Introduction

This guide documents the design, fabrication, and assembly of a custom-built Diver Propulsion Vehicle (DPV) — a lightweight, modular, and efficient underwater scooter engineered for recreational diving and marine exploration.

The DPV project merges mechanical design, marine robotics, and electrical integration into a single, cohesive engineering build. It serves as both a functional underwater vehicle and a demonstration of applied systems engineering from CAD modeling to propulsion testing.

Design Overview

Purpose:
To develop a compact, neutral-buoyant DPV capable of propelling a diver or swimmer efficiently while maintaining high maneuverability and safety.

Key Design Features:

Weight: ~8 lbs (in air)
Max Speed: ~1.5 m/s (≈ 3 knots)
Runtime: 45–80 minutes (depending on throttle use)
Construction: Sheet metal frame + 3D-printed components
Control: Waterproof rotary throttle with magnetic kill switch
Power: Modular lithium-ion battery pack (4S or 6S)

Mechanical Design

The frame evolved from a T-slot aluminum structure into a single folded aluminum chassis, which integrates the thruster mounts and enclosure supports.

Core Components:

Main Frame: 5052-H32 aluminum sheet, folded into a cross-bar assembly.
Enclosure: 4-inch acrylic or polycarbonate tube, sealed with dual O-ring flanges.
Handles: Ergonomic 3D-printed PLA+ grips, directly mounted to the frame.
Mounting Hardware: M3/M4 stainless bolts throughout, with printed alignment fixtures.

Design Software:
Modeled in SolidWorks, with all files available for iterative refinement and customization.

Manufacturing Methods:

FDM 3D printing (PLA+, PETG for structural parts)
CNC-machined aluminum coupling rings
Laser-cut sheet metal frame

Propulsion & Electrical System

Thrusters:
Dual Flipsky thrusters are used for balanced thrust. Props are mounted counter-rotating (CW/CCW) to cancel torque.

Electronics Layout:

ESCs: 2 × BasicESC or BasicESC 500 modules
Controller: Thruster Commander with potentiometer input
Kill Switch: Magnetic reed switch (lanyard-mounted safety cutoff)
Throttle: Waterproof rotary dial with mechanical coupling
Power Monitor: Inline volt/amp meter for battery tracking

Safety Controls:

Magnetic kill-switch automatically disables power when released.
Soft-start throttle logic prevents sudden torque spikes.
Fused battery input for circuit protection.

Wiring Summary:

10 AWG power lines to bus bar → ESCs → Thruster Commander
XT90 connectors for modular battery swaps
Waterproof penetrators (M10–M14) for cable management

Battery & Power Management

Battery Configuration:

4S 18Ah or 6S 22Ah lithium-ion pack
XT90 or XT60 quick-disconnect terminals
Inline power meter with total mAh tracking

Estimated Endurance:

Low-speed cruise (125–250W): 60–80 minutes
High-speed (~700W): 20–30 minutes

Voltage Safety:

Stop use when pack drops near 13V (4S) or 19.5V (6S)
Never discharge below 12V (4S) or 18V (6S) to prevent cell damage

Assembly Procedure

Mount Components
- Attach thrusters to frame (props facing inward/upward for torque balance)
- Secure enclosure clamps to frame
- Install hand grips and hardware
Prepare Enclosure
- Mount Thruster Commander and potentiometer assembly
- Wire ESCs and bus bar connections
- Integrate reed switch and throttle dial coupler
- Seal endcaps with O-rings, apply silicone lubricant
Install Electronics
- Route thruster cables through M14 penetrators
- Connect ESCs → Commander → Power meter → Battery
- Test kill switch functionality
Final Integration
- Compress O-ring seals, insert locking cords
- Calibrate throttle range and kill switch engagement
- Mount enclosure to frame clamps securely

Testing & Calibration

Pre-Dive Testing:

Verify thruster rotation direction (pushing away from frame)
Confirm ESC initialization tones
Ensure reed switch disengages motor on removal
Check voltage and mAh before submersion

Pool Validation:

Start at low throttle to observe thrust direction and buoyancy
Adjust ballast/foam to achieve neutral buoyancy
Conduct 10–15 minute endurance tests before open water trials

Safety Guidelines

Always use a buddy system when diving.
Avoid running thrusters out of water.
Never insert fingers or tools near propellers.
Remove magnetic kill switch before handling propellers.
Monitor voltage during use; do not exceed depth ratings of enclosures.
Avoid sand or silt near thrusters to preserve coatings.

Performance Goals & Future Improvements

Target Metrics:

Speed: 3–4 knots
Runtime: 45–60 minutes
Depth Rating: 30+ meters (testing phase)

Future Enhancements:

6S high-output power system for increased thrust
Integrated PCB for throttle and telemetry
Improved ergonomic hand grips
Mounting points for GoPro or navigation lights
Smart BMS with Bluetooth telemetry

Project Reflection & Purpose

This DPV project exemplifies the practical integration of mechanical, electrical, and marine design disciplines. It represents a holistic approach to hands-on marine engineering, blending rapid prototyping, materials testing, and safety-critical design in one platform.