4" duct and 120mm fan adapters and fittings

NEW in November 2019: added duct-end-vent model.

This is a collection of adapters to combine 4" ducts (as commonly used for venting clothes dryers) and 120 mm "computer case" fans in various ways.

Make your own small-scale ventilation systems with commodity parts. Exhaust the fumes from your 3D printer or soldering iron.

Components

Duct components and adapters:

• fan-to-duct-inner.scad bolts to a fan and fits into the end of 4" duct. While the taper will often let it fit fairly snugly, additional materials may be desired to secure the duct — tape, glue, screws. If using screws, be sure to pre-drill the hole to avoid cracking apart the plastic layers.

• fan-to-duct-outer.scad bolts to a fan and is the size of 4" duct, so it accepts tubes designed to insert into 4" duct.

• duct-end-vent.scad is a rigid end-piece without any mountings that fits into the end of 4" duct, with a square rather than round outside shape. Its design purpose was to protect a free end of flex duct and slightly discourage it from rolling;

Note that 4" ducts are widely varying in fit and you may need to adjust the sizes or add tape or other filler to make a snug connection.

Fan components:

• fan-louver.scad provides moderate weather/finger protection for a 120 mm fan mounted to the other side of a panel. (It would be oversized if used for a duct, but a redesign would be feasible.)

• stator.scad is a simple stator (in the fluid dynamic sense, not the electric motor sense) for 120 mm fans. When using two fans in series, placing the stator between them will provide a moderate improvement in performance. Print two copies and glue them together, using the 1/4" center hole for alignment while gluing.

• fan-table-edge-clamp.scad adds a flat plate sticking out of the side of an assembly of the other 120 mm components, which may be used with a clamp to secure the assembly to the edge of a flat surface perpendicular to the direction of the duct. This design needs work — it lacks some tolerances and room for nut/bolt insertion.

Also on GitHub: https://github.com/kpreid/3dp-duct-and-fan-fittings