Critical Speed Formula:
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Definition: Critical speed is the theoretical angular velocity that excites the natural frequency of a rotating object, like a shaft or rotor.
Purpose: It helps engineers design rotating systems to avoid resonance and potential failure at certain rotational speeds.
The calculator uses the formula:
Where:
Explanation: The formula converts the natural frequency of the system from radians per second to revolutions per minute.
Details: Calculating critical speed is essential for preventing resonance in rotating machinery, which can cause excessive vibrations and potential failure.
Tips: Enter the gravity value (default 9.81 m/s²) and the static deflection of the shaft in meters. All values must be > 0.
Q1: What happens at critical speed?
A: At critical speed, the rotational frequency matches the system's natural frequency, causing resonance and potentially dangerous vibrations.
Q2: How is static deflection measured?
A: Static deflection is the displacement of the shaft under its own weight, typically measured at the midpoint for a simply supported shaft.
Q3: Why is the 30/π factor used?
A: This factor converts radians per second to revolutions per minute (1 rad/s ≈ 9.549 rpm).
Q4: Is this formula for simple or complex systems?
A: This is for simple, single-mass systems. Complex systems may require more advanced analysis.
Q5: Should operating speed be above or below critical speed?
A: Typically, systems are designed to operate either well below (75% of Nc) or well above (125% of Nc) the critical speed.