Theory
As water passes's over the above apparatus, it will cause the propeller to spin. As the propeller spins reflective tape will cause the infrared beam of light emitted by the senor to be reflected back into the sensor. The reflected beam will trigger a counter that records how many times beam of light has been reflected.
Fabrication
All fabrication was done by Nathaniel House and Derek Bruno in the Crosby Laboratory at the University of Maine.
The housing block of polyethylene was created by drilling multiple concentric holes for the shaft of the propeller, a hole for the photoelectric sensor, and the handle.
The shaft spins inside two brass sleeve bearings. There is a groove in the shaft with a cir clip attached to keep the propeller shaft from being pulled out. A set screw in the back holds theshaft in from the rear.
Here is a large Exploded view of the design
Below are more photos of the completed vane anemometer.
Back of apparatus with refelctive tape showing
Entire apparatus with mounting handle