DIY 5-inch racer build.

§ 01What we're cloning

The Neros Archer is a US-built 5-inch FPV designed for ISR + tactical payload work — small, fast, hard to source overseas. We can't and don't need to clone the mission systems. What we DO clone is the airframe envelope and propulsion class, swap in a Jetson Orin NX 16GB for autonomy, and bias the build for data-capture reliability over kinetic mission specs. (The earlier draft of this build used an Orin Nano Super 8GB — we moved to the NX once the AIGP pipeline's YOLO11n-pose + EKF + planner stack outgrew the Nano's 67-TOPS budget on the 25 m/s ATTACK profile.)

The DIY rig is intentionally not a race drone. Optimize for reliability + predictable dynamics so the residual-dynamics model sees clean data. Save the speed chase for Ohio.

§ 02Build at a glance

§ 03Bill of materials

Prices are 2026 USD street estimates. Always check current pricing at GetFPV, Pyrodrone, RaceDayQuads, RotorRiot, or the manufacturer direct. "Alt" rows are tested-good substitutes if the primary is OOS.

buy-link convention: buy opens a search at the primary retailer in a new tab. alt opens the suggested alternate.

§ 04Tools & consumables

Buy once, use forever. Most of these are shared across the team.

§ 05Cost summary

§ 06Propeller guide

The single biggest tunable on a quad is the propeller. Diameter, pitch, blade count, and material decide the entire personality of the build — efficiency, top speed, response sharpness, motor temperature, ESC current. For this rig we prioritise predictable dynamics for the sim-to-real model, not raw top speed.

§ 06.1 — Reading a prop label

The standard FPV label is DD×P×B — diameter × pitch × blade count. A 5×4.3×3 prop is 5 inches across, theoretically advances 4.3 inches per rotation, and has 3 blades.

§ 06.2 — Blade count tradeoffs

2-blade props are the most efficient; 3-blade is the universal default for race + freestyle; 5-blade trades efficiency for bite.

§ 06.3 — Material

Race-class props are polycarbonate (PC). Reinforced variants (PC + glass fill) last longer but cost a touch of response sharpness. For data capture you want consistency — swap any prop with chips, cracks, or splay-out, because a damaged prop changes dynamics non-linearly and pollutes the IMU trace the residual-dynamics model is trying to learn from.

§ 06.4 — Rotation pattern (props-out)

BetaFlight default for our build is "props out" — top-front blades spin away from the camera. Each motor takes one direction; iFlight / HQ ship props in matched pairs (2 CW + 2 CCW per pack of 4).

     ╲ CW M4 (FL)          M1 (FR) CCW ╱
         ╲                          ╱
            ╲                    ╱
                ╲    [FC ↑]   ╱
                    ╲      ╱
                       ╳
                    ╱      ╲
                ╱    [BAT]   ╲
            ╱                    ╲
         ╱                          ╲
     ╱ CCW M3 (BL)          M2 (BR) CW ╲

Pyramid mark on the prop hub points UP (away from the motor).
Mismatched direction = motor stalls + ESC overheats on takeoff.

§ 06.5 — Recommended sets by use case

§ 06.6 — Stocking strategy

Props are consumables. Plan:

• 1 set in service on the drone (4 props).
• 1 set spare ready to swap at the field (4 props).
• 5–10 sets stocked for a 30-minute training campaign per drone.
• Replace any prop after visible chip, dent, or audible vibe on bench-test. A damaged prop will desync motors and overheat the ESC.
• Discard the matched set. One bad prop = replace all four on that drone. A 0.05 g imbalance reads through the gyro and pollutes the data we're trying to capture.

§ 07Component stack

§ 08Assembly order

1. Frame prep. Unbox, deburr arms with 1000-grit, dry-fit all 8 frame screws. Confirm arm-plate orientation matches the camera bay you want.
2. Mount motors. Confirm CW/CCW pattern matches your ESC firmware. Industry-standard layout: M1 = front-right CCW, M2 = back-right CW, M3 = back-left CCW, M4 = front-left CW. Note the layout BEFORE soldering — if you get this wrong you'll fly inverted, briefly.
3. Solder motor leads to ESC. Twist three wires per motor, solder to numbered ESC pads. Pre-tin both. After all four are soldered, multimeter-test for shorts pad-to-pad and pad-to-XT60.
4. Mount ESC. 4 × M3 × 6 into the bottom plate via the soft-mount silicone grommets. Orient so the XT60 pigtail can reach the rear of the frame.
5. Solder XT60 + capacitor. Capacitor across battery leads on the ESC PDB side (negative stripe = ground). Heat-shrink the cap.
6. Stack the FC. 4 × M3 × 22 standoffs into the ESC mount points. Drop the Kakute H7 V2 on, FPV cam connector toward the front. Use included vibration isolators.
7. Connect ESC ↔ FC. 8-pin signal cable from ESC into the FC ESC port. Don't reverse it — pinout is keyed but a yanked cable can defeat the key.
8. Wire the radio. ELRS RX → FC UART6 (RX/TX/5V/GND). Mount RX on the rear with double-sided tape, antennas in a V (perpendicular polarization for diversity).
9. Wire the VTX. Walksnail VTX → FC UART3 (telemetry) and ESC 5V pad (power). Antenna out the back, secured with self-amalgamating tape.
10. Seat the NX module. Open the DAMIAO carrier, drop the Orin NX 16GB module into the SO-DIMM slot at ~30°, press flat until both retention latches click. Apply thermal paste to the module's heat-spreader, mate the heatsink, screw down.
11. Mount the top plate + DAMIAO carrier. 4 × M3 × 30 aluminum standoffs from the ESC plate up to the top plate. PETG carrier mount screws to the top plate with M3 × 6. Slip the 40 mm cooling fan into the channel between the carrier heatsink and the top plate; fan wires to one of DAMIAO's GH1.25 2-pin 5 V taps.
12. Wire NX power · XT30 direct. One XT30 male-to-female pigtail from the ESC PDB 6S pads to the DAMIAO's XT30 input. No external BEC needed — the carrier accepts 6S directly and runs its own buck to 5 V for the module. Verify polarity (red = +, black = −) before first power-up. Skip this row entirely if you fell back to J401 — see the BEC line in the BOM.
13. Wire MAVLink. DAMIAO ships with a GH1.25 4-pin cable for UART. Crimp/solder the free end to FC UART4: pin order on DAMIAO's UART header is 5V — TX — RX — GND. Connect TX ↔ FC RX4, RX ↔ FC TX4, GND ↔ FC GND. Don't tie the 5 V wire to the FC — the FC has its own 5 V rail.
14. Mount the camera. RPi Cam 3 Wide on the +20° PETG tilt mount, 22-pin → 15-pin ribbon to DAMIAO CSI0. Route ribbon away from ESC power leads to reduce EMI on the lane.
15. Final pass. Cable ties on everything, hot-glue on connectors that shake loose (RX coax, J401 GPIO header), antenna polarization check, battery strap fits. Visual inspection for solder bridges. Confirm the NX module's latches are still seated — the SO-DIMM can lift on hard landings if its retention clips aren't fully clicked.
16. Bench test. Props OFF. Smoke check at 6S. Read FC over USB in BetaFlight, confirm all 4 motors spin correct direction at 5 % throttle. Confirm NX boots (jtop on the host laptop over USB-C debug).

§ 09Power & wiring

FC pin assignments · Kakute H7 V2

§ 10Camera mount & tilt

§ 11Firmware · BetaFlight 4.5

The FC ships with BetaFlight 4.4 or generic INAV. We flash BetaFlight 4.5 because the H7 target file + RPM filter implementation are mature. Steps:

1. Install BetaFlight Configurator 10.10+ on the dev laptop. Linux/macOS/Windows.
2. Enter DFU. Short BOOT pad to GND, plug USB. The board enumerates as STM32 in DFU mode.
3. Pick the target. HOLYBRO-KAKUTEH7-V2 (or ...-V2.1 depending on the rev silkscreen).
4. Flash latest stable. Tick "Full chip erase". Reboot.
5. CLI configuration. Paste the configuration dump from build-guide v3 — sets ports, motor protocol (DSHOT600), RPM filtering, ELRS as primary RX, MAVLink on UART4 for the companion.
6. Calibrate accel + gyro. Drone level on the bench. Both calibrations in Setup tab.
7. Save & reboot. Quick power-cycle to verify settings persist.

§ 12Companion compute · Jetson Orin NX 16GB

The Orin NX shares its SO-DIMM 260-pin pinout with the Orin Nano — software you flash through the Nano's SDK Manager runs on the NX with identical JetPack images. The differences that matter for the build: 2× memory (16 GB vs 8 GB · headroom for the planner cache and EKF history buffer), 1.5× compute (100 TOPS vs 67 TOPS at MAXN · the YOLO11n-pose + segmentation + perception-aware PPO observation pass all fit inside the 33 ms frame budget at 25 m/s ATTACK profile), and ~67 % more power (25 W vs 15 W MAXN · the reason we sized the BEC to 6 A).

1. Flash JetPack 6.2+ via NVIDIA SDK Manager to the NVMe on a host laptop with the NX module + J401 in recovery mode (jumper REC↔GND while plugging USB). Skip the SD-card route — NVMe boot is ~6× faster and the NX module has no eMMC.
2. Boot, set hostname aigp-rig-01 through -04. Disable cloud-init dialog, enable SSH.
3. System packages.

   sudo apt install -y python3-pip python3-dev libgstreamer1.0-dev \
                        libcamera-dev v4l-utils mavlink-router

4. Camera driver. NX + IMX708: install the upstream imx708 overlay (NVIDIA forum thread B-15924, same as Nano). Confirm with v4l2-ctl --list-devices.
5. MAVLink bridge. mavlink-router from FC UART (/dev/ttyTHS1) → onboard UDP :14550. Our autonomy listener subscribes there.
6. Autonomy stack. git clone the AIGP repo (race pipeline), install the conda env, run python race/onboard/runner.py --rig=01. Use the same engine files (apex_yolo11n_pose.engine) compiled for Orin NX — re-compile with trtexec if your host built them for Nano.
7. Power-budget check. Set NX to MAXN mode: sudo nvpmodel -m 0 (yes, on the NX, mode 0 = MAXN/25 W; mode 1 = 15 W; mode 2 = 10 W). The 6 A BEC + 1000 µF cap absorb the boot spike (~5 A for 200 ms); confirm with a clamp meter on the 5 V rail during first cold boot.
8. Active cooling — required. The Orin NX hits thermal throttle at 87 °C. In our stack the 40 mm fan blows across the J401 heatsink at ~5000 RPM (5 V input, ~0.3 A). Without it, sustained 25 W on a sealed canopy will throttle to half-speed in < 60 s.

§ 13First-flight checklist

§ 14Tuning & PID notes

The default BetaFlight PIDs for a 5″ 6S race quad are reasonable. Three deviations for our build:

• D-term lowpass down to 100 Hz. The NX carrier on the top plate adds mass; bigger arm inertia = lower D-term frequency.
• Yaw P raised ~10 %. The +20° tilted camera + top-plate NX shift CoG slightly forward of the prop disk; yaw authority needs a nudge.
• Throttle expo +20. Smoother stick → motor curve gives the safety pilot more usable low-throttle range during hover trim.

RPM filter is on (default with BLHeli_32 + bidirectional DShot). If motors get noisy after a crash, balance the props before re-tuning.

§ 15Maintenance & spares strategy

§ 16Purpose · sim-to-real bridge

The DIY rig exists specifically to capture ~30 minutes of real-flight telemetry for the residual-dynamics model (playbook §04). Flight budget:

• ~10 min indoors, netted space · lightweight gate mockup · low speed
• ~15 min outdoors, daylight · dusk · shadow
• ~5 min high-dynamic · banking · recovery

§ 17Flight PCB v2 · custom carrier (stretch goal)

• Need on-board watchdog MCU — DAMIAO has no failsafe peripheral; if the NX brown-outs or thermal-trips, the FC has no way to know unless we add an STM32 sniffing the 5 V rail.
• Need stack-pattern footprint — DAMIAO is 87 × 50 mm; matching the standard 30.5 × 30.5 mm FC stack pattern would let us drop the dedicated carrier PETG mount entirely.
• Need shielded CSI/MAVLink routing — DAMIAO's connector placement is fine for IoT, but for the racing application we'd want CSI and MAVLink on opposite edges to keep ESC EMI off the camera lanes.

If we end up doing a v2 PCB, the design targets below describe what it would look like. Otherwise the DAMIAO V1.1 is good enough for the sim-to-real bridge and the first competition season.

Design targets

What we keep vs. what we drop

Development plan · in priority order

1. Reference-design study · pull the public NVIDIA Jetson Orin Nano/NX SO-DIMM Carrier Reference Design (DA-10797-001) and the Foxconn AS0B226 mech drawing.
2. Schematic capture in KiCad 9. Critical pins: PCIe x1 lanes (M.2), CSI-2 lanes, UART1, USB3.0, VDD_5V, power-good signaling.
3. Power chain · 6S → 5V/8A buck simulation in TI WEBENCH. Confirm ≥ 92 % at 4 A typical (NX MAXN + camera).
4. Layout · 4-layer · keep CSI differential pairs ≤ 50 Ω · matched-length to ±5 mils · separate analog ground island under the buck.
5. Prototype · OSH Park or JLCPCB · 5 boards, 5 sets of stencils. Hand-place the NX socket (1.0 mm pitch SO-DIMM).
6. Bring-up · power into VBAT input, no module yet · verify 5 V rail under 4 A load · verify 3.3 V LDO · verify watchdog boots.
7. Module test · seat NX, flash JetPack via USB-C OTG, confirm UART1 + CSI0 + M.2 enumerate.
8. Flight test · drop into a Nazgul5, fly the racing-doctrine pipeline end-to-end.

§ 18Quick-buy parts list

Flat scannable checklist with one buy button per item. For alternates, detailed notes, and direct-from-manufacturer links see the full § 03 BOM above.