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Single source of truth for all geometry-driving variables used in FreeCAD CAD, PRUSA slicing, hardware specification, and master specification. No other document may redefine these values. Open this file before starting any CAD work.

libdrone V2.4.6 — Global Parametric Variable Table¶

This file is the single source of truth for all geometry-driving variables used in: - FreeCAD CAD - PRUSA slicing profiles - Hardware specification - Master Specification - Any V2.4.6+ libdrone documentation

All geometry entry fields in FreeCAD must reference these variables directly (=Variables.Name syntax). No other Markdown files may redefine these values.

[1] FRAME GEOMETRY¶

[2] ARM GEOMETRY¶

[3] ROD ARCHITECTURE¶

Arm orientation logic: - FL/RL arms: normal orientation → +5 mm & +2 mm - FR/RR arms: inverted → −5 mm & −2 mm - Rod length: 333.0 mm (scaled from 258mm at 255mm wheelbase — confirm in FreeCAD Assembly)

[4] SANDWICH BODY GEOMETRY¶

Derived: - SandwichHeight = #PETGBotLayerThick + 3× #PCCFLayerThick + #PETGTopLayerThick = 16.0 mm ✓ - Layer stack (bottom → top): PETG 3mm / PCCF 3mm / PCCF 3mm / PCCF 3mm / PETG 4mm - V2.4.6: PETG top layer is now a clean structural surface — battery rails, MIPI channel, wire channels, GX12 chimney, fan slot all live in the Platform (see section [12]), not the X body. - Rod interference fit (#RodDiaChannelCore) applies ONLY to PETG bottom layer core zone

[5] TAB GEOMETRY¶

Lock geometry: T-profile — tab widens at tip by #TabLockWidth. PCCF layers have matching T-slot pocket — tab cannot be pulled out without fracturing PCCF. Tab slides in from side during assembly.

[6] MOTOR MOUNT GEOMETRY¶

Derived: - ORingRimOD = #ORingCBoreDia + 2 × #ORingRimWall = 8.0 mm

[7] CABLE MANAGEMENT GEOMETRY¶

V2.4.6: All cable management features (MIPI channel, wire channels, battery lead notch, fan slot) have moved from the X body PETG top layer into the Platform (see section [12]). Variables below remain valid — they now describe Platform geometry.

[8] BATTERY SPOILER — REMOVED (V2.4.6 DECISION)¶

Dropped. The always-on fan + open-frame design provides adequate electronics cooling without a dedicated air scoop. The spoiler added complexity, a crash-release failure mode, and ~3g with no measurable benefit in hover-dominated mapping flights. All #Spoiler variables are retired. Do not reference in CAD.

Notes: - Fan is always-on, hardwired to FC 5V pad. No switching, no thermostat. - Fan EXHAUSTS rearward — sucks air through the electronics zone front-to-rear. - In forward flight: ram air enters through front arm root gaps and battery zone → crosses FC/ESC/VTX → fan pulls it out rear face. - In hover: fan creates pressure differential pulling prop wash through open lateral gaps. - 5V nominal draw ~70mA. Optional: wire to 3.3V LDO for ~35mA and near-silent operation. - Fan slot is in the rear face of the Platform rear shroud — not in the X body sandwich. - Ball bearing variant — adequate for always-on low-RPM clean-air application.

[9] GX12-7 DUAL PAYLOAD CONNECTOR GEOMETRY (V2.4.6 — replaces GX12-12)¶

CONNECTOR POLARITY (V2.4.6 — physically verified): DRONE side (Platform chimney): GX12-7 MALE panel mount — pins face upward toward payload — dust cap protects pins between payload swaps — anti-rotation flats prevent spinning when payload is connected/disconnected — secured with double nut + Loctite 243 blue against vibration PAYLOAD side (payload cable): GX12-7 FEMALE cable mount — sockets receive drone-side pins — swapped with each payload module

Shared geometry (identical for both connectors):

CHIMNEY BORE PROFILE — D-D SHAPE (critical for anti-rotation): The chimney bore is NOT a simple round hole. The male connector body has two parallel flats machined opposite each other. The bore must match this D-D profile to prevent the connector from rotating when payloads are connected/disconnected. In FreeCAD Sketcher: draw a circle diameter #GX12ChimneyBoreOD (11.87mm), then add two parallel constraint lines at ±(#GX12ChimneyBoreFlatFlat/2) = ±5.40mm from centre, trim the circle arcs outside those lines. Result: D-D profile. The nut bears against the Platform underside at the #GX12BodyOD (11.67mm) collar.

VIBRATION RETENTION: Single nut is insufficient — drone vibration will back it off in flight. Use: double nut (inner against Platform, outer locks against inner) + Loctite 243 blue (medium strength) on the outer nut thread. The chimney housing also prevents connector body rotation.

Position variables (A = left/signal, B = right/power):

Notes: - Both chimneys share the same Y position — side by side at Y = −66mm. - Connector A wire exit faces LEFT (toward signal wire channel at X = −20mm). - Connector B wire exit faces RIGHT (toward power wire channel at X = +20mm). - Battery exits RIGHT — Connector B chimney (X = +25mm, OD = 18mm) does not obstruct. Battery rail inner width 41mm, battery 40mm — battery clears chimney at X = +25mm. ✓ - Verify both chimneys clear ESC edge and FC standoffs in FreeCAD Assembly before commit.

Pinout — Connector A (LEFT, X = −25mm): signal + power PIN 1 5V regulated (FC BEC, 2A continuous) PIN 2 GND primary PIN 3 UART4 TX (FC → payload) PIN 4 UART4 RX (payload → FC) PIN 5 I2C SCL (400kHz) PIN 6 I2C SDA (400kHz) PIN 7 SPARE

Pinout — Connector B (RIGHT, X = +25mm): data + aux PIN 1 GND shield PIN 2 GPS TX tap (via 1MΩ series resistor on FC side) PIN 3 UART5 TX (FC → payload, secondary) PIN 4 UART5 RX (payload → FC, secondary) PIN 5 AUX GPIO 1 (master enable / radio switch 1, 3.3V) PIN 6 AUX GPIO 2 (camera control / radio switch 2, 3.3V) PIN 7 SPARE

[9b] BATTERY RAIL GEOMETRY¶

Side-slide battery architecture. Battery exits RIGHT side of Platform. Platform is the middle layer — battery never requires backplane removal. Tri-blade props oriented one blade vertical (by hand after disarm) for clearance.

Reference battery: Tattu 150C-1800mAh-6S-XT60 — 78×40×53mm (L×W×H) Orientation: 78mm nose-to-tail, 40mm side-to-side, 53mm vertical. Battery centred on X body core: front edge +39mm, rear edge −39mm from body centre.

Notes: - Battery rails are integral to the Platform middle layer — NOT the X body top PETG layer. - LEFT rail: longer — includes GX12 chimney integrated at electronics zone. - RIGHT rail: open right end for battery exit. Closed left end (endstop wall). - Battery slides in from RIGHT, locks against LEFT endstop wall. - Strap runs laterally (left-to-right), buckle on RIGHT side — accessible during swap. - Prop clearance verified: battery at 40mm wide, at centre position, 48.9mm clearance per side to nearest motor. ✓ - Prop orientation for battery swap: rotate each tri-blade prop so one blade points UP (2 sec per arm by hand after disarm).

[10] MAST INTERFACE GEOMETRY (sensor payload)¶

[11] GPS/CAMERA BRACKET GEOMETRY¶

V2.4.6 change: Bracket carries GPS (top) + Camera (middle) ONLY. VTX has moved from this bracket into the electronics zone of the Platform. MIPI cable (225mm) runs nose-to-tail through the Platform MIPI channel from camera to VTX. Camera-to-VTX distance: ~198mm. 225mm cable leaves ~26mm service loop. ✓

V2.4.6 change: Camera tilt is now FIELD-ADJUSTABLE via a two-bolt arc-slot mechanism. No tools beyond a 2.5mm hex key. Full adjustment takes ~15 seconds. Use cases: 0–10° for terrain mapping, 15–20° for general/camping, 25–30° for skating/acro.

Adjustable tilt mechanism — how it works: - The camera plate is a separate printed part (not one piece with the bracket upright). - PIVOT BOLT: upper M3, fixed hole in bracket upright. Camera plate rotates around this. - SLOT BOLT: lower M3, runs in a 3.3mm-wide arc slot. Tightening locks the plate at angle. - Arc slot is centred on the pivot bolt, radius = #BracketPivotSpacing = 20mm. - Slot arc length covers the full 30° range (0° to 30°). - Visual index marks at 0°, 5°, 10°, 15°, 20°, 25°, 30° are embossed on bracket face. - Finger-readable in field — no protractor needed. - Both bolts M3 × 8mm cap head (hex socket). 2.5mm hex key. Torque: finger-tight + 1/4 turn. - No spring, no detent — friction lock only. Adequate for the low vibration forces on the bracket.

Camera plate geometry: - Rectangular plate: 26mm wide × 22mm tall × 4mm thick. - Camera body slot: 19mm wide × 19mm tall (HDZero camera ±0.5mm), centred. - Pivot hole: Ø3.3mm, upper centre. - Slot clearance hole: Ø3.3mm in camera plate, aligns with bracket arc slot at any angle.

Index marks (embossed 0.4mm deep on bracket face, beside the arc slot): 0° → label "MAP" (level, terrain mapping) 10° → label "10" 15° → label "15" (default) 20° → label "20" 25° → label "25" 30° → label "ACRO"

[12] ASSEMBLY OFFSETS & CLEARANCES¶

• Rod entry chamfer: 0.5 mm × 45°
• Tab T-lock clearance: 0.2 mm per side (slide fit)
• Motor head → arm face: air gap required under passive cover
• Passive cover: contacts ONLY o-ring bosses in motor head zone
• Section views in CAD required for validation at every revision

[13] PLATFORM GEOMETRY (V2.4.6 NEW, V2.4.6 UPDATED)¶

The Platform is the middle structural layer — a single PETG part that sits on top of the X body sandwich and extends forward (camera/GPS zone) and rearward (electronics zone) beyond the X body footprint.

Three-layer architecture: BOTTOM: X body sandwich + arms (structural core) MIDDLE: Platform — camera bracket / battery / electronics / fan / antenna TOP: Backplane — hot-swap payload interface (air quality, mapping, etc.)

V2.4.6 change: Platform has a STEPPED WIDTH profile. Battery zone and nose: 40mm wide (battery-constrained, prop-clearance verified). Electronics zone (Y = −44mm to tail): 50mm wide (+5mm each side). The step provides a physical ledge that retains the ESC laterally, improves PCB security, and gives a wider landing footprint at the tail. The step begins exactly at the electronics zone front, 5mm behind the battery rear edge. The Backplane width matches the widest zone (50mm) to provide continuous coverage.

All positions are measured from the X body centre (body nose-tail axis = Y axis, positive = nose, negative = tail; lateral axis = X axis, positive = right).

Prop clearance summary (updated for stepped width — verified geometrically): Camera bracket (+110 to +50mm): 12.7mm/side @ 40mm width ✓ Battery (+39 to −39mm): 48.9mm/side @ 40mm width ✓ Step transition at Y = −44mm: step occurs here, width → 50mm ESC (−44 to −89mm): 20.9mm/side @ 50mm width ✓ (was 25.9mm @ 40mm) Motor Y position (−116.7mm): 15.7mm/side @ 50mm width ✓ TIGHTEST POINT — verify in CAD VTX (−104 to −133mm): 17.4mm/side @ 50mm width ✓ (was 22.4mm @ 40mm) Fan (−138 to −148mm): 22.4mm/side @ 50mm width ✓ (was 27.4mm @ 40mm)

⚠ The 15.7mm clearance at Y = −116.7mm (motor Y, step zone) is the new tightest point. This is above the 15mm design minimum but has zero headroom. Verify in FreeCAD cross-section view BEFORE printing the Platform. If clearance reads < 15mm in CAD, reduce #PlatformWidthElec by 1mm (to 48mm) before proceeding.

Backplane width update: #BackplaneWidth updated from 40mm to 50mm to match the wider electronics zone. Battery zone right edge remains open for battery egress — this is unaffected by width step. All three post pairs (Y = +39, −39, −148mm) remain at their Y positions. Post pair at Y = +39mm (battery front) sits at the step transition — posts at X = ±17mm which is within the narrow zone (±20mm) — posts are unchanged. ✓

Backplane interface: - Top surface of Platform electronics zone (50mm wide) is the backplane mounting surface. - Dual GX12-7 female connectors protrude above Platform surface. - Backplane modules locate on GX12-7 connectors and M3 boss pads. - Hot-swap: unscrew M3s, unplug both GX12-7s, lift backplane module. - Battery swap does NOT require backplane removal.

[14] BACKPLANE GEOMETRY (V2.4.6 NEW)¶

The Backplane is a PETG crash exoskeleton — a diamond/hexagonal open lattice that sits on top of the Platform, spanning from the battery front to the fan rear. Primary role: protect electronics and battery on falls and side impacts. Secondary role: standardised mounting surface for payload modules (air quality, etc.).

NOT a solid cover — ~65% open area for airflow. Fan exhausts freely through rear zone. Battery swaps sideways (RIGHT) under the open right edge of the lattice — no removal needed.

Payload modules mount ON TOP of the backplane. Backplane is the interface layer. GX12-7 male connector (drone side) passes through a reinforced boss ring in the lattice.

Attachment posts (3 pairs, one per side at each position): Post pair A: Y = +39 mm (battery front edge — front of backplane) Post pair B: Y = −39 mm (battery rear edge — rear of battery zone) Post pair C: Y = −148 mm (fan rear — tail of backplane) Posts are integral to Platform — printed as part of Platform body. Backplane lattice seats on post tops. M3 screw through lattice into post.

Battery zone (Y = +39 to −39 mm): RIGHT SIDE FULLY OPEN — no beam or rail on right edge in this zone. Battery slides out RIGHT under open lattice edge. No backplane removal needed. Left edge: standard lattice beam (structural, retained).

Fan exhaust zone (Y = −138 to −148 mm): NO lattice material — fully open for rearward fan exhaust. Backplane tail beam runs across at Y = −148 mm only (tail edge).

GX12 zone (Y = −66 mm, X = −25 mm): Reinforced boss ring in lattice: #BackplaneGX12BossOD × #BackplaneGX12BossThick. Drone-side GX12-7 male connector protrudes upward through boss ring. Payload female cable connector plugs in from above.

Lattice pattern (recommended — verify in FreeCAD): Two longitudinal spine beams (left and right edges, full length). Transverse ribs every #BackplaneRibSpacing — 10 ribs total. Diagonal cross-members at 45° in alternating bays for racking resistance. Extra rib at Y = +39 mm (battery front post), Y = −39 mm (battery rear post). No diagonals in battery zone right side — open for battery egress.

Estimated mass: ~7 g (35% fill, 187×50×1.5mm envelope, PETG Natural). Material: PETG Natural. Intentionally flexible — impact energy distributed through lattice. Post-process: heat-gun pass optional. Epoxy wipe not required (not structural load path).

[15] PI BAY AND COMPANION INTERFACE GEOMETRY¶

The Pi bay is a thin-walled PETG tray printed separately from the Backplane. It sits on top of the Backplane in the mast zone, raising the payload mast mounting surface by 6mm. It houses an optional Pi Zero 2W compute module. When the Pi is not fitted, a printed cover plate fills the bay.

The companion UART harness is pre-installed in every drone during build — a 4-wire JST-SH loom soldered to the FC companion UART, routed through the Platform signal channel, terminated at the Pi bay base. It is capped and unused when no Pi is fitted. FC UART6 is reserved as COMPANION permanently.

Pi bay mass targets:

hw_pi_bay_empty_target      = 4.0 g    # PETG tray + cover plate
hw_pi_zero_2w_target        = 11.0 g   # Pi Zero 2W (when fitted)
hw_pi_buck_converter_target = 5.0 g    # 5V buck from battery rail (when fitted)
hw_pi_wiring_target         = 3.0 g    # companion harness inside drone (always)
hw_companion_harness_total  = 3.0 g    # pre-installed during build, always

Note: The Pi bay raises the payload mast boss pad surface by #PiBayInternalHeight (6mm) above the Backplane surface. Payload mast height references must account for this when the bay is fitted. The bay is fitted on ALL builds. The Pi is optional.

END — libdrone V2.4.6 Unified Variable Table¶

Revision History¶