Centrifugal Compressor 120mm Case Fan Conversion

thingiverse

Conversion kit transforms a 120mm case fan with a hub approximately 39-40mm in diameter into a centrifugal compressor with a double volute. 7.3.18 UPDATE: Added a second impeller base capable of accommodating fans with larger hubs (from ~42 to ~46mm, possibly up to 47mm with sanding). This base is taller than the original due to internal clearance needs, so additional spacers may be required to stand the diffuser far enough from the fan case. This conversion kit includes straight and 90-degree outlet nozzles, two flavors of inlet bells (tall/quiet and short/quick-to-print), adapters for 80 and 92mm case fans as boosters on the inlet, and five impeller options. Note that two of these impellers are designed to attach magnetically to an "advanced" impeller base with adjustment points for axial alignment, tilt, and balance; the other three are slip-fit if you prefer a simpler installation process. *** 7.3.18 NOTE: Consider your needs carefully before selecting this design. Fans and compressors come in various shapes and sizes for a reason -- there's no one-size-fits-all solution. This design is ideal for reusing old case fans for low-to-moderate-pressure air-pump-type applications like remote cooling and inflatables, and it's optimized for quiet, low-power operation. If you need to move a lot of air with minimal pressure difference between up and downstream, an axial fan is the better choice. For high-pressure spaces or lots of air movement, consider an air compressor or positive displacement pump. This design can't do everything, so choose wisely based on your specific needs. *** I conducted subjective/qualitative testing to find a balance between noise level and power, and I'm finally posting this after many design iterations because the backswept impeller hits this target zone nicely. I've included other impeller options (straight-tip and foreswept-tip designs) for those who want to experiment, as actual performance may vary depending on fan power. For example, a .2A fan works fine, but a .3A fan is recommended for optimal performance. For quantifiable performance measurement, the backswept impeller on a .3A fan fills a 13-gallon kitchen trashbag in 16-18 seconds. To print this conversion kit, you'll need: * 1 Diffuser (the big star-shaped part that transfers air from the impeller into the volute) * 1 Volute (the snail-shaped thing) * 1 nozzle (straight or 90-degree) * 1 inlet bell (tall or short -- tall is best for tall impellers or booster fans, and it's quieter, but it may choke a short fan somewhat) * 1 adapter if using a booster fan OR if you want something protective to keep bigger stuff out of the impeller (80 or 92 mm depending on your fan) * EITHER: 1 Impeller base and 1 impeller cone (straight or backswept, backswept is recommended)(best/most tunable/complex) OR 1 impeller (short foreswept, foreswept, or straight)(these are simpler to print and mount but harder to balance and may not hold their balance unless you glue them on) Materials needed: * 120mm case fan (I recommend at least 0.2A, and a model with ball bearings would be best long-term compared to sleeve bearing types) * Sheet of heavy plastic film (or similar) at least as big as your case fan * Hot glue gun * 4x M3x12-16mm bolts * 4x M3 nuts * 4x M3x12 bolts if you want to use one of the inlet fan adapters, plus whatever bolts and nuts (probably M4s) you need to attach your inlet fan of choice * 4x M5x12mm bolts * 8x M3x8mm grub screws (flat point) * 5x M3x4mm grub screws (flat point) + 3x M3x6mm grub screws (cone point) if using impeller base * 6x 1x5mm magnets if using impeller base * Superglue if using impeller base