Lee Spring wants to help you understand how to count coils in #compressionsprings
. The total number of coils is counted from tip to tip. Springs with closed ends or with closed and ground ends have one inactive coil at each end. #Springs
with open ends are considered to have virtually no inactive coil. #Springs
with open ends ground are considered to have about one-half inactive coil at each end.The active coils are what make a spring a spring. The active term should really be applied to any portion of a spring that stores and releases energy. In the case of a compression spring, the active portion will expand as the spring is compressed. The opposite is typical of an extension spring. The action of a clutch spring tightening down on a shaft is typical of the diameter change as a torsion spring winds up.
When designing a spring and specifying its dimensions, it is critical that the number of coils is counted correctly, as this can have a huge effect on the strength of the spring. It is a straightforward process - simply start at one end of the spring, where the wire has been cut, then follow the wire round – every time you go through 360o that counts as a full coil (180o = ½ coil; 90o = ¼ coil etc.)