Making a Ruben's tube that runs from deodorant for free

A Ruben's tube is a closed tube with many holes drilled into it. It has a diaphragm at the end of the tube, so that sound waves from an external source can easily enter the tube. 

It can be used to demonstrate the effects of soundwaves visually, such as standing waves or pressure differences in speakers through music. All music and sound is made up of waves. These waves make particles oscillate back and forth quickly, which vibrate your eardrum and allows your brain to sense sound.

The speaker in this case would be the red piston. Anything that oscillates (moves back and forth) is capable of producing a sound wave. The darker areas that move to the right are called compressions, where particles are pushed closer together. The lighter parts in between are rarefactions, where there is a lack of particles, as they have migrated to the compressions. The pressure of the wave changes as it passes a point - the red dots experience high pressure at the compressions, and then low pressure at the rarefactions. If the pressure was modelled as a wave, it would like look this:

The pressure that passes a point will fluctuate due to the speaker disturbing the air.

If these waves are sent down a tube, they will bounce of the end and form what's known as a standing wave.

Of course, the waves do not just pass each other like shown above- they add up and interact with each other. We can draw another wave that shows the sum of the 2 waves moving in opposite directions, and we get a still wave that oscillates but doesn't move.

At compressions, the flammable gas in the tube is forced out more, so larger 'spouts' of fire come out of these holes. At rarefactions, gas is almost sucked back into the tube, so there are very small spouts, or no fire at all, emerging from these holes.

A more detailed diagram of this Rubens tube is shown below:

This is simply a diagram showing how the gas is injected and where the materials are from. The sound chamber is added so that the Ruben's tube can work with larger speakers, so that the difference is amplified and larger peaks and smaller troughs are made.

First, a metal pipe was drilled through. It is essential all the holes are the same size so that when no sound is playing, the flames from all the holes are equal. To ensure this. the holes were drilled roughly, and a layer of aluminum tape was placed over them. This was then precisely poked with a needle above the existing holes, so that they were all uniform.

Next, a piece of PVC tubing was cut to size and drilled to allow a screw to hold it in place. The end was heated until malleable, and then a valve was screwed in to create strong threads when the PVC cooled again.

The hole from this PVC was then 'copied' over to the main flame tube, with an identical hole where the two fit snugly together, forming a seal.

The screw holds these two parts together and stops the pvc from slipping out over continued use, which would lead to a dangerous gas leak. Layers of Teflon plumber's tape was used to ensure a seal, so that all holes would receive equal pressure gas.

 

The check valve that was used to create the threads in the PVC can then be screwed in. More Teflon tape is used as the threads may wear over time, allowing the gas in the tube to escape through the threads. Having Teflon tape prevents this from happening.

Once one side of the check valve is screwed in, the other threaded side can be used to connect the whole assembly to a gas source.

The attachment to connect any deodorant bottle to a pipe was pulled off from a disassembled butane blowtorch. You can find a similar one here, which requires this piece to operate. It is connected to a gas hose that leads into a copper pipe with a 15mm bolt on it that screws into the valve. If you do not have a broken blowtorch laying around, this part is essential to provide a safe connection to the can of deodorant.

The end of the gas hose is then screwed into the valve to make an airtight and gas tight fit, allowing the flow of fuel to easily be regulated with the red valve.

The diaphragm can be made with a tin can with a hole in the back, some clingfilm stretched tightly over the opening, and a rubber band to maintain tension in the film.

The film means this assembly can hold gas airtight, but easily allows sound from exterior sources to enter and cause waves in the tube.

The back of the tin is superglued and then hot glued to the broom handle, that fits tightly over the end of the metal tube. This method of double gluing ensures no leaks, as the superglue holds a tight bond and the hot glue fills any remaining holes.

Some planks of wood can then be cut to size, with notches being made by drilling large holes in a sections of wood, and then cutting them down the middle to create semi circular channels to hold the Ruben's tube securely.

Using green cable ties, the Ruben's tube can be attached to the frame. This allows for it to be held in front of a speaker so that it can be tested. The Ruben's tube is complete