Calder Mobile Simulator
Build a hanging mobile the way Alexander Calder did — a tree of arms, each balancing a plate against everything below it — and the physics answers back: an arm floats level only when its two loads have equal moments (load × distance from the pivot), otherwise the heavy end swings straight down. Drag masses, arm lengths and pivots, auto-balance any arm to its centre of mass, watch it sway, and export SVG/PNG. Client-side.
A right-leaning chain — each arm balances a single plate against the whole sub-mobile below it. Calder's signature.
Click any arm or plate to edit it.
Each arm is a lever. It balances when the load on the left times its distance from the pivot equals the load on the right times its distance: mass × arm = mass × arm.
A real rigid arm that isn't balanced doesn't tilt a little — it swings until the heavy end hangs straight down. Calder's craft was to balance every arm exactly, so the whole thing floats and turns in a breath of air.
Wires are treated as weightless (the ideal-lever model): the plates carry the mass. An arm balances about its pivot when the two hanging loads have equal moments — load × distance from the pivot. Green dashes mark where the pivot would have to sit to balance the selected arm; the seesaw in the panel compares the two moments. Sway is a gentle idle animation for balanced arms; the resting pose (level or heavy-end-down) is the real physics.