sl-mechanical
cd9299ded8
OpenSCAD parametric model for SaltyBot two-wheeled self-balancing robot chassis: - 600mm wheelbase, 170mm hoverboard hub motor fork dropouts - MAMBA F722S FC mount (30.5x30.5mm M3 pattern, 6mm nylon standoffs) - Battery tray for 24V 4Ah pack (185x72x52mm) with strap slots + vent holes - Jetson Nano B01 mount plate (58x58mm M3 pattern, 8mm standoffs) - Front/rear bumper brackets with 22mm EMT conduit saddle clamps - Longitudinal ribs, lightening holes, cable routing slots - BOM (32 line items) and step-by-step assembly notes Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
122 lines
5.1 KiB
Markdown
122 lines
5.1 KiB
Markdown
# SaltyBot Chassis — Assembly Notes
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**Task:** bd-1iy5 — Rev A — 2026-02-28
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---
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## Overview
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```
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[Front bumper rail — 22mm EMT]
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├─ bumper_bracket(front=+1) ──────────────────────┐
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│ │
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┌───────┴──────────── Main Deck (640×220×6mm Al) ─────────┴───────┐
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│ ← Jetson mount plate (rear/+X) FC mount (front/−X) → │
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│ [Battery tray hanging below centre] │
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└───┬──────────────────────────────────────────────────────────┬───┘
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│ │
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Motor fork (L) Motor fork (R)
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Hub motor CL: ±300mm from deck centre │
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Axle height: 310mm above ground │
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├─ bumper_bracket(front=-1) ──────────────────────┘
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[Rear bumper rail — 22mm EMT]
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```
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---
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## Step-by-step Assembly
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### 1 Fabricate / print parts
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- Send deck plate DXF (export from OpenSCAD → DXF) to CNC router or waterjet cutter.
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- Print motor fork brackets in PETG 5 perimeters / 40% gyroid for prototype, or send STEP to machine shop.
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- Print battery tray, FC pad, Jetson plate, bumper brackets in PETG.
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- Export STEP: OpenSCAD → Render (F6) → Export as STL, then convert with FreeCAD for STEP.
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### 2 Verify motor axle dimensions
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- Measure actual hoverboard motor axle: diameter and flat-to-flat.
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- Adjust `MOTOR_AXLE_D` and `MOTOR_AXLE_FLAT` in `chassis_frame.scad`.
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- Re-export fork dropout slot.
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### 3 Motor forks → deck
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1. Thread M5 T-nuts into underside of deck edge slots (or use M5 rivet nuts).
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2. Align fork bracket to deck edge; fasten with 4× M5×16 SHCS + flat washer each side.
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3. Apply Loctite 243 to threads. Torque to 4 N·m.
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### 4 Motors into forks
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1. Slide hub motor axle into dropout slot (flat side aligns with slot).
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2. Fit flat washer then flanged M14 axle nut; torque to 35–40 N·m.
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3. Feed motor phase wires and hall-sensor cable through deck cable slot.
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### 5 Longitudinal ribs
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1. Align ribs with edge grooves on deck underside.
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2. Secure with M4×12 SHCS through pre-drilled holes; torque 2.5 N·m.
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### 6 Battery tray
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1. Pass any wiring harness through deck wire-pass hole before mounting tray.
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2. Align tray mounting ears to deck M4 threaded inserts (or rivet nuts).
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3. Fasten 4× M4×12 SHCS. Torque 2.5 N·m.
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4. Insert battery pack; route Velcro straps through slots and cinch.
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### 7 FC mount (MAMBA F722S)
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1. Place silicone anti-vibration grommets onto nylon M3 standoffs.
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2. Lower FC onto standoffs; secure with M3×6 BHCS. Snug only — do not over-torque.
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3. Orient USB-C port toward front of robot for cable access.
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### 8 Jetson Nano mount plate
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1. Press or thread M3 nylon standoffs (8mm) into plate holes.
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2. Bolt plate to deck: 4× M3×10 SHCS at deck corners.
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3. Set Jetson Nano B01 carrier onto plate standoffs; fasten M3×6 BHCS.
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### 9 Bumper brackets
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1. Slide 22mm EMT conduit through saddle clamp openings.
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2. Bolt bracket to deck edge: 4× M5×16 SHCS per bracket.
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3. Position bumper rail flush with motor OD outer edge; tighten saddle clamp bolts.
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### 10 Cable routing
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- Route motor phase cables along longitudinal ribs; secure with cable clips.
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- FC ↔ ESC/VESC harness exits through front cable slot.
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- Jetson USB/UART ribbon exits through rear cable slot.
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- Power harness (battery XT60 → BMS → 24V bus) runs under deck along centreline.
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---
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## Critical Dimensions (verify before machining)
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| Dimension | Nominal | Tolerance |
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|-----------|---------|-----------|
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| Wheelbase (axle C/L to C/L) | 600 mm | ±1 mm |
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| Motor fork slot width | 24 mm | +0.5 / 0 |
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| Motor fork dropout depth | 60 mm | ±0.5 mm |
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| FC hole pattern | 30.5 × 30.5 mm | ±0.2 mm |
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| Jetson hole pattern | 58 × 58 mm | ±0.2 mm |
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| Battery tray inner | 185 × 72 × 52 mm | +2 / 0 mm |
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---
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## OpenSCAD Rendering Notes
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```bash
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# Render full assembly preview (F5 in GUI)
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openscad chassis_frame.scad
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# Export individual part STL for slicing
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openscad chassis_frame.scad -D "PART=\"motor_fork\"" -o motor_fork_right.stl
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# Export deck DXF (set DECK_THICKNESS=0.01 for 2D projection)
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openscad chassis_frame.scad -D "RENDER_2D=true" -o deck_plate.dxf
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```
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**Slicing profile (PETG, structural parts):**
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- Nozzle: 0.4mm | Layer: 0.2mm
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- Perimeters: 5 | Infill: 40% gyroid
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- Supports: Yes (motor fork dropout slot)
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- Orientation: Fork bracket printed vertically (load axis = layer direction)
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---
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## Safety Notes
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- Verify axle nut torque after first 10-minute ride — hub motors vibrate and may back off.
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- Battery tray is rated for packs ≤185×72×52mm; confirm dimensions before ordering cells.
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- Ground all aluminium chassis parts to power-common to avoid RF interference with FC.
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- Do **not** run robot without bumpers fitted — uncontrolled runaway risk.
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