Compact and Customizable Boot Dryer/Ventilator (SCAD)

I wanted a boot dryer, but I never felt like spending $50+ on a thing that works, but will probably suck up a bunch of floor detritus and fall over because my boots weigh more than it does. I wear 10" steel-toe boots, and almost never wear anything else. My boots are the only thing that ever needs to be dried in a timely manner.

Based on that motivation, I came up with a design that is compact and can simply be dropped into a pair of boots as they sit on the floor. It's not heated, but I wouldn't consider it safe to attempt such a thing in PLA without complications that nobody else would be willing to replicate.

I designed the duct length to be configurable, but not field-adjustable. To accommodate smaller printers and/or much taller boots, the duct may be segmented using extensions. The duct joints are intended to simply be glued together, though you're free to tweak the clearance until you get a press fit or something. The ducts have external fins which help keep the boot upper, tongue, and any padding from resting against the duct and restricting airflow.

There are wiring compartments on either side of the fan, and there is clearance for wire passage between them. This should make it possible to use a DC fan with room to include a small power converter. I just used an old AC fan because I had one. The extra space may also be useful for an electronic timer or something.

I used an 80x42 fan, but that's not a common size. Common sizes would be 80x25 and 80x38. While 25mm DC fans are ubiquitous, many are underpowered and can't handle much pressure. Make some effort to choose a decent fan. You will likely find that performant DC fans can outperform RPM-limited AC fans here. A DC fan will also tend to be lighter (makes the assembly less top-heavy), but an AC fan will be a bit simpler to install. FWIW, the fan I used is an old 120V Comair Rotron Sprite SU2A1 (80x42, 11W, 34CFM max, 0.15" WC max).  It's a heavy, expensive fan designed for reliability, not performance.  That said, it's a 30 year old ball-bearing fan with an erstwhile creep-deformed press-fit plastic rotor.  It's exceptionally noisy.  Don't take it as a recommendation.  

I designed everything to use hot-set drywall screws or deck screws. They work well and I have them. Thicker fans need longer screws than can be typically found in machine screws. Longer drywall screws tend to be larger diameter. The prerendered files either use 1.75" #6 bugle-head drywall screws or 2.5" #9 conical flat head deck screws, depending on the fan thickness. See the notes in the SCAD file for more info or to specify different size screws (#6, #7, #8, and #9 are supported with either style head)

All you need is a fan, a cord, a switch, and four screws. The AC cord is a plain 18-2 lamp cord. The switch dimensions are listed in SCAD and can be changed. I designed around junk that I had laying around, but all of these things are on Amazon.

I'm including preconfigured SCAD files and prerendered STL for 80x25, 80x38, 80x42, 92x25, and 92x38 fans, along with an assortment of prerendered ducts and extensions.

It should be possible to print everything without supports, but I used a small amount of painted-on supports on the central bridge of the plenum. I used brims on the ducts, extensions, and the fan collar. Everything else prints flat and glues together without much fuss.

As always, read the SCAD file for design and build notes.

Category: Household