How It Works
Roller Chain Power Transmission
Roller chains transmit power through positive engagement between chain links and sprocket teeth. Unlike belts, chains do not slip, providing precise speed ratios for power transmission.
Chain Pitch
The pitch is the distance between consecutive roller centers. ANSI chain numbers indicate pitch:
- ANSI 40 = 4/8" = 1/2" (12.7mm) pitch
- ANSI 60 = 6/8" = 3/4" (19.05mm) pitch
- The last digit indicates chain type: 0=standard, 5=lightweight
Sprocket Teeth and Speed Ratio
The speed ratio equals the ratio of sprocket teeth:
Speed Ratio = N2 / N1
Where N1 is driver teeth and N2 is driven teeth. A ratio of 3:1 means the driven shaft rotates at 1/3 the driver speed with 3x the torque.
Chain Length Formula
Chain length in pitches is calculated as:
L = 2C/p + (N1+N2)/2 + [(N2-N1)/(2*pi)]^2 * (p/C)
Where C = center distance, p = pitch, N1/N2 = teeth. Results are rounded to even number of pitches to avoid offset links.
Service Factors
Design power = Transmitted power x Service factor. Service factors account for:
- 1.0: Uniform load, smooth operation (fans, centrifugal pumps)
- 1.2-1.4: Light shock, moderate load variation (conveyors)
- 1.4-1.7: Heavy shock, frequent starts (crushers, reciprocating)
- 1.7-2.0: Severe duty (rock crushers, heavy presses)
Minimum Sprocket Teeth
Small sprockets cause chordal action - speed variation as chain engages teeth:
- 9 teeth: Absolute minimum (rough operation)
- 12 teeth: Low-speed, moderate duty
- 17 teeth: Recommended minimum for smooth operation
- 21+ teeth: High-speed applications
Chordal variation = 100 * (1 - cos(180/N))%
Quick-Select Applications
Roller Chain Drive Calculator
Calculate chain length, speed ratio, chain velocity, tension, and verify sprocket sizing for roller chain power transmission.
Calculate exact chain length needed for a given configuration.
Chain Length Formula:
L = 2C/p + (N1+N2)/2 + [(N2-N1)/(2*pi)]^2 * (p/C)
L = length in pitches, C = center distance, p = pitch, N = teeth
ANSI roller chain specifications. Click a row to select that chain.
| ANSI | Pitch | Tensile (kN) | Weight (kg/m) | HP @ 1000 RPM |
|---|
Results
Design Guidelines
| Parameter | Recommended | Notes |
|---|---|---|
| Min teeth (driver) | 17-21 | Reduces chordal action |
| Max speed ratio | 7:1 | Single stage limit |
| Chain speed | < 20 m/s | Standard lubrication |
| Center distance | 30-50 pitches | Optimal range |
| Safety factor | 7-10 | Normal service |
| Wrap angle | > 120° | On small sprocket |
Key Formulas
Pitch Diameter:
PD = p / sin(180/N)
Chain Velocity:
v = p * N * RPM / 60000
Chain Tension:
T = P / v
p = pitch (mm), N = teeth, P = power (W), v = velocity (m/s)