STATUS: This is still a work in progress. The model seems sound, but I haven't printed it out yet because I'm waiting for hardware.

Changelog

• 2023-01-19: bugfix, removed rod shaft overhangs in roof model
• 2023-01-17: added optional hole for wires to the floor, small typos
• 2023-01-16: initial upload

Description

A double-louver, cylindrical Stevenson screen that you can customise to your heart's content. I've done my best to make the parameters easy to understand and configure, especially via the Customizer in Thingiverse and OpenSCAD.

If you have a small printer like me, you can specify the outer diameter, height of a single ring, and louver angle, and let it calculate the inner chamber diameter. Or if you need a chamber of a certain size because you have a big piece of measuring equipment, you can specify the inner diameter and let it calculate the outer chamber diameter. Or specify both diameters and louver angle, and let it calculate the height of a ring. Et cetera!

You can generate models for:

• a bottom ring with a mounting bolt hole, an exit hole for wires, and a floor to reduce reflected light or radiated heat from the ground
• a ring (you'll need multiples of this)
• a ring with a set of struts meeting in the middle with a little platform for you to strap or bolt measuring equipment to
• a ceiling
• a slanted roof

You stack all the parts on top of each other. The whole thing goes together with three M3 threaded rods and some square nuts, although you can also customise that too: you can make the rods thicker or thinner, or add more rod shafts for strength.

The whole thing is meant to be printed without supports, as long as your louver angle doesn't go beyond 45°. Two parts, the ceiling and the roof, should be printed upside-down (they will be flipped automatically for you).

I'd recommend printing in PETg, because it's more resistant to water, decomposition, and UV light than PLA is.

Bill of materials

• Printed pieces (adjust the number of normal and carriage rings according to how many sensors you need to stuff in there)
  • 1 × floor
  • 6 × normal rings
  • 1 × carriage ring
  • 1 × top
  • 1 × roof
• Hardware (if you've customised your model to have more or fewer than 3 rod shafts, adjust the values below)
  • 3 × M3 threaded rods, 160mm (these look good)
  • 6 × M3 square nuts
  • 3 × washers that'll fit an M3 shaft
  • some sort of bolt/washer combo or screw appropriate to your mounting setup (you could use a wooden post, a piece of plastic pipe with an end cap, a shelving bracket -- whatever makes sense; the default hole size will fit an M6 bolt so you may need to adjust `mounting_bolt_diameter` to match what you have)

Tools

• A small crescent wrench that'll fit your square nuts
• Whatever you need for your chosen mounting setup
• (optional) Bolt cutters, a hacksaw, or a cutoff wheel

Warnings/apologies

Note that it doesn't work in Thingiverse's Customizer, and I don't know if that's the fault of my script or Thingiverse. It works fine in OpenSCAD though (tested on 2021.01 and newer).