Connector for Arctic P14 fans

thingiverse

COVID is primarily spread through aerosols exhaled by an infected person. These can drift in the air for extended periods, infecting others in the same space. Filtering out these infectious aerosols is an important concern for maintaining adequate indoor air quality. More information on this may be found in the recent Positions on Infectious Aerosols document from ASHRAE (the body that establishes ventilation standards for North America), at https://www.ashrae.org/file%20library/about/position%20documents/pd_-infectious-aerosols-2022.pdf. A DIY approach is the widely-used "Corsi-Rosenthal Box" (https://cleanaircrew.org/box-fan-filters/), which are extremely cost-effective - the CDC has just released data validating their performance (https://www.sciencedirect.com/science/article/pii/S0360132322011507) - but can be a bit loud. Rob Wissman (https://thewiss.blogspot.com/2022/11/at-home-cadr-testing-for-air-cleaner.html) has been doing some really interesting work with computer fans to create quieter and more energy efficient versions (the original C-R boxes run around 65W or so, which isn't that much, but these can operate at <10W, and are much quieter without being a lot more expensive). I have been building a few things inspired by his efforts. This is a connector for Arctic P14 fans (you can get 5-packs of the PWM PST variant for a good price). They slide between the front and back layers at the corners, and have a slot that captures the diagonal rib that's in there. There are threaded holes for M4 hex bolts that line up with the holes in the fans, and then 6 more in the side for attaching other things. Note that the diagonal rib means to attach two fans together, you need to start with one connector on one fan, and the other on the other, so that both require the same diagonal movement to connect them. Each one has two little notches that are only relevant if you are putting them on the corner of the fan that has the power line coming off it. You need to pull the power cord out of its little notch in the fan body to insert the connector to keep it from getting pinched, and then you can put it back afterwards. I'll upload a 4-way connector at some point when I get around to it. Note that this print requires that your printer be well-calibrated so that you don't have trouble screwing the M4 bolts into the printed holes. I would suggest running a calibration test first and adjusting horizontal expansion accordingly. https://www.thingiverse.com/thing:4766295 works better although I put a more detailed explanation of the concept on the original version at https://www.thingiverse.com/thing:3535060. Without calibrating like this my experience is you probably won't get the bolts to go in, but once you've done it you don't have to re-calibrate often if you don't change materials / settings. I haven't run one for months and I expect to be consistently able to be able to start bolts of this size by hand, and then run them in with one finger worth of force on a small allen key. I printed it laid flat so there were two vertical threaded holes and six horizontal ones and there isn't really any difference in the way the bolts go in.