TRIDIX Screen - 3-Layer Double Helix - a Modular Helical Radiation Shield ( Stevenson Screen )

TRIDIX Screen – The Modular 3-Layer Double Helix Radiation Shield (Stevenson Screen)

Are you looking for a helical modular solar radiation shield that is aerodynamically perfectly shaped? Whether you use the universal STLs with your favorite slicer or drop the perfectly pre-configured Bambu Studio 3MF file into your workflow – the TRIDIX Screen - a helical radiation shield with a twist – is exactly what you and your weather sensors need.

The story behind it (or… If I had only known...):

Actually, I just wanted to reliably collect my local weather data and integrate it into Home Assistant. Starting with a ready-made Shelly WS90 weather station, I quickly wanted some redundancy and built two additional ESP32 with precise SHT45 and BMP585 sensors. Everything ran great – until the sun came out and I noticed the catastrophic temperature deviations. 

A proper weather protection housing (Solar Radiation Shield / Stevenson Screen) was needed! What was available to buy was either unaffordable, or, in the case of budget options and my own DIY attempts, the measurement distortions during maximum and prolonged sunlight were still too high despite the shielding, or the long-term weather protection was inadequate. So, I spontaneously bought a Bambu Lab P1S to be able to print a model from the internet in ASA. If someone had told me beforehand what an avalanche of material tests, failed prints, and thermodynamic problems this would entail – I probably would have left it alone!  

In the end, I scrapped it all and designed a custom double-spiral enclosure offering maximum radiation shielding alongside maximum ventilation and triple weather protection: the 'TRIDIX Screen – The Modular 3-Layer Double Helix Radiation Shield'.

Update v2.1 - The Cone Cap (Optional Roof Cover):

Recent storm testing proved the helix design keeps the sensor core perfectly dry. However, water tended to pool on the flat center of the standard Tropical Roof, which could accelerate material aging.

To solve this, version 2.1 introduces the Cone Cap. This optional add-on sits directly on top of the Tropical Roof to provide maximum weatherproofing and longevity:

• Constant-Angle Runoff: A conical design eliminates the flat layer "terracing" effect typical of 3D-printed domes, ensuring rain beads off instantly.

• Capillary Protection: A precise overhang with a 2mm vertical rim acts as a drip edge, preventing water from creeping between the layers.

• Waterproof Chimneys: Integrated 12mm spacers wrap around the mounting holes, sealing the threaded rods and nuts from water ingress.

• Extra Thermal Shielding: The dual-roof layer acts as a secondary thermal insulator against harsh zenith sunlight.

You can easily toggle and scale the Cone Cap alongside the other accessories using MakerWorld's built-in Parametric Model Maker. 

⚠ Hardware Note: If you plan to install the Cone Cap, remember to add +12 mm to the total length of your three central M5 threaded rods to account for the integrated spacer chimneys!

My "Filament Hybrid" & Material Tips:

An honest word about printing: This housing has taught me an incredible amount about filaments and 3D printing! The geometrically simple parts (base, sealing ring, tropical roof) were easy to manufacture from Spectrum ASA Standard. 

But the complex, flat 120-degree helix louvers? An absolute disaster with standard ASA (warping from hell!). I had to pivot to a hybrid solution here: I printed the base disk, top disk, and all black and white helix segments from extremely tough Spectrum PCTG (as well as PETG). (A quick tip for enclosed printers like the P1S: I had to keep the top glass lid open while printing PCTG and PETG to avoid heat creep and clogs. Your mileage may vary, but it's worth keeping in mind!) The Inner-Shield, on the other hand, was made of Spectrum ASA 275. 

My Tip for makers:

If I had known about the ASA 275 (e.g., from Spectrum) beforehand, I probably would have printed the entire weather station out of it! It combines the UV and heat resistance of classic ASA, but can be printed almost as smoothly and warp-free as PETG or PLA at lower temperatures. 

What does TRIDIX mean? (The Technology):

The name stands for Triple Layer + Di(Double)-Helix. Unlike simple, store-bought shields, this design uses the principle of fractionated shielding: 

- Layer 1 (Outer): The white, outer helix louvers reflect direct sunlight and break the wind.

- Layer 2 (Middle): The black, inner louvers intercept scattered radiation and the self-heat emitted by the outer shell.

- Layer 3 (Inner-Shield): Creates a thermally completely neutral zone in the core. This shape is tailor-made for an FS200 sintered filter probe (perfect for the Sensirion SHT45). The probe is maximally protected from radiation but remains fully exposed to continuous airflow. 

In addition, the double helix structure creates a spiral vortex effect in the wind, which prevents heat accumulation during calm conditions via a chimney effect. Even against extreme driving rain, the sensor is protected by capillary effects on the interleaved segments. 

Features & Assembly (Optimized for 3D Printing):

- Interlocking 120-degree Segments: A continuous spiral can hardly be printed cleanly. Therefore, each 360-degree layer of the TRIDIX is divided into three interlocking 120-degree segments. Although these louvers require support structures, don't worry! If you are using the universal STLs in PrusaSlicer or Cura, simply enable snug or tree supports for the overhangs. For Bambu Lab users, the support material is already perfectly pre-configured in the included bonus 3MF file!

- Rod-guided Dual Helix: The black and white segments are alternatingly stacked onto three M5 threaded rods via half-height guide sleeves (Alternating Stacked Helix), which serve as a massive structural spine.

- Infinitely scalable: The system is vertically modular. You start with a 2-tier minimum and can stack as many layers as your sensor requires space.

Required Hardware (Cheap & Easy to Source!)

Luckily, you don't need any special or expensive hardware. All you need to buy is 1 meter of M4 and 1 meter of M5 threaded rod. You can get these at any hardware store for about 1-3 Euros each, and one meter is plenty for the entire build.

Important: I used zinc-plated rods for testing, but I recommend buying stainless steel to prevent ugly rust stains outdoors!

To cut them to size, a simple manual hacksaw or an oscillating multitool with a metal blade works perfectly. (An angle grinder works too if you are impatient, but it's a bit overkill).

The Rod Length Cheat Sheet:

(Note: I have already factored in the extra 8mm clearance at the top and bottom for the nuts in all these measurements!)

1. The Main Spine (3x M5 threaded rods): 

(Rule of thumb: Each additional tier adds 24mm to the length!)

(Cone Cap Add-on: If you use the v2.1 Cone Cap, you must add +12 mm to all M5 measurements below!)

    2 Tiers: 3x 126 mm (Minimum setup - 1x 120deg-Louver-Set [1xBase & 2xCore Segments] + 1x 120deg-Louver-Set [2xCore & 1xRoof Segments])

    3 Tiers: 3x 150 mm

    4 Tiers: 3x 174 mm

    5 Tiers: 3x 198 mm

2. The Outer White Supports (3x M4 threaded rods):

(Attention: Because of the base plate design, one of the three rods must always be 12mm longer than the other two!)

(Note: I have already factored in the extra 6mm clearance at the top and bottom for the nuts in all these measurements!)

    2 Tiers: 1x 76 mm   &  2x 64 mm

    3 Tiers: 1x 100 mm  &  2x 88 mm

    4 Tiers: 1x 124 mm  &  2x 112 mm

    5 Tiers: 1x 148 mm  &  2x 136 mm

3. The Inner-Shield Core (3x M4 threaded rods):

    This length is highly individual and depends entirely on your specific sensor and how many inner plates you need to stack.

    Minimum setup (2 tiers + small roof): 3x ~55 mm

    Large FS200 sintered probe (like the SHT45): 3x ~95 mm

Customizing Your Setup (Parametric Accessories):

Every installation spot is different! Need a different pole mount diameter for the base plate or a longer wall mount? Download the included .scad file to tweak all mounting and roof accessories directly in OpenSCAD!

If you don't want to install any software, you can easily use the web-based customizer on my MakerWorld profile instead: https://makerworld.com/en/models/3420865-tridix-the-3-layer-double-helix-radiation-shield#profileId-3897885

Note: The fundamental double-helix geometry is mathematically optimized for aerodynamics, a perfect fit, and ideal printability. It is non-parametric and can therefore only be provided as a finished STL file. To give you maximum flexibility for your specific installation, all mounting and roof accessories are fully parametric!

 - Base Plate (Foot): Adjust the inner pole diameter (0–35 mm) and sleeve height to fit any mast, or set the height to 0 for flat wall-bracket mounting.

- Wall Mount Bracket: Customize the arm length (130–220 mm), wall plate height, and rib thickness to clear deep roof overhangs.

- Sealing Ring: Fine-tune the diameters and easily toggle the lateral sensor cable slot on or off.

- Tropical Roof: Scale the flat inner area diameter (120–170 mm), the outer umbrella diameter (170–245 mm), and the rim height for extra protection in regions with heavy driving rain.

- Cone-Cap: The base diameter of the cap is intelligently linked to the Tropical Roof's flat area to always guarantee a perfect, leak-proof drip edge. You can freely scale the height of the conical dome (5–30 mm), as well as the height (10–40 mm) and outer diameter (10–20 mm) of the spacer chimneys for the M5 nuts.

A Note on Print Quality: Function over Form:

These 120-degree segments are geometrically quite challenging to print. The clear rule here is: function comes before flawless aesthetics! Don't be too hard on yourself or your printer if the surfaces have minor imperfections. Since the TRIDIX Screen will be hanging outside in all weather conditions and isn't a design piece for your living room, minor visual defects (like slight layer shifts, which I solved with a 0.3 mm Z-hop for PCTG) are completely irrelevant.

To get the best possible overall result, To get the best possible overall result, I highly recommend placing your Z-seam strategically (Note: This is already perfectly pre-configured if you use the included Bambu Studio 3MF file!): If you are slicing the STLs yourself, paint the seam for the black segments onto the hidden outer edge, and for the white segments onto the hidden inner edge. These act as "sacrificial edges are clean so the segments interlock seamlessly.

Open Source Community & Feedback:

The TRIDIX Screen is an experimental weather protection housing (Solar Radiation Shield / Stevenson Screen). Long-term tests regarding extreme driving rain tolerance and temperature deviations in midsummer are still pending. Print the shield, test it in your IoT setups, and feel free to give me feedback on how it performs in practice!

Happy printing, and enjoy your highly precise weather data!