# SaltyBot Sensor Head — Assembly Diagram
**Rev A — 2026-02-28 — sl-mechanical**

---

## Overview

The sensor head mounts on top of the 25 mm OD vertical stem.
Five printed/machined parts stack on a split collar platform.

---

## TOP VIEW (schematic)

```
                         FRONT (+X)
                            ↑
              [IMX219 arm]  |  [IMX219 arm]
                  90°       |       0°
                  ↑    +---------+    ↑
                  |    |         |    |
    [IMX219]←----[•]---| RPLIDAR |---[•]----→[IMX219]
      270°        |    |  Ø70mm  |    |         90°
                  ↓    |         |    ↓
                       +---------+
                       |  PLAT   |
                       | Ø120mm  |
                       | (octag) |
                       +---------+
                  ↑    |         |    ↑
      [RS arm]---[•]---| COLLAR  |---[•]
                       |  Ø52mm  |
                       +---------+
                            |
                         25mm stem
                            ↓
```

---

## SIDE VIEW (section through front, to scale)

```
  Z
  ↑
  │
  │   RPLIDAR A1M8 (Ø70 × 30 mm)
  │  ┌────────────────────┐ ← Z ≈ 52 mm (top of RPLIDAR)
  │  │  ██████████████    │
  │  │  ██  A1M8  ██    │ ← Z ≈ 22 mm (bottom of RPLIDAR)
  │  └────────────────────┘
  │       │    │    │    │   ← M3×30 bolts (4 off)
  │  ┌────┴────┴────┴────┐
  │  │  rplidar_ring.scad│ ← Z = 14..18 mm  (4 mm ring)
  │  │   [silicone gromm]│ ← grommets 8 mm below ring
  │  └───────────────────┘
  │  ┌───────────────────┐
  │  │   P L A T F O R M │ ← Z = 36..44 mm
  │  │  (octag, Ø120mm)  │
  │  └───────────────────┘
  │       │ COLLAR │
  │  ┌────┴────────┴────┐
  │  │  COLLAR FRONT    │ ← Z = 0..36 mm
  │  │  │ stem bore │   │
  │  │  COLLAR REAR     │
  │  └──────────────────┘
  │          │
  │     25 mm STEM
  └─────────────────────────────────────── X
```

> **Note on Z references:** Z=0 is the bottom of the collar.
> Stem clamp bolts lock the sensor head at chosen height on the mast.

---

## IMX219 Arm (side view — one arm shown)

```
  Platform edge                          Camera PCB
      │                                      │
 ─────┤══════════════════════════════════════╗
      │  ←── 52 mm arm ──────────────────►  ║  IMX219
 ─────┤══════════════════════════════════════╝ ← 10° nose down
      │ 2× M4                          4× M2
      │ base bolts                     PCB bolts
      │ [slot: CSI ribbon through arm length]
```

---

## RealSense Arm (side view)

```
  Platform edge
      │ 2× M4
 ─────┤
      │  Base       ←── 75 mm arm ──────────────────►
 ─────┤  plate
      │  (flat)     ══════════════════════════════════╗
                                                      ║ ← 10° nose down
                                                      ║  D435i
                                                      ║  90×25×25
                                                 1/4-20 nut (captured)
```

---

## Assembly Sequence

| Step | Action |
|------|--------|
| 1 | Print 2× `collar_half` (flat-face-down; mirror one in slicer) |
| 2 | Print 1× `platform` |
| 3 | Print 1× `rplidar_ring` |
| 4 | Print 1× `realsense_bracket` |
| 5 | Print 4× `imx219_arm` (one per direction) |
| 6 | Seat 4× M3 silicone anti-vibration grommets in platform holes |
| 7 | Place rplidar_ring on grommets; pass 4× M3×30 SHCS from platform bottom up through ring |
| 8 | Set RPLIDAR A1M8 on ring; tighten M3×30 into RPLIDAR tapped holes (fingertight) |
| 9 | Thread 1/4-20 hex nut into realsense_bracket pocket; bolt D435i onto bracket |
| 10 | Bolt realsense_bracket to platform front with 2× M4×16 SHCS |
| 11 | Bolt 4× imx219_arm to platform with 2× M4×16 SHCS each |
| 12 | Snap IMX219 PCBs onto arm face plates with 4× M2×6 BHCS each |
| 13 | Route CSI ribbon cables through arm slots toward platform centre |
| 14 | Assemble collar halves around stem (flat faces mating); tighten M4×30 clamping bolts |
| 15 | Tighten M4 set screw in front collar half to lock height |
| 16 | Torque RPLIDAR M3 bolts: 0.5 N·m |

---

## Fastener Summary

| Qty | Size | Use |
|-----|------|-----|
| 2 | M4×30 SHCS | Collar clamping bolts |
| 1 | M4×10 set screw | Collar height / rotation lock |
| 2 | M4×16 SHCS | RealSense bracket to platform |
| 8 | M4×16 SHCS | IMX219 arms to platform (2 per arm) |
| 4 | M2×6 BHCS | IMX219 PCB to face plate (per arm; ×4 arms = 16 total) |
| 4 | M3×30 SHCS | RPLIDAR ring to platform (through grommet) |
| 4 | M3 anti-vibration grommet | Silicone, M3, Ø6 | Between platform and RPLIDAR ring |
| 1 | 1/4-20 hex nut | Captured in RealSense bracket |
| 2 | M4 hex nut | Captured in collar rear half |
| 8 | M4 flat washer | Under head of all M4 bolts |

---

## Print Settings

| Part | Material | Infill | Perimeters | Notes |
|------|----------|--------|-----------|-------|
| collar_half (×2) | PETG | 40% | 5 | Flat-face-down; print support-free |
| platform | PETG or PLA | 30% | 4 | Top-face-up |
| rplidar_ring | PETG | 30% | 3 | Flat |
| realsense_bracket | PETG | 35% | 4 | Base on bed; arm horizontal |
| imx219_arm (×4) | PETG or PLA | 30% | 3 | Flat, arm along X |
