1. What is a Motor Pulley RPM Calculator?

Definition: This calculator determines the rotational speed (RPM) of a motor pulley based on surface speed (SFM) and diameter.

Purpose: It helps mechanical engineers, technicians, and DIYers properly size pulleys and belts for motor systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( RPM \) — Revolutions per minute
• \( SFM \) — Surface feet per minute
• \( D \) — Diameter in inches
• \( 3.82 \) — Conversion constant (12/π)

Explanation: The formula converts linear surface speed to rotational speed based on the pulley's circumference.

3. Importance of RPM Calculation

Details: Proper RPM calculation ensures correct power transmission, prevents belt slippage, and maintains optimal motor performance.

4. Using the Calculator

Tips: Enter the surface speed in feet per minute and the pulley diameter in inches. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is SFM in motor systems?
A: Surface Feet per Minute measures how fast a point on the pulley's circumference moves linearly.

Q2: Why is 3.82 used in the formula?
A: It's the conversion factor from feet to inches (12) divided by π (3.1416), approximately 12/π = 3.82.

Q3: How does diameter affect RPM?
A: Larger diameters result in lower RPM for the same SFM, as the circumference increases.

Q4: What's a typical SFM for belt drives?
A: Common ranges are 3,000-6,000 SFM for standard V-belts, but consult manufacturer specifications.

Q5: Can I use this for other rotating components?
A: Yes, the formula works for any rotating cylindrical component when you know SFM and diameter.