FOLLOWING DIN EN 13906-1,2,3
Order : Dware
Project : HeliSpring
Subproject : Dimensionig extension spring
Project item : Metallfedern
Spring ID : S.202
Calculated by : André Dewispelaere
Organization : Dware
Date : 26/07/2021

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
Calculated wire properties Symbol Unit Value
Wire diameter d mm 1.600
Minimum value tensile strength Rm N/mm˛ 1910
Modulus of rigidity G N/mm˛ 70000
Modulus of Elasticity E N/mm˛ 180000

Design specifications Symbol Unit Value
Minor axial spring force F1 N 30.0
Major spring force F2 N 92.0
Stroke length sh mm 31.0
Number of loading cycles Ncy Mcy 0.010
Outside diameter not greater than De mm 0.00
Imposed spring index w -- 7.00
Coiling -- -- cold
Initial tension force to apply -- -- Yes
Coiled with -- -- Bench
Hand of coils -- -- right
Spring end A ETA -- german loop
Spring end B ETB -- german loop
Shot peening -- -- No
Geometry calculation Symbol Unit Value
Calculated wire diameter dc mm 1.44
Selected wire diameter d mm 1.600
Wire diameter deviation Ad mm 0.020
Mean diameter of coil D mm 11.10
Spring index w -- 6.94
Outside diameter of spring De mm 12.7
Inside diameter of spring Di mm 9.5
Initial torsional stress τ0 N/mm˛ 175.0
Attainable initial tension force F0i N 25.4
Number of active coils n -- 21.00
Spring rate R N/mm 1.997
Initial tension force F0 N 26.1
Coil pitch at free length m0 mm 1.620
Coil space at free length a0 mm 0.000
Nominal free length of spring LK mm 35.6
Length of spring end A LHA mm 8.0
Number inactive coils spring end A nnaA -- 0.00
Length of spring end B LHB mm 8.0
Number inactive coils spring end B nnaB -- 0.00
Total number of coils nt -- 21.00
Spring free length inside loops L0 mm 51.6
Calculation spring diagram Symbol Unit Value
Minor deflection s1 mm 2.0
Length at minor deflection L1 mm 53.6
Minor spring force F1 N 30.0
Major deflection s2 mm 33.0
Length at major deflection L2 mm 84.6
Major spring force F2 N 92.0
Maximum permissible deflection sn mm 49.3
Maximum permissible spring length Ln mm 100.9
Maximum permissible load force Fn N 124.6
Strength calculation Symbol Unit Value
Stress correction factor k -- 1.202
Corrected minor torsional stress τk1 N/mm˛ 249
Corrected major torsional stress τk2 N/mm˛ 763
Permissible static torsion stress τP N/mm˛ 860
Safety factor on major stress SF -- 1.13
Tors stress at max permiss length τn N/mm˛ 860
Permissible static torsion stress τP N/mm˛ 860
Safety factor at max permis length SFn -- 1.00
Strength domain -- -- static
Permissible endurance stress τeN N/mm˛ 860
Permissible upper torsional stress τkO N/mm˛ 860
Safety factor upper torsion stress SFO -- 1.13
Corrected lower torsional stress τkU N/mm˛ 249
Corrected stroke torsional stress τkh N/mm˛ 514
Permissible stroke torsion stress τkH N/mm˛ 611
Safety factor on variable stress SFH -- 1.19
Length of wire for spring Symbol Unit Value
Length of wire spring end A lHA mm 25.4
Length of inactive coils A lnaA mm 0.0
Length of active coils lK mm 733.1
Length of inactive coils B lnaB mm 0.0
Length of wire spring end B lHB mm 25.4
Total length of wire lw mm 784.0
Mass of spring mw g 12.5