Introduction: Tesla Tornado Christmas Tree
Second Prize in the
Homemade Holidays Contest
Here is a Christmas tree with a twist!
This metre-high tube uses a magnetically-driven Tesla Pump to create a beautiful water vortex. With green food colouring and lights behind it, it makes an awesome alternative to a Christmas tree!
Nikola Tesla patented the Tesla Pump (U.S. patent #1,061,142) in 1913. It featured only flat discs to supply pressure from the pump, and makes use of the same "adhesion of fluids to a surface" and boundary layer principles as the simple, but effective, Tesla Turbine.
This Tesla Tornado is made using a Subaru blower fan motor, complete with its 3-position speed switch mounted on the base. The blower motor has a flywheel fabricated out of Lexan with 6 neodymium magnets mounted in it. It magnetically couples with 6 magnets in the Tesla Pump disc pack, which is inside the vortex tube.
The Tesla pump discs are magnetically driven by the blower motor flywheel magnets, so there is no direct connection. The pump disc pack is self-centering, and there is no rotating shaft, shaft bearings, or seals required!
Step 1: Materials and Tools
1.) Subaru Heater Blower Motor, complete with stock plug-in 3-speed switch and resistor circuit. (from 1980's-90's Subaru or other equivalent electric motor)
2.) Lexan Polycarbonate tube, approximately 1 metre or more in length. 6 inch is a good diameter.
3.) 7.5 cm length of same 6" tube as above for motor mount. (or custom length to your motor specs)
4.) 2 of 8 inch x 8 inch Lexan plate, 1/4 inch thick. (one for Motor mount plate and one Tube bottom plate)
5.) 3 of brass threaded rod, 1/4 inch x 8cm, for motor mounting, with wingnuts and washers.
6.) 12-volt heavy-duty on-off switch.
7.) 6 of 1/2 x 1/2 inch neodymium magnets, preferably N52 strength
8.) 6 of 3/8 inch x 1/32 inch neodymium magnets for each layer of discs (typical 8 discs x 6 each = 48 magnets)
9.) Fondue base, found at a Thrift store
10.) Polycarbonate solvent (methylene chloride)
11.) 12-volt car battery or equivalent
12.) CD discs, from 3 to 30 depending on design. (less discs require more rpms to get same effect. I found 8 discs worked well)
13.) Crazy Glue
14.) 4 of 1/4 inch bolts, nuts. Brass or stainless preferred, for bolting Motor Plate to Tube Plate.
Circle-cutter attachment for a drill press. (Can substitute a jigsaw if necessary)
1/4 inch tap for threaded holes.
Drill and 1/4 inch bits
Step 2: Make a Magnetic Flywheel
The flywheel can be made of 1/2 inch polycarbonate plate, or two pieces of 1/4 inch plate glued together. It is about 5 inches in diameter, and has 6 equidistant magnets placed in it by drilling 6 of 1/2 inch holes in the poly. The magnets should fit tightly.
Use a drop of Crazy glue to hold the magnets in place once they are inserted into the flywheel.
The centre of the flywheel must be same as the shaft size of the blower motor. In my case a 1/4 inch centre hole worked well. Back up the shaft with a washer before mounting the flywheel, and make sure the shaft nut doesn't back off by using Loctite on it.
Step 3: Mount the Motor
Remove the blower wheel from the Subaru blower motor, and prep the motor for use by cleaning it. Use the original nut from the shaft to hold on the new flywheel.
The motor mount is simply a 7.5-cm long piece of 6 inch polycarbonate tubing, glued to a piece of 8 inch square polycarbonate. The motor is held in place by 3 of 8-cm threaded rods and wing-nuts. The rods are screwed into 3 threaded holes in the motor support plate, and then through the 3 mounting tab holes of the original motor.
Step 4: Mount the Switches and Wiring
Drill 1/4" or 3/8 " holes in the fondue stand for the switches and mount them. The 3-position switch that comes with the motor can be mounted there. The shut-off switch can go beside it, once the wires are run to it that cut off the main power from the battery.
Note that the resistor that comes with the blower wiring is normally inside the heater duct, where it's red-hot coils get cooled by the blowing air. It must be located in a place open to air flow, and at least a foot away from combustibles. An good alternative wold be a 20 amp capacity motor control rheostat for the 12-volt blower motor.
It's tempting to use a 120-volt AC motor as the drive motor, but don't do it unless it is a sealed unit. The chance of spilled liquids getting on the motor is too great. 12-volt is generally considered safe as far as shocks go compared to household voltages.
Step 5: Make the Vortex Tube
Obtain a one-metre long, or to suit, piece of 6 inch Polycarbonate tubing. Expect to pay $100 or more for a metre.
I don't advise to use plexiglas or acrylic for this project, as it tends to be too brittle and can shatter easily. Polycarbonate is virtually bulletproof in case of "eventualities" such as the motor flywheel coming apart at speed.
Drill 4 holes in the outer corners of one of the 8 inch poly squares. Drill 4 holes in the other square to correspond to the previous holes.
Make sure the end of the tube is square, flat and smooth, and apply solvent-glue (Methylene Chloride) to the tube end with it centred on the 8 inch poly square. Allow to set, and the Tornado Tube part s ready!
Step 6: Make a Tesla Pump Disc Pack
The Tesla Pump is a disc-based pump invented by Nikola Tesla In the early 1900's. It is based on the principle of adhesion of fluids on a rotating surface can impart momentum and pressure to the fluid.
The 8 discs in this case are CD discs. They are spaced 1/32 inch apart with thin neodymium magnets. There are heavy magnets attached to the disc pack to provide the magnetic coupling with the motor flywheel.
I use Crazy glue to attach the magnets. It helps to scratch up the surfaces of the CD discs and the magnets with sandpaper to increase adhesion of the glue. I also use Marine GOOP around the larger magnets for additional support.
Glue the first 6 magnets equidistant from each other, and about 1/4 inch from the rim. The following magnets will line up automatically by placing discs and magnets on top of the previous ones, and gluing them in place.
Although the disc pack is usually self-centering when running, a suction cup and stub shaft helps keep the disc pack stuck to the bottom. I used some plastic oil-drain washers as thrust washers, and a small length of CD spindle shaft, attached with hot glue to a suction cup, to act as a steadying centre spindle. The other CD discs get crazy-glued to this basic bottom piece.
There is room for experimentation in regards to this driven disc pack, and the best simple way to keep it on the bottom when running.
Step 7: Give It a Whirl !
After carefully mounting the motor, flywheel and wiring, and testing the basic motor running, place the vortex tube plate against the motor plate and bolt them together with the 1/4 inch bolts and nuts.
The bolted poly plates sit on top of the fondue stand. (make sure you use a well-made heavy-duty stand, as there will be considerable weight on the legs from the water in the tube.)
The disc pack gets put in the tube. I used a long dowel to push down the disc pack suction cup to the bottom and to centre the discs.
Fill a foot or so high with water, and turn on at a low setting to try it out!
Don't try to progress to max speed setting too fast, or the magnetic coupling may be lost, and you will have to start again from 0 rpm. Using the more powerful N52 magnets helps keep the magnetic couple better.
A vortex all the way to the bottom should form within a few seconds if all works well.
Step 8: Fun Things to Try
I used red and silver sparkles to add some zest. Too many sparkles of large size will clog the discs temporarily. If that happens, turn off the vortex and wait a few seconds, then turn it on again...that will tend to purge the clog. In retrospect, the disc spacing could be wider to accommodate this. 1/16 to 1/8 inch disc spacing would likely work better with the sparkles.
Add coloured lights behind the poly tube for cool effects. A flashlight or laser shining into the vortex from the top works good too.
I added a ping-pong ball and got interesting effects. The ball can be held completely submerged in the vortex, and its height can be controlled easily with the speed of the Tesla disc pump.
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