🌀 Torsion Spring Calculator
Calculate Torsion Spring Rate
Mean diameter = Outer diameter - Wire diameter
Steel: 30,000,000 PSI, Stainless: 28,000,000 PSI, Music Wire: 30,000,000 PSI
How to Use This Calculator
Enter Wire Diameter
Input the diameter of the torsion spring wire in inches.
Enter Mean Diameter
Enter the mean coil diameter in inches. Mean diameter = Outer diameter - Wire diameter.
Enter Active Coils
Input the number of active coils. For torsion springs, this is typically the total number of coils.
Enter Modulus of Elasticity
Enter the modulus of elasticity (Young's modulus) of the spring material in PSI. Use 30,000,000 PSI for steel (default).
Calculate
Click calculate to get the torsion spring rate in lb·in/degree and N·mm/degree.
Formula
k = (E × d⁴) / (3667 × n × D)
Where:
- k = Torsion spring rate (lb·in/degree)
- E = Modulus of elasticity (PSI)
- d = Wire diameter (inches)
- n = Number of active coils
- D = Mean coil diameter (inches)
- 3667 = Conversion constant
Torque Calculation:
T = k × θ
Where T = Torque, k = Spring rate, θ = Deflection angle (degrees)
Example Calculation
If you have:
- Wire diameter: 0.125 inches
- Mean diameter: 1.0 inch
- Active coils: 10
- Modulus of elasticity: 30,000,000 PSI
Calculation:
k = (30,000,000 × 0.125⁴) / (3667 × 10 × 1.0)
k = (30,000,000 × 0.000244) / 36,670
k = 7,320 / 36,670 = 0.20 lb·in/degree
About Torsion Spring Calculator
The Torsion Spring Calculator is an essential tool for engineers and designers working with torsion springs. Unlike compression or extension springs that work with linear force, torsion springs provide rotational force (torque) when twisted. Torsion spring rate defines the torque required to rotate the spring by one degree. This calculator helps determine spring rate from spring dimensions and material properties.
When to Use This Calculator
- Spring Design: Calculate torsion spring rate for custom spring designs
- Spring Selection: Verify torsion spring specifications meet application requirements
- Door Mechanisms: Design torsion springs for doors, lids, and hatches
- Tool Design: Calculate spring rates for clamps, vises, and tensioning devices
- Quality Control: Verify manufactured torsion springs meet specified rates
Why Use Our Calculator?
- ✅ Instant Results: Get torsion spring rate calculations immediately
- ✅ Easy to Use: Simple interface requiring only dimensions and material properties
- ✅ Multiple Units: Results displayed in both lb·in/degree and N·mm/degree
- ✅ 100% Free: No registration or payment required
- ✅ Accurate: Uses standard torsion spring design formulas
- ✅ Educational: Includes detailed formula explanations and examples
Common Applications
Garage Doors: Calculate torsion spring rates for garage door systems where springs counterbalance door weight.
Automotive Hoods and Trunks: Design torsion springs that provide appropriate lift assistance for vehicle hoods and trunks.
Industrial Equipment: Design torsion springs for clamps, positioning devices, and mechanisms requiring rotational force.
Consumer Products: Calculate spring rates for mousetraps, clipboards, and other products using torsion springs.
Tips for Accurate Results
- Count all coils as active coils for most torsion springs
- Use correct modulus of elasticity - this significantly affects results (typically 28-30 million PSI for steel)
- Torsion springs use Young's modulus (E), not shear modulus like compression springs
- Ensure proper end configuration - spring rate can be affected by how the spring ends are formed
- Real springs may vary ±10% from calculated values due to manufacturing tolerances
Frequently Asked Questions
What's the difference between torsion springs and compression springs?
Compression springs work with linear force (pushing/pulling), while torsion springs work with rotational force (torque). Torsion springs resist twisting and provide torque based on rotation angle, not linear deflection.
Why do torsion springs use Young's modulus instead of shear modulus?
Torsion springs primarily experience bending stress, which is related to Young's modulus (E). Compression/extension springs experience torsional stress, which uses shear modulus (G). The formulas reflect these different stress types.
How do I calculate torque from spring rate?
Torque = Spring Rate × Deflection Angle. For example, if spring rate is 0.2 lb·in/degree and you deflect it 90 degrees, torque = 0.2 × 90 = 18 lb·in.
Can torsion springs be used for both clockwise and counterclockwise rotation?
Torsion springs can work in either direction, but they're typically wound and installed for a specific rotation direction. The spring rate calculation is the same regardless of direction.
What happens if I exceed the maximum deflection angle?
Exceeding maximum deflection can cause permanent deformation, reduced spring rate, or failure. Always stay within the manufacturer's recommended deflection range, typically 90-360 degrees depending on spring design.