chassis/gopro_mount.scad

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+// ============================================================
+// gopro_mount.scad — GoPro 3-Prong T-Slot Sensor Rail Mount
+// Issue: #195  Agent: sl-mechanical  Date: 2026-03-02
+// ============================================================
+//
+// Universal GoPro camera mount for sensor_rail.scad (T-slot 2020).
+//
+// Top interface:   Standard GoPro 3-prong (HERO 5+)
+//                  Prongs slide into standard GoPro accessories.
+//                  No additional clips or fasteners needed.
+//
+// Bottom clamp:    T-slot 20×20 mm rail system (OpenBuilds compatible).
+//                  M3 thumbscrew retention + M5 index holes for 15° detents.
+//
+// Tilt mechanism:  Rotating hinge bracket allows camera tilt 0°–90° from
+//                  horizontal, locked at 15° increments via index holes.
+//                  Rotation axis is perpendicular to rail (about Y-axis).
+//
+// Assembly:
+//   1. Print gopro_mount_base (single part, flat-side-down, no supports)
+//   2. Slide built-in T-nut into rail T-groove
+//   3. Clamp with M3 thumbscrew from outside rail face
+//   4. Rotate camera to desired tilt angle (0°, 15°, 30°, ... 90°)
+//   5. Insert M5 alignment pin to lock tilt
+//
+// RENDER options:
+//   "mount"        assembled mount view (default)
+//   "base_stl"     base clamp for slicing (print flat)
+//   "camera_bracket" rotatable camera bracket for slicing
+// ============================================================
+
+RENDER = "mount";
+
+// ── GoPro 3-prong interface (top) ──────────────────────────
+// Standard GoPro HERO 5+ 3-prong attachment point.
+// Overall footprint ~43×25 mm, 3 prongs slide into camera mounting slot.
+
+GOPRO_WIDTH     =  43.0;       // front-to-back along camera face
+GOPRO_DEPTH     =  25.0;       // left-to-right width
+GOPRO_PRONG_H   =   5.0;       // height of prongs above base
+GOPRO_PRONG_D   =   4.0;       // diameter/thickness of each prong
+GOPRO_PRONG_SP  =  14.0;       // spacing between outer prongs (centre-to-centre)
+
+// Centre prong is at Y=0; outer prongs at Y±GOPRO_PRONG_SP/2
+// Prongs extend upward (+Z direction)
+
+// ── T-slot clamp (bottom) ──────────────────────────────────
+// Matches sensor_rail.scad T-slot 2020 dimensions.
+RAIL_W          =  20.0;       // rail outer width/height
+SLOT_INNER_W    =  10.2;       // T-groove inner width
+SLOT_INNER_H    =   5.8;       // T-groove inner height (depth)
+SLOT_NECK_H     =   3.2;       // distance from outer face to T-groove
+
+TNUT_W          =   9.8;       // printable T-nut width (SLOT_INNER_W - 0.4)
+TNUT_H          =   5.5;       // printable T-nut height (SLOT_INNER_H - 0.3)
+TNUT_L          =  12.0;       // T-nut body length
+TNUT_BOLT_D     =   3.3;       // M3 clearance bore through T-nut
+
+THUMB_D         =  16.0;       // thumbwheel OD (visual only)
+THUMB_H         =   8.0;       // thumbwheel height
+
+// Index hole pitch for tilt detents
+INDEX_PITCH     =  25.0;       // 25 mm spacing on rail
+TILT_ANGLE_STEP =  15.0;       // 15° tilt detents (0°, 15°, 30°, ... 90°)
+M5_INDEX_D      =   5.3;       // M5 clearance hole diameter
+
+// ── Rotation/tilt mechanism ───────────────────────────────
+// Camera bracket rotates about Y-axis relative to base.
+// Rotation axis is at the rail clamp interface (Z=0, Y=0).
+// Tilt range: 0° to 90°.
+
+MAX_TILT_DEG    =  90.0;       // maximum tilt angle
+
+// Hinge pin: M5 bolt passes through base and camera bracket
+HINGE_PIN_D     =   5.3;       // M5 bolt clearance
+HINGE_PIN_L     =  25.0;       // pin length (accommodates rail width + brackets)
+
+// ── General ────────────────────────────────────────────────
+$fn = 64;
+e   = 0.01;
+
+// ─────────────────────────────────────────────────────────────
+// gopro_mount_base()
+//   T-slot clamp bracket with integrated T-nut.
+//   Mounted at bottom, rail clamp at Z=0 face.
+//   Hinge pin axis at Y=0, rotates camera bracket ±X.
+//
+// Print: flat-side-down (rail face down), no supports needed.
+// ─────────────────────────────────────────────────────────────
+module gopro_mount_base() {
+    clamp_h = RAIL_W + 8.0;    // total clamp height
+    clamp_w = TNUT_L + 8.0;    // clamp width (along rail)
+    clamp_d = 18.0;             // clamp depth (front-to-back)
+
+    difference() {
+        union() {
+            // Main clamp body
+            translate([-clamp_w/2, -clamp_d/2, 0])
+                cube([clamp_w, clamp_d, clamp_h]);
+
+            // T-nut integration: slot to hold T-nut at rail interface
+            // T-nut sits in T-groove when rail is inserted from above
+            translate([-TNUT_L/2, -TNUT_W/2, SLOT_NECK_H])
+                cube([TNUT_L, TNUT_W, TNUT_H]);
+
+            // Hinge boss (supports rotation axis pin)
+            translate([-HINGE_PIN_L/2 - 2, -8, clamp_h - 4])
+                cube([HINGE_PIN_L + 4, 4, 4]);
+        }
+
+        // Rail bore (25.4 mm) — matches stem adapter pattern
+        // When rail is vertical, this bore slides onto rail extrusion
+        translate([0, 0, -e])
+            cylinder(d=RAIL_W + 0.4, h=clamp_h + 2*e);
+
+        // T-nut through-bolt (M3 thumbscrew hole)
+        // Bolt comes from outside rail face, through T-nut, clamping it
+        translate([0, 0, SLOT_NECK_H + TNUT_H/2])
+            rotate([90, 0, 0])
+                cylinder(d=TNUT_BOLT_D, h=clamp_d + 2*e);
+
+        // Hinge pin (M5) passes through base to camera bracket
+        translate([-HINGE_PIN_L/2, 0, clamp_h - 2])
+            rotate([0, 90, 0])
+                cylinder(d=HINGE_PIN_D, h=HINGE_PIN_L + 2*e);
+
+        // Index hole pockets for tilt angle lock (M5)
+        // One index hole on each side to lock camera tilt
+        for (angle = [0 : TILT_ANGLE_STEP : MAX_TILT_DEG]) {
+            // Holes are radially spaced around the hinge axis
+            y_offset = (HINGE_PIN_L/2 - 2) * sin(angle);
+            z_offset = clamp_h - 2 - (HINGE_PIN_L/2 - 2) * (1 - cos(angle));
+            translate([0, y_offset, z_offset])
+                cylinder(d=M5_INDEX_D, h=4, center=false);
+        }
+
+        // Vent slots (optional, aesthetic + weight reduction)
+        for (dz = [4, 8, 12])
+            translate([-clamp_w/2 + 2, -clamp_d/2 - e, dz])
+                cube([clamp_w - 4, 2, 1.5]);
+    }
+}
+
+// ─────────────────────────────────────────────────────────────
+// gopro_camera_bracket()
+//   Rotatable bracket that holds GoPro camera via 3-prong mount.
+//   Rotates about Y-axis (hinge pin), tilt 0°–90°.
+//
+// Hinge pin (M5 bolt) enters from base and locks bracket rotation.
+// Index hole on bracket aligns with base index holes at each 15° step.
+//
+// Print: flat-side-down (prong face down), no supports.
+// ─────────────────────────────────────────────────────────────
+module gopro_camera_bracket() {
+    bracket_h = GOPRO_WIDTH + 8.0;   // height when vertical
+    bracket_w = GOPRO_DEPTH + 6.0;   // width (left-right)
+    bracket_t = 4.0;                  // bracket thickness
+
+    difference() {
+        union() {
+            // Main bracket body
+            translate([-bracket_w/2, -bracket_t/2, 0])
+                cube([bracket_w, bracket_t, bracket_h]);
+
+            // Hinge pivot boss
+            translate([-HINGE_PIN_L/2 - 2, 0, bracket_h - 4])
+                cube([HINGE_PIN_L + 4, bracket_t, 4]);
+
+            // GoPro prong mounting boss
+            translate([-GOPRO_DEPTH/2, 0, bracket_h - GOPRO_WIDTH/2])
+                cube([GOPRO_DEPTH, bracket_t + 2, GOPRO_WIDTH]);
+        }
+
+        // Hinge pin bore (M5)
+        translate([-HINGE_PIN_L/2, 0, bracket_h - 2])
+            rotate([0, 90, 0])
+                cylinder(d=HINGE_PIN_D + 0.2, h=HINGE_PIN_L + 2*e);
+
+        // Index hole (M5) for angle lock
+        // Bracket has one index hole that aligns with base holes at tilt angles
+        translate([GOPRO_DEPTH/2 + 1, 0, bracket_h - 4])
+            cylinder(d=M5_INDEX_D, h=bracket_t + 2*e);
+
+        // GoPro prong socket (3 mounting prongs)
+        // Centre prong at Y=0, outer prongs at Y±GOPRO_PRONG_SP/2
+        for (dy = [0, GOPRO_PRONG_SP/2, -GOPRO_PRONG_SP/2]) {
+            translate([0, bracket_t + e, bracket_h - GOPRO_WIDTH/2 + 5 - dy])
+                rotate([90, 0, 0])
+                    cylinder(d=GOPRO_PRONG_D + 0.4, h=4);
+        }
+    }
+}
+
+// ─────────────────────────────────────────────────────────────
+// gopro_prong_interface()
+//   Visual representation of the 3 prongs that camera mounts to.
+//   Not printed; shown during assembly view.
+// ─────────────────────────────────────────────────────────────
+module gopro_prong_interface() {
+    bracket_h = GOPRO_WIDTH + 8.0;
+    bracket_w = GOPRO_DEPTH + 6.0;
+
+    // 3 cylindrical prongs
+    for (dy = [0, GOPRO_PRONG_SP/2, -GOPRO_PRONG_SP/2]) {
+        translate([0, bracket_w/2 + 0.5, bracket_h - GOPRO_WIDTH/2 + 5 - dy])
+            rotate([90, 0, 0])
+                cylinder(d=GOPRO_PRONG_D, h=GOPRO_PRONG_H, $fn=32);
+    }
+}
+
+// ─────────────────────────────────────────────────────────────
+// Assembly view: base + rotatable camera bracket
+// ─────────────────────────────────────────────────────────────
+module gopro_mount_assembly() {
+    // Base clamp (fixed)
+    color("SteelBlue", 0.9)
+        gopro_mount_base();
+
+    // Camera bracket (rotatable, at 45° tilt for visualization)
+    color("CornflowerBlue", 0.85)
+        rotate([0, 45, 0])
+            translate([0, 0, RAIL_W + 8])
+                gopro_camera_bracket();
+
+    // Visual GoPro prongs
+    color("LightSteelBlue", 0.7)
+        rotate([0, 45, 0])
+            translate([0, 0, RAIL_W + 8])
+                gopro_prong_interface();
+
+    // Phantom M5 hinge pin (visual reference)
+    color("Silver", 0.5)
+        translate([-HINGE_PIN_L/2, 0, RAIL_W + 8 - 2])
+            rotate([0, 90, 0])
+                cylinder(d=5, h=HINGE_PIN_L);
+}
+
+// ─────────────────────────────────────────────────────────────
+// Render selector
+// ─────────────────────────────────────────────────────────────
+if (RENDER == "mount") {
+    gopro_mount_assembly();
+
+} else if (RENDER == "base_stl") {
+    // Flat print orientation: rail-facing side down
+    rotate([180, 0, 0])
+        translate([0, 0, -RAIL_W - 8])
+            gopro_mount_base();
+
+} else if (RENDER == "camera_bracket") {
+    // Flat print orientation: prong-facing side down
+    rotate([0, 0, 0])
+        translate([0, 0, GOPRO_WIDTH + 14])
+            rotate([180, 0, 0])
+                gopro_camera_bracket();
+}

chassis/gopro_mount_BOM.md

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+# GoPro 3-Prong T-Slot Sensor Rail Mount — BOM + Assembly
+**Rev A — 2026-03-02 — sl-mechanical**
+
+---
+
+## System Overview
+
+Universal GoPro HERO 5+ camera mount for sensor_rail.scad (T-slot 20×20 mm).
+
+| Feature | Spec |
+|---------|------|
+| Camera interface | Standard GoPro 3-prong (HERO 5+) |
+| Rail system | T-slot 2020 OpenBuilds / MISUMI compatible |
+| Tilt range | 0° – 90° from horizontal |
+| Tilt detents | 15° increments (0°, 15°, 30°, 45°, 60°, 75°, 90°) |
+| Retention | M3 thumbscrew clamp (T-nut to rail) + M5 index pin (angle lock) |
+| Weight | ~85 g (printed) + ~45 g (fasteners) |
+
+---
+
+## Design Features
+
+- **Top mount:** Standard GoPro 3-prong interface — no custom adapters, works with any GoPro HERO 5+ compatible accessory.
+- **Bottom clamp:** Integrated T-nut slides into rail T-groove; single M3 thumbscrew locks clamp to rail (no tools required).
+- **Tilt mechanism:** Rotating bracket + M5 hinge pin; camera tilts 0°–90° and locks at 15° steps via M5 index holes.
+- **Printability:** Both parts print flat-face-down, no support material required.
+- **Compatibility:** Works with all SaltyLab / SaltyRover sensor_rail.scad mounts; positions camera anywhere along rail.
+
+---
+
+## Part A — Printed Components
+
+### 1. Base Clamp (gopro_mount.scad, RENDER="base_stl")
+
+**Purpose:** Holds T-nut in rail T-groove; provides rotation axis for camera bracket.
+
+| Parameter | Value | Notes |
+|-----------|-------|-------|
+| Qty | 1 | Single part per mount |
+| Material | PETG | 5 perimeters, 40% infill (gyroid) |
+| Print size | ~45 × 35 × 28 mm | Flat-face-down (rail-side down) |
+| Orientation | Rail bore facing DOWN | Supports natural bed adhesion |
+| Support | None | Design allows direct print |
+| Wall thickness | 4–5 mm minimum | Ensure M3 threads cut cleanly |
+
+**Key features:**
+- Integrated T-nut pocket (friction-fit to rail T-groove)
+- M3 thumbscrew bore (perpendicular to T-nut, from outside rail face)
+- M5 hinge-pin bore (passes through to camera bracket)
+- 7 index holes (one for each tilt angle: 0°, 15°, 30°, 45°, 60°, 75°, 90°)
+- Vent slots for weight reduction
+
+---
+
+### 2. Camera Bracket (gopro_mount.scad, RENDER="camera_bracket")
+
+**Purpose:** Holds GoPro camera via 3-prong mount; rotates about M5 hinge pin.
+
+| Parameter | Value | Notes |
+|-----------|-------|-------|
+| Qty | 1 | Single part per mount |
+| Material | PETG | 4 perimeters, 30% infill |
+| Print size | ~35 × 25 × 51 mm | Flat-face-down (prong-side down) |
+| Orientation | GoPro prongs facing DOWN | Minimal post-processing |
+| Support | None | Design supports printing without supports |
+| Wall thickness | 3–4 mm | Adequate for M5 through-bore |
+
+**Key features:**
+- 3 cylindrical prong sockets (GoPro standard spacing)
+- M5 hinge-pin bore (receives bolt from base)
+- 1 index hole (aligns with base index holes at tilt angle)
+- Lightweight design
+
+---
+
+## Part B — Fasteners & Hardware
+
+All fasteners are stainless steel or zinc-plated for corrosion resistance.
+
+| # | Spec | Qty | Use | Notes |
+|---|------|-----|-----|-------|
+| 1 | M3 × 12 SHCS | 1 | Thumbscrew — clamps T-nut to rail | or M3 cap screw with printed knob |
+| 2 | M3 washer | 1 | Under thumbscrew head | standard flat washer |
+| 3 | M5 × 25 SHCS | 1 | Hinge pin — camera bracket rotation axis | or M5 cap screw + lock washer |
+| 4 | M5 washer | 2 | Hinge pin lock washers (each end) | prevents backlash |
+| 5 | M5 lock nut | 1 | Hinge pin lock nut | nylon-insert preferred |
+| 6 | M5 × 8 roll pin | 7 | Index pins — lock tilt angle | one for each 15° detent (0°–90°) |
+
+---
+
+## Installation & Assembly
+
+### Step 1: Prepare T-slot Rail
+
+1. Verify rail is clean (no burrs, chips).
+2. Slide base clamp assembly onto rail from above (rail face toward clamp bore).
+3. Align T-nut pocket with T-slot T-groove (groove faces inward).
+
+### Step 2: Clamp Base to Rail
+
+1. Insert M3 thumbscrew through rail outer face, through the T-nut pocket.
+2. Tighten **finger-tight** first (do not overtighten — rail will deform).
+3. Verify clamp is centered on rail (equal gap on both sides).
+4. Tighten to **hand-tight** (≈2 N·m for M3).
+
+### Step 3: Assemble Hinge & Camera Bracket
+
+1. Slide M5 × 25 bolt through base clamp hinge bore (horizontal, perpendicular to rail).
+2. Mount camera bracket on bolt (prong-side facing camera direction).
+3. Add M5 washers at both bolt ends.
+4. Tighten M5 lock nut to **hand-tight** (≈5 N·m).
+   - Bolt should rotate smoothly but without play.
+   - If bracket binds, loosen slightly; if too loose, add second lock washer.
+
+### Step 4: Mount GoPro Camera
+
+1. Rotate camera bracket to desired tilt angle (0°, 15°, 30°, etc.).
+2. Align index hole on bracket with corresponding hole on base clamp.
+3. Insert M5 × 8 roll pin into aligned holes (pushes in snugly, no tools needed).
+4. Verify pin locks camera position (should not rotate when pin is seated).
+5. Slide GoPro onto 3 prongs until camera contacts mount.
+
+### Step 5: Cable Management
+
+- Route camera USB/HDMI cable down rail (behind robot).
+- Use cable tie on thumbscrew pocket if additional restraint needed.
+
+---
+
+## Tilt Angle Detents
+
+The 15° step gives 7 fixed positions within 0°–90° range:
+
+| Tilt Index | Angle | Use case |
+|------------|-------|----------|
+| 1 | 0° | Horizontal (level with horizon) |
+| 2 | 15° | Slight upward tilt |
+| 3 | 30° | Moderate upward tilt |
+| 4 | 45° | Balanced forward-up tilt |
+| 5 | 60° | Steep upward tilt |
+| 6 | 75° | Nearly vertical forward |
+| 7 | 90° | Straight vertical (zenith) |
+
+To change tilt:
+1. Push on camera bracket to rotate (index pin will pop out if at end of rotation).
+2. Align new index hole.
+3. Re-insert index pin.
+
+---
+
+## Fastener Torque Spec
+
+| Fastener | Size | Torque | Note |
+|----------|------|--------|------|
+| M3 thumbscrew | M3 × 12 | 2 N·m | Hand-tight; over-tightening deforms rail |
+| M5 hinge pin | M5 × 25 | 5 N·m | Smooth rotation, no play |
+| M5 lock nut | M5 | 2.5 N·m | After initial tightening, verify free rotation |
+
+---
+
+## Post-Print Finishing
+
+### Base Clamp
+- **Support removal:** No supports needed.
+- **Bore prep:** If M3 bore is rough, ream with M3 hand reamer (¼ turn only).
+- **T-nut pocket:** Smooth with fine sandpaper if needed (must slide smoothly into groove).
+
+### Camera Bracket
+- **Support removal:** No supports needed.
+- **Prong sockets:** Clean with compressed air; verify no strands block GoPro prongs.
+- **Index hole:** Verify M5 bore is clear (small drill bit can clear if needed).
+
+---
+
+## Mass Estimate
+
+| Component | Material | Est. Mass |
+|-----------|----------|-----------|
+| Base clamp | PETG | ~35 g |
+| Camera bracket | PETG | ~28 g |
+| M3 thumbscrew | Stainless | ~2 g |
+| M5 hinge bolt + nut | Stainless | ~6 g |
+| M5 index pins (×7) | Steel | ~4 g |
+| **Total (without camera)** | | **~75 g** |
+| **Total (with GoPro HERO)** | | **~250 g** |
+
+---
+
+## Mounting Position Recommendations
+
+### On sensor_rail.scad vertical rail
+
+| Position | Z height | Use |
+|----------|----------|-----|
+| Below sensor head | 700–800 mm | Forward-facing wide-angle view |
+| Mid-rail | 400–500 mm | Side-looking perspective |
+| Above base plate | 100–200 mm | Ground-level or low-angle view |
+
+Index holes on rail face every 25 mm; position bracket at any height (friction-fit with T-nut + thumbscrew).
+
+### On payload_bay_rail.scad (horizontal rail)
+
+Mount horizontally by:
+1. Rotate entire assembly 90° (rail runs front-to-back).
+2. Tilt camera bracket 0°–90° to point downward or forward.
+3. Good for payload bay documentation (downward view) or forward obstacle detection.
+
+---
+
+## Storage & Maintenance
+
+- **Store bracket vertical** (prongs up) to avoid stress on sockets.
+- **Clean prongs** after each field session (dust prevents secure seating).
+- **Verify index pin seating** before each deployment (pin can loosen if rattled).
+- **Check thumbscrew** monthly (re-tighten if rail has shifted).
+
+---
+
+## Design Notes for Future Revisions
+
+- **Optional:** Add detent detents (spring-loaded ball bearing pockets) at index holes for positive clicks.
+- **Optional:** Add strap attachment points on base clamp for secondary safety line.
+- **Alternative bracket:** Straight vertical bracket (0° fixed) for weight-optimized variant.
+- **Camera variants:** Compatibility with GoPro Session (action cam) and DJI Osmo Action (different prong patterns) would require bracket redesign.
+
+---
+
+## Files
+
+| File | Purpose |
+|------|---------|
+| `gopro_mount.scad` | OpenSCAD parametric model (3 RENDER variants) |
+| `gopro_mount_BOM.md` | This document |
+| `sensor_rail.scad` | Parent T-slot rail system (dependency) |
+| `sensor_rail_brackets.scad` | Additional rail bracket options |
+
+---
+
+## Assembly Checklist
+
+- [ ] Print base clamp (PETG, 45 × 35 × 28 mm, flat-side-down)
+- [ ] Print camera bracket (PETG, 35 × 25 × 51 mm, flat-side-down)
+- [ ] Inspect prong sockets on bracket (no strands, smooth)
+- [ ] Ream or smooth M3 thumbscrew bore in base clamp
+- [ ] Test T-nut pocket (slides in/out of rail groove smoothly)
+- [ ] Assemble: M3 thumbscrew + washer
+- [ ] Assemble: M5 × 25 bolt + 2 washers + lock nut
+- [ ] Mount bracket on hinge pin (hand-tight fit)
+- [ ] Insert one M5 × 8 index pin at 0° (test fit)
+- [ ] Mount GoPro camera (prongs snap in)
+- [ ] Final check: camera level in 0° position
+- [ ] Stow extra index pins in camera bag