Spring types
Conical springs and progressive response
A conical or variable-pitch helix can change its response over the travel.
Progressive contact
In a conical spring, coils of different diameters may contact at different points and nest. In a variable-pitch spring, closer-pitch regions can close first. Active turns then change, potentially increasing rate as compression proceeds.
Use the right model
A constant-pitch cylindrical rate alone does not describe changing contact or a progressive curve. This calculator estimates only cylindrical round-wire bodies; these geometries need a different analysis.