Date: Tue, 5 Nov 2002 19:51:19 +0000


Subject: RE: Flame tube


I built one last month which I very loosely (and cheaply) modelled off of
Zig Peacock's at the Lecture Demo Workshop in Boise with very rough notes.

Here's what I used:

5 ft of 5 inch diameter galvanized stovepipe from Home Depot, an end cap,
a 'reducer' (the thing that takes you from smaller diameter to larger diameter
pipe-- get two if you have a bigger speaker), a brass elbow with one side
barbed and the other threaded with a nut, a length of hose that will fit
your gas source, hoseclamps, plastic cement for cracks and joints (don't
worry, it won't melt), 5 inch speaker, piece of foam or rubber for the interface
between speaker basket and pipe.

Here's how I put it together:

Put some glue on the corrigated end of the pipe, stick on the reducer, let
it set upright. Drill a hole in the end cap big enough to put your threaded
end of the elbow. Maybe use two washers before you screw it on. I cemented
here too. Mount speaker at the big-diameter end of reducer with foam or
rubber "washer" between them. I mounted it with bailing wire--be creative.
Put the end cap on the non-corrugated end of the pipe (they are the same
diameter at room temp, so I stuck the pipe in ice water and the cap in boiling
water to get them together). Don't glue here, as you might want to make
a double-length pipe later. Finally, draw a straight line down the length
of the pipe on the opposite side of the seam. I drilled one hole every cm,
and my hole was as big as the ball in a ball-point pen. Also, I didn't drill
one too close to the glue seam-- maybe 3 cm away. Finally, I put a bead
of cement wherever I saw cracks and joints.

Improvement suggestion:

It was suggested to me that I might make an airtight enclosure for the speaker
so that no gas leaks through the surrounds. 'Sounds like a good idea because
gas definitely leaks out there (I've lit it) and there is noticibly less
flame-height at the speaker-end because of this leak. My thought is to use
a cylindrical piece of tupperware, cut the bottom out, mount one end to the
back of the speaker, and put a rubber diaphragm over the other end. This
would also allow you to slap the rubber to do a 'pre-demo' buildup if you

In any case, get the tube working first.

I've had no problems with explosions or fire but proceed at your own risk.

Also, propane works well too if you need it portable.

Good luck! Have fun!

Erik Herman
University of Arizona
Teacher Prep Program

>-- Original Message --
>Date: Tue, 05 Nov 2002 13:23:31 -0500
>From: "Kent Fisher"
>To: ,
>Subject: Flame tube
>I'm interested in building a flame tube -- basically a large "gas grill"
>with a speaker in one end that shows standing waves by the corresponding
>heights of the flames. I have a student who has the know-how to build
>one, but we'd appreciate any information & advice -- or, best of all,
>some plans! In particular, we're wondering whether anyone knows anything
>about choosing the hole spacing and diameter.
>As a related demonstration, my student was suggesting that, instead of
>putting gas in the tube and burning it, we might put two immisicble
>liquids with different densities in a clear plastic tube and see whether
>the periodic density gradient produced by standing waves would result in
>a visible pattern. Does anyone know if this has been tried before?
>Kent Fisher
>Columbus State Community College
>Biological & Physical Sciences
>482 Nestor Hall
>(614) 287-2515