One robot, two jobs: clean, then paint.

Repainting an old house, the paint is the easy part — maybe 20% of the work. The other 80% is the dirty, dangerous bit: wash off the grime and dead algae, scrape and sand the failing paint, fill, prime — all of it up a ladder. Prep is the product, not paint. A robot that only sprays automates the easy fifth and leaves the hard, fall-prone work to people.

So we don’t build a paint robot. We build one access platform — a device that rides a bottom-anchored, tensioned rope guideway. It climbs the rope on a hoist, so its reach is just the length of rope: a two-storey house or a six-storey block, the same machine, no new arm. Wall rollers press it to the facade to take the sanding force, while roof and ground rails shift the whole guideway sideways, stripe by stripe. On its mount go swappable heads on a common quick-change interface — here a soft-wash head (with wastewater reclaim) and a force-controlled sanding head, the two jobs that are most of the work; a shrouded paint head is the same idea, one module later. Get that shared mount right and wash-head, sand-head, paint-head — later an inspection head — are just modules.

This is the low-fidelity design model — deliberately rough — to get the architecture and proportions right before any metal exists. Drag it around; hit Head to swap Wash ⇄ Sand on the mount, Exploded view to see the parts on the one shared interface, or Work cycle to watch it climb a stripe and index across. Low fidelity, real intent.