SPRINGS 135 



proportional to the number of active turns. In a compression spring, the number of 

 active turns mil be the total number of turns less 2K turns, assuming IM dead turns 

 at each end of the spring. 



DEFLECTION 



Calculate the deflection per turn and total deflection by the formulas given in 

 the tables on pages 133 and 134. For compression springs, the number of active or 

 effective turns N will be the total number of turns less 2M turns. ; 



GENERAL SPECIFICATIONS 



Compression Springs. — Ends must be ground square. Minimum and maximum 

 inside and outside diameters will be determined by the space restrictions imposed by 

 the application. Both ends of the compression spring should be guided on either the 

 outside or inside or both. All compression springs should be wound right hand 

 except where they operate inside one another, in which case they should be wound 

 oppositely. Minimum working length of the spring under compression should allow a 

 minimum clearance between effective turns equal to 10 per cent of the wire diameter. 

 Additional compression beyond this minimum working should not be permitted. 



Extension Springs. — They may be close wound with or without initial tension, 

 or they may ]5e open wound. They should always be wound without initial tension 

 when load capacity is an important factor. All extension springs should be wound 

 right hand unless required otherwise. Maximum working length determines the 

 position of the spring beyond which additional extension should not be permitted. 



FINISHES 



Steel springs to resist moisture or atmospheric corrosion should be cadmium 

 plated. For appearance, they may be enameled, lacquered, or japanned. Springs 

 made of nonferrous metals are usually not finished in any manner. 



STANDARD DESIGN PROCEDURE 



By using a form such as given on page 136, the procedure in designing springs 

 can be standardized. The data relating to the actual dimensions and characteristics 

 of the spring are obtained from the inspection or test department. 



STANDARD DRAWINGS 



Examples of standard drawings on sheets 83-2 X 11 in. for the three types of heh- 

 cal springs, compression, tension, and torsion, are shown on page 137. Drawing need 

 not be to scale. Wire sizes should be specified in inches, not gage numbers. Use 

 decimals for specifying wire diameters and fractions of inches for rectangular materials. 

 Also dimension the thickness of rectangular wire so as to indicate how the wire is to be 

 wound. Indicate finish, if any. In dimensioning the drawing, indicate the permissi- 

 ble manufacturing tolerances as given in table above, but tolerances as large as per- 

 missible should always be specified. Load tolerances should be indicated as plus or 

 minus, the mean value to correspond with the specific rate. 



The notations and dimensions as given in the drawings show^n here should be 

 given. 



