Extension Spring Calculations

1. Wire Diameter from Outer and Inner Diameter:

• If you only have the Outer Diameter (OD) and Inner Diameter (ID) and need to calculate Wire Diameter (WD), use the formula: (OD - ID) ÷ 2 = WD.

2.  Outer Diameter from Inner Diameter and Wire Diameter:

• To determine the Outer Diameter (OD) when you have Wire Diameter (WD) and Inner Diameter (ID), use this formula: 2 * WD + ID = OD.

3.  Inner Diameter from Outer Diameter and Wire Diameter:

• If you have Outer Diameter (OD) and Wire Diameter (WD) and want to calculate Inner Diameter (ID), use the formula: OD - 2 * WD = ID.

4. Mean Diameter:

• Calculate the Mean Diameter (MD) by subtracting (1) one Wire Diameter (WD) from the Outer Diameter (OD), or by adding (1) one Wire Diameter (WD) to Inner.

5. Length Inside Hooks from Body Length (Using Machine Hooks):

• To calculate the Length Inside Hooks (LIH) from the Body Length (BL) using machine hooks, use this formula: 3/4 Inner Diameter (ID) * 2 + BL = LIH.

6. Body Length from Length Inside Hooks (Using Machine Hooks):

• When you need to calculate Body Length (BL) from Length Inside Hooks (LIH) using machine hooks, use this formula: LIH - (3/4 Inner Diameter (ID) * 2) = BL.

7.  Length Inside Hooks from Body Length (Using Cross-Over Hooks):

• For length calculations with cross-over hooks, multiply the Inner Diameter (ID) by two and add it to the Body Length (BL).

8. Total Coils from Body Length:

• To find the total number of coils based on Body Length (BL), divide BL by Wire Diameter (WD) and then subtract one Wire Diameter to get the total number of coils.

9. Extension Spring's Index:

• Calculate the spring index by dividing Mean Diameter (MD) by Wire Diameter (WD).

10. Extension Spring Constant K / Rate:

• Calculating the extension spring's rate (K) involves several factors, such as shear modulus (G), wire diameter (d), outer diameter (D), the number of active coils (na), Young's modulus (E), and Poisson's ratio (V). The formula is: k = Gd^4 /[8D^3 na], where G = E/2(1 + V) and d = D outer - d.

11. Calculate Your Extension Spring's Load:

• To determine the load on your extension spring, multiply the spring's rate (R) by the distance it will travel (DT).

12.  Calculate Your Extension Spring's Initial Tension:

• Initial tension is the force between your extension spring coils before extension. This tension is calculated using the formula: Load = Stress * Wire Diameter^3 ÷ 2.55 * Mean Diameter.

13. Calculate Your Extension Spring's Distance Traveled:

• Find the distance traveled (DT) by dividing the load (L) you plan to apply by the spring's rate (R).

14. Calculate Your Extension Spring's Rate from Load and Travel:

• If you know the load and travel distance for your extension spring, you can determine the spring's rate (R) by dividing the load by the distance traveled.

Conclusion: In the intricate world of extension spring design, precision and accurate calculations are paramount. Our free online extension spring calculator provides a user-friendly and efficient solution. By inputting a few key measurements, you can ensure that your extension spring meets the requirements of your application. For detailed instructions on using our calculator, please visit our dedicated pages for compression, extension, and torsion spring calculations.