Build — V1
V1 is a 100 mm regular tetrahedron: six printed edge assemblies, four outward air-core vertex coils, insulating corner couplers, and an overhead electronics platform. The design uses no cutting or machining — the screen is printed, not a metal tube, and the structure is the frame.
The edge
The most important physical decision was replacing the earlier helix assumption with straight parallel bundles. Straight strands preserve the source symmetry the centroid math expects, multiply authority through parallel copper, and keep the cut-to-centroid null Schur-exact.
Cross-section of one edge. Twenty 22 AWG strands press into keyed grooves on a printed spar — the groove floor is the positional datum, the lip only retains. All strands run the same direction and are paralleled at both ends (a serpentine single wire cancels its own field). A resistive conductive-PLA sleeve screens the strand potentials and is eddy-transparent by resistivity; it bonds to the star hub at exactly one end.
Full parts list
For one L = 100 mm build (Track A, magnetic). Quantities scale per the build order: single edge → full six → vertex coils → simultaneous drive. Source: build/EDGE_BOM_2026-06.md + build/K4_SYSTEM_SPEC_2026-06.md.
| item | spec | qty | source |
|---|---|---|---|
| Structure (printed) | |||
| Edge spars | Ø10 mm round, 20 keyed grooves, end flanges; L = 100 mm | 6 | plain PLA/PETG (on hand) |
| Screen sleeves | ID 13 mm, 1.2 mm wall; half-shells (iter) or tube (keeper) | 6 | Protopasta Conductive PLA |
| Vertex couplers | insulating, registers 3 spars + VC port + 4 lead channels | 4 | plain PLA/PETG |
| Coil cradles | clip to VC port, grip coil OD, winding center at vertex+25 mm | 4 | plain PLA/PETG |
| Overhead platform + star hub | mast + disk; electronics + single ground point | 1 | plain PLA/PETG |
| Conductors | |||
| Magnet wire | 22 AWG solderable enamel (MW 80-C); ~2 m per edge ×6 + slack | 1 spool (8 oz) | Remington Industries |
| Vertex coils | Dayton LW181 air-core, 1.0 mH, 18 AWG, Ø49×17.8 mm — AIR CORE ONLY, never IC steel-core | 4 | Parts Express / Dayton |
| Copper foil tape | screen bond bands + star-hub pad | on hand | — |
| Electronics — stage 1 (single-edge rig) | |||
| Controller | Teensy 4.1, NO-PINS (supply-flagged — order first) | 1 | SparkFun / PJRC / Amazon |
| Stacking headers | SparkFun Teensy stackable kit (female up) + male strip (shield down) | 1 set | SparkFun / Adafruit #400 |
| Audio shield | Teensy Audio Adapter, Rev D2 (Teensy 4.x pinout) | 1 | PJRC / SparkFun |
| Amplifier | dual audio power amp (existing) — line-out can't drive a bundle directly | 1 | on hand |
| Ballast resistors | 2 Ω, ≥10 W, NON-inductive (thick-film); defines I=V/R into the mΩ bundle | 2 (→6 for full) | DigiKey / Mouser |
| Pickup coil | small sense coil → audio-shield line-in (phase-locked lock-in) | 1 | hand-wound |
| Vertex-coil drive (DC family — NOT the audio path) | |||
| Current source | linear (OPA548/LM675 + sense R) preferred, or DRV8871 H-bridge + LC | 4 ch | DigiKey / Mouser |
| Sense shunts | per-channel current sense → Teensy ADC | 4 | DigiKey / Mouser |
| Consumables / tools (mostly on hand) | |||
| Insulative tape / heatshrink | lead dressing; tape for iteration, shrink at settled lugs | on hand | — |
| Ferrite clamp-ons | common-mode chokes at the platform end of each pair | on hand | — |
| 3D printer | Bambu A1 (256 mm bed — not the mini) | 1 | Bambu Lab |
| Iron, multimeter, LCR | assembly + acceptance checks | on hand | — |
Deliberately excluded: iron/ferrite in the field region (air-core linearity is the product), aluminum frame members near the tetrahedron, copper tube (the printed screen replaces it), and the corner-electrode / MHz / array hardware (gated, later build phases).
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Patent pending.