Size an extension-type constant force spring: enter your strip dimensions or work backward from a target load. Force is reported as a nominal range (±10%), per industry tolerance.
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Send us these specs for an engineering review and quote.
Reference only. Force tolerance ±10% and ID/OD tolerance ±10% per industry standard. Life reference is derived from published catalog data for Type 301 strip, not a manufacturer life curve — confirm critical designs with our engineers. One life cycle = one extension and retraction of the same strip section.
P = E · b · t³ / (26.4 · Rn²), where E is elastic modulus, b strip width, t strip thickness, and Rn the neutral-layer radius of the coil. Enter your strip and coil geometry, or enter a target force and let the calculator solve for the strip width.
A constant force spring is a prestressed flat strip wound tightly on itself. As it unwinds, the strip always bends back to the same natural radius, so the restoring force barely changes with extension — unlike a helical spring, where force rises with deflection. Learn more about our custom springs.
Thinner strip and a larger natural diameter lower the bending stress and extend fatigue life, but reduce the force. If the stress light is red, increase the natural inside diameter or reduce the strip thickness and recalculate.
Each light compares the strip bending stress with reference bands derived from published Type 301 catalog data. Green means roughly 20,000+ life cycles, yellow roughly 13,000, red is below that. The bands apply to Type 301 stainless strip only.
The life reference is derived from published catalog data for Type 301 stainless strip, not a manufacturer life curve. One life cycle = one extension and retraction of the same strip section. Confirm critical designs with our engineers.
Turn your design into real samples.
We prototype custom springs in days, not weeks. Send us your specs to get started.
Get a quoteWorking on a different spring type? See all Zigoal spring calculators, or learn more about our custom springs.
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Hi there, I am Annie Lin, the key account manager of Zigoal, my team and I would be happy meet you and learn all about your business, requirements & expectations.
Your information will be kept strictly confidential.
Hi there, I am Annie Lin, the key account manager of Zigoal, my team and I would be happy meet you and learn all about your business, requirements & expectations.
Your information will be kept strictly confidential.
Hi there, I am Annie Lin, the key account manager of Zigoal, my team and I would be happy meet you and learn all about your business, requirements & expectations.
Your information will be kept strictly confidential.
Hi there, I am Annie Lin, the key account manager of Zigoal, my team and I would be happy meet you and learn all about your business, requirements & expectations.
Your information will be kept strictly confidential.
Hi there, I am Annie Lin, the key account manager of Zigoal, my team and I would be happy meet you and learn all about your business, requirements & expectations.
