saltylab-firmware/chassis/gopro_mount_BOM.md

GoPro 3-Prong T-Slot Sensor Rail Mount — BOM + Assembly

Rev A — 2026-03-02 — sl-mechanical

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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)

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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.

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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

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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

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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°)

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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.

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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.

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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

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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).

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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

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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.

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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).

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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.

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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

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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