1. What is a Pulley Size Calculator When RPM Is Known?

Definition: This calculator determines the required diameter of a driven pulley based on the drive pulley diameter and their respective RPMs.

Purpose: It helps mechanical engineers, technicians, and DIYers properly size pulleys to achieve desired rotational speeds in belt-driven systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( D2 \) — Driven pulley diameter (inches)
• \( D1 \) — Drive pulley diameter (inches)
• \( RPM1 \) — Input (drive) rotational speed
• \( RPM2 \) — Output (driven) rotational speed

Explanation: The pulley diameters are inversely proportional to their rotational speeds - a larger driven pulley will rotate slower than the drive pulley.

3. Importance of Proper Pulley Sizing

Details: Correct pulley sizing ensures optimal power transmission, prevents belt slippage, and achieves desired machine speeds for efficient operation.

4. Using the Calculator

Tips: Enter the drive pulley diameter (D1) in inches, input RPM (RPM1), and desired output RPM (RPM2). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Can I use this for multiple pulley systems?
A: This calculates for a single pair of pulleys. For multiple pulleys, calculate each stage separately.

Q2: Does belt type affect the calculation?
A: The basic ratio remains the same, but belt type affects power transmission capacity and minimum pulley diameters.

Q3: What if I know D2 and need to find D1?
A: Simply rearrange the formula: \( D1 = D2 \times (RPM2/RPM1) \).

Q4: How precise do pulley diameters need to be?
A: Standard pulleys come in specific sizes - round your result to the nearest available size.

Q5: Does center distance between pulleys matter?
A: Center distance affects belt length and wrap angle but not the speed ratio calculation.