Torsion spring Here are the usual limits for (cold manufactured) torsion springs: Basic formulae for torsion springs
Symbol |
Unit |
Detail |
Formulae |
a |
mm |
Initial space between coils |
a ≥ (0.24 w -0.64) d0.83 |
AD |
mm |
Tolerance on mean diameter |
|
D |
mm |
Mean diameter |
D = De - d |
Dd |
mm |
Diameter of the shaft |
|
De |
mm |
external diameter |
De = D + d |
Di |
mm |
Inside diameter |
Di = De - 2 d |
d |
mm |
Wire diameter |
d = De-D |
E |
N/mm2 |
Elastic modulus |
|
G |
N/mm2 |
Torsion modulus |
|
Lbr |
mm |
Length of ends |
|
LK0 |
mm |
Initial length of the body |
LK0 = d (n + 1.5) |
M1, M2 |
N.mm |
External torque related to α1, α2 |
M1 = R (α1 - α0) M2 = R (α2 - α0) |
Mn |
N.mm |
Maximal allowable torque |
|
N |
- |
Number of cycles |
|
n |
- |
Number of active coils |
|
q |
- |
stress correction factor |
|
R |
N.mm/° |
spring rate |
|
R' |
N.mm/° |
spring rate related to the body |
|
Ra, Rb |
mm |
radius to apply external loads |
|
Rm |
N/mm2 |
Ultimate tensile strength |
|
w |
- |
spring index |
w = D / d |
α0 |
° |
initial external angle |
|
α1, α2 |
° |
Operating angles related to M1, M2 |
α1 = M1 / R + α0 α2 = M2 / R + α0 |
αh1, αh2 |
° |
angular defelctions |
αh1 = M1 / R αh2 = M2 / R |
αh |
° |
Operating angular travel between M1 and M2 |
αh = α2 - α1 |
αhn |
° |
Greatest allowable deflection |
αhn = Mn / R |
α n |
° |
Greatest allowable angle |
αn = Mn / R + α0 |
γ |
° |
angle between ends |
γ = 360 ( n - E(n) ) |
r |
Kg/dm3 |
Density |
|
σzul |
N/mm2 |
Maximum allowable flexion stress |
|
σq2 |
N/mm2 |
Corrected stress related to M2 |