Belt Drive Calculator
Calculate speed ratio and belt length for a two-pulley belt drive system.
Driven Pulley Speed
875.0 RPM
Driven Pulley Speed vs Driver Pulley Diameter (D1)
Formula
## Belt Drive Speed and Belt Length Belt drives transmit power between shafts using friction between a belt and pulleys. ### Speed Ratio **N2 = N1 x D1 / D2** (assuming no belt slip) ### Belt Length (open drive) **L = 2C + pi(D1 + D2)/2 + (D2 - D1)^2 / (4C)** where C is the shaft centre distance. This approximate formula works well for standard configurations.
Exemplo Resolvido
150 mm driver at 1750 RPM driving a 300 mm pulley, centres 500 mm apart.
- 01Speed ratio = 300/150 = 2.0
- 02Driven speed = 1750 / 2.0 = 875 RPM
- 03Belt length = 2x500 + pi(150+300)/2 + (300-150)^2/(4x500)
- 04L = 1000 + 706.9 + 11.25 = 1718 mm
Perguntas Frequentes
How much belt slip should I expect?
Well-tensioned V-belts typically have 1-3% slip. Timing (synchronous) belts have zero slip. Flat belts may slip 2-5%. Account for slip by reducing the calculated driven speed accordingly.
How do I select a standard belt size?
Calculate the required belt length, then choose the next available standard size from the manufacturer. Standard V-belt lengths come in set increments (typically 25 mm steps for industrial belts).
What determines the centre distance?
Minimum centre distance should be at least the larger pulley diameter. Maximum is limited by belt sag and tension requirements. Ideal range: C = 0.7 to 2.0 times the sum of pulley diameters.
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