Engineering Spring Design Calculations Nomenclature b Dm E F H ID K L N OD P S Radial width of material (mm) = (OD - ID) / 2 Mean diameter (mm) = (OD + ID) / 2 Modulus of elasticity (N/mm2 ) Deflection (mm) Free height (mm) = WH + f Inside diameter (mm) Multiple wave factor, see Table 1 Length, overall linear (mm) Number of waves (per turn) Outside diameter (mm) Load (N) Operating stress (N/mm2 ) S1 S2 t WH Z σ Operating stress at lower WH (Must be less than σ) Operating stress at upper WH Thickness of material (mm) Work Height (mm) = H - f Number of turns Material tensile strength Multiple Wave Factor (K) N 2,0-4,0 K 3,88 Table 1 Dm 4,5-6,5 2,90 7,0-9,5 2,30 10,0 & Over 2,13 b Single-Turn Gap-Type or Overlap-Type N must be a whole number Formulas: Deflection=f = PKDm3 Ebt3 N4 Operating Stress=S = * ID OD 3πPDm 4bt2 N2 Example: Smalley Part Number SSR-0200 Where: P = 151,2 N t = 0,61 mm b = 3,81 mm OD = 50,42 mm ID = 42,80 mm Dm = 46,61 mm N = 4 E = 20.7x104 K = 3.88 WH = 2,36 mm Deflection= f = WH f Calculate free height and operating stress for Smalley part number SSR-0200 (Gap-Type, Single-Turn, Carbon Spring Temper Steel). H WH f t N (20.7x104 (151,2)(3.88)(46,61)3 )(3,81)(0,61)3 (4)4 * 42,80 50,42 * Free Height= H = (WH +f)=2,36+1,10= 3,46 mm Operating Stress= S = N/mm2 (3)(π)(151,2)(46,61) (4)(3,81)(0,61)2 (4)2 N Dm WH f N H b WH f N t = 1,10 mm = 732,2 N/mm2 *Calculated free height may vary from manufactured spring height due to variations in raw material and manufacturing process. 137 smalley.com • +1 847.719.5900 Free Samples Easy Customization
