Wire material name. Supported: music_wire, chrome_vanadium, stainless_302, phosphor_bronze, beryllium_copper. Determines shear modulus G and allowable stress lookup.

Spring wire diameter in inches. Common music wire range: 0.010-0.250 in. Must match available wire gauge for the chosen material.

Mean coil diameter (D) in inches, measured center-to-center of the wire cross-section. Spring index C = D/d should fall between 4 and 12 for practical designs. Typical: 0.1-3.0 in. Spring index C = D/d should be 4-12 for manufacturability.

Unloaded free length of the spring in inches. Must exceed solid length to allow deflection. Ratio Lf/D > 4 indicates buckling risk. Unloaded spring length. Typical: 0.5-6.0 in for compression springs.

Total number of coils including inactive end coils. Active coils = total minus end coils (2 for closed ends). Typical range: 3-20.

End condition of the spring. Closed and ground is standard for precision springs. Affects inactive coil count and solid length calculation. If omitted, defaults to closed_ground.

Deflection from free length at the normal working load, in inches. Must be less than (free_length - solid_length).

Maximum applied load in pounds. If provided, overrides the load calculated from spring rate and working deflection. Used when the design load is known directly.