1. What is a Shaft Critical Speed Calculator?

Definition: This calculator determines the critical speed of a rotating shaft, which is the speed at which the shaft becomes dynamically unstable.

Purpose: It helps mechanical engineers and designers ensure shafts operate below critical speeds to prevent resonance and failure.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( N_c \) — Critical speed (revolutions per minute)
• \( g \) — Acceleration due to gravity (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 above critical speed can cause excessive vibrations, bearing failures, and catastrophic shaft breakage.

4. Using the Calculator

Tips: Enter the shaft deflection in meters and gravity (default 9.81 m/s²). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What causes shaft deflection?
A: Deflection results from the shaft's weight, load, material stiffness, and support conditions.

Q2: How do I measure shaft deflection?
A: Use dial indicators or laser measurement tools while the shaft is stationary under its own weight.

Q3: What safety margin should I use?
A: Typically operate at least 20% below critical speed, or 30% above if quickly passing through critical speed.

Q4: Does this work for multi-mass systems?
A: This is for simple uniform shafts. Complex systems require more advanced analysis.

Q5: How to reduce critical speed?
A: Increase shaft diameter, use stiffer material, reduce unsupported length, or add supports.