Common features are listed at the bottom of the Home Page

On the Helical Extension Spring Design form a statically loaded spring can be designed by entering a loaded length and corresponding load and, optionally, any restrictions on spring diameter. For cyclic loading a second loaded length and load, and an expected life are entered. The latter three input boxes are not visible for steady load conditions.
The loaded length inputs are designated "provisional". The fixed distance between them and the corresponding difference in loads establishes a spring rate. That, in turn, establishes the initial deflection for the first loaded position which, added to the calculated free length, provides the true loaded lengths.

Pressing the Calculate button on the Extension Spring Design form, when all required entries have been made, produces the results screen listing the input values with a report of all the calculated properties. If there are undesirable features in the design such as high or low spring index, too few active coils or potential overstress, warning messages may appear with suggestions for improving the design. On acknowledgement, you can study the results and if you want to make changes, pressing the Review Input will return you to the Design screen where you can edit the input and press Calculate again to see the results.

When the Calculate button on the Analysis input form is pressed, if there are undesirable features such as too few active coils, or high or low spring index, or the possibility of excessive stress, information messages appear. After acknowledgement, you can accept the input, or press the Review Input button to return to the data input form. There you can edit the input and press Calculate again to see the results.