1. What is a Pulley RPM Calculator?

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

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

Explanation: The speed ratio is inversely proportional to the pulley diameter ratio. A larger driven pulley will rotate slower than the drive pulley.

3. Importance of Pulley RPM Calculation

Details: Proper RPM calculation ensures equipment operates at designed speeds, prevents motor overload, and maintains system 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: What if I know RPM2 and need to find D1 or D2?
A: Rearrange the formula: \( D1 = \frac{RPM2 \times D2}{RPM1} \) or \( D2 = \frac{RPM1 \times D1}{RPM2} \).

Q2: Does belt thickness affect the calculation?
A: For precision, measure pulley diameter at the belt's pitch line (center of belt thickness).

Q3: Can I use this for multiple pulley systems?
A: Yes, calculate sequentially from driver to final driven pulley.

Q4: What about belt slip?
A: This assumes no slip. For real-world applications, add 2-5% to calculated RPM2.

Q5: How does this relate to torque?
A: Torque is inversely proportional to RPM - as RPM decreases, torque increases, and vice versa.