Overview
Project Background
Only 20% of water bodies are sampled regularly due to the inherent inefficiency of manual water sampling processes — requiring a boat launch, specialized equipment, crossing the water surface, and taking multiple samples at different depths. Voluntary sampling groups face inconsistency in technique and availability, while funding cuts have reduced professional monitoring capacity.
The Water Monitoring Robotic Boat (WMR) is a low-cost, high-utility tool that enables a single state employee to sample more lakes per day with greater accuracy and consistency. The 3D-printed hull fits in a car trunk and can be carried to remote lake access points using integrated backpack straps. Once deployed, the boat autonomously travels to waypoints, collects water samples, and streams real-time telemetry to a web application.
Hardware Design
CAD, Fabrication & Parts
All structural components designed in SolidWorks and Siemens NX, sliced in Creality, and 3D-printed in PLA at 20% infill for optimal buoyancy. Each part validated side-by-side against the CAD model.
CAD vs Built PartsSide-by-side comparison of SolidWorks CAD models and 3D-printed PLA parts — hull sections (front/rear deck lids, front/middle/rear haul), motor holder, jet housing inner/middle/outside, and propeller assembly
Mechanical Architecture
System Design & Build
Hull Design
4-section 3D-printed PLA hull (60cm × 12cm) split to overcome 3D printer volume limits. Printed at 20% infill to minimize weight while maintaining structural integrity. Watertight coating applied after pool testing revealed minor porosity in PLA — resolved in testing phase.
Jet Propulsion
Brushless DC motor (790kv) driving a 4-blade propeller through a custom jet housing. 4-blade selected over 3-blade and 2-blade after comparative testing — higher blade surface area compensates for motor power limitations, delivering better acceleration and 3.5kg peak thrust at 75g/amp efficiency. Peak speed: 15 knots.
Water Sampling
Peristaltic pump moves water through tubing to one of two sample modes: at-depth samples (5m, 10m, 20m) using weighted tube for chemical testing, and sterile surface samples for microbial and eDNA analysis. Maximum spool capacity: 5m of tubing. Sample capacity: 0.5L total.
Sensor Suite
Arduino UNO integrating analog pH sensor (SEN0161), turbidity sensor (SEN0189), waterproof temperature probe (DFR019E), and TDS sensor. All data streamed to a live web server and downloadable as CSV. Parameters: pH, turbidity, temperature, TDS, moisture.
Power & Control
6S Li-ion battery (22.2V, 2000mAh) powering brushless ESC (80A) and all electronics. 2.4GHz 6-channel RC transmitter/receiver for manual override. Full manual authority retained throughout autonomous mission for safety.
Electronics & Testing
Integration & Validation
On Water & Electronics BayFully assembled boat running on water (left) and internal electronics bay showing ESC, LiPo battery, peristaltic pump, and wiring harness (right)
Sensor & Arduino WiringComplete wiring diagram — Arduino UNO connected to analog pH sensor, turbidity sensor, waterproof DS18B20 temperature probe, and TDS sensor via breadboard
Pool Testing
Validation & Results
4-Hour Pool ValidationEndurance testing in NMIMS campus pool — waterproofing, jet propulsion, and RC control validated at speed
Bench & Water TestingElectronics assembly verification in sink, waterproofing checks, and pool-side launch preparation
Performance Specs
Technical Parameters
| Parameter | Value |
|---|---|
| Empty Weight | 1.2 kg |
| Overall Length | 60 cm |
| Overall Width | 12 cm |
| Max Speed | 15 knots |
| Range | 2.5 kn |
| Battery | 6S Li-ion, 22.2V, 4.5Ah |
| Peak Thrust | 3.5 kg @ 60% throttle |
| Propulsion | Water-jet, 790kv Brushless + 80A ESC |
| Sampling Depth | Up to 3m (5m spool capacity) |
| Sample Capacity | 0.5L total |
| Hull Material | PLA, 20% infill, 4 sections |
| Total Cost | INR 16,800 (~$200 USD) |
Challenges & Learnings
Engineering Problem-Solving
- Hull porosity — PLA printed hull showed minor water ingress; resolved by applying waterproof coating, restoring full buoyancy and watertight integrity
- Propeller selection — tested 2-blade, 3-blade, and 4-blade propellers; 4-blade selected for superior acceleration with underpowered motor due to higher blade surface area
- Weight distribution — water sampling unit in payload bay shifted CG; redistributed ballast and electronics placement to maintain stable trim at speed
- Choppy water jet suction loss — intakes near water surface lose suction on waves; identified as solvable with deeper intakes on removable grates in next iteration
- TDS chip unavailability — the connecting chip for TDS sensor was unavailable in India; documented as future work, alternative measurement approach identified
- Budget constraint — PixHawk autopilot module (INR 10,000) was out of budget; implemented RC control with full manual override as reliable fallback, achieving all primary objectives
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Project Info
Role
Lead Mechanical Designer & Electronics
Team
Nikhil Khandelwal, Alay Sanchania, Devansh Shah
Institution
NMIMS — Narsee Monjee Institute, Mumbai
Mentor
Dr. Rajnish Katarne
Date
November 2023
Cost
INR 16,800 (~$200 USD)
Tools & Technologies
SolidWorksSiemens NXArduino UNO3D Printing (PLA)Brushless MotorsCreality SlicerArduino IDEpH SensorTurbidity SensorTDS ProbePeristaltic PumpRC 2.4GHzWater Sampling
Key Skills
Mechanical
Hull design, DFM, 3D printing, propulsion, water-tightness
Electronics
Arduino, sensor integration, ESC/motor control, wiring harness
Testing
4hr pool endurance, propeller benchmarking, waterproofing validation