1. What is a Critical Speed Calculator?

Definition: This calculator determines the critical speed (Nc) of a rotating shaft based on gravitational acceleration and shaft deflection.

Purpose: It helps mechanical engineers and designers avoid resonance in rotating systems by calculating the speed at which vibration amplitudes peak.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( N_c \) — Critical speed (revolutions per minute)
• \( g \) — Gravitational acceleration (9.81 m/s²)
• \( \delta \) — Static deflection of the shaft (meters)

Explanation: The formula relates the natural frequency of the shaft to its static deflection under gravity.

3. Importance of Critical Speed Calculation

Details: Operating near critical speed can cause excessive vibrations leading to mechanical failure. This calculation helps ensure safe operating ranges.

4. Using the Calculator

Tips: Enter the gravitational acceleration (default 9.81 m/s²) and the measured static deflection of the shaft in meters. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What units should deflection be measured in?
A: Deflection should be in meters for this calculator. Convert from mm by dividing by 1000.

Q2: Why is 30/π part of the formula?
A: This converts from radians per second to revolutions per minute (rpm).

Q3: What affects shaft deflection?
A: Material stiffness, shaft length, diameter, and load distribution all affect deflection.

Q4: How close can I operate to critical speed?
A: Typically, operate below 70% or above 130% of critical speed to avoid resonance.

Q5: Does this account for multiple critical speeds?
A: No, this calculates only the first critical speed. Complex systems may have multiple critical speeds.