Due to different materials, wire diameters, spring constants, heat treatment, etc. tension springs have different loads and lengths.
When the tension spring is not under tension, each circle is close together. Under tension, the weakest part of the tension spring is the place where the linear change is the largest. Most of the calculation formulas of the tension coil spring are that the tension load of the spring acts on the axis of the coil so the basic compression springs for the relationship between load-deflection and load-stress are exactly the same. The shape of the two ends of the tension spring can be classified into those that process the end of the spring into a hook and use other mounting accessories. The extension spring is essentially the same as the compression coil spring. The so-called design precautions here are aimed at the inherent problems of the tension spring—the deflection of the hook, the stress concentration and the initial tension, the shape of the parallel hook and the shape of the installation accessories, etc.
