5.1 Calculation formula of cylindrical helical torsion spring
Table 12-2-29
| Project | Unit | Formula and Data |
| Material diameter d | mm | d≥³√ 32TnK1/πσBp Where σBp – allowable bending stress,Check according to Table 12-2-6.K1=(4C-1)/(4C-4),Or check according to Table 12-2-20 |
| Effective coils n | Coil | n=Ed4φ/3667D(Tn-T1) Where E – elastic modulus |
| Stiffness T’ | N.mm/(°) | T’=Ed4φ/3667Dn |
| Minimum working torque T1 | N.mm | T1=T’φ1 |
| Torsion angle at maximum working torque φn | (°) | φn=Tn/T’ |
| Working limit torque Tj | N.mm | Tj=πd3σj/32K1,Class II σj=0.625σb,Class Ⅲ σj=0.8σb. |
| Working limit torsion angle φj | (°) | φj=Tj/T’ |
| Inner diameter of spring under working limit torsion angle D’1 | mm | D’1=D-[n/(n+φj/360)]-d |
| Spacing δ | mm | No special requirements,σ=0.5 |
| Pitch t | mm | t=d+ δ |
| Free height H0 | mm | Ho=nt+D |
| Helix angle α | (°) | α=arc tan t/πD |
| Spring Extending length L | mm | L=πDn/cosα+L0,Where L0 is the extension arm length |
| Stability index n>nmin | coil | nmin=(φj/123.1)4<n ,If the ultimate torsional deformation angle φj<123°, this item can not be calculated. |
