Spinifex

An original kinetic sculpture built around a geared drivetrain: five bodies turning about two parallel shafts at a fixed 3:1 ratio.

I modelled the mechanism in CAD, built the animation rig, and produced a set of technical renders and motion studies from the model.

The drivetrain

The drive is a 20-tooth spur pinion on the output of a 12 V JGY370-D7 gearmotor, meshing with a 60-tooth spur gear. The two shafts are parallel and 60 mm apart, carried on 608 bearings in the rear plate and front bearing spacer.

That pair sets the ratio the sculpture runs at: the pinion turns three times for every turn of the main shaft, and the two gears turn in opposite directions. A single M8×1.25×40 hex bolt clamps the 60-tooth gear to the 590 mm blade disc, so bolt, gear and disc rotate as one body about the main shaft. The output shaft and its pinion form the second.

Rendering the motion

The animation is a mechanical study rather than a camera orbit: the camera is fixed in an orthographic isometric view and only the parts move. Rotation is applied about each shaft axis rather than each part’s own origin, and every frame is rebuilt from the rest pose, so the loop closes instead of accumulating drift.

The loop is one half-turn of the main shaft. Four spokes on the disc repeat every 90 degrees and the hex bolt head every 60, so 180 degrees is the shortest rotation that returns the whole assembly to an identical state, and the pinion covers exactly thirty of its teeth in the same interval. Edges come from the CAD solids with hidden-line removal, in the studio’s technical drawing palette.