Compression Spring Calculator

Compression Spring Rate Formula:

\[ K = \frac{G \times d^4}{8 \times D^3 \times N} \]

Shear Modulus (G):

N/mm²

Wire Diameter (d):

Mean Coil Diameter (D):

Active Coils (N):

number

Spring Rate (K):

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1. What is the Compression Spring Rate Formula?

The compression spring rate formula calculates the stiffness of a helical compression spring. It determines how much force is required to compress the spring by a certain distance.

2. How Does the Calculator Work?

The calculator uses the compression spring rate formula:

\[ K = \frac{G \times d^4}{8 \times D^3 \times N} \]

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: Spring rate is crucial for designing springs that provide the required force at specific deflections. It's essential in applications ranging from automotive suspensions to industrial machinery.

4. Using the Calculator

Tips: Enter all values in the specified units. Ensure wire diameter and mean coil diameter are measured accurately as they significantly affect the result.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical shear modulus for spring steel?
A: For common spring steels, G is approximately 79,300 N/mm² (79.3 GPa).

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

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

Q4: How do inactive coils affect the calculation?
A: Only active coils (those free to deflect) should be counted in N. Ground ends typically add 0.5 inactive coils per end.

Q5: Can this formula be used for extension springs?
A: The basic formula is similar, but extension springs have additional considerations like initial tension that affect their force-deflection characteristics.