1. What is Pulley Sizing For RPM?

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

Purpose: It helps mechanical engineers, technicians, and DIY enthusiasts properly size pulleys to achieve desired rotational speeds in machinery.

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 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 Proper Pulley Sizing

Details: Correct pulley sizing ensures optimal machine performance, prevents belt slippage, and maintains proper torque transmission in power transmission systems.

4. Using the Calculator

Tips: Enter the input RPM, drive pulley diameter, and driven pulley diameter. All values must be > 0. The calculator will determine the output RPM.

5. Frequently Asked Questions (FAQ)

Q1: What if I know the desired output RPM and need to find pulley size?
A: Rearrange the formula: \( D2 = D1 \times (RPM1 / RPM2) \) to calculate the required driven pulley diameter.

Q2: Does belt thickness affect the calculation?
A: For precise calculations, use the pitch diameter (center of belt thickness) rather than the outer pulley diameter.

Q3: How does this apply to multi-pulley systems?
A: For multiple pulleys, calculate each stage sequentially, using the output RPM of one stage as the input for the next.

Q4: What about belt slippage?
A: This formula assumes no slippage. In practice, allow 1-3% RPM reduction for potential slippage in V-belt drives.

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