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Optimum dimensions of a Rubens Tube? Answered

There are several Instructables posted for Rubens Tubes, and I have seen a few elsewhere.

I'd like to make one myself, for demonstration purposes, but I'm wondering if there is an optimum set of dimensions?

I have seen diameters from about 2-10cm, and lengths from about 80cm to 2m.

And what diameter holes should I drill?

If it makes a difference, I'll be fuelling it with mains natural gas (methane) in a school lab.

(And, while I'm here, what would be a good rescued speaker to drive it?  An old PC speaker?)


What about push-pull speakers ? One at each end, in anti-phase.

The gas type affects the hole size, you have to make sure the burn velocity is comparable to the jet speed.


(Sorry Steve, hit Best instead of reply - that's the second time this week!)

I'm after minimum work and maintenance - it will probably end up spending 51 weeks of the year wedged in a cupboard.  So, I plan to use a single speaker at one end, and a solid cap at the other (although I am also considering a rubber diaphragm so that children can shout at it and affect the flames...)

I don't know the pressure of the gas supply, but it doesn't burn back down a half-inch pipe, and makes a flame over a foot long when lit directly at the pipe (instead of at the Bunsen).

So, looking at that, as long as you have a tube and holes, it will work...

(There are some other interesting demonstrations on that link)

You may have to play a bit with the gas pressure, but it looks like it.
Would be a neat thing for Halloween.....


Ha, I just had a mental image of a row of little pumpkin lanterns, all with flames coming out the top like candles.

Your school probably has a stereo set that will suffice, if you turn the volume up enough.
The rubber diaphragm (AKA deflated latex balloon) at one end is a great idea. Twelve years after the science lesson, I still remember being able to shout at those flames to make them dance!
That tube must've been about a meter and a half long, with centimeter-diameter holes. The smaller the holes, I'd imagine, the more sensitive they'll be to changing air pressure.