1. What is Extension Spring Rate?

The extension spring rate (k) measures how much force is required to extend a spring by a unit length. It's a fundamental property that determines the spring's stiffness and behavior under load.

2. How Does the Calculator Work?

The calculator uses the extension spring rate formula:

Where:

• \( k \) — Spring rate (N/m)
• \( G \) — Shear modulus of material (Pa)
• \( d \) — Wire diameter (m)
• \( D \) — Mean coil diameter (m)
• \( N \) — Number of active turns

Explanation: The equation shows that spring rate is directly proportional to the shear modulus and the fourth power of wire diameter, and inversely proportional to the cube of coil diameter and number of turns.

3. Importance of Spring Rate Calculation

Details: Knowing the spring rate is essential for designing mechanical systems, ensuring proper force application, and predicting spring behavior under load.

4. Using the Calculator

Tips: Enter all values in the specified units. Ensure wire diameter and coil diameter are in meters. Number of turns can be a decimal value for partial turns.

5. Frequently Asked Questions (FAQ)

Q1: What is typical shear modulus for spring materials?
A: For steel springs, G ≈ 79.3 GPa. For stainless steel, G ≈ 69 GPa. For music wire, G ≈ 81.7 GPa.

Q2: How does wire diameter affect spring rate?
A: Spring rate increases with the fourth power of wire diameter - doubling wire diameter increases rate by 16x.

Q3: What is mean coil diameter?
A: It's the diameter measured from the center of the wire on one side to the center of the wire on the opposite side.

Q4: What are active turns?
A: Active turns are those that contribute to spring deflection. End turns that are closed or hooked don't count.

Q5: Can this be used for compression springs?
A: The same formula applies to compression springs, but active turns calculation may differ.