Nothing but a toy! Fun tho, counter rotating blades give a trippy pattern.
If you do decide to print one for yourself. You'll need a few things.
5mm rod of some sort, I happened to use stainless steel as I had a surplus of it, but about anything would do. Wood would be a fine choice. As I left just enough of the rod protruding so that no other fasteners would be needed, all held in place by the shell/lid and it's holes.
Superglue. For gluing the gears to the rods and crank. Note that the 62th gear SHOULD NOT be glued to the rod! It must freewheel.
The Backwave disc gets glued to the protruding printed shaft of the Spur Gear (62 teeth) file.Would suggest making this the first thing you glue and let dry completely. As otherwise it'd impede the counter-rotating front disc and the gears behind.
Washers wouldn't hurt, but I didn't use any and it operates smoothly and just fine without.