Project: Tornado Simulator
This started off with a demonstation I saw while at the Bristol Science Museum. In the center of a room they had this enormous spinning vortex of white mist that you could walk through. After a bought 5 minutes, I worked out how it was done and plotted about making my own. On a smaller scale of course,....for now ;-)
This is my own design for this simulator and it works very well. It took a lot of time to get this design right and working properly.
The main design realies on low pressure of air at the center of the vortex. This is created by a radial blower fan sitting at the top of the machine, which blows more than sucks. It also creates the spinning motion slightly.
The mist is created by an Ultra-Sonic Water atomiser (nebulizer) at the bottom of the machine. These are incredibly interesting and very hard to find! They have a ceramic plate at the top of the unit which when fed with an AC signal between 1-2Mhz (waters bond breaking frequency) the ceramic plate knocks the water molecules apart. The water molecules then become almost the same weight as air and leave the water liquid, rising to the surface as mist. The mist is cool and gives off the same smell as just after a thunder storm. People use these as room humidifiers that put moisture back into the air. I found my atomiser at a garden center, sold for water displays, for £30.
*It is extremely painful if you put your finger into the jet of mist when the unit is running! As I found out :-) I believe this is because your body is made from 90% water and when the ultrasound waves hit your finger, it starts to atomise your blood inside your finger! Also the frequency is so high that it just barely registers on your neverous system.
The atomiser and the light is placed into the stainless steel container and filled to just over an inch above the atomiser plate. At the top of the container I put a cylindrical tube with holes drill into the side to allow the mist to pass through but not the water splashes. There is also a hole drilled at the bottom to allow for water droplets to pass back into the container.
In the above photo your can see there is an air hole. This was done because the mist produced will not travel through the small holes on their own and need a small breeze to flow up the pipe and out. This is done with a small cpu fan mounted to the side of the base which sucks air in from outside and directs it into the mist container. I put a small pot on the cpu power to adjust the amount of mist entering the chamber. This method makes sure that no water enters the base of the tornado generator (just for looks really). Both the top and the base holders are made from buckets cut in half, to keep it cylindrical looking.
Next up is the machines main unit.
This is where it got a bit more difficult to make this project. The main tornado chamber needs to be cylindrical to keep the air flowing in a circular movement and free from eddies. So you cant use big bolts and things to hold the unit together if you want a nice looking stable tornado. It also needs to be just more than 50% enclosed to keep it stable. The bases for each end of the chamber are pyrex (or something) dishes of designed for salads I found at a grocerie store. They are 11" in diameter and can be drilled with a bit of care as they crack easily.
The back wall or connecting half cylinder is a sheet of 1mm thick aluminium 500x500mm. The sides are strengthened by two strips of pine wood that also add a nice look to the unit. They are varnished and nut and bolted to the aluminium sheet. The sheet is nut and bolted to both bases on the inside. The entire unit was then sprayed in a graphite black plaint.
The top of the unit houses the radial fan, controller and halogen light.
The radial fan is homemade, but I could have probably bought one such as a ceiling extractor. The motor is an old electric car aerial extender that runs on 12V and the fan blade is a spare part from a vacuum cleaner (hover I think). This was the perfect combination as the blade fitted the shaft of the motor perfectly and it works on DC, so I could easily control the speed. More on this later. The light is a 12V 10W Halogen that is mounted at an angle to illuminate the vortex in the center. The top cover as I have already said is half a bucket, but I have glued foam on the inside to help deaden the noise of the motor.
The motor controller:
This is a simple PWM DC controller built from a 555 timer and 2N3055 transistor. The advantage of doing it this way, is you can adjust the speed of the motor fluidly and ultimitly create a fast F5 tornado (more noise) or a slow gentle F1 tornado (quite for constant use).
Now comes the main trick of the unit. Its quite simple but took me a long time to work out!
A small amount of air needs to be fed back into the tornado chamber to start and keep the vortex rotation going. It helps to keep it stable at slow speeds and allows for a quicker cold startup. This may look simple but took a couple of weeks of playing around to work this one out! It need to come in from the same direction as the motor blade is rotating.
The power supply for the mist maker draws quite a lot of power from the mains (24VAC 1.2A). The power supply for the fan/light comes from an old laptop PSU (12V 2.2A).
This was a fun and interesting project. I still have it in use today in the corner of my room! Humidifying the room (same effects as a downpour of rain or a bathroom shower).
More action shots:
The amount of things you can do with these things are infinite. You can put a dye into the water of the mister and change the colour of the tornado, or you can put bits of paper (or ants :-) )into the tornado and watch them get sucked up slowly, or you can just put your hand or head into the vortex and feel the breeze!
If you build one of these, please email me and let me know how it turned out!
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© Oliver Hunt 2006-2008