b'c oMMonc oMPressions PrinGt erMinoLoGySymbol Units Description FormulaD mm, in Mean diameter D = De - dDe mm, in External diameter De = D + dDi mm, in Internal diameter Di = D - dd mm, in Wire diameter d = De - DE,Mpa, PSI Modulus of elasticity E = /L1, L2 N, Lbf Target loads (related to target heights/lengths)Fc Th N, Lbf Theoretical load/force at set erminologysolid Closed and SquaredClosed and Ground Fn N, Lbf Load/force related to Ln (smalledClosed and squared end com- Closed and ground ended com-length) pression springs are the mostpression springs are also com-fe Hz Natural frequency common. This end type allows themon but they are more expensive. k - Stress correction factor spring to stand vertically whenClosed and ground ends will help L0, FL mm, in Free length/height placed on a flat surface. The lastyour compression spring stand Tcoil on either end is closed. Thisvertically straight on a flat surface D1, D2 mm, in Target Length/distance (related to target loads) end type is suited for compres- when the slenderness ratio is too sion springs with a low slender- large. Lc mm, in Solid length Lc = d(n+ni+nm) ness ratio.Ld mm, in Length of wire Ld = p D [ 2 + nm + n / Cos(z)]LK mm, in Buckling lengthLn mm, in Smallest allowed operatingLn = d (n + ni +nm) + Salength (geometric)Lr mm, in Smalled allowed operating length (stress)M g, lb Mass M =Ld pd2 10-3 / 4m mm, in Spring pitch m = [ L0 - d (ni + nm) ]/nN Number of cyclesn Number of active coils n = G d4 / (8 R D3)ni Coils related to the endsnm Number of dead coils Double ClosedOpen Ended nt Total number of coils nt = n + nm + 2 Double closed ends are very simi- Open ended compression springs R, KSR N/mm,Spring Rate R = G d4 / (8 n D3) orlar to closed and squared endedare uncommon since the spring Lbf/in (L1-L2) / (D1-D2) compression springs. Instead ofwill not be able to stand unless Rm Mpa, PSI Ultimate tensile strength the spring having one closed coilsupported by a shaft or mandrel. Sh mm, inSpring travel Sh = D1 - D2 at the ends, it has two. They areThere is a pitch between each coil used to provide stability whenon an open ended compression W Nmm,Stored energy W = 0.5(L1+L2)(D1-D2) your spring has a high slender- spring. Joule ness ratio. This end type helps w - Spring index w = D / d prevent buckling.c oMMons PrinGd esiGnM ateriaLsMaterial Stress CorrosionApplicationResistanceBrass Low Yes Water resistantPhosphor Bronze Low Yes Electrical connectivityStainless SteelLow Yes Corrosive (302/304) environmentsOil Tempered Medium No Large diametersHard Drawn MB Medium No Low costMusic Wire High No High stress188'