1. What is the Pulley Size RPM Formula?

Definition: This calculator determines the output RPM of a driven pulley based on input RPM and pulley diameters.

Purpose: It helps mechanical engineers, technicians, and DIYers design and troubleshoot pulley systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( RPM2 \) — Output RPM of driven pulley
• \( RPM1 \) — Input RPM of drive pulley
• \( D1 \) — Diameter of drive pulley (inches)
• \( D2 \) — Diameter of driven pulley (inches)

Explanation: The output RPM changes inversely with the ratio of pulley diameters - smaller driven pulleys increase speed, larger ones decrease speed.

3. Importance of Pulley RPM Calculation

Details: Proper RPM calculation ensures equipment operates at designed speeds, prevents mechanical stress, and maintains efficiency.

4. Using the Calculator

Tips: Enter the input RPM, drive pulley diameter, and driven pulley diameter. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Does belt thickness affect the calculation?
A: For precision, measure pulley diameter to the belt's pitch line, especially with V-belts.

Q2: What if I have multiple pulleys?
A: Calculate stage by stage - the output of one becomes the input for the next.

Q3: How does this relate to torque?
A: While RPM increases with smaller driven pulleys, torque decreases proportionally.

Q4: Can I use this for metric measurements?
A: Yes, as long as both diameters use the same units (mm, cm, etc.).

Q5: What about belt slippage?
A: This formula assumes no slippage. For critical applications, account for 1-3% slippage.