Post Deflection Calculator

An optical post supporting a cantilevered load acts as a fixed-free beam. A mount or optic whose center of gravity is offset horizontally from the post axis exerts a bending moment M = F × offset at the post tip, producing a lateral deflection δ = ML² / (2EI) at that tip, where L is the exposed post height, E is the elastic modulus, and I = πd⁴/64 is the second moment of area for a solid circular cross section. Taller or narrower posts are disproportionately compliant — deflection scales as L² and as d⁻⁴. The tool computes lateral deflection, angular tilt at the post top, and the resulting beam walk-off at a downstream target for both single- and double-pass reflection geometries. It also estimates the natural frequency of the loaded post, which is relevant for vibration sensitivity on active tables.