# dronefactory24.uk Transmedium Superdrone - parametric build spec (prototype P1)

Dimensions are nominal targets for a first prototype, to be refined in CAD against the actual hull kit and
motors purchased. All values metric. This spec plus the exploded view and the FreeCAD macro
(`build_step_skeleton.py`) let a prototyping shop generate a STEP skeleton and iterate.

## Mass and balance target
- All-up weight (AUW): 1.2 - 1.6 kg
- Air thrust-to-weight: ~3.6 : 1 (4 x 2207-class at ~1.2 kg thrust each on 6S)
- Neutral-to-slightly-positive buoyancy submerged; ballast pump trims +/- 5% displacement

## Hull (bullet / torpedo)
- Overall length: 520 mm (nose cone 140 mm + body 300 mm + tail 80 mm)
- Body outer diameter: 110 mm; wall 3 mm ABS
- Split line: horizontal seam, O-ring groove 2 mm, 6 x M3 bolts
- Dry bay: 260 mm usable length, IP-sealed, holds FC stack + LiPo + RX/VTX
- Flood/ballast bay: tail 80 mm, peristaltic pump + reservoir bag 120 ml

## Arms / rotors (4, folding)
- Boom: 6061 aluminium tube OD 12 mm, ID 10 mm, length 180 mm from hull centreline
- Arm pitch: 4 arms at +/- 45 deg from longitudinal axis (X quad)
- Motors: 2207-class, M3 x 4 bolt circle 16 mm; props 5 inch (127 mm)
- Fold hinge: single M4 pivot per arm, detent at 0 deg (flight) and 90 deg (stow/dive)

## Water propulsion
- 1 x sealed underwater thruster (U-series, ~2-7 kgf) on tail centreline, or 2 x flanking
- Thruster lead through M10 cable penetrator, potted

## Seawater auxiliary cell
- Aluminium electrode: the frame tube (6061), exposed length ~120 mm
- Magnesium electrode: sacrificial-anode rod 12 mm dia x 80 mm, in a flow channel
- Flow channel: 16 mm bore, opens to sea via a one-way scoop when submerged
- Output: ~5-30 W to a buck converter feeding the avionics bus only (current-limited)

## Electronics bay layout (fore to aft)
1. FPV camera + VTX (nose, behind clear cap)
2. Flight controller + 4-in-1 ESC stack on 30.5 mm standoffs
3. 6S LiPo (1300-2200 mAh) on hook-and-loop, CG at 40% body length
4. ELRS RX, depth/pressure sensor (MS5837-class) on the bulkhead
5. Ballast pump + reservoir (tail)

## Penetrations (all O-ring or potted)
- 4 x motor leads (top), 1 x thruster lead (tail), 1 x ballast tube, 1 x antenna, 1 x charge/balance port

## Tools to assemble
Screwdriver, 1.5/2.0/2.5 mm hex, soldering iron, a butterknife (to pry the hull seam), epoxy, O-ring grease.