How to Make a Self Priming Centrifugal Pump

This is a centrifugal pump that only needs to be primed before pumping begins then it can continue on it's own.

To make this pump you will need:
-Threaded rod (driveshaft)
-Hose adaptor
-Hose/ Tubing
-Sheet of neoprene
-2x sheets of plastic 
-1x plastic disc(laser cut)
-bottle neck and bottle cap
-19x nuts and bolts
-38x washers
-3x wooden blocks(moulds to be vacuum formed)
-thin sheet of aluminium
-hot glue gun
-waterproof sealant
-epoxy resin

Step 1: Backplate

Backplate
1) On the back plate mark out where the 3 inner components (impeller and 2 blocks) are going to go, as well as the outer shape of the pump.
2) In the centre of where the impeller will go, mark out and drill a single hole for both the inlet hose and driveshaft.
3) Attach hose adapter through the inlet hole.

Step 2: Outer Casing

Outer Casing
1) Create a 'tear-drop' shaped mould(the wooden block pictured) for the casing of the pump's face from a block of wood. Again vacuum form this.
2) With a waterproof sealant, seal around the edges of the casing where holes may have occurred from the vacuum forming process.
3) Drill an outlet hole at the top of the 'tear' shaped casing and attach a bottle neck using a glue gun.
4) Make sure  to keep an edge of plastic around the shape that has been vacuum formed (for bolts). 

Step 3: Inner Shapes

Inner Shapes
1)Create a mould for the inner shapes from wood. These should be as thick as the mould for the outer casing.
2)These wooden blocks are then to be vacuum formed to create the shapes inside 
3)Glue inner shapes onto desired position on the outer casing
4)Place the backplate over this, if the inner shapes do not touch the backplate layer it up with something like wood or plastic with the desired thickness that will allow this.

Step 4: Flat Surface and Neoprene Seal

Flat Surface(so that the seal is flush with the casing)
1) on a thin piece of plastic mark out the shape of the front casing (this will help to seal) and cut it out, the thickness of this should be enough so that it can be bolted.

Neoprene Seal
1)Repeat the same step as for the flat surface onto a sheet of neoprene

Step 5: Impeller

Impeller
1)Cut a plastic disc of diameter 110mm, it is recommended to have slits in the disc for the blades to make it sturdier. (ideally a laser cutter should be used). In the centre of the disc drill a hole for the driveshaft.
2) To make the blades, cut the sheet of aluminium into 5 small sheets of length 60mm width 35mm and bend into shape.
3) Using epoxy resin attach the blades to the disc to create the impeller.
4) Put the driveshaft through the hole in the impeller and bolt in place.

Step 6: Attaching the Parts

Attaching the parts
1)Put the driveshaft with the impeller through the hose adapter at the backplate.
2)On the neoprene, outer casing, backplate and flat surface mark out and drill 19 holes where the nuts and bolts will be attached.
3)Using washers, nuts and bolts attach the above parts together.
4) Using the waterproof sealant seal around the edges where leakage may occur, to ensure pump is watertight.
5) For the outlet, glue gun some hosing onto a bottle cap and screw into the bottle neck
6) For the inlet use a piece of bicycle inner tubing and pin a very small hole into it for the driveshaft
     ii) attach hosing on one side of this and with the other side attach to the hose adapter. Finally keep all of this together with a cable tie.