HELICAL SPRINGS
FOLLOWING DIN EN 13906-1,2,3
Order : Dware
Project : HeliSpring
Subproject : Extension Spring Design
Project item : Metallfedern
Spring ID : S.202
Calculated by : André Dewispelaere
Organization : Dware
Date : 03.12.2025 




   Spring wire grade




 Nr, Cl, Spring Wire Grade       ,      E,     G,  rho,  Rm1, Rco




421, CR, 1.4310 X10CrNi18-8 HS   , 180000, 70000, 7.90, 2050, 700
1 Calculated wire properties Symbol Unit Value
2 Wire diameter d mm 1.600
3 Minimal ultimate tensile strength Rm N/mm˛ 1910
4 Module of rigidity G N/mm˛ 70000
5 Module of Elasticity E N/mm˛ 180000

1 Design specifications Symbol Unit Value
2 Minor axial spring force F1 N 30.0
3 Major spring force F2 N 92.0
4 Stroke length sh mm 31.0
5 Number of load cycles Ncy Mcy 0.010
6 Outside diameter not greater than De mm 0.00
7 Imposed spring index w -- 7.00
8 Coiling -- -- cold
9 Initial tension force to apply -- -- Yes
10 Coiled with -- -- Bench
11 Hand of coils -- -- right
12 Type spring end A ETA -- german loop
13 Type spring end B ETB -- german loop
14 Shot peening -- -- No
15 Geometry calculation Symbol Unit Value
16 Calculated wire diameter dc mm 1.44
17 Selected wire diameter d mm 1.600
18 Wire diameter deviation Ad mm 0.020
19 Mean diameter of coil D mm 11.10
20 Spring index w -- 6.94
21 Outside diameter of spring De mm 12.7
22 Inside diameter of spring Di mm 9.5
23 Initial torsional stress τ0 N/mm˛ 175.0
24 Attainable initial tension force F0i N 25.4
25 Number of active coils n -- 21.00
26 Spring rate R N/mm 1.997
27 Initial tension force F0 N 26.1
28 Coil pitch at free length m0 mm 1.620
29 Coil space at free length a0 mm 0.000
30 Nominal free length of spring LK mm 35.6
31 Length of spring end A LHA mm 8.0
32 Number inactive coils spring end A nnaA -- 0.00
33 Length of spring end B LHB mm 8.0
34 Number inactive coils spring end B nnaB -- 0.00
35 Total number of coils nt -- 21.00
36 Spring free length inside loops L0 mm 51.6
37 Calculation spring diagram Symbol Unit Value
38 Minor deflection s1 mm 2.0
39 Length at minor deflection L1 mm 53.6
40 Minor spring force F1 N 30.0
41 Major deflection s2 mm 33.0
42 Length at major deflection L2 mm 84.6
43 Major spring force F2 N 92.0
44 Permissible maximal deflection sn mm 49.3
45 Permissible maximal spring length Ln mm 100.9
46 Permissible maximal load force Fn N 124.6
47 Strength calculation Symbol Unit Value
48 Stress correction factor k -- 1.202
49 Corrected minor torsional stress τk1 N/mm˛ 249
50 Corrected major torsional stress τk2 N/mm˛ 763
51 Permissible static torsion stress τP N/mm˛ 860
52 Safety factor on major stress SF -- 1.13
53 Tors stress at permiss max length τn N/mm˛ 860
54 Permissible static torsion stress τP N/mm˛ 860
55 Safety factor at permis max length SFn -- 1.00
56 Strength domain -- -- static
57 Permissible endurance stress τeN N/mm˛ 860
58 Permissible upper torsional stress τkO N/mm˛ 860
59 Safety factor upper torsion stress SFO -- 1.13
60 Corrected lower torsional stress τkU N/mm˛ 249
61 Corrected stroke torsional stress τkh N/mm˛ 514
62 Permissible stroke torsion stress τkH N/mm˛ 611
63 Safety factor on variable stress SFH -- 1.19
64 Length of wire for spring Symbol Unit Value
65 Length of wire spring end A lHA mm 25.4
66 Length of inactive coils A lnaA mm 0.0
67 Length of active coils lK mm 733.1
68 Length of inactive coils B lnaB mm 0.0
69 Length of wire spring end B lHB mm 25.4
70 Total length of evolved wire lw mm 784.0
71 Mass of spring mw g 12.5