A 3d-printable displacement pump using a gerotor. It requires many vitamins. Its volumetric efficiency is, well... Somewhat higher than zero. Why won't thingiverse show my animated gif's!? Download gerotor-pump.zip to see a moving cutaway view. For it to work pretty much requires acetone-polishing and sanding. Also fish bubbler tubing, 4.5mm BB's, an o-ring, some ABS glue, and oil/grease.This is a 3d-printable displacement pump which uses the gerotor, a specially-shaped inner and outer gear whose teeth mesh perfectly at all points to form a chamber which changes size during rotation. There are four parts: inner rotor, outer rotor, case, and lid. There are also "vitamins", the pump requires. I use 4.5mm airgun ammunition for ball-bearings, and a 5/8"-3/4" O-ring as a top seal. The O-ring can be easily changed to whatever you have on-hand, larger bearings would be a bit trickier. You will need to block half the outlets with ABS cement once you figure out which ones you want to close and which ones you want to keep. Does it work? Yes! Badly! But it works! Getting two rotating 3d-printable objects even slightly close to the required tolerances for pumping water is not the easiest task. Lots of acetone-polishing, sanding, pounding, grinding, abusing-a-dremel-as-a-poor-mans-lathe, lubrication, and a fair bit of English were involved. The result is impressive only in that it works at all. It definitely works better at pushing than sucking, at least. If you want to experiment with the .scad, it REQUIRES OPENSCAD 2014.05.30 OR NEWER! It uses a new for() feature which allows you to build arrays of points from a loop. This is revolutionary. Things which took minutes to do before are now fast enough to ANIMATE. So yes, it is worth it. Many, many thanks to whoever created this file and put it on the net, I couldn't have done this without you! http://www.bconnex.net/elen/public_html/resources/Gerotor_Modeling_with_NX3.pdf [edit] This has become a dead link, but the PDF is in downloads too!