SPRINGS 



133 



TABLES FOR CALCULATING HELICAL SPRINGS 



COMPRESSION SPRING FORMULAS 

 Spring index = -r or -r- = 5 (minimum) 



Round 



-FL-^ 



AUd 



w = 



F = 



0.3927Sd' 

 (D - d)Y 



MWL - (2.25d) 

 l.lOd 



SP(D - d)3 



(maximum) 



Gd' 

 Fv = FN 

 FL =Fn + MWL 



FL - {2.25d) 

 N 



Pitch 



Load per inch of deflection = P/Fn 



Solid length = (iV + 2.25)d 



MWL = (l.lOdiV) + (2.25d) 



Square 



-K 



-i 



^kd 



_ 0A44Sd' 

 "^ ~ (.D - d)Y 



°-'^^- (o^d + 

 5.58P(0 - d)' 

 Gd' 

 Fa = FN 

 FL =Fn + MWL 



(maximum) 



Pitch = 



--[<i^+0] 



iV 



Load per inch of deflection = P/Fn 

 SoUd length = ro.48d ( ^^ ^ + l) ■'^l 



^TFL =[ 0.53d (^+l)^] 



Rectangular 



_h-FL-^ 



_t , 



^k 



Sbt VbV 



3.185(1) - 6)y 

 11.16P(D - 6)2 



(maximum) 



Gbt(b' + m 

 Fh = FN 

 Fi. = Fn + MWL 



Pitch 



.--['(i^+O] 



iV 



Load per inch of deflection = P/Fn 

 Solid length = ro.48f (g-^-g + •'^1 



MWL = [o.sat^ ^^ ^ + l) N~\ 



EXTENSION SPRING FORMULAS 



Fn =F X N Pitch = EL/N Load per inch deflection = P/Fn 



Round 



r-l;'^^ 



AUd 



Square 



-r-TnJ: 



^Wd~^ 



Rectangular 



-|FL[- 



AWt 



w = 



0.3927Sd^ 



(D - d)Y 



N = —r (maximum) 

 a 



W = 



0.4445^3 



(D 



N = 



d)Y 

 FL 



0A8d 



F = 



8P{D - dy 

 Gd^ 



t 



D 



W = 



F = 



5.58P{D 



- d 



dy 



+ 1 



N = 



Sbt Vb'- + r- 

 S.185Y(D - b) 

 FL 



OASt 



{^ 



+ 1 



Gd' 



F = 



U.16P{D - by 

 GbtiV- + f) 



