Enter Belt Drive Data
Example Data Table
| Item | Example Value | Meaning |
|---|---|---|
| Driver pulley | 150 mm | Input pulley diameter |
| Driven pulley | 300 mm | Output pulley diameter |
| Center distance | 700 mm | Distance between shaft centers |
| Driver speed | 1440 RPM | Motor or input shaft speed |
| Total slip | 2% | Estimated belt and pulley slip |
Formula Used
Pitch diameter = pulley diameter + belt thickness.
Open belt length = 2C + π(D + d) / 2 + (D - d)² / 4C.
Crossed belt length = 2C + π(D + d) / 2 + (D + d)² / 4C.
Driven RPM = driver RPM × driver pitch diameter ÷ driven pitch diameter × (1 - slip ÷ 100).
Belt speed = π × driver pitch diameter × driver RPM ÷ 60.
Power = (tight side tension - slack side tension) × belt speed.
Torque = net driving tension × driver pitch radius.
Tension capacity ratio = e raised to μθ ÷ sin(groove angle ÷ 2).
How to Use This Calculator
Select the unit used by your pulley and center distance values.
Choose open drive for parallel belt motion.
Choose crossed drive when shafts rotate in opposite directions.
Enter both pulley diameters and center distance.
Add belt thickness to estimate pitch line length.
Enter driver RPM and expected slip percentage.
Add belt tensions if you want power and torque output.
Press Calculate to view the results above the form.
Use CSV or PDF buttons to save the calculation.
Linear Belt Drive Calculation Guide
What This Tool Measures
A linear belt drive transfers motion between two pulleys. It can also move a belt surface at a useful linear speed. This calculator estimates belt length, output speed, belt velocity, wrap angle, power, torque, and traction margin. It uses pitch diameter, not only outside pulley diameter. Belt thickness can shift the working line of motion.
Why Pitch Diameter Matters
The pitch line is the path followed by the belt body during motion. A thicker belt rides slightly above the pulley face. Because of that, the effective diameter can be larger than the measured pulley diameter. This change affects belt length. It also affects output RPM and surface speed. Small changes may matter in accurate machines.
Speed and Ratio
Speed ratio depends on the driver and driven pitch diameters. A small driver and large driven pulley reduce output speed. A large driver and small driven pulley increase output speed. Slip lowers the final driven RPM. This is why the calculator includes a slip field. Use measured slip when available.
Belt Length and Center Distance
Belt length depends on pulley sizes and shaft spacing. Open belt drives are common for shafts rotating in the same direction. Crossed drives reverse the rotation direction. They usually need more belt length. They also create different contact geometry. The center distance must be suitable for the selected drive type.
Power and Tension
Power depends on belt speed and net driving tension. Net tension is the tight side tension minus slack side tension. A higher speed can transmit more power with the same net tension. A higher tension difference also increases power. The calculator also estimates driver torque from pitch radius and net tension.
Traction Check
Belt drives can slip when tension demand exceeds friction capacity. The friction check compares actual tension ratio with theoretical capacity. The result is a guide, not a final design approval. Real belts also depend on material, wear, alignment, temperature, and pulley condition. Always confirm important designs with manufacturer data.
FAQs
What is a linear belt drive?
A linear belt drive uses pulleys and a belt to transfer rotary motion. The moving belt surface can also provide useful linear travel.
What is belt pitch diameter?
Pitch diameter is the effective working diameter of the pulley and belt. This calculator estimates it by adding belt thickness to pulley diameter.
Why does slip reduce driven RPM?
Slip means the belt does not perfectly follow pulley motion. The driven pulley receives slightly less motion, so its final RPM becomes lower.
What is open belt drive?
An open belt drive connects two pulleys without crossing the belt. It is usually used when shafts must rotate in the same direction.
What is crossed belt drive?
A crossed belt drive twists the belt between pulleys. It is commonly used when the driven shaft must rotate opposite the driver shaft.
How is belt speed calculated?
Belt speed is calculated from driver pitch diameter and driver RPM. It equals pulley circumference multiplied by revolutions per second.
Can this calculator estimate power?
Yes. Enter tight side and slack side tension. The calculator multiplies net tension by belt speed to estimate transmitted power.
Is the traction status final?
No. It is a quick check based on friction and wrap angle. Final selection should use belt maker data and safety factors.