Introduction: Improved Electrostatic Turbine Made From Recyclables
This is a completely scratch-built, electrostatic turbine (EST) that converts high voltage direct current (HVDC) into high speed, rotary motion. My project was inspired by the Jefimenko Corona Motor which is powered by electricity from the atmosphere:
The turbine was constructed from the following items: plastic tubes and drinking straws, nylon spacers, cardboard, sheet metal connecting and mounting hardware as well as a HVDC power source used in place of the earth's electric field. The turbine features a clear plastic housing that reduces the risk of accidental HV contact while permitting an inside view of the turbine for classroom and science fair demos. When operating the turbine in a darkened room, corona discharge produces a ghostly, blue-violet glow that illuminates the inside of the housing. A side-by-side comparison of an earlier version of the EST shows the smaller, more streamlined profile. I used simple hand tools and an electric drill for construction.
Caution:This project can produce ozone gas and should be operated in areas with adequate ventilation. Work gloves are recommended when working with sheet metal due to sharp edges. Lastly, HVDC is not always user-friendly, so act accordingly!
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Step 1: How Does the EST-3 Work?
The EST has 6 foil electrodes with razor sharp edges that encircle a plastic rotor. There are 3 series-wired, hot electrodes that deposit charged particles on the rotor's surface. Hot electrodes alternate in polarity with 3 grounded rotors (in this case: Hot-Gnd-Hot-Gnd-Hot-Gnd). The hot electrodes spray the rotor with like charges, which the electrodes then repel, causing the rotor to spin. Through the process of induction, each hot electrode attracts the rotor segment that was electrically neutralized by the preceding ground electrode. The rotor has a sheet metal backing to optimize the electric field gradient between each electrode's leading edge and the rotor's surface.
The action of hot electrodes spraying ions on the rotor coupled with ground electrodes on clean-up detail enabled the unloaded turbine to reach 3,500 RPM using an industrial grade ionizer. The sketch shows a prototype EST with 8 electrodes which was a miserable failure due to internal arcing between electrodes placed too closely together.
Take-away Lesson: Make sure electrodes are properly insulated and/or spaced apart before using a high output power source; otherwise, your turbine could be reduced to a smoking hot mess!
Step 2: Locate Plastic Tubes for Housing & Rotor
I found these acrylic tubes in the scrap bin of a local plastics store. I used them to make the turbine housing and rotor. The exact dimensions don't matter. One tube should fit inside the other with several cms clearance all around. Rigid plastic bottles, such as vitamin containers, with the tops and bottoms cut off would also work.
Step 3: Cut Out Electrodes From a Turkey Pan
Six electrodes were cut from a discarded aluminum turkey basting pan left over from a dinner party. (Construction Tip: Use a pan for cooking a large bird, metal is heavier and less likely to bend.) I cut the length of each electrode approximately equal to the rotor length while making an effort not to crush to rolled edges.
Step 4: Insert Electrode Support Rods
I inserted an 8-32, threaded rod segment through the hole of each electrode (fit was spot on!!). Segments were 3.0 cms longer than the turbine housing.
Step 5: Flatten Leading Edges of Electrodes
I removed corrugations and dings in the foil with a rolling pin.
Step 6: Trim & Round Off Electrode Edges
Leading edges of each electrode were trimmed to 1.0 cm using a paper cutter. The corners were rounded with a hobby file to reduce corona leakage.
Step 7: Cut Retainer Plates & End Caps for Housing & Rotor
I cut a set of 6 cardboard discs to make housing end caps; another set of discs for rotor end caps; and finally, I cut a third set of discs to make retainer plates for the bearings.
Step 8: Check End Caps, Rotor & Housing
I slipped the rotor and housing end caps over a 1/4 inch diameter, hardwood dowel that served as the turbine shaft. Later in the construction, the dowel was upgraded to an acrylic rod for improved appearance. I verified end cap placement and checked that the rotor was concentrically positioned in the housing. (Construction Tip: Wrap paper tape smeared with wood glue around discs until they fit tightly in tubes.)
Step 9: Re-Drill Housing End Caps for Bearings
I used wood glue to assemble the housing and rotor end caps. Next, holes were drilled 60 deg apart along the outer circumference of the housing end caps so they could accept threaded support rods. A second ring of holes 120 deg apart was drilled midway between the outer ring and the center. A corresponding hole set was drilled through the retainer plates. Initially, I drilled out the centers of the housing end caps to accept metal bearings. However, they drew sparks from the tips of the electrodes as the turbine approached full power.
I found a work-around that involved 1/4 inch ID, non-conducting nylon spacers as bearings. I secured them with three 8-32 nylon bolts inserted through the retainer plate. There was some rolling resistance when I hand spun the rotor, but the turbine probably wouldn't scorch and turn into a SHM (smoking hot mess). :>D
Step 10: Drill Mounting Holes in Housing
I drilled two, 1/4 inch mounting holes through each end of the housing tube. The holes accepted 1/4 inch nylon bolts with lock washers and hex nuts.
Step 11: Attach Connecting & Support Hardware to Electrodes
Two ring connectors were slipped over each ground rod as shown. I used rubber grommets (3/16" ID) as stand-offs. This procedure was repeated for the electrified end of the turbine. Everything was temporarily secured with nylon acorn nuts to check for a good fit. (Rotor was not installed at this point.)
Step 12: Prep Rotor Assembly
Initially, I covered the rotor tube with a metal sheet cut from a beer can and then spiral wound plastic tape around the tube. Later, when powering up the turbine, it wasn't long before internal arcing from the electrodes punctured the tape and ruined the rotor -- !@#$, another toasted turbine! (Three puncture arcs appear as starbursts in the low light picture).
A better idea was to remove the original tape and cover the sheet metal with a thicker insulating material possessing higher dielectric strength. I used a sheet of heavy duty plastic cut from a package of dog treats which I secured with tape.
Step 13: Install Rotor Assembly
I removed ground end hardware from the turbine and inserted the completed rotor until the shaft fully engaged the bearings. Ring connectors were added at the 5:00 and 7:00 o'clock positions for power input.
Step 14: Repair & Insulate Electrodes
The turbine was unlikely to work properly b/c several leading edges were bent while inserting the rotor assembly. My work-around was to disassemble the turbine and then epoxy a coffee stir stick to each electrode as a support beam. The sticks were prepped using med/fine sand paper and then colored with a silver paint pen.
I used 12 color-coded straw sections (0.5 cm ID x 3.5 cm) to insulate the support rods. Each section slipped over a support rod, passing through both grommet and end cap holes.
Step 15: Reassemble Turbine & Adjust Gaps
After putting the turbine back together (again!) and series-wiring the hot and ground electrodes, I atached input wires to the binding posts. Gap distances were adjusted by torquing the acorn nuts at the end of each rod until leading edges were within 1 mm of the rotor's surface. I cut a sleeve from a 1/4 inch ID "Big Gulp" straw and slipped it over the axle ends to limit side-to-side rotor movement.