Experimental Results

Test 1: May 26, 2016

Our first test was to determine whether our turbine actually spun when we hooked it up to a water pump. At first, it did not.  We had to use putty to reshape the water inlet so that the narrower opening increased the pressure of the water shooting into the turbine. After a few tries, we finally got the turbine to spin.

The rate was decent, but we weren't able to sit the turbine housing (a repurposed CD case) clicked onto its base the way we'd originally intended, and water was exiting from the sides as well as the bottom of the case. We ended up prying the nylon spacer off the base, and sanding it down so that there was more headroom in the turbine. This improved our situation slightly. We were still suspicious that the turbine stack was grazing the sides of the case enough to cause slowness and inefficiency. We were also not happy with the amount of friction between the turbine stack and the spindle it rotates around, and the turbine stack and the bottom spacer. We tried silicon lubricant, but once it was wet it actually got stickier and made things worse.

Test 2: June 1, 2016

On this day, we tested our turbine again, and tried adjusting the size of the outflow holes at the bottom of the case by changing them from six round holes to three large crescents. Result were worse. We ended up taping over the mod to narrow it back down a bit.

Once we got the turbine spinning (slowly with the water test, unfortunately), it was time to work on the stator. We wired up our coils to a full bridge rectifier, and attached that to an oscilloscope to see whether we were actually generating current. Then we spun our rotor on a Dremel tool underneath the stator, so we could vary our speeds and determine maximum DC voltage output. At first, results were promising, as waveforms did appear on the oscilloscope. It's alive! At top speed we got about 4 Volts.

We had also planned to try measuring our output with a DMM, but before we got the chance, disaster struck. One of our team turned the Dremel to a higher speed than before, and a magnet flung itself loose from the top of the rotor, shattered the side of the turbine housing, and disappeared into the lab - only to be found with difficulty in a box on the table with the oscilloscope. Thankfully no one was struck, and the only equipment that was damaged was our turbine.

Test 3: June 8, 2016

We completely reworked our turbines. We used the shattered casing to house a waterwheel turbine, with a rotor like the original version. The blades are cut from an aluminum can and glued to a CD at the top and a nylon spacer with ridges dremeled into it at the bottom.

We taped the housing together with duct tape, and kept the water inlet the same. This worked fine. We tested it with the pump circulating water from a bucket, just as we did with the other tests. The waterwheel spun very nicely. We hooked a DMM to the stator, and found that at the speed the pump was running we were generating 2.2 mV. This is not enough energy to power a typical device, but it's proof that we were indeed generating electricity with our turbine!

We took our original Tesla turbine and housed it in a spiral-shaped housing made of acetate film glued between two pieces of acrylic. The turbine spins on bearings, which are screwed into the top and base of the housing. We are using the same rotor and stator that we'd had in the original housing.

We glued the pieces together with E6000.  Water enters through an ordinary gutter pipe and drains through holes drilled in the base. The magnets are very close to the top of the housing, for maximum interaction with the stator, but there is about half an inch of room between the rotor and the base of the housing.

For our test, we dumped 7 gallons of water into a tub that was taped to our drainage pipe; we had about 7 feet of head. Our turbine only spun for a few seconds, as the water drained through very rapidly, but we were able to verify that our rotor works! It spun much more quickly than it had when we did the test with the water pump, but not nearly as fast as when we'd spun it on a dremel.  Our DMM read 2.9 mV at top speed. I feel that this is definite proof of concept, but if we want to generate usable electricity we're going to need to up the scale, as in more and stronger magnets, on a wider rotor.

There was little water leakage from the side of the housing, which is a better result than we had with the original housing. The rotor had been packed in so tightly that we actually had friction problems from the CDs being too close to the housing's sides. More room helped the water flow correctly, and the CDs spin more rapidly.

Looking to the Future

We will need to cut our stator windings off their current mount and move them further apart, and then remount them so that the sides of the windings are all exactly the same distance from each other. Then we can mount 12 magnets to a larger rotor instead of 6, and they will all be pushing electrons simultaneously.

Another design issue is that we have a steel screw in our housing too close to our magnets; it interacts with their magnetic field and slows the spin down slightly. We can replace it with brass.