# How to Make a Ruben's Tube

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## Introduction: How to Make a Ruben's Tube

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Made By Manish Kumar, Murtaza Tunio and Minaam Abbas

The Ruben's Tube is a physics experiment demonstrating a standing wave. It demonstrates the link between sound pressure and sound waves.

A length of pipe is perforated along the top and sealed at both ends - one seal is attached to a small speaker or frequency generator, the other to a supply of a flammable gas (propane tank). The pipe is filled with the gas, and the gas leaking from the perforations is lit. If a suitable constant frequency is used, a standing wave can form within the tube. When the speaker is turned on, the standing wave will create points with oscillating (higher and lower) pressure and points with constant pressure (pressure nodes) along the tube. Where there is oscillating pressure due to the sound waves, less gas will escape from the perforations in the tube, and the flames will be lower at those points. At the pressure nodes, the flames are higher. At the end of the tube gas molecule velocity is zero and oscillating pressure is maximal, thus low flames are observed. It is possible to determine the wavelength from the flame minima and maxima by simply measuring with a ruler.

Since the time averaged pressure is equal at all points of the tube, it is not straightforward to explain the different flame heights. The flame height is proportional to the gas flow as shown in the figure. Based on Bernoulli's principle, the gas flow is proportional to the square root of the pressure difference between the inside and outside of the tube. This is shown in the figure for a tube without standing sound wave. Based on this argument, the flame height depends non-linearly on the local, time-dependent pressure. The time average of the flow is reduced at the points with oscillating pressure and thus flames are lower.

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## Step 1: What You Need

Materials:

Drilling Machine
A Long Metal Tube
Gas Pipe
Gas Cylinder
Speaker Wire
Guitar Amplifier
Crocodile Clips
Stands for the Ruben's Tube
Wire Strippers
Screw Drivers
Scissors
Amplifier Wire (PC to Amplifier)
Lighter

## Step 2: Dismantling the Amplifier

Disconnect the wire connected to the speaker. Next Unscrew the back lid and the speaker itself from the amplifier.

## Step 3: Drilling Holes Into the Tube

Purchase a hollow metal tube from a scrap yard. Use the drill machine to drill holes in the tube approximately 1 inch apart.  From one side attach a gas pipe and cover the other side by using a balloon or cardboard. My metal tube was approximately 5 ft long and consisted of 50 holes. This way the tube will act as a closed system except for the holes on the top.

## Step 4: Creating Crocodile Clip Wires

Cut approximately a foot of speaker wire and strip the insulation off from each end. Solder the crocodile clip to the speaker wire. Make two of these wires. Strip off some insulation from the wire attached to amplifier. Use the crocodile clip wire to now attach the wire to the speaker itself.

## Step 5: Closing the Tube

Cut a hole of the same diameter as the tube in cardboard using the paper cutter and stick it to the end with the balloon on it using super glue.

## Step 6: Stands

Place the tube on the stands. I got them made separately from a factory.

## Step 7: NCH Tone Generator

Download a tone generator of the internet. I downloaded NCH Tone Generator. It was a 14 day free trial but it was worth it. :)

## Step 8: Attaching the Gas Cylinder

Attach the Gas Cylinder to the Gas Pipe. Make sure it is fastened tightly.

## Step 9: Attaching the Speaker

Super Glue the speaker to the cardboard piece attached to the Ruben's Tube. I Didn't do this step, instead I simply held the speaker near the cardboard during the experiment. It works perfectly fine both ways.

## Step 10: Last Minute Adjustments

Plug in the amplifier wire into the PC and the amplifier. You can see the settings I used for the experiment.

Drive Gain : 10
Drive Volume: 10
Clean Volume: 10
Treble: 0.5
Middle: 1
Bass 1:

PS: The higher the frequency, the greater the amplitude needed.

## Step 11:

Switch on the gas supply, plug in the amplifier in a power supply, light the gas and enjoy :) I used a 480 Hz frequency to generate a sine wave as seen in the pictures. Enjoy watching the Ruben's Tube with music too. :) Fire dancing to music can be an amazing scene.

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## 53 Discussions

Which type gas used here???

This tube (along with most tubes) is using a propane cylinder.

What is the diameter of the metal tube?

I am 15 and I am doing this as a school project and placing the tube under some type of metal and seeing if this contraption will make bread. If I am doing this what type of metal is preferable that will be safe for what I am doing and also bake the bread.

How most Rubens tubes are shown being built on the internet are not safe and this is a perfect example.
1) one end should be welded shut. do you want the card board to burn and shoot gas from the end when the card board fails.
2) You do not use hose clamps on flame effects feeding gas. use propane lines with NPT threads and threaded fittings on the tube or swaglok fittings.
3) The end that the speaker is placed should not use latex gloves or anything else with a low melting point. It needs to be a high temp rubber. Not doing these things can result in a catastrophic failure of large amounts of gas coming out of the end and even having a flaming propane hose whipping around in the air. Taking my steps would also help make it NFPA 160 compliant for safety to be used in front of an audience. NFPA 160 is the code that covers fire in front of an audience that governments around the world use to regulate fire in front of an audience. Don't put your self and other innocent bystanders at risk
I am a professional Flame effect artist.
www.trailertrashman.com

Hey look, somebody who knows what they're talking about!

Another problem I see with this is that no mind is being given to the materials that are being used for hoses/etc. Are they going to dissolve with them come into contact with a petroleum product?

Everything you are doing with this that is made of "plastic" should be lined with PTFE (teflon). If you don't want to do that, you should use "fuel lines" from an automotive supply store (which will be petroleum compatible).

You made my point exactly. I used to work at a business that makes hydrogen fuel cell and the NPT/Swagelok fittings came to mind. Thanks for making it safer.

Thank you, but I am 16 and unaware of a lot of stuff you mentioned above. But, I know that if it is welded shut you NEVER get good results. However I had the gas pipe end welded. And I always have a fire extinguisher nearby and I performed this experiment under adult-supervision.

What happens if we can't afford an amplifier? Will the ruben's tube still work without an amplifier?

yes,it will all u need is a boofer...it is an important part of the ruben's tube, a amplifier or a boofer should be there. thank you hope it will help you..

Also, use rubber not cardboard and a speaker roughly the same diameter of your tube.
Retired Chem Teacher

can you be more specific about which rubber to use?? surgical gloves or balloon will do? what should I use?? balloon or surgical gloves??

hello, I have completed this project.. But still I hav'nt attached a music system, for the orther end I have used a cardboard and a tape to cover it..will the speaker work with cardboard packing...

hi... please please please answer my questions.. I'm 16 and we're making this for our project.. I just wanted to ask these questions to clarify because I'm afraid it will blow up..

1. I see you used propane. Can we use LPG / Liquefied Petroleum Gas?

2. If we use LPG, will the rubber on the end burn up?

3. How thick is the latex rubber? can we use like, surgical gloves?

I really really hope you see this as soon as possible... Thank you so much... anyone who sees this may help me too..

Probably too late to answer you but LPG is propane. They are one in the same.

LPG is a liquid when compressed. When the pressure is reduced, as in when it comes out of the tank, it becomes a gas.

The gas needs to be gas! Seriously though, your fuel needs to be gaseous. If you don't want to use propane, you could try natural gas (for example, form a lab gas outlet) or possibly butane. The logic behind this is that the speaker creates areas of high and low pressure in the gas, which I don't think would happen with liquid.

Also, use rubber not cardboard and a speaker roughly the same diameter of your tube.
Retired Chem Teacher

Try smaller diameter pipe from plumbing section and put smaller holes 1/2" or less apart.
Retired Chem Teacher

I plan on putting it on my desk, good idea? be desk has two "layers" (I guess) a lower layer where all the computer's and stuff go and the upper level where there is.. Nothing, at all... good idea? I think it would be cool.

As long as it isn't too close to the ceiling or any objects you should be fine, but remember the paint on the wall may be flammable, and even if not you will have huge soot marks. I wouldn't risk it, but yeah