Last year I saw a video on Youtube, it was simple to make. Just have a jar with water, some sparkles and liquid soap. Simply shape the jar and wonderful tornado would appear. The tornado would die soon and needed to stir it often.
My solution : Magnetic stirrer
Magnetic Stirrer are used in labs to stir liquids during some kind of experiment. This will create tornado and will not die, at-least till the battery is good
Watch "Tornado in jar" on YouTube - https://youtu.be/m3-UR-r8X_Y
Step 1: What You Need?
1. Two large & strong magnets
2. Two small strong magnets
3. 12V DC fan
4. 9v Battery and connector
5. Small switch
6. Some wood
7. RGB LED Strip / just Blue LED Strip
8. Glass Jar(s)
9. Heat shrunk tube
11. Cold Cream Cap
1. Soldering Iron
2. Soldering wire
5. Drilling machine
6. Paper tape
7. Black acrylic paint
Step 2: Concept
As we have learnt
1. Like poles repel
2. unlike poles attract
In the base two magnets are rotated in fast speed, that makes the small magnets in the jar move in similar direction and speed
Step 3: Wooden Base
We need a good strong base, to be sure that kid cannot poke their fingers in it or any other kind of injury
I used wood to built the base, Size just to include the fan and a 9 V battery. Using drill machine drill holes in the wood and fix them together in rectangle.
Remember did not leave any space so the fan was quite tightly fitted
Used a thick cardboard as top lid. Cut out the piece to fit the cold cream cap. Cold cream cap is semi transparent. This is useful for LED lights
Step 4: Lights, Fan and Stirrer
Lights :A rgb LED strip, which works on 12v was used. I replaced the red led with the blue led.
Using paper tape stick the led strip in place ( center of the lid )
Fan : Stick strong magnets on the fan, remember that the North pole of one magnet and south pole of other should point upwards
Magnetic Stirrer : This is the most tricky part
I used 5MM X 5mm n52 magnets. One North pole up and south pol of other. Used 5mm heat shrunk tube And using soldering iron seal them as shown
You can try different shapes, I experimented with the lengths and shapes, but the ones above worked fine
Step 5: Problems
Problem 1 : The glass jar available are not exactly flat
I have used pickle and olives bottles, which do not have flat bottom. the stirrer bounces inside the jar and the tornado gets killed.
Problem 2 : Stirrer magnets size and shape
My magnets were 5MM X 5MM, not good. You should use 5MM X 2MM that would reduce toggles
Problem 3 : Water weight and Surface tension
Add some liquid soap to the water. Reduce water in the jar or use smaller jar
Problem 4 : Speed of fan
Faster the fan goes, faster the stirrer goes and may cause stirrer to bounce. Control it by using lower volts or a variable resister ( 1K ohms ).
Step 6: Switch Off Lights and Relax
I made it with two different jars with different length stirrer
I switch the jars and watch