Calculator
Example Data Table
| Use Case | Front Teeth | Rear Teeth | Center Distance | Power | Static Tension |
|---|---|---|---|---|---|
| City bicycle | 50 | 22 | 460 mm | 250 W | 400 N |
| Commuter load | 55 | 24 | 485 mm | 350 W | 450 N |
| Light test rig | 46 | 28 | 430 mm | 180 W | 330 N |
Formula Used
Pitch diameter: D = teeth × pitch ÷ π
Belt pitch length: L = 2C + π(D1 + D2) ÷ 2 + (D1 - D2)² ÷ 4C
Belt teeth: teeth = pitch length ÷ pitch
Speed ratio: ratio = front teeth ÷ rear teeth
Crank torque: torque = power ÷ angular speed
Belt force: force = torque ÷ front pitch radius
Tensile stress: stress = tension ÷ belt cross section
Composite mass: mass = belt volume × density
Carbon mass: carbon mass = total mass × carbon fraction
How to Use This Calculator
Enter the sprocket teeth first. Add the center distance between the two shafts. Keep the pitch value equal to the belt system you are reviewing. Then enter cadence, power, and static tension.
Add belt width, thickness, density, and carbon fraction. These values help estimate stress and material mass. Press Calculate to see the result above the form. Use the CSV or PDF button to save a report.
This tool is for planning and comparison. Final belt choice should follow the correct product chart, frame limits, and manufacturer installation guidance.
Carbon Belt Drive Planning Guide
Why Belt Geometry Matters
A carbon belt drive needs careful geometry. The belt cannot be shortened like a chain. The center distance, sprocket teeth, and pitch must agree. A small mismatch can affect tension. It can also change bearing load. This calculator gives a first planning check. It estimates the pitch length and rounds it to whole belt teeth. That makes comparison easier during early design.
Material View
The chemistry side is useful for composite review. A carbon drive belt is a composite part. It contains strong carbon reinforcement and flexible polymer material. The carbon fraction field estimates how much of the belt mass is reinforcement. The remaining mass is treated as polymer and other material. This does not replace a laboratory test. It helps compare concepts with the same assumptions.
Tension and Stress
Belt tension affects grip, load transfer, and bearing life. Low tension can cause tooth jump. Very high tension can add stress to the frame and bearings. The calculator estimates tight side and slack side tension from power and torque. It also divides tension by belt area. The result is shown as stress in MPa. This gives a quick way to compare belt width and expected load.
Power and Efficiency
Efficiency changes the useful output power. A small loss becomes important with long use. The calculator estimates output power and yearly loss energy. These values help compare clean drive layouts, test rigs, and commuter builds. They also help document assumptions before choosing parts.
Practical Notes
Use measured values whenever possible. Frame flex, alignment, pulley wear, and temperature can change real performance. Check clearance around the belt path. Review pulley engagement. Keep the belt clean and aligned. Use this calculator as a design worksheet, not as a final approval method. Always confirm final sizing with the correct belt and sprocket data.
FAQs
1. What does this calculator estimate?
It estimates belt length, belt teeth, speed ratio, torque, belt force, stress, mass, carbon content, efficiency loss, and yearly energy use.
2. Is this an official sizing tool?
No. It is a planning calculator. Use official belt charts and installation guides before selecting final parts.
3. Why is belt length rounded?
Carbon belt systems use whole tooth counts. The calculator rounds the estimated pitch length to the nearest whole belt tooth.
4. What pitch value should I enter?
Enter the pitch that matches the belt system being reviewed. If unsure, check the belt specification before calculating.
5. Why is carbon mass estimated?
The estimate helps compare composite material assumptions. It uses belt volume, density, and carbon mass fraction.
6. What does slack side tension mean?
Slack side tension is the lower tension side during power transfer. A negative value means the setup needs review.
7. Can this calculator be used for motorcycles?
It can compare basic geometry, but high power systems need detailed engineering checks and verified product data.
8. Why include efficiency?
Efficiency shows useful output power and estimated loss. It helps compare drive layouts over weekly and yearly use.