features Lowest cost, light loads, low RPM Self lubricated bearings, low cost durable, higher load, shock resistance Minimum friction,precise tracking, medium load, high RPM
Common Uses Low frequency drive and lift cable applications Medium RPM, load drive, index, and lift cable systems High speed drive and index cable systems