Extension Spring Loop Guidelines
In designing extension springs, it is important to be aware that as the space occupied by the machine loop is shortened, the transition radius is reduced and a substantial stress concentration occurs. This contributes to shortened spring life and premature failure. Most extension spring failures occur in the area of the end. To maximize the life of the spring, the path of the wire should be smooth and gradual as it flows into the end. Tool marks and other stress concentrations should be held to a minimum. A minimum bend radius of 1.5 times the wire diameter is recommended.