A water pump powered by a 550-size brushed DC motor. It's intended use is as a damage control pump in RC boats, but it moves a good bit of water (~1.5GPM at 6000rpm, can handle twice that) so there are many uses that it could be put to. Disclaimer: This is a fast centrifugal pump and you can be hurt by it! I take no responsibility for what you make and/or use, because hey, I have no control over this after it leaves my keyboard :) So be careful!! :) *Note, the impeller changed since that picture was taken. It flows more now :)
You will need the following non-printed pieces: 550-size motor, 2 M3x8mm hex-head screws, 4 M3x30mm hex-head screws, 1 Dubro brass collar (1/8" I.D.), 30mm of 5/16"(8mm) brass tubing. Some acetone to make a slurry with.
-The stl file has all three parts of the pump: motor mount plate, pump body, and the impeller. Print the parts in ABS. Fettle all through-holes with a 3mm or 1/8" drill bit. Fettle the 2 countersink holes in the mount plate with a 7mm or 1/4" drill bit. (By hand!)
-Mount your 550-size motor to the mount plate with a pair of M3x8mm screws.
-Fettle the hole for the 8mm tubing such that it's a tight fit for the brass tubing. Push the tubing in. Some people trim the brass with a Dremel such that the tube is inserted further into the pump body without intruding in the volute (chamber) of the pump; gives more surface area for adhesion. When you're happy with the fit, remove the tubing and set aside.
-Fettle the bore of the impeller with a 1/8" (3.2mm) drill bit, then on the free end, fettle the larger bore with a 5/16"(8mm) drill bit. This larger bore only goes 1/3 to 1/2 way down, and provides a space for the brass collar which engages the motor shaft. Use a Dremel cutoff wheel to make 3 or 4 notches in the circumference of the collar. Set aside.
-Mix an ABS/Acetone slurry. I don't have a proportion for you to go by, Mine is slightly less solid than toothpaste, smears easily.
-Put some of the slurry on the outside of the brass tubing, and push it into the pump body. Make sure that the tubing doesn't go into the chamber.
-Put some of the slurry into the large bore on the impeller, and press the collar down in. Note: Make sure that the setscrew is screwed well into the bore. Try not to get any slurry into that setscrew hole!
-Let the parts sit overnight (~12 hours) for the slurry to harden.
-Carefully drill out (I do it with a drill bit in hand) the setscrew borehole. Back the setscrew out of the bore. Chase the bore with a 1/8" (3.2mm) drill bit. By hand is good :)
-Fit the impeller onto the motor shaft, tighten the setscrew to engage the flat of the shaft.
-Fit the motor (on the mount plate, with the impeller on) to the pump body. Orientation of the mount plate and pump body does not matter. Use the 4 M3x30mm screws to fasten the pump body to the mount plate.
-Connect your motor to your choice of battery (within its limits, obviously) and test!
**If I missed something or skipped a step, please let me know. It's a lot of instructions for a simple procedure. If you are in doubt, ask before you injure yourself or break something!