sl-mechanical
3e4764b3eb
Add parametric OpenSCAD designs for the SaltyRover stable 4-wheel variant. Reuses existing 25mm stem, sensor head, and all SaltyLab sensor mounts without modification. Files: - saltyrover_chassis.scad 480×500mm deck, stem collar, FC+Orin standoffs, motor attachment holes, battery tray opening; RENDER deck_2d for waterjet/CNC DXF - rover_motor_mount.scad L-bracket + axle clamp plate per motor; uses caliper-verified axle dims from BOM.md; dropout slot for tool-free motor swap; RENDER bracket_2d for CNC DXF - rover_battery_tray.scad Slide-out tray for 2-4 × 420×88×56mm packs laid flat (low CG); T-slot rails, spring latch - rover_stem_adapter.scad Flange + split clamp locks 25mm stem to deck collar; 550mm stem option for rover height - rover_BOM.md Assembly sequence, fastener table, mass estimate (~13.4kg), height stack diagram Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
229 lines
8.2 KiB
Markdown
229 lines
8.2 KiB
Markdown
# SaltyRover Chassis — BOM + Assembly Notes
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**Rev A — 2026-03-01 — sl-mechanical**
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**Issue: #73**
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---
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## Overview
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SaltyRover is the stable 4-wheel variant of SaltyLab.
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Low CG, wide track — designed not to tip over.
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Reuses the 25 mm vertical stem, sensor head, RPLIDAR, RealSense,
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IMX219 camera mounts, and roll cage from SaltyLab without modification.
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```
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Top view (schematic):
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Forward (+Y)
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│
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◉─────────────────────◉ ← front axle (AXLE_BASE/2 = 170 mm forward)
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│ [Orin NX] │
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│ [battery] │ ← flat packs below deck (low CG)
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│ [battery] │
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│ [FC] │
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◉─────────────────────◉ ← rear axle
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│
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stem (centre)
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Dimensions (approx):
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Robot width (tyre-to-tyre): ~810 mm (TRACK_W=540 + 2×TIRE_W/2)
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Robot length (axle-to-axle): ~340 mm (AXLE_BASE)
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Deck width: 480 mm
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Deck length: 500 mm
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Ground clearance: ~50 mm (deck bottom to ground)
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Overall height (with 550 mm stem + sensor head): ~800 mm
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```
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---
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## Height Stack
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```
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Z from ground:
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Z = 0 mm — ground
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Z = 50 mm — chassis bottom (battery tray floor)
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Z = 109 mm — deck bottom face
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Z = 117 mm — deck top face (Z=0 in SCAD coords)
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Z = 127 mm — motor axle CL (+10 mm above deck top)
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Z = 139 mm — deck stem collar top (117+22)
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Z = 145 mm — stem adapter flange top (139+6)
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Z = 173 mm — stem clamp top (145+28)
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Z = 723 mm — stem top with 550 mm rover stem
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```
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---
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## File Index
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| File | Description | RENDER |
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|------|-------------|--------|
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| `saltyrover_chassis.scad` | Main deck plate, stem collar, standoffs | `assembly` / `deck` / `deck_2d` |
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| `rover_motor_mount.scad` | L-bracket + axle clamp plate, 4× | `assembly` / `bracket` / `clamp_plate` / `bracket_2d` |
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| `rover_battery_tray.scad` | Slide-out battery tray, 2–4 packs | `assembly` / `tray` / `rail` / `latch` / `tray_2d` |
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| `rover_stem_adapter.scad` | Flange + split clamp, locks stem to deck | `assembly` / `base_flange` / `clamp_front` / `clamp_rear` |
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---
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## Part A — Deck Plate (`saltyrover_chassis.scad`)
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### Structural parts
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| # | RENDER | Qty | Material | Process | Notes |
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|---|--------|-----|----------|---------|-------|
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| 1 | `deck_2d` | 1 | 8 mm 5052-H32 Al | Waterjet or CNC router | 480×500 mm blank |
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| — | — | — | **or** 8 mm PETG FDM | Print in sections, bolted lap joints | Prototype only |
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### Fasteners (deck to motor brackets)
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 2 | M5×20 SHCS | 16 | Motor bracket flange to deck (4 per corner × 4) |
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| 3 | M5 hex nut | 16 | Captured on deck underside |
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| 4 | M4×16 SHCS | 4 | Stem adapter flange to deck collar |
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| 5 | M4 flat washer | 4 | Under bolt head |
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---
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## Part B — Motor Brackets (`rover_motor_mount.scad`)
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Print or CNC 4×. Each bracket handles one drive motor.
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### Printed parts
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| # | RENDER | Qty | Material | Settings | Notes |
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|---|--------|-----|----------|----------|-------|
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| 6 | `bracket` | 4 | PETG or PC | 5 perims, 60% infill | Print flange face down; add M5 inserts or use nuts |
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| 7 | `clamp_plate` | 4 | PETG | 4 perims, 40% infill | Axle retention; print flat |
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**CNC alternative:** `bracket_2d` → DXF, CNC route from 10 mm 6061-T6 Al plate.
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### Fasteners
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 8 | M4×20 SHCS | 8 | Axle clamp plate to bracket (2 per motor × 4) |
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| 9 | M4 hex nut | 8 | Captured in bracket |
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| 10 | Axle lock nut | 4 | Axle tip retention — **verify axle thread before ordering** (BOM.md: Ø≈10 mm tip) |
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| 11 | M5×20 SHCS | 16 | Bracket flange to deck (from item 2 above) |
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> ⚠ **Axle note:** BOM.md caliper values: base OD 16.11 mm, D-cut OD 15.95 mm, flat chord 13.00 mm.
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> Verify AXLE_D / AXLE_FLAT / BEARING_OD in `rover_motor_mount.scad` before printing.
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---
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## Part C — Battery Tray (`rover_battery_tray.scad`)
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### Printed parts
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| # | RENDER | Qty | Material | Settings | Notes |
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|---|--------|-----|----------|----------|-------|
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| 12 | `tray` | 1 | PETG | 4 perims, 30% infill | Print open-top face up; no supports |
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| 13 | `rail` | 2 | PETG | 5 perims, 40% infill | T-slot slide rail; print top-face down |
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| 14 | `latch` | 1 | PETG or TPU 95A | 4 perims, 30% infill | Spring retention clip; TPU gives better snap feel |
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### Fasteners
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 15 | M4×12 FHCS | 6 | Slide rail to deck underside (3 per rail, countersunk) |
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| 16 | M4 T-nut or nyloc | 6 | Captured under deck for rail bolts |
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| 17 | M3×10 SHCS | 2 | Spring latch to tray end |
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| 18 | Velcro strap 25 mm × 500 mm | 4–8 | Battery pack retention (1–2 per pack through tray floor slots) |
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### Batteries
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| # | Part | Qty | Spec |
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|---|------|-----|------|
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| 19 | Battery pack | 2–4 | 24 V, **420×88×56 mm** (BOM.md caliper-verified) |
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| 20 | BMS board | 1 | Matched to cell chemistry; mount to deck underside near Y+ wall |
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---
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## Part D — Stem Adapter (`rover_stem_adapter.scad`)
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| # | RENDER | Qty | Material | Settings | Notes |
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|---|--------|-----|----------|----------|-------|
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| 21 | `base_flange` | 1 | PETG | 5 perims, 40% infill | Print flat; add M4 brass inserts or use through-bolts |
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| 22 | `clamp_front` | 1 | PETG | 5 perims, 40% infill | Flat-face down |
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| 23 | `clamp_rear` | 1 | PETG | 5 perims, 40% infill | Mirror; flat-face down |
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### Fasteners
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| 24 | M4×20 SHCS | 2 | Stem clamp clamping bolts |
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| 25 | M4 hex nut | 2 | Captured in clamp rear half |
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| 26 | M4×8 set screw | 1 | Rotation lock (front half) |
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| 27 | M4×16 FHCS | 4 | Flange to deck collar (countersunk) |
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### Stem tube
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| # | Part | Qty | Spec | Notes |
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|---|------|-----|------|-------|
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| 28 | Vertical stem | 1 | 25 mm OD × 1.5 mm wall 6061-T6 Al, **550 mm length** | Cut from 1 m stock; SaltyLab uses 1000 mm |
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> Sensor head, RPLIDAR, cameras, and roll cage from SaltyLab mount
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> directly onto this 25 mm stem — no modifications required.
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---
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## Motors
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Same hoverboard hub motors as SaltyLab. **4× required for rover.**
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| # | Part | Qty | Spec |
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|---|------|-----|------|
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| 29 | Hub motor | 4 | 10×2.125" tire, 36V nominal, ~350W; axle OD 16.11mm (caliper) |
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| 30 | Motor cable extension | 4 | 6-pin JST-PH 300 mm hall sensor + 3-phase power |
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---
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## Mass Estimate
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| Assembly | Est. mass |
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|----------|-----------|
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| Al deck plate | ~1.4 kg |
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| Motor brackets × 4 (PETG) | ~0.5 kg |
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| Hub motors × 4 | ~7.2 kg |
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| Battery packs × 2 | ~1.4 kg |
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| Battery tray (PETG) | ~0.3 kg |
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| Stem + sensor head (from SaltyLab) | ~1.5 kg |
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| Electronics (FC + Orin + wiring) | ~0.6 kg |
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| Stem adapter + hardware | ~0.2 kg |
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| Fasteners | ~0.3 kg |
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| **Total estimate** | **~13.4 kg** |
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> Wide 540 mm track + low 117 mm deck height → tip-over angle > 45°.
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> CG is at approximately Z = 200 mm with packs flat and full payload.
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---
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## Assembly Sequence
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1. **Deck plate:** Cut or print `deck_2d`. Waterjet preferred for Al.
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2. **Motor brackets:** Print (or CNC) 4× `bracket` + 4× `clamp_plate`.
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- Test-fit axle D-cut bore before assembling to deck.
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3. **Slide rails:** Print 2× `rail`. Bolt to deck underside.
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4. **Stem adapter:** Print `base_flange` + `clamp_front` + `clamp_rear`.
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- Insert stem through deck collar bore; seat flange on collar top.
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- Bolt flange with 4× M4×16 FHCS.
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- Slide clamp halves on stem above flange; tighten M4 clamping bolts (1.5 N·m).
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- Tighten M4 set screw.
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5. **Motor brackets:** Slide flange into deck edge slot; 4× M5×20 bolts.
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- Do not torque until axle alignment is confirmed.
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6. **Motors:** Drop axle into bracket dropout slot. Install clamp plate.
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- Tighten clamp M4 bolts. Axle lock nut finger-tight + ¼ turn.
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7. **Battery tray:** Slide tray in from +X with packs loaded.
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- Latch snaps at full insertion.
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8. **Sensor head + stem accessories:** Install from SaltyLab as-is.
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- Recommend 550 mm stem for rover (sensor head at ~720 mm, stable).
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---
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## Tools Required
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- M3/M4/M5 hex drivers
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- Torque wrench: M5 structural bolts 4 N·m, M4 clamp bolts 1.5 N·m
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- Thread locker (Loctite 243 blue) on axle lock nuts and stem clamp set screw
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- Dial caliper — verify axle dimensions before bracket print/CNC
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