Autonomous Factory · wind-up walker

Trotter

A desk-scale quadruped in the Spot silhouette, rebuilt in CAD as a wind-up walker. Twist the knob at the tail, set it down, and it trots off on four legs. No motor, no battery, no electronics — a single rubber band drives two crankshafts.

1 rubber band 5.1 oz in PETG 44.1 mm per crank turn

Intro clip

Wind it up.

Four legs, one band.

Shafts, gears, rods, pins and caps, all in PETG — and one rubber ring that powers the lot. Keep scrolling to wind it up and walk it.

Wind the knob.

The fluted knob at the tail turns a double-D shaft. 30 to 50 turns twist one 45 mm rubber band, doubled over a 100 mm span down the middle of the chassis.

Lid off.

The band runs from a front anchor pin back to the winder hook. No spring, no motor, no cell — the twist in that band is the entire power supply.

Sixteen teeth into eight.

The winder pinion meshes a crown gear on the rear crankshaft, 16 teeth into 8. Two coupling rods tie the rear cranks to the front pair, so all four discs stay in phase.

Cranks become steps.

Each leg hangs on a crank pin 4 mm off axis and rocks against a fixed guide pin 20 mm above it. That geometry alone makes a step: 8 mm of lift, ±11.3° of swing, knees rigid at 76.5°.

44.1 millimetres a turn.

Diagonal pairs land together — front-left with rear-right — so two feet are always down. One crank revolution carries it 44.1 mm; a full wind walks it 0.66 to 1.1 m across the desk.

Six jobs, one walker.

Each colour belongs to the piece itself rather than being painted on afterwards. Pick a job to see which pieces do it.

Trotter standing on a pale oak desk beside a window in morning light

Built for a desk.

5.8 × 4.3 × 4.8 in overall — about the footprint of a paperback. It walks on anything flat: a desk, a kitchen table, a hard floor. Wind, set down, let go.

Side profile: knees fixed at 76.5°, and the flat blade above each hip that carries the guide slot.

A hand winding the tan fluted knob at the tail of the robot — Winding is the whole interface — three fingers on the tan knob.

Exploded view of the walker with the lid, panels, crankshafts, legs and fasteners separated — Everything separates: lid, deck panels, crankshafts, rods, legs and caps.

Two children watching Trotter walk across a wooden playroom floor — Nothing to charge and no batteries to go flat.

Wound by hand, walked by one band.

0 oz: in PETG
0 mm: per crank turn
0: rubber band, no battery

Overall: 5.8 × 4.3 × 4.8 in
Chassis: 143 × 56 × 46 mm, 2.5 mm walls
Material: PETG
Crank throw: 4 mm (8 mm of foot lift)
Gear train: 8-tooth pinion into a 16-tooth crown
Travel: 44.1 mm per crank turn
Rubber band: one 45 mm ring, doubled
Wind: 30–50 turns, then set it down

Trotter on a white studio background, three-quarter view