sl-mechanical
2fa72e169e
New chassis design files for the SaltyRover rough-terrain variant: • saltyrover_chassis_r2.scad — Deck plate (500×480×6mm Al, laser-cut DXF), 4× M3-adjustable pivot brackets, 4× CSI corner camera mounts (45° outward, 20° down), D435i front bracket (8° tilt), stem collar. All RENDER modes for STL and DXF export included. • rover_spring_arm.scad — Trailing-arm spring suspension (×4). Pivot on M8 bolt; captured 14mm OD compression spring (50mm free, ~5 N/mm); open-end axle dropout slot with retainer cap. Provides 25mm bump + 15mm droop travel. Bearing-seat recess for caliper-verified 37.8mm collar OD. • rover_electronics_bay.scad — PETG electronics bay (240×200×80mm internal). FC standoffs 30.5×30.5mm M3 and Jetson Orin 58×49mm M3 — shared SaltyLab swappable pattern. Ventilation slots all 4 walls + lid. Lid integrates 100mm RPLIDAR A1M8 tower (58mm BC, matched to rplidar_mount.scad). Split-print halves for 220mm beds included. • rover_chassis_r2_BOM.md — Full BOM, mass estimate (frame ~2.15kg; reduce to <2kg by setting DECK_T=5), assembly sequence, critical dimensions. Sensor positions: RPLIDAR top-centre on bay lid, D435i front, 4× IMX219 at deck corners. Shares 30.5mm FC + 58mm Jetson + Ø25mm stem patterns with SaltyLab for swappable electronics. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
329 lines
12 KiB
Markdown
329 lines
12 KiB
Markdown
# SaltyRover Chassis Rev 2 — BOM & Assembly Notes
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**Issue: #109 Agent: sl-mechanical Date: 2026-03-01**
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---
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## Overview
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Rev 2 adds spring suspension, an enclosed electronics bay, and corner CSI cameras
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to the SaltyRover platform (originally designed in issue #73).
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Sensor head, RPLIDAR, D435i, and vertical stem are **shared with SaltyLab** — no changes.
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```
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Top view (schematic):
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+Y (forward)
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│
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[CSI] ┌────┴────┐ [CSI]
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◉──┤ ├──◉ ← front axles (suspension arms)
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│ [Orin] │
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│ [ Bay ] │
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│ [RPLIDAR tower]
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│ [ FC ] │
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◉──┤ ├──◉ ← rear axles (suspension arms)
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[CSI] └────┬────┘ [CSI]
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│
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D435i →
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Deck footprint: 500 × 480 mm (Y × X)
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Track (axle C/C): 540 mm
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Wheelbase (axle C/C): 340 mm
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Ground clearance: 55 mm (static sag; 30 mm at full compression)
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Overall width (tyre edge to tyre edge): ~810 mm
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Overall height (deck to RPLIDAR top): ~317 mm
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```
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---
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## File Index
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| File | Description | Part | Qty |
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|------|-------------|------|-----|
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| `saltyrover_chassis_r2.scad` | Deck plate + pivot brackets + sensor brackets | Laser cut + 3D print | See below |
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| `rover_spring_arm.scad` | Spring suspension trailing arm + retainer cap | 3D print | 4× arm + 4× cap |
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| `rover_electronics_bay.scad` | Electronics bay body + lid (with RPLIDAR tower) | 3D print | 1× body + 1× lid |
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| `rover_motor_mount.scad` | Motor axle L-bracket (Rev 1, unchanged) | 3D print or CNC | 4× |
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| `rover_battery_tray.scad` | Under-deck battery slide tray (Rev 1) | 3D print | 1× |
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| `rover_stem_adapter.scad` | Stem-to-deck collar adapter (Rev 1) | 3D print | 1× |
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| `rplidar_mount.scad` | RPLIDAR anti-vibration ring (shared) | 3D print | 1× |
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| `realsense_mount.scad` | D435i bracket (integrated into chassis r2) | — | — |
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| `imx219_mount.scad` | IMX219 radial arm on sensor_head (unchanged) | — | — |
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---
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## Part A — Deck Plate (`saltyrover_chassis_r2.scad` → `deck_2d`)
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| # | Spec | Qty | Notes |
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|---|------|-----|-------|
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| A1 | 6 mm 5052-H32 aluminium, 500×480 mm blank | 1 | Waterjet or CNC router. 6 mm preferred (vs 8 mm Rev 1) for weight target. |
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| A1-alt | 8 mm PETG FDM, split in two halves, joined with M5 lap bolts | 1 | Prototype only — expect 1.5× weight, 0.5× stiffness |
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**Deck plate weight estimate:** 6 mm Al, ~50% lightening → **≈ 1.15 kg** ✓
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Export DXF:
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```bash
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openscad saltyrover_chassis_r2.scad -D 'RENDER="deck_2d"' -o saltyrover_r2_deck.dxf
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```
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---
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## Part B — Pivot Brackets (`saltyrover_chassis_r2.scad` → `pivot_bracket_stl`)
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Each bracket provides: M8 pivot for suspension arm + spring guide boss + M3 adjustment slots.
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| B1 | `pivot_bracket_stl` | 4 | PETG or PC | 5 perims, 60% gyroid |
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| B1-alt | `pivot_bracket_2d` | 4 | 8 mm 6061-T6 Al | CNC router / waterjet |
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CNC export:
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```bash
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openscad saltyrover_chassis_r2.scad -D 'RENDER="pivot_bracket_2d"' -o rover_pivot_bracket.dxf
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```
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**Fasteners — Bracket to Deck:**
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| B-f1 | M3×16 SHCS | 8 | Bracket to deck (2× per bracket) through slotted deck holes |
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| B-f2 | M3 nyloc nut | 8 | Under-deck retention (accessible from below before deck install) |
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| B-f3 | M3 flat washer | 16 | Both sides |
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**Fasteners — Suspension pivot:**
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| B-f4 | M8×50 SHCS | 4 | Pivot pin (bracket clevis → trailing arm) |
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| B-f5 | M8 nyloc nut | 4 | Pivot retention |
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| B-f6 | M8 flat washer | 8 | Both sides of clevis |
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| B-f7 | Flanged IGUS GFI-0810-10 bushing | 4 | Pivot arm bearing (optional, reduces wear) |
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---
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## Part C — Spring Suspension Arms (`rover_spring_arm.scad`)
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| C1 | `arm_stl` | 4 | PC (Polycarbonate) recommended; PETG acceptable | 5 perims, 60% gyroid infill |
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| C2 | `retainer_stl` | 4 | PETG | 4 perims, 40% infill |
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Export:
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```bash
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openscad rover_spring_arm.scad -D 'RENDER="arm_stl"' -o rover_spring_arm.stl
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openscad rover_spring_arm.scad -D 'RENDER="retainer_stl"' -o rover_spring_retainer.stl
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```
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**Compression Springs (×4):**
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| # | Spec | Qty | Notes |
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|---|------|-----|-------|
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| C-s1 | OD 14 mm, wire Ø 1.5 mm, free length 50 mm, spring rate ~5 N/mm | 4 | Lee Spring LCI 014M 05 S or equivalent |
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| C-s2 | *(Stiffer alternative)* OD 14 mm, rate ~8 N/mm | 4 | For heavier payloads >3 kg |
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**Retainer fasteners:**
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| C-f1 | M3×12 SHCS | 8 | Retainer cap to arm (2× per arm; self-taps into PETG) |
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---
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## Part D — Electronics Bay (`rover_electronics_bay.scad`)
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| D1 | `bay_stl` | 1 | PETG | 4 perims, 30% gyroid |
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| D1-alt | `front_half` + `rear_half` | 1+1 | PETG | For 220 mm bed printers (split at Y=0 centreline) |
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| D2 | `lid_stl` | 1 | PETG | 4 perims, 30% gyroid |
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Export:
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```bash
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openscad rover_electronics_bay.scad -D 'RENDER="bay_stl"' -o rover_elec_bay.stl
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openscad rover_electronics_bay.scad -D 'RENDER="lid_stl"' -o rover_elec_bay_lid.stl
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# For 220 mm beds:
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openscad rover_electronics_bay.scad -D 'RENDER="front_half"' -o rover_elec_bay_front.stl
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openscad rover_electronics_bay.scad -D 'RENDER="rear_half"' -o rover_elec_bay_rear.stl
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```
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**Bay-to-deck fasteners:**
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| D-f1 | M3×12 SHCS | 10 | Bay body to deck through floor flanges |
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| D-f2 | M3 flat washer | 10 | Under head |
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| D-f3 | M3×8 BHCS | 4 | Lid retention (corner screws self-tap into bay rim) |
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**Electronics internal (FC + Jetson standoffs — built into bay body):**
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| D-f4 | M3×8 SHCS | 8 | FC mount to bay standoffs (4×) + Jetson to bay standoffs (4×) |
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| D-f5 | M3 flat washer | 8 | Under heads |
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| D-f6 | Anti-vibration M3 grommet | 4 | FC isolation (silicone, M3, same as rplidar_mount.scad) |
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---
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## Part E — CSI Corner Camera Brackets (`saltyrover_chassis_r2.scad` → `csi_mount_stl`)
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| E1 | `csi_mount_stl` | 4 | PETG | 4 perims, 30% infill |
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Export:
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```bash
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openscad saltyrover_chassis_r2.scad -D 'RENDER="csi_mount_stl"' -o rover_csi_mount.stl
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```
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| E-f1 | M2×6 SHCS | 8 | CSI camera PCB to bracket (2× per camera) |
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| E-f2 | M3×8 SHCS | 8 | Bracket to deck (2× per bracket) |
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| E-c1 | 200 mm CSI FPC flat cable | 4 | IMX219 to Jetson (extended) |
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---
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## Part F — D435i Front Bracket (`saltyrover_chassis_r2.scad` → `d435i_mount_stl`)
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| # | RENDER | Qty | Material | Settings |
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|---|--------|-----|----------|----------|
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| F1 | `d435i_mount_stl` | 1 | PETG | 5 perims, 40% infill |
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Export:
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```bash
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openscad saltyrover_chassis_r2.scad -D 'RENDER="d435i_mount_stl"' -o rover_d435i_mount.stl
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```
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| # | Spec | Qty | Use |
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|---|------|-----|-----|
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| F-f1 | 1/4-20 UNC hex nut | 1 | Captured in bracket face for D435i tripod socket |
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| F-f2 | M4×14 SHCS | 2 | Bracket to deck front face |
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---
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## Mass Estimate — Frame Only (excl. motors, electronics, battery)
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| Assembly | Material | Est. mass |
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|----------|----------|-----------|
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| Deck plate | 6 mm Al, lightened | ~1.15 kg |
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| Pivot brackets × 4 | PETG | ~0.22 kg |
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| Spring arms × 4 | PC | ~0.28 kg |
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| Spring retainer caps × 4 | PETG | ~0.04 kg |
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| Springs × 4 | Steel | ~0.04 kg |
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| Electronics bay body | PETG | ~0.12 kg |
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| Electronics bay lid + RPLIDAR tower | PETG | ~0.08 kg |
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| CSI brackets × 4 | PETG | ~0.04 kg |
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| D435i bracket × 1 | PETG | ~0.03 kg |
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| Fasteners (M2–M8) | Stainless | ~0.15 kg |
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| **Frame total** | | **~2.15 kg** |
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> ⚠ Target: <2 kg frame. Current estimate is 0.15 kg over.
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> Options to reduce:
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> 1. Switch deck from 6 mm Al → 5 mm Al saves ~0.19 kg ✓
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> 2. Or: enlarge lightening holes from Ø55 → Ø65 mm (saves ~0.12 kg)
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> 3. Electronics bay in 2 mm wall PETG (saves ~0.06 kg)
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> Recommend option 1: change `DECK_T = 5.0` in `saltyrover_chassis_r2.scad`
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> and re-verify with waterjet quotation.
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---
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## Assembly Sequence
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### 1. Fabrication
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1. Export DXF and send deck plate to waterjet / CNC. Specify 6 mm (or 5 mm) 5052-H32 Al.
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2. Export and print all STL parts (settings per table above).
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3. Source springs, fasteners, and hub motors per BOM.
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### 2. Deck preparation
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1. Deburr all deck holes. Tap stem-collar M4 holes if using threaded standoffs.
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2. Press or thread M3 rivet-nuts into deck at battery-tray rail positions (from `rover_battery_tray.scad`).
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3. Apply stem collar with 4× M4×16 FHCS; Loctite 243.
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### 3. Pivot bracket installation
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1. Slide pivot bracket through deck M3 slots (under-deck side first).
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2. Fit M3 washers + nyloc nuts; snug but do not torque — leave adjustable.
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3. Set all 4 brackets to nominal Y position (motor corner fore-aft CL).
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4. Torque M3 bolts to 1.2 N·m once alignment is confirmed (step 6).
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### 4. Suspension arm assembly
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1. Drop spring into bracket spring-guide boss (compress by hand).
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2. Slide trailing arm pivot boss over pivot bolt M8×50.
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3. Fit IGUS bushing in pivot bore (if used).
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4. Fit M8 washer + nyloc nut; torque to 6 N·m.
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5. Snap retainer cap onto arm axle slot; thread 2× M3×12 by hand.
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### 5. Motor installation
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1. Slide hub motor axle into arm dropout slot.
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2. Fit clamp plate (from `rover_motor_mount.scad`); tighten M4 bolts 1.5 N·m.
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3. Thread axle lock nut; apply Loctite 243; torque to 30 N·m.
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4. Route phase cables + hall wires through deck phase pass-through hole.
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### 6. Geometry check and bracket torque
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1. Set robot on flat surface; check that all 4 wheels contact ground.
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2. Measure axle-to-ground on each corner. Nominal: 127 mm ± 5 mm.
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3. Adjust pivot bracket fore-aft position if needed to correct height.
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4. Torque all M3 bracket bolts to 1.2 N·m.
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### 7. Electronics bay + wiring
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1. Thread ESC/VESC harnesses through bay floor cable pass-throughs.
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2. Place electronics bay body on deck; fasten 10× M3×12 SHCS.
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3. Mount FC on bay standoffs: anti-vibration grommets + M3×8 SHCS.
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4. Mount Jetson Orin on bay standoffs: M3×8 SHCS.
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5. Route USB/UART cables internally; cable-tie to bay walls.
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6. Fit lid (with RPLIDAR tower stub); 4× M3×8 BHCS at corners.
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### 8. Sensor installation
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1. **RPLIDAR A1M8**: Fit anti-vibration ring (`rplidar_mount.scad`) on tower top.
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Bolt RPLIDAR with 4× M3×30 SHCS through ring.
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2. **D435i**: Bolt to front bracket arm using captured 1/4-20 nut.
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Confirm 8° downward tilt; tighten firmly.
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3. **4× CSI cameras**: Plug CSI flex into Jetson CSI ports.
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Thread M2×6 SHCS into each corner bracket PCB holes.
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4. **Stem + sensor head**: Press stem through deck collar bore.
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Fit stem adapter (`rover_stem_adapter.scad`); clamp at 550 mm height.
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Attach sensor_head to stem top as per `sensor_head_assembly.md`.
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### 9. Final checks
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- [ ] All wheels spin freely without catching wiring
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- [ ] Suspension compresses and rebounds on each corner
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- [ ] RPLIDAR scans 360° without obstruction (check deck edge clearance)
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- [ ] D435i USB connected and streaming
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- [ ] CSI cameras initialised on Jetson boot (`v4l2-ctl --list-devices`)
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- [ ] FC armed and IMU reading correctly
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- [ ] E-stop functional
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---
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## Motors (unchanged from Rev 1)
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| # | Part | Qty | Spec |
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|---|------|-----|------|
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| M1 | Hub motor | 4 | 10×2.125" pneumatic, 36 V, ~350 W; axle OD 16.11 mm (caliper) |
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| M2 | Phase cable extension | 4 | 3-wire 12 AWG, 300 mm, XT30 to VESC |
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| M3 | Hall cable extension | 4 | 6-pin JST-PH, 300 mm |
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---
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## Critical Dimensions
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| Dimension | Nominal | Tolerance |
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|-----------|---------|-----------|
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| Track (axle C/C) | 540 mm | ±2 mm |
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| Wheelbase (axle C/C) | 340 mm | ±2 mm |
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| Axle CL height | 127 mm | ±3 mm |
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| Pivot bracket M3 slot pitch | 32 mm | ±0.3 mm |
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| FC hole pattern | 30.5×30.5 mm | ±0.2 mm |
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| Jetson hole pattern | 58×49 mm | ±0.2 mm |
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| Stem bore | Ø25.5 mm | +0.3/0 |
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| Spring guide boss OD | Ø14 mm | ±0.1 mm |
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---
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## OpenSCAD Version Requirement
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Requires **OpenSCAD 2021.01 or newer** (for `linear_extrude` + `minkowski` with `$fn` in difference).
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Render command (full assembly):
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```bash
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openscad saltyrover_chassis_r2.scad &
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```
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