V-Belt Drive.
Calculate belt length, speed ratio, belt linear speed and power capacity for V-belt drives. A/B/C/D/E sections per ISO 4184 / IS 2494. Includes correction factors for arc of contact and length.
v = π·D₁·N₁ / 60000 (m/s)
α = π − 2·sin⁻¹((D₂−D₁)/(2C))
T₁/T₂ = e^(μ·α/sin(β/2)) where β = 38° groove
V-belt section reference (IS 2494)
| Section | Top width | Thickness | Min D pulley | Power range (kW) |
|---|---|---|---|---|
| Z | 10 mm | 6 mm | 50 mm | 0.4 – 4 |
| A | 13 mm | 8 mm | 75 mm | 0.75 – 7.5 |
| B | 17 mm | 11 mm | 125 mm | 2 – 25 |
| C | 22 mm | 14 mm | 200 mm | 5 – 75 |
| D | 32 mm | 19 mm | 355 mm | 20 – 250 |
| E | 38 mm | 23 mm | 500 mm | 50 – 500+ |
V-Belt Length Calculation
V-belt drives transmit power between pulleys via friction in a wedge groove. Belt length must match the available stock sizes; getting it within 1-2% is usually sufficient because of tensioner adjustment.
Belt Length Formula
L = 2C + π(D₁ + D₂)/2 + (D₂ − D₁)²/(4C)
Where L = belt pitch length, C = center distance, D₁ = small pulley pitch diameter, D₂ = large pulley pitch diameter.
Worked Example
Small pulley 100 mm, large pulley 250 mm, center distance 400 mm:
- L = 2 × 400 + π × (100+250)/2 + (250-100)²/(4 × 400)
- L = 800 + 549.8 + 14.1 = 1364 mm
- Round up to nearest stock belt: SPA 1400 or A-section 55"
Wrap Angle Warning
The arc of contact on the smaller pulley should be ≥ 120° for adequate friction:
- θ_small = 180° − 2 × arcsin((D₂−D₁)/(2C))
- If <120°, use idler pulley or increase center distance
V-Belt Types
- Classical (A, B, C, D): imperial, general purpose
- Narrow (SPA, SPB, SPC, SPZ): metric, higher power density
- Cogged (AX, BX, CX): better small-pulley flexibility
- Banded: multiple belts joined for high-shock applications
Tensioning
Proper tension is critical. Too loose → slip and burn. Too tight → bearing damage. Use a tension gauge or measure deflection: 1% of span at recommended force.
Related Tools
For motor sizing, see Motor HP Calculator. For gear-drive alternatives, Gear Calculator.