Spring Design
Design information for engineers, such as spring calculation formulas,
which are the basis of spring design, can be found here.
- Tokai Spring HOME
- Spring Design
- Flat Spiral Springs: Calculation Formulas
Flat Spiral
Springs
Meaning of Symbols
The symbols used for spring design are shown in Table 1 below. The values of the longitudinal elastic modulus (E) are based on Table 2.
Table 1. Symbols and units used in calculations
| Symbol | Meaning of Symbol | Unit |
|---|---|---|
| E | Longitudinal elastic modulus | N/mm2 |
| b | Material width | mm |
| t | Plate thickness | mm |
| l | Total length | mm |
| M | Moment | N・mm |
| k | Spring constant | N・mm/rad |
| σ | Stress | N/mm2 |
Table 2.Longitudinal elastic modulus：E（N/m㎡）
| Material | E Value | |
|---|---|---|
| Spring steel material | 206×103 | |
| Stainless steel | SUS302
SUS304(Correspond to X5CrNi18-9,1.4301,S30400) SUS631(Correspond to X7CrNiAl17-7,1.4568,S17700) |
186×103 186×103 196×103 |
| Nickel-silver wire | 108×103 | |
| Phosphor bronze wire | 98×103 | |
| Beryllium copper wire | 127×103 | |
Basic Calculation Formulas Used For Design
The basic formula for calculating the spring constant when winding is given by the following formula.
Also, the stress when any moment occurs can be calculated with the following formula.
