KEVOS® MAKEOS · Springs
Helical Extension Spring Check
What load and body stress will this extension spring have at its working extension?
Rate, load at extension including initial tension, and Wahl-corrected body stress of a round-wire helical extension spring.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Wire diameter | mm | Wire diameter. |
| Mean coil diameter | mm | Mean coil diameter = outside diameter − wire diameter. |
| Active coils | coils | Active body coils (hooks or loops are often counted as about one extra coil; follow the maker’s convention). |
| Shear modulus | GPa | Shear modulus of the wire material. |
| Initial tension | N | Initial tension wound into the spring, from the maker’s data or a load test (the load needed before coils separate). |
| Extension from free length | mm | Extension beyond the free length at the working position. |
| Allowable body shear stress | MPa | Allowable body stress for the material and duty; hooks usually limit extension springs. |
Method and formulas
- Rate k = G d⁴ ÷ 8D³Na.
- Load F = Fi + k x.
- Body stress τ = K × 8FD ÷ πd³ with the Wahl factor K; initial-tension stress τi = 8Fi D ÷ πd³ (uncorrected).
- Example: the default spring has k = 1.8797 N/mm and carries 56.993 N at 25 mm extension.
Limitations
- Hook and loop stresses are not calculated and usually govern failure; check them with the maker.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a return or counterbalance spring
- Specify initial tension and rate
- Compare spring options
Who it is for
- Design engineers
- Spring buyers
- Maintenance engineers
What you get
- Spring rate
- Load at the working extension
- Body shear stress
- Stress from initial tension
Interpreting the result
- Compare the initial-tension stress with the range your spring maker can achieve for the index.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 325–332. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
