1. What is a Pulley Speed Calculator?

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

Purpose: It helps mechanical engineers, technicians, and DIYers design and troubleshoot belt-driven systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

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

3. Importance of Pulley Speed Calculation

Details: Proper pulley speed calculation ensures optimal machine performance, prevents component damage, and helps achieve desired operational speeds.

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 have multiple pulleys in my system?
A: Calculate each stage sequentially, using the output RPM from one pair as the input RPM for the next.

Q2: Does belt thickness affect the calculation?
A: For precision, measure pulley diameter at the belt's pitch line, but for most applications, outer diameter is sufficient.

Q3: How does this relate to torque?
A: While this calculates speed, torque is inversely proportional to speed ratio (ignoring losses).

Q4: What about belt slip?
A: This calculation assumes no slip. In practice, allow for 1-3% speed reduction due to slip.

Q5: Can I use this for metric measurements?
A: Yes, as long as both diameters use the same units (mm, cm, etc.), the ratio remains valid.