1. What is the Spring Rate Formula?

The spring rate formula calculates the stiffness of a compression spring, defined as the force required to compress the spring by a unit distance. It's a crucial parameter in spring design and selection.

2. How Does the Calculator Work?

The calculator uses the spring rate formula:

Where:

• \( K \) — Spring rate (N/mm)
• \( G \) — Shear modulus of material (N/mm²)
• \( d \) — Wire diameter (mm)
• \( D \) — Mean coil diameter (mm)
• \( N \) — Number of active coils

Explanation: The formula 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 mean diameter and number of active coils.

3. Importance of Spring Rate Calculation

Details: Accurate spring rate calculation is essential for proper spring selection in mechanical designs, ensuring the spring provides the required force at specified deflections.

4. Using the Calculator

Tips: Enter all values in consistent units (mm for dimensions, N/mm² for shear modulus). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical shear modulus for spring materials?
A: For steel springs, G ≈ 79,300 N/mm²; for stainless steel ≈ 69,000 N/mm²; for phosphor bronze ≈ 41,400 N/mm².

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

Q3: What is mean coil diameter?
A: It's the average diameter of the spring coils, calculated as (outer diameter - wire diameter) or (inner diameter + wire diameter).

Q4: What counts as an active coil?
A: Active coils are those free to deflect under load. Ground ends typically count as 1 inactive coil (0.5 per end).

Q5: How accurate is this calculation?
A: This provides theoretical spring rate. Actual rate may vary slightly due to manufacturing tolerances and end conditions.