A small wind tunnel for testing aerodynamic drag on parts.

There are 2 velocity mount inserts, one uses paper straws bundled together and the other is fully 3D printed. The fully 3D printed one will use a reel of filament (~1kg). The straw velocity mount uses much less but requires more work to cut the straws to 5cm and bundle ~600 of the cut straws together (See photos).

There are also a couple of sizes of MDF/Acrylic sheets in the downloads. The length of the MDF and acrylic in the picture is 550mm which is definitely long enough for most objects that would fit in the wind tunnel. If you plan on using a longer pieces of MDF/acrylic then I would get a thicker bottom sheet or I would find a way to support it to stop it from bending as much. I bought the acrylic from cutmyplastic and got the MDF from Kitronik and cut it in my friends laser cutter.

The velocity mount and fan mount have captive nuts in them which requires the print to be paused at certain layers assuming a 0.2mm layer height. Pause the prints at layers 161, and 191 for the velocity mount, and pause the print at layers 111, 134, and 141 for the fan mount.

** I HAVEN'T TESTED THE CIRCLE INSERT, PRINT AT YOUR OWN RISK **

** Parts you'll need: **

• 200mm PC fan
• 16 m4x30mm bolts
• 4 m4x80mm bolts
• 20 m4 nuts
• 2 sheets of 3mm thick MDF
• 2 sheets of 3mm thick acrylic
• 2 packs of 100 paper straws (if using the straw insert)
• Fan controller and casing

** Tools you'll need: **

• Screwdriver
• Drill with drill bits (if the velocity mount/fan mount warps then you'll need to drill the holes bigger on the sheets)
• Hacksaw/Bandsaw (for cutting the straws)
• Glue gun (for sticking the straws into the insert)
• Elastic bands (for bundling the straws together)

** Instructions **

• Print the parts; insert the captives m4 nuts at the right layers.
• Attach the MDF/acrylic sheets to the fan mount and velocity mount using the m4x30mm bolts
• Attach the 200mm fan to the fan mount using the m4x80mm bolts
  • ** Straw insert instructions **
  • Cut the straws so they are 5cm long using the bandsaw or hacksaw. Its easier to cut them if you keep them in the packaging.
  • Bundle the 5cm straws together using elastic bands. Its easier to bundle them if you bundle smaller numbers together using small elastic bands then wrap a big elastic band over the smaller bundles, then remove the small elastic bands.
  • Glue the straw bundle in place using a hot glue gun.
• Push the velocity insert into the velocity mount.
• Done!

14/09/2024 V1: Added a circle velocity mount, a straw velocity mount, and hex velocity mount. Added feet for wind tunnel.

09/10/2024 V1.1: Increased hole spacing for fan mount from 153mm to 154mm.

08/12/2024 V1.2 Misaligned bolt holes for acrylic on the fan mount. Fixed this issue. Changed the velocity mount to be able to remove the various patterns so you can put something inside the wind tunnel without having to unscrew one of the acrylic sheets.

13/12/2024 V1.3: Added flat head holes to remove the inserts easier. Redacted the hex and circle velocity mount and made a circle insert for the straw velocity mount.

19/01/2024 : Added Solidworks files for Fan Mount, Velocity Mount, and Straw Insert. Velocity mount needs mirror fixing for bolt holes.