sl-mechanical
5bb5c7f863
Replaces placeholder 185x72x52mm battery spec with caliper-verified pack dimensions. 2 packs side-by-side is the default config. Geometry impact: - PLATE_DEPTH reduced to 210mm (2x88mm + 17mm margin each side) - Battery zone: 420x176mm centred between motor forks (fits 600mm wheelbase) - Mount holes repositioned: 4 per pack x 2 packs = 8 M4 holes at (±(BATT_L/2 - 18), ±BATT_W/2) - Velcro strap slots: 25mm wide, pierce full plate depth at x=±BATT_L/4 - 4-pack expansion: optional M5 shelf bolt holes when BATT_PACKS=4 (only viable 4-pack layout is 2+2 underdeck — analysed in BOM) - Battery ghost in assembly preview shows 2-pack deck layout 4-pack analysis (added to BOM): in-line 840mm > wheelbase, side-by-side 352mm > plate depth → 2+2 underdeck shelf is the only viable 4-pack configuration Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
151 lines
7.0 KiB
Markdown
151 lines
7.0 KiB
Markdown
# SaltyBot Chassis — Bill of Materials
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**Task:** bd-1iy5 / prototype-baseplate
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**Rev:** B — 2026-02-28 (updated with caliper-verified axle measurements)
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**Agent:** sl-mechanical
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---
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## ⚠ Axle Measurement Update (Rev B)
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PR #7 (`chassis_frame.scad`) used placeholder values. The table below records the
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**caliper-verified** hub motor axle dimensions. All new designs must use these.
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| Feature | Measured | PR #7 placeholder | Delta |
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|---------|----------|-------------------|-------|
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| Axle base diameter (round, near hub) | **16.11 mm** | 14 mm | +2.11 mm |
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| D-cut shaft OD | **15.95 mm** | — (not modelled) | new |
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| D-cut flat chord | **13.00 mm** | — | new |
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| Total axle protrusion | **65.5 mm** | ~60 mm est. | +5.5 mm |
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| Base section length | **15.0 mm** | — | new |
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| D-cut section length | **43.35 mm** | — | new |
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| Tip / shoulder | **3.0 mm** | — | new |
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| Bearing seat collar OD | **37.8 mm** | — | new |
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| Tire OD | **254 mm** (10×2.125") | 170 mm motor OD only | — |
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| Axle CL height above ground | **127 mm** | 310 mm (wrong) | −183 mm |
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`chassis_frame.scad` should be updated in a follow-on task to match Rev B values.
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---
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## Structural / Fabricated Parts
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### Prototype Base Plate (`prototype_baseplate.scad`) — Rev B
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| # | Part | Qty | Material | Cut size | Notes |
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|---|------|-----|----------|----------|-------|
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| 1 | Prototype base plate | 1 | 6mm 5052-H32 aluminium **or** 8mm clear acrylic | 680×220mm blank | Laser or CNC; export DXF from `RENDER="plate_2d"` |
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| 2 | Dropout clamp — lower (L+R) | 2 | 8mm 6061-T6 aluminium | 90×70mm blank each | Round bore Ø16.51mm; `RENDER="clamp_lower_2d"` |
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| 3 | Dropout clamp — upper (L+R) | 2 | 8mm 6061-T6 aluminium | 90×70mm blank each | D-cut bore (Ø16.25mm, 13.6mm flat chord); `RENDER="clamp_upper_2d"` |
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| 4 | FC standoff M3×6mm nylon | 4 | Nylon | — | MAMBA F722S vibration isolation |
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| 5 | Ø4mm alignment pin | 8 | Steel dowel | 16mm length | Clamp-to-plate alignment (2 per clamp stack) |
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### Full Chassis (`chassis_frame.scad`) — Rev A (placeholder values — pending Rev B update)
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| # | Part | Qty | Material | Notes |
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|---|------|-----|----------|-------|
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| 6 | Main deck plate | 1 | 6mm 5052 aluminium plate, 640×220mm | CNC router or waterjet; all holes per `chassis_frame.scad` |
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| 7 | Longitudinal rib (front) | 1 | 4mm 5052 aluminium, 600×40mm | Laser-cut; press-fit into deck slots |
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| 8 | Longitudinal rib (rear) | 1 | 4mm 5052 aluminium, 600×40mm | Same file, symmetric |
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| 9 | Motor fork bracket (L) | 1 | 8mm 6061 aluminium | **Update fork slot to Ø16.51mm before cutting** |
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| 10 | Motor fork bracket (R) | 1 | 8mm 6061 aluminium | Mirror of item 9 |
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| 11 | Battery tray | 1 | 3mm PETG FDM or 3mm aluminium fold | `chassis_frame.scad` — `battery_tray()` module |
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| 12 | FC mount plate / standoffs | 1 set | PETG or nylon FDM | Includes 4× M3 nylon standoffs, 6mm height |
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| 13 | Jetson Nano mount plate | 1 | 4mm 5052 aluminium or 4mm PETG FDM | B01 58×58mm hole pattern |
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| 14 | Front bumper bracket | 1 | 5mm PETG FDM | Saddle clamps for 22mm EMT conduit |
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| 15 | Rear bumper bracket | 1 | 5mm PETG FDM | Mirror of item 14 |
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---
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## Motors
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| # | Part | Qty | Source / Spec | Notes |
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|---|------|-----|---------------|-------|
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| 16 | Hoverboard hub motor | 2 | 10×2.125" pneumatic tire, 36V nominal, ~350W | Axle: Ø16.11mm base / Ø15.95mm D-cut / 13mm flat; bearing seat Ø37.8mm — **all caliper-verified** |
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| 17 | Motor hall-sensor cable extension | 2 | 6-pin JST-PH 300mm | Route through deck cable slot |
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| 18 | Axle lock nut | 4 | M16×1.5 or thread-matched to actual axle tip | Confirm thread at tip before ordering; calipers show Ø≈10mm at tip |
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---
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## Electronics Mounts
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| # | Part | Qty | Spec | Notes |
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|---|------|-----|------|-------|
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| 13 | STM32 MAMBA F722S FC | 1 | 36×36mm PCB, 30.5×30.5mm M3 mount | Oriented USB-C port toward front |
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| 14 | Nylon M3 standoff 6mm | 4 | F/F nylon | FC vibration isolation |
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| 15 | Anti-vibration grommet M3 | 4 | Ø6mm silicone | Under FC mount pads |
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| 16 | Jetson Nano B01 module | 1 | 69.6×45mm module + carrier | 58×58mm M3 carrier hole pattern |
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| 17 | Nylon M3 standoff 8mm | 4 | F/F nylon | Jetson board standoffs |
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---
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## Battery
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> **Rev B update:** previous placeholder (185×72×52 mm) replaced with real pack dimensions.
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| # | Part | Qty | Spec | Notes |
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|---|------|-----|------|-------|
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| 18 | Battery pack | 2 (default) | 24V, 420×88×56 mm each | Sit side-by-side on deck (2-pack = 420×176 mm footprint). Up to 4 packs with underdeck shelf. |
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| 19 | Velcro strap 25mm × 500mm | 4 | One per strap slot × 2 slots × 2 packs | Pass through 25mm plate slots at x=±105mm; cinch over pack |
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| 20 | BMS board | 1–2 | Matched to cell chemistry | Mount to deck underside near battery centre; one BMS can parallel both packs |
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| 21 | 4-pack underdeck shelf plate | 0 (option) | 6mm Al, 440×200mm | Required only for 4-pack config; attaches via M5 shelf bolts; carries 2 more packs below main deck |
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| 22 | M5×20 shelf bolt + nut | 8 | SS, for underdeck shelf | Only for 4-pack config; M5 holes in main plate are pre-punched when `BATT_PACKS=4` |
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### Battery footprint analysis
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| Config | Width (Y) | Length (X) | Fits on 600mm wheelbase? | Notes |
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|--------|-----------|-----------|--------------------------|-------|
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| 2-pack (default) | 176 mm | 420 mm | ✅ Yes | Centred between forks |
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| 4-pack (in-line) | 176 mm | 840 mm | ❌ No | 840 > 600 mm wheelbase |
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| 4-pack (side-by-side) | 352 mm | 420 mm | ❌ No | 352 > 210 mm plate depth |
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| 4-pack (2+2 underdeck) | 176 mm | 420 mm | ✅ Yes | 2 packs below main deck via shelf |
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---
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## Bumper Rail
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| # | Part | Qty | Spec | Notes |
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|---|------|-----|------|-------|
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| 21 | 3/4" EMT conduit | 2 | 22mm OD, 660mm length | Front and rear bumper rail; bent or straight |
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| 22 | Conduit saddle clamp M4 | 6 | 3D-printed integral to bracket (items 9/10) | Back-up: standard pipe clamp 22mm |
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---
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## Fasteners
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| # | Part | Qty | Spec |
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|---|------|-----|------|
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| 23 | M5×16 SHCS | 24 | ISO 4762, SS |
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| 24 | M5 hex nut | 24 | ISO 4032, SS |
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| 25 | M4×12 SHCS | 12 | ISO 4762, SS |
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| 26 | M4 hex nut | 12 | ISO 4032, SS |
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| 27 | M3×10 SHCS | 20 | ISO 4762, SS |
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| 28 | M3 hex nut | 20 | ISO 4032, SS |
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| 29 | M3×6 BHCS | 8 | FC + Jetson board bolts |
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| 30 | M14×1.5 axle nut | 4 | One each side per motor, flanged | Confirm axle thread pitch on actual motors |
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| 31 | Serrated washer M14 | 4 | Axle anti-rotation |
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| 32 | Flat washer M5 | 48 | SS |
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---
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## Tools Required for Assembly
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- Torque wrench (M14 axle nuts: 35–40 N·m; M5: 4 N·m)
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- M2.5 / M3 / M4 / M5 hex drivers
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- Thread locker (Loctite 243 blue for all structural fasteners)
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- Dial caliper — verify motor OD, axle flat before machining fork slot
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---
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## Estimated Masses
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| Assembly | Est. mass |
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|----------|-----------|
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| Aluminium deck + ribs | ~1.1 kg |
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| Motor forks (×2 Al) | ~0.4 kg |
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| Motors (×2) | ~3.6 kg |
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| Battery (6S 4Ah LiPo) | ~0.7 kg |
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| Electronics (FC + Jetson + wiring) | ~0.5 kg |
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| Bumpers + brackets | ~0.3 kg |
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| Fasteners | ~0.2 kg |
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| **Total estimate** | **~6.8 kg** |
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