Electrostatic Turbine: Basic & Enhanced Versions

Static electricity is high voltage (HV) at low current. That unexpected ZAP! occurring when you walk across a carpet and touch a metal object demonstrates HV conduction by ionized air particles. Ion wind turbines use electrostatic forces acting between these particles to produce mechanical movement.

I decided to go green by making this desk-top project from mostly dollar-store hardware; re-purposed plastic, cardboard and aluminum disposables from my kitchen recycling bin as well as some curbside junk from the neighbors next door. The turbine uses foil electrodes that encircle a plastic, tubular rotor. Each electrode has a sharp edge that sprays a stream of positive or negative ions on the rotor's surface. When these electrodes are arranged so they alternate in polarity around the rotor, each electrode repels a rotor segment carrying the same charge and simultaneously attracts that rotor segment carrying charges deposited by the preceding electrode.

Many sources of static electricity --from old CRT screens that "crackle and pop" when powered up, to room air ionizers -- will spin a reasonably well constructed turbine. You can view an enhanced version, constructed from better components and featured on this page w/the basic version, in operation here.

TOOLS

The tools required for this project are a(n): marking pencil; felt tip pen; ruler; compass; protractor; utility scissors; metal saw; desktop paper punch; high speed electric drill with 1/32,” 1/8 “ and 1/4 “ bits; assorted grit sandpapers; sanding block; miniature hobby file and some Gorilla Glue. In addition to the parts listed in STEP 1 you will need a rubber band as well as rolls of paper and cellophane tapes.

CAUTIONS
Unlike many DIY electrostatic motors that creep along at hundreds of RPM, this bad boy can spool up to thousands of RPM in only seconds when sufficiently powered. Work carefully and don’t forget the safety glasses! Also, operate the turbine in a ventilated area if you smell ozone gas. So let's begin...

Here is a list of the parts (there's plenty of opportunity to improvise if a specific part is not available).

A. Rotor Assembly
1. Cylinder (1) 3 oz plastic container of Pounce Cat Treats
2. Conductive Liner 2-1/4 x 7” aluminum strip cut from soda can
3. Disks (2) 2-1/4” dia disks with 1/8” center hole cut from 1/8” cardstock
4. Shafts (2) 1/8” dia x 6” metal rod; #6 x 1-1/2“ metal bolt with lock washer & nut
5. Collars (2) #6 de-threaded nylon nuts


B. Rotor Cage Assembly
1. Floor & Roof Disks (4) 3-3/4” dia disks with 1/4” center hole cut from 1/8” cardstock
2. Bearings (2) #6 nylon flat washers
3. Hubs & Insulators (10) 1/4“ dia x 1/8” flanged, nylon screw insulators

4. Support Columns (4) 1/4” dia x 2-7/8” wood dowels


C. HV Electrode Assembly
1. Power Rods (4) 1/4” dia x 2-7/8” wood dowels
2. Conductive Jackets (4) foil chewing gum wrappers
3. Ionizers (4) 2-1/4” x 2-1/2“ strips cut from aluminum pie pans
4. Connecting Leads (2) 4” of #20 AWG insulated wire
5. Lead Clamps (8) plastic push pins
6. Input Terminals (2) ring connectors w/#20 AWG insulated input leads


D. Final Assembly
1. Fly wheel (1) 2-1/4” dia disk with 1/8” center hole cut from 1/8” cardstock
2. Flywheel Spinner (1) metal tip from ballpoint pen
3. Project Base (1) 1/8“ cardstock
4. Turbine Shroud (1) cardboard peanut container (4" dia x 3-1/8")
5. HV Rim Insulators (1) plastic, snap-on, peanut container lids
6.Mounting Stand-offs (2) empty plastic or styro thread spools
7. Power Source (1) DIY HV X-former w/multiplier or a commercial HVDC source

Construct rotor by removing the top and bottom ends of a cat food container to form a 2” long cylinder. Remove label and sand edges with fine paper until level.

Cut aluminum strip to specified size and line inside of cylinder. Trim width as needed to minimize overlap. Strip will serve as a conductor to attract ions to the rotor and also provide a seat for the rotor disks.

Covers from 3-ring binders are perfect sources for 1/8” cardstock used for this project. First, remove the plastic sheathing from the binder. Cut and drill three disks as specified for the rotor and flywheel.

Insert the #6 x 1-1/2” metal bolt through the holes. Clamp disks firmly against the bolt head with a lock washer and nut. Chuck assembly in an electric drill. Using a sanding block and medium grit paper carefully grind disks to a diameter of 2-1/4.” Rub a thin layer of glue on the surfaces and edges of the disks to strengthen the cardstock. Allow disks to dry and sand lightly with fine grit paper until surfaces are smooth.

Press fit one disk into each end of the cylinder; they should fit snugly and rest against the aluminum liner installed in STEP 2. The outer disk surfaces should be flush with the edges of the cylinder. If the disk diameter is too small, just wrap some paper tape around the circumference to achieve the necessary diameter. Trim excess tape until disk surfaces are level.

Bond the liner to the inner cylinder wall with a small amount of glue. Do not glue the end disks in place at this time — you will need to balance the rotor later. Place the third disk aside for later use in STEP 13.

Cut the rotor shaft to size and slide it through the disk centers. Make shaft collars by removing threads from two #6 nylon nuts with round hobby file until they fit snugly over the shaft. Slide one collar to the end of the shaft and secure with glue. Place this assembly and remaining collar aside at this point.

Cut and drill center holes for the four disks to make the cage floor and roof. Remove 1/8” from the edges of the disks to make a flattened base for mounting your turbine. Sand edges until level.

Mark placements on one of the disks with a protractor to accommodate four support columns and four power rods. The placements must be equally spaced at 45 degrees and 1/4” from the circumference. Use this disk as a template for the three remaining disks.

Make the eight placement holes in each disk with a paper punch. Verify alignment of the holes as well as the flat edges of all disks. Apply glue sparingly to join two disks to make the cage floor. Repeat this step with the two remaining disks to make the roof.

Construct left and right rotor bearings from nylon insulators using a #6 nylon flat washer which is centered and glued to the flanged side of the insulator. Carefully enlarge the center hole of each disk pair with a hobby file. Press fit the bearing assembly through the hole so the flange seats firmly against each disk’s surface.

Assemble rotor cage by placing two insulators over each column with the flanged side facing outward and 1/4“ of the column protruding past the flange. If necessary, wrap a layer of cellophane tape around each column to keep the insulators from slipping. Insert columns into the 12, 3, 6 and 9 o’clock positions with respect to the flat edge of the floor disk.

Before inserting columns into the corresponding roof holes, insert the axle assembly in the cage so the axle passes through both floor and roof bearings. Attach and adjust the roof so that both disks are parallel and rest solidly on the insulator flanges.

Push the axle through until the shaft collar rests against the roof bearing. Slide the remaining collar on the opposite end of the axle. Hold everything together temporarily with a rubber band.

Adjust the movable collar to allow rotor to spin freely when the cage is placed on its side. If the rotor stops in the same position, disassemble it and apply paper tape to the rotor’s inner wall to counter balance. Once the rotor is balanced, glue the end disks to the plastic cylinder. However, do not glue support columns to the floor and roof disks at this time.

Because the turbine runs on little current, all metal surfaces (except ionizer edges!) must be smooth to reduce corona leakage. Begin power rod construction by drilling a 1/32” center hole about 1/2“ deep into both ends of each rod. Wrap the rods with chewing gum foil to make conductive jackets. Ensure that all edges are smooth.

Make a 1/8“ lengthwise crease on both sides of each ionizer strip and fold inwards. Wrap a strip around each power rod so the fold is on the inside of the foil roll.

Enlarge the remaining holes in the floor and roof disks slightly with a round file to accommodate the jacketed rods. Position the rods so that the folded edges of the ionizers face the rotor’s surface. Assemble the rotor-cage assembly using glue to secure the columns; but do not glue to power rods in place.

Secure ionizers to the rods with glue allowing about a 1/8“ gap between each electrode edge and the rotor.

Select two rods at one end of the cage that are mutually opposite. Join them together with a connecting lead and two clamps by removing sufficient insulation from both lead ends. Wrap several turns of the bare wire around the metal shaft of each clamp. Place a ring connector with lead wire under the head of one clamp. Press clamp shafts firmly into the center holes that you drilled in the rods in STEP 9. Repeat this procedure for the other end of the cage.

Insert remaining clamps into the free end of each power rod to secure them in the placement holes of the disks. Adjust the electrode-rotor gap by turning the clamps to achieve the correct distance

Secure the flywheel and spinner on the rotor shaft with glue.

Your turbine is almost ready to roll :>). Just peel off the label and carefully remove the bottom of the peanut container with a can opener without damaging the container rims. Insert the entire rotor-cage assembly from the bottom so that the top lip of the container serves as a backstop.

Cut out a 3-1/2" diameter circle from both snap-on lids and use them to insulate the container rims from the HV leads and clamp shafts. These lids will also keep the turbine in place.

Decorate the flywheel with a felt pen and glue two thread spool stand-offs to the container. Mount the everything on a cardstock base. I attached rubber feet and input terminals to the base for a more finished appearance.

I powered my turbine with a DIY, 12-stage, Crockcroft-Walton multiplier. However, a blinged-out power source isn't essential; almost any commercial electronic ionizer rated at 6 kV or better is adequate. Even a large diameter CRT can provide momentary power for the turbine.

Tape a large sheet of aluminum foil to the screen, fold the edges to reduce corona leakage and attach an insulated wire from the sheet to one of the turbine’s inputs. Connect the remaining terminal to a suitable ground.

The following variables will affect your turbine’s performance: (a) electrode-rotor gap, (b) bearing friction, (c) rotor balance and (d) inter-electrode distance. The first three items are very important if you select weaker power sources for your turbine.

Irregular gap distances will produce uneven electrostatic forces on the rotor causing the shaft to rattle in bearings with too much wiggle room (if the bearings that are too tight, the rotor will bind). Of course, an imbalanced rotor also will limit performance.

Because the average breakdown voltage of air is ~3 kV /millimeter, non-insulated or closely spaced electrodes can arc causing a sudden power loss and a drop in speed.

Construction Tip: A mini flourescent backlight from discarded handheld computer makes a great indicator of corona breakdown. Glue the lamp along the length of the shroud and attach one lead to ground; leave the other end unconnected as an antenna. The lamp will flicker if any flashover occurs in the turbine.

Consider mounting your project on a wood cigar box with stand-offs. Place your preferred power supply inside the box. I used a DIY, HV X-former w/a multiplier potted in candle wax and then wired in an ON/OFF switch (left) as well as a DC power input connector (right). Next, I sprayed the shroud with high-gloss, metallic paint and replaced the cardstock flywheel with a plastic fan blade. I glued a plastic fruit smoothie cover on one of the snap-on lids to serve as a fan blade cover. Lastly, I used rub-on letters to identify the project. (The wording on the shroud should read: "Electrostatic Turbine," but I ran out of letters!)

To optimize performance, I replaced the nylon bearings with oiled, stainless steel flat washers and added an extra pair of ionizing electrodes to increase torque (see sketch for details). When this maxed-out version was connected to an industrial ionizer w/an output of 12 kV @ 1.0 mA, it sounded like this. Input voltage of this enhanced design should top off at 12 - 13 kV. Higher voltages may arc and could permanently toast your turbine :>O. That's all for now. Thanks for your interest in this project!