OK, for the first stage, you need to get your hands on:
-A PLASTIC BOTTLE (we used a highland spring bottle because it was the right shape and size for our screw, but you could use anything)
-SOME HOSEPIPE, or other form of tubing
-A TAPERED SCREW. For our actual one, we used one that had been rapid prototyped, but we also made another which would work, using a cone shape and little sections of a material-such as roofing underlay-to create a spiral
-A THREADED METAL ROD
-NUTS (to fit metal rod)
-LOADS OF SILICON
-HOT GLUE GUN
Step 1: Stage 1
You'll need to make/obtain a screw- like the pictures shown.
-The one in the plastic bottle has been designed on a CAD package and rapid prototyped
-The other has been made from a vacuum form of a small cone (to make the cone shape), and little sections of a material a kin to roofing underlay (flexible, rubbery, plasticy material), formed into a spiral shape around the cone (just glued on with a hot glue gun)
Next you need to get your metal rod and nuts.
-Drill a hole in the top (small end) of the cone, the same diameter as your rod.
-Screw one of the nuts onto the road, a couple of centimetres from one end.
-Place your screw onto the rod (ensuring the short end of the rod is sticking out the top of the cone.)
-Screw another nut onto the rod, to hold the screw (make sure it's really tight and the screw does not spin around the rod) - it may be an idea to use a resin of some kind to seal the nuts to the screw to make sure no slipping occurs
Get your bottle/whatever you want to use as a casing
-Cut the bottom off (to fit the screw inside)
-Put screw inside and cut top of bottle at an appropriate place for the top of the screw to just stick out
-Determine a point for the outlet and drill a hole where it's needed
-Sand down the top part of the bottle so that it has the same curvature as the bottle and stick and seal it there with silicon (don't use hot glue because the plastic bottle will melt and buckle)
-You need to create a disk for the open end at the outlet side of the bottle
-Measure the diameter of your bottle
-Mark out your shape on a sheet of acrylic and either cut and sand it to fit/use a laser cutting machine
-Make sure you have a hole in the centre for the axle
Before you put this disk on over the axle, screw a wing nut down (in line with the cut edge of the bottle), put a washer on next, then the acrylic disk, then another washer and another nut (loosely, just to act as a guide for the motor/power source)
Drill a hole in the bottle cap and then hot glue a piece of hosepipe of desired length onto the cap, aligned with the hole.
Screw the bottle cap onto the outlet you made earlier and you are ready to go! (Will try and upload video for you)