Thursday, May 26, 2016

Water Pump

This is a water pump fabricated from scratch based on the directions of Gerald Recktenwald at Portland State University, found here:  The housing was constructed from PVC plastic using a mill, mostly used as a precise drill press.  A centered N size through hole fits a bronze bushing and o-ring seat for the motor shaft.  On the other side, a 1" forstner bit is used to make the cylindrical chamber for the impeller (yellow) and a 1.25" forstner bit makes a seat for an o-ring.  On the top of the grey and the middle of the clear sheet, two Q sized holes are tapped with a 1/4" NPT pipe threads for the barbed hose connectors.  Four holes allow a zip tie to hold the motor in place.  Finally, the clear and grey pieces were attached with screws to compress an o-ring, sealing the other side of the pump from water.

The bronze bearing was fabricated on a lathe.  A through hole was drilled concentric to the outer diameter of a bronze rod.  The end of the rod was beveled to allow it to be pressed into the N hole mentioned above.  A small seat was made with an end mill to house the tiny o-ring which sealed the motor shaft from water.  The rod was then parted to make the bearing.

Finally, an impeller was fabricated on a Makerbot 3D printer from a design I created in Solidworks.  The impeller is not anything fancy, and is not optimized at all.  Part of the point of this project for students is to design their own impellers and then to test the efficiency of the pump.  Nevertheless, the pump worked when I tested it (at least as soon as i figured out which side was the inlet and outlet).

In the video below, you can see that the pump can supply a limited amount of potential energy; as the outlet tube is raised, the flow rate diminishes until its maximum pumping height is reached where the flow rate is zero.

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