Design procedure for helical compression spring of circular cross section

**1) Diameter of wire:**

Shear stress

Wahl’s stress factor

Also refer for k value from DHB Figure

Where **d** = diameter of spring wire

**‘c’**generally varies from **4 to 12** for general use

**2. Mean Diameter of Coil**

Mean coil diameter **D = cd**

Outer diameter of coil **D**_{o}**= D d**

Inner diameter of coil **D**_{i}**= D - d**

**3. Number of coil or turns**

Axial Deflection

**where i = Number of active turns or coils**

**4. Free length**

Where,

y = Maximum deflection

Clearance ‘a’ = 25% of maximum deflection or a = xdi, for x value refer figure in DHB Assume squared and ground end

**∴****Number of additional coil n = 2**

**5. Stiffness or Rate of spring**

**6. Pitch**