A Rubens Tube

The Rubens Tube is a fascinating physics demonstration tool.  It was first developed by Heinrich Rubens back in 1904.  But, I’m not going to insult your intelligence and repeat what wikipedia has to say.  You can check that out yourself.

I love the device because it is such a crowd-pleaser.  I like to set up my tube at a party or Mindshare event and watch people’s reaction to it.  It couples music and fire, two very primitive and ingrained human infatuations.  It’s hard to resist, really.  People will naturally stare at the fire, but only after a few beats do they realize that it’s dancing to the music.  Suddenly they’re asking questions and wish to know more.  If you ever see me around my tube at a party, you’ll notice I spend a lot of time describing how it works to those around me.  I don’t intend to lecture, but they keep asking the questions.  I certainly don’t mind.

The physics of a Rubens tube is quite simple really.  When tones are played through the speaker on the end, the gas resonates in the tube, much like it would in a musical instrument.   A standing wave of pressure gets set up inside the tube.  The sections of the tube with higher pressure will have higher flames.  The opposite is true for the areas with lower pressure.  This creates a sine-wave of fire along the length of the tube.  The tube can resonate with multiple frequencies at the same time, but they’re all harmonics of the base resonant frequency of the tube.  It is not acting as a graphic equalizer, with low frequencies on one end and high on the other.  Many people make that mistake, though.

At the moment I’ve got a few Rubens tubes that I like to bring to parties.  I’m currently building a new one for a much larger permanent installation in my backyard.  I’ve also got plans for a few more interesting tubes in the works.  Eventually…

I’ve got a short series of How-To Posts so people can build their own Rubens Tube at home.  Be very respectful of fire, and use your common sense.  These things are about as dangerous as a barbeque grill, but they’re not very safe either.

Here are a couple of youtube videos I made a few years back of my most reliable 8′ 8″ aluminum Rubens tube. Enjoy!