Tornado simulator

[iPaintball]

I'm planning on building a 3 feet tall tornado simulator. It will be an open air design, to be able to see how air currents and close objects effect the vortex. It will be very similar to this:

Another shot:

I will be using a small 4" fan from Wallmart as a the current generator, and a more powerful 120mm 120VDC cooling fan as the updraft fan. I will wire in two pots to adjust speed and air flow and the base and top will be mad of OSB.
If anyone has built one of these befor, feel free to give me advice...

[clide]

After seeing http://www.weatherscapes.com/techniques ... do_machine I built a tiny one with stuff I had laying around.
http://www.spudfiles.com/spudtech_archi ... php?t=9888

I still need to try and get a video of that thing since the pictures didn't do it justice.
Edit: Just got a quick video of it.
[GVideo]http://video.google.com/videoplay?docid ... 7320416619[/GVideo]

[iPaintball]

That thing is LOUD! Both fans I have are about 35 decibels. In other words, they are SUPER quiet. Nice simulator though!
EDIT: How did you make the funnel shaped piece at the bottom?

[clide]

Yeah it is pretty loud, especially for its size. It is a little quieter if I am running at the proper voltage, but tornadoes are loud too so it just adds realism 8)

The funnel shape was made on my lathe. It is just a solid chunk of PVC rod that connects the top and bottom sections. The guide that I linked to has a pretty nice how-to (page 12) on making a large funnel shaped piece out of a sheet of plexiglass.

[iPaintball]

I wish I had a lathe... I know about the way to do it using plexiglass sheet, but I saw what appeared to be tooling grooves on your funnel, so I just wasn't sure how you did it.