# Optimum dimensions of a Rubens Tube?

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?)

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7 years ago
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.

Steve
Kiteman (author)  steveastrouk7 years ago

(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).

7 years ago
This is an interesting link, off the wikipedia entry.

http://www.fysikbasen.dk/English.php?page=Vis&id=6

Steve
Kiteman (author)  steveastrouk7 years ago
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)
7 years ago
You may have to play a bit with the gas pressure, but it looks like it.
Would be a neat thing for Halloween.....

Steve
Kiteman (author)  steveastrouk7 years ago
Ha, I just had a mental image of a row of little pumpkin lanterns, all with flames coming out the top like candles.

7 years ago
What ? You too ?
V-Man7377 years ago
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.
Kiteman (author)  V-Man7377 years ago
Thanks.