V-Belt Pulley Selection Guide

V-Belt Pulley Selection Guide

Choosing the right pulleys is as important as selecting the correct belt. This guide covers pulley sizing, matching, and selection for V-belt drives.

Pulley Groove Profiles

V-belt pulleys (sheaves) have grooves that match specific belt cross-sections:

Belt Type Groove Angle Min. Pulley Diameter
3L 30° - 34° 1.5"
4L / A 30° - 38° 2.5" (3" recommended)
5L / B 30° - 38° 4" (5.4" recommended)
AX / BX (cogged) 38° - 40° Smaller than standard

Why Minimum Pulley Size Matters

Using pulleys smaller than the recommended minimum causes:

  • Excessive belt bending stress
  • Heat buildup
  • Shortened belt life
  • Reduced efficiency

Tip: Use cogged belts (AX, BX) when you must use small pulleys.

Speed Ratio Calculation

The speed ratio between pulleys is determined by their diameters:

Driven Speed = Driver Speed × (Driver Diameter ÷ Driven Diameter)

Example: 1800 RPM motor with 4" driver pulley and 8" driven pulley:

Driven Speed = 1800 × (4 ÷ 8) = 900 RPM

Pulley Alignment

Proper pulley alignment is critical for belt life. Misalignment causes:

  • Uneven belt wear (one side wears faster)
  • Belt tracking off pulley
  • Increased noise
  • Shortened belt and bearing life

Checking Alignment

  1. Place a straightedge across both pulley faces
  2. The straightedge should contact both pulleys evenly
  3. Check both angular alignment (pulleys parallel) and offset (pulleys in same plane)

When to Replace Pulleys

  • 🔴 Groove walls worn shiny or smooth
  • 🔴 Groove profile worn (belt rides too deep)
  • 🔴 Cracks or damage visible
  • 🔴 Pulley wobbles on shaft
  • 🔴 New belt slips despite proper tension

Worn pulleys destroy new belts quickly. Always inspect pulleys when replacing belts.

Shop V-belts for your pulley system.