Prototype versions
V1 to V4
Problem
What the build needed to solve
My contribution
Enclosure CAD, roof and vent geometry, internal sensor housing, clamp/support integration, FDM prototype fabrication, wind-load screening, and ESP32 power-debug support.
The project required a compact outdoor enclosure for an urban air-quality sensing node. The mechanical challenge was balancing airflow, rain-path control, internal sensor packaging, cable routing, solar/LiPo power integration, and clamp-mounted support. The enclosure needed to remain serviceable while reducing wall flex and local stress around fasteners.
Constraints
Design boundaries
Package gas sensors, particulate sensing, ESP32 communication hardware, GPS, LiPo battery, solar wiring, and custom PCB inside one serviceable enclosure.
Preserve airflow to the sensing region while reducing direct rain entry.
Use FDM-printed PLA and approximately 0.100 in wall thickness for prototype screening.
Use M2 hardware for internal sensor support and M4 hardware for larger enclosure/clamp features.
Use direct bolts and nuts instead of heat-set inserts to avoid local PLA heat deformation.
Screen clamp/support geometry against a 140 mph wind-load case.
Build log
Design evolution
The enclosure evolved through multiple physical and CAD revisions. The main design changes were driven by printability, rain shielding, airflow, internal sensor packaging, clamp stiffness, and power-system debugging.
Revision
Failure mode
Design change
Result
V1
Basic enclosure volume but weak cable/service planning
Added roof concept and internal packaging direction
Established core packaging problem
V2
Box-like shell had clamp stiffness and routing issues
Added external clamp feature and revised housing direction
Identified mount-load transfer problem
V3
Outdoor prototype worked physically but needed better sensor and roof fit
Added gabled roof, solar panel placement, support bracket, clamp base
Proved outdoor mounting concept
V4
Wiring, sensor retention, and wall flex still needed improvement
Revised internal housing, mesh region, clamp support, and roof geometry
Improved serviceability and load path
Power debug
ESP32 rail dropped from 4.5 V to 2.1 V
Revised switching and power routing
Restored roughly 4.1 to 4.3 V operation
Details
Technical details
System function
Outdoor air-quality sensor enclosure
Prototype material
FDM-printed PLA
Wall thickness
~0.100 in
Approximate enclosure size
7.71 in tall x 5.49 in deep x 4.55 in wide
Internal standoff height
~0.315 in
Internal hardware
M2 screws
External/clamp hardware
M4 screws
Fastening method
Direct bolts and nuts, no heat-set inserts
Roof strategy
Gabled roof and overhang
Vent strategy
Lower mesh/vent area and roof gap
Cable access
Top opening, no full gasket seal
Wind case
140 mph
Wind pressure
0.418 psi
Total wind force
13.95 lbf
Conservative hand-calc stress
0.825 ksi
Conservative wall-strip displacement
0.142 in
First-pass FoS
~5.5 using a 4.5 ksi PLA screening allowable
Fastener reaction estimate
~8.8 lbf
Preliminary 3D simulation stress
~127 psi
Electrical issue
ESP32 rail oscillation from 4.5 V to 2.1 V
Electrical result
Restored ~4.1 to 4.3 V operation
Testing
Results
Wind case screened
140 mph
Wind force
13.95 lbf
Hand-calc stress
0.825 ksi
Preliminary simulation stress
~127 psi
Post-fix operation
~4.1-4.3 V
The enclosure was screened using two different analysis levels. A conservative wall-strip hand calculation estimated 0.825 ksi peak stress, 0.142 in displacement, and FoS near 5.5 under the 140 mph wind case. A separate preliminary 3D model showed lower stress, around 127 psi, because the full enclosure, clamp, fillets, and internal housing distributed load through the assembly. These values are different analysis methods, not directly competing results.
Bench integration identified ESP32 brownout behavior when the full sensor and communication stack was connected. The rail dropped from roughly 4.5 V to 2.1 V before the fix. Revised switching and power routing restored operation around 4.1 to 4.3 V, after which the prototype was deployed outdoors with solar panel, clamp support, cable routing, and sensor packaging installed.
Scope note: The hand calculation and preliminary 3D model are screening methods with different assumptions, not final qualification results.
Reflection
Engineering lessons
- The enclosure problem was not just making a box; the real tradeoff was airflow, rain-path control, internal packaging, cable access, power reliability, printability, and clamp load transfer.
- The strongest mechanical change was adding a more structured roof, internal housing, lower mesh/vent region, and clamp/back support to reduce wall flex and improve serviceability.
- The main remaining risks are local screw-hole stress, clamp-root fillets, printed-layer anisotropy, cable-entry rain path, and long-term outdoor PLA exposure.
- Future work should use controlled water exposure testing, measured cable-strain inspection, and a refined simulation model with documented material properties.
Gallery
CAD, fabrication, and test views
V4.0 CAD model
Revised enclosure with roof, clamp support, and packaging geometry
V4.0 sectioned CAD view
Internal housing, sensor volume, mesh region, and load path
Clamp/support CAD
Rear support geometry transferring enclosure load into mount
Preliminary Simulation
Preliminary structural screening under wind-load condition
V1.0 physical prototype
First roofed enclosure concept
V2.0 physical prototype
Printed box used to evaluate clamp integration
V3.0 physical prototype
Gabled roof and clamp support physical revision
Deployment photo
Outdoor clamped prototype with solar panel and sensor package