134 



HANDBOOK OF MECHANICAL DESIGN 



TABLES FOR CALCULATING HELICAL SPRINGS 



TORSION SPRING FORMULAS 



Pitch = FLIN 



E = modulus of elasticity 



F = deflection of 1 turn, in in. 



Fn = total deflection, in in. 



FL = free length, in in. 



G — torsional modulus of elasticity 



I = length of rod (effective spring length un- 

 coiled), in in. 



MWL = minimum working length, in in. 

 N = number of effective turns 

 P = load, in lb. 

 R = length of arm, in in. 

 S = stress, in lb. per sq. in. 

 W = carrjang capacitj' in lb. 

 Y = Wahl factor 



