(update 20.0602: the original stl:s are, technically speaking, broken and modern slicers cannot slice them (older slicers could handle them, though). Therefore I added re-constructed bottles as "V2020" STLs. I also added a .3mf in case you prefer. I kept the original STLs as it might be a useful excercise to compare them for someone learning about 3D printing?)

I created this fan gadget for my elderly parents as a surprise, as they love the game "Heck Meck". However, friends (apparently, many friends of mine play the game still) asked for copies too, and at some stage I e-mailed the game inventor, Reiner Knizia, to ask if I could possibly share the design at thingievierse, as the worm design is part of the game for which Knizia has copyright (see https://www.knizia.de/ for details with respect to the game). He was indeed very kind to me and granted the publication for non-commercial use (and he asked for a soap dispenser :-).

I made three sizes of the dispenser, namely the XVII80, XVIII90, and XVII100 which can hold 2dl, 2.75dl, and 3.5dl, respectively (please don't ask about the naming convention).

The thread is the same size in all cases, diameter 27mm with 4mm of elevation per revolution. This works with many common soap brands (for attaching the pump), eg I have successfully verified brands (in Sweden) such as "Bliw" and "Palmolive". For increasing the strength around the thread, I advice to use the support element (eg, load it via "object->settings" if slic3r is used, and set it to 60% fill). Please do not forget the post-processing step.