# Compression-spring rate and stress
# Scope: Close-coiled helical spring, linear elastic stiffness; no fatigue rating.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

wire = 2 mm
meanDiameter = 20 mm
activeCoils = 8
shearModulus = 79 GPa
compression = 10 mm

stiffness := shearModulus*wire^4/(8*meanDiameter^3*activeCoils) [N/mm]
force := stiffness*compression [N]

check force budget: force <= 30 N

scenario alternative: wire = 1.6 mm