Implementation plan
From design review to first calibrated wind-tunnel data, in seven phases (indicative durations for a part-time student team with shop support).
| Phase | Work | Deliverable / exit test | Duration |
|---|---|---|---|
| 0. Close open items | Measure the downstream duct floor height and width and the space under the test-section exit; confirm side-load full scales and the largest model to be rolled; drawing review by an engineer / the shop; get vendor drawings (NMRV030, worm gearmotors, cam followers, V-wheels) | Signed-off REV B drawings | 2 wk |
| 1. Balance | Buy 7075 bar; wire-EDM the balance; CMM the necks and plates; bond and wire 24 gauges; insulation, zero and warm-box drift checks | Gauged balance, 6 live bridges, >10 GΩ to ground | 4-6 wk |
| 2. Roll spindle | Machine spindle, housing, caps, adapter, bracket; buy bearings, locknut, gearbox, motor, encoder; assemble and preload | ±90° roll, encoder within 0.05° of the inclinometer | 3-4 wk |
| 3. Calibration | Build the calibration hardware (CAD and drawings WT-6C-300 to 310 done); calibrate on the roll spindle at 7 roll angles; run the 233-point schedule with balance_calibration_fit_6c.py | cal.json that passes (check points ≤ 0.5 % FS) | 3-4 wk |
| 4. Pitch sector + yaw carriage | Pitch sector and yaw carriage CAD and drawings done (all yaw/pitch combinations clear; yaw drawings preliminary). Next: confirm the bay dimensions, release the yaw drawings, FEA, switches; fabricate; install in the bay | Full range with no collisions; repeatability ≤ 0.05° | 6-8 wk |
| 5. Electronics + software | Rig box (Pi, controller, drivers, ADCs, supplies, E-stop); grbl configuration; rig service (sequencer, interlock, DAQ, tares); station GUI; data reduction | Automated α-sweep with tares and logged data | 4-6 wk (parallel with 2-4) |
| 6. Integration + validation | Install, home, verify the envelope with a dummy model; wind-on checks at 70 and 100 mph; test a reference model (e.g. a NACA 0012 wing) and compare with published data; uncertainty estimate | Validated lift curve and drag polar; lab procedure | 2-3 wk |
Purchased parts and budget
The same breakdown as on the Project costs page.
| Item | Qty | Low (USD) | High (USD) |
|---|---|---|---|
| Hardware: machined and 3D-printed parts | |||
| Machined metal parts: JLCCNC quote + finishing steps (materials, drawing tolerances, staff-quoted parts, anodize), DHL Express delivered, less coupons | 49 pcs | 2,180 | 3,490 |
| 3D-printed reference pod WT-6C-004, PC-ABS (JLC3DP quote) | 1 | 113 | 113 |
| Subtotal | 2,293 | 3,603 | |
| Hardware: bought mechanical parts (drives, bearings, rolling elements, calibration) | |||
| Roll bearings 6907-2RS (2), KM7 locknut + washer | set | 40 | 60 |
| Roll drive: NMRV030 50:1 worm gearbox + NEMA 23 motor | 1 + 1 | 120 | 180 |
| Pitch and yaw drives: NEMA 17 + 40:1 / 30:1 worm gearmotors | 2 | 150 | 300 |
| Cam followers (4), V-wheels (8), 608 / R5 bearings, two m1.25 20T gears, shaft collars, fasteners | set | 200 | 350 |
| Calibration: dead weights, cable, lab jack, 0.01 deg inclinometer | set | 200 | 350 |
| Subtotal | 710 | 1,240 | |
| Electronics and instrumentation | |||
| Compute / motion (7 lines) | - | 220 | 270 |
| DAQ / sensors (12 lines) | - | 370 | 450 |
| Power / safety (9 lines) | - | 340 | 410 |
| Cables / connectors (9 lines) | - | 340 | 410 |
| Enclosure / misc (2 lines) | - | 140 | 180 |
| Strain gauges (24 x CEA-13, 350 ohm), AE-10 adhesive, gauge wire, terminals, coatings | 24+ | 400 | 600 |
| Subtotal | 1,810 | 2,320 | |
| Total project cost | 4,813 | 7,163 |
Import duty on the China orders, if charged as a separate line, is not included (see Project costs).
Risks and mitigations
| Risk | Effect | Mitigation |
|---|---|---|
| Drag resolution at 70 mph | ±15-20 % on minimum drag | run drag-critical tests at 100 mph; careful tares; base-pressure correction |
| Wires / tubes bridging the balance | parallel load path, false readings | thin wires with slack loops; no tubing across the balance; pressure tare check |
| Thermal drift | zero shift | matched gauge lot, temperature compensation, thermistor, frequent wind-off zeros |
| Stepper EMI / vibration | noise in µV signals | self-locking worms, drivers disabled during sampling, shielding |
| Backlash in roll / yaw | attitude error | approach from one side; output encoders; IMU in the pod |
| Collision with the walls | damage | envelope interlock per model, limit switches, E-stop, dry run with a dummy model |
| EDM / gauge-face quality | low or unequal sensitivity | CMM inspection; calibration absorbs the rest |
| Unconfirmed bay dimensions | yaw rails or sector do not fit | Phase 0 measurement; the yaw drawings (5xx) stay preliminary until then |
Open decisions
- Downstream duct floor height and width at the yaw rails (assumed 11.35 in below the centreline, 36 in wide).
- Space under the test-section exit: at ±15° yaw the carriage plate and inner rail reach about 2.3 in under the test-section floor. Either confirm the space is open or trim the carriage.
- Side-load full scales (8 lbf / 10 in-lbf / 30 in-lbf assumed) and the largest model span to be rolled.
- Station GUI software stack (the ADC is decided: 6x NAU7802; ADS1263 is the upgrade path).
- Gearbox-adapter wire window (WT-6C-204) for the 270° cable twist of calibration mode; encoder multi-turn homing on the pitch and yaw pinions.
- Small mounts not yet designed: pitch/yaw encoder mounts, SCL3300 inclinometer mount, limit-switch brackets and hard stops, Pico sensor-node mount, J0 connector bracket (they depend on the purchased switches and sensor boards).
- Whether motion is allowed with the wind on.