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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.

Step 1: What You Need


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
Amplifier Wire (PC to Amplifier)
Which type gas used here???
<p>This tube (along with most tubes) is using a propane cylinder.</p>
<p>What is the diameter of the metal tube?</p>
<p>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. </p>
How most Rubens tubes are shown being built on the internet are not safe and this is a perfect example. <br>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. <br>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. <br>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 <br>I am a professional Flame effect artist.<br>www.trailertrashman.com
<p>Hey look, somebody who knows what they're talking about!<br></p><p>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?<br><br>Everything you are doing with this that is made of &quot;plastic&quot; should be lined with PTFE (teflon). If you don't want to do that, you should use &quot;fuel lines&quot; from an automotive supply store (which will be petroleum compatible).</p>
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.
<p>What happens if we can't afford an amplifier? Will the ruben's tube still work without an amplifier?</p>
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. <br>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...
<p>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..</p><p>1. I see you used propane. Can we use LPG / Liquefied Petroleum Gas?</p><p>2. If we use LPG, will the rubber on the end burn up?</p><p>3. How thick is the latex rubber? can we use like, surgical gloves?</p><p>I really really hope you see this as soon as possible... Thank you so much... anyone who sees this may help me too..</p>
<p>Probably too late to answer you but LPG is propane. They are one in the same.</p><p>LPG is a liquid when compressed. When the pressure is reduced, as in when it comes out of the tank, it becomes a gas.</p>
<p>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.</p>
Also, use rubber not cardboard and a speaker roughly the same diameter of your tube. <br>Retired Chem Teacher
Try smaller diameter pipe from plumbing section and put smaller holes 1/2&quot; or less apart. <br>Retired Chem Teacher
<p>I plan on putting it on my desk, good idea? be desk has two &quot;layers&quot; (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.</p>
<p>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</p>
<p>guys what kind of metal tube.. going on selecting a random metal tube can cause HORROR !! first off it can metal downn ... 2nd temp it can handle all thesee matters i guess... i would prefer u guys can be more specific :D any great job and dont take me harshlyy.. sorry if i was.. and please tell what kind of tube !</p><p>WHICH METALL :)</p>
<p>How to make the fitting for the tube on the pipe...</p>
would be awesome to make a 2d version of this
While not proclaiming any experience directly related, this does ring a little intuition bell that it would seemingly be related to the 'ram air' affect use in tuning the air intake on cars to alter/maximize the pressure of the intake charge at the right time in the 4 stroke cycle. <br> <br>Time and time again I keep seeing things that are relate to frequencies. This would seem to be one of them. <br> <br>Cool stuff! And without 'dangerous experiments', our society would never have gotten off the ground. No one should stifle their curiosity! Have at it!
<p>wonder if you could use this to tune the length of an exhaust?</p>
I was wondering how hot the pipe gets? Wouldn't the end fittings melt?
What is the diameter of the tube you used?
Internal Diameter was 5 cm. External was probably 5.4 cm.
Where did you get the stands from?
I got them welded from a factory.
I have built a tube just like yours with a colleague, you can see it in action here: http://www.youtube.com/user/rubenstube101
Wow, that looks really good. If you liked my Instructable, then please rate it and follow me for more awesome stuff. :)
What size of holes are drilled along the top and does it matter what gas pressure you have?
Umm the smallest size you get is better. Ours was around 2mm each. The gas pressure doesn't matter really but greater gas pressure is better. Please Follow me. :P
I have a question about this step (covering the audio input end). When you are done does it look like the pic with the yellow balloon? I am unclear about the cardboard. <br><br>I can see that touching the speaker cone to a rubber membrane would transfer sound energy rather easily but if covered with cardboard it would be pretty stiff.<br><br>If you are using the balloon as the transfer media, does the gas pressure inflate the balloon?<br><br>And another question: what size drill bit did you use? Do you have any guess as to what the effect of larger or smaller holes may have?<br><br>Thanks.
1) Yeah i used two balloons, i cut hole in the cardboard of the same diameter as the tube and like fit it there. The cardboard only acts as a structure to hold the speaker in place. It isn't completely necessary, i didn't use it either. <br><br>2) Yes the gas pressure does inflate the balloon that's why I covered it with like 5 balloons and then reinforced it with tape. :)<br><br>3) Well, i am not certainly sure if the size of the drill bit makes a difference, but I do know that gas stoves have small holes so it is advisable to have small holes otherwise the gas might escape quicker. :)
propane is heavier than air...I was told that natural gas is preferred because anything that does not burn up will float away instead of collecting in the tube to explode. Hope you have access to N gas, for safety
It would probably work well with a set of old computer speakers too. Just take the one speaker that has the volume and power controlls, and disconect the other. Detach the speaker from the body, extend the wires and use that. Then the volume controll and such can be tucked away some where nicely. Cheaper than an amp.
An Amplifier will help to increase the sound quality etc, also you can adjust bass and treble etc that way :)
Nice experiment, never heard of it, but could be nice to experiment with resonances and finding out ideal baffles. (If you don't explode first)
Hi Mani, great job man! Keep up with your passion and make all Pakistanis proud. Good job on the combat robot too.
Thank you :) do you live in Pakistan too?
Nope, I used to. Did my Alevels before moving abroad to go to college. I feel immense pleasure and pride when I see people like you stepping up and just doing what you enjoy. Kudos and hats off to you! Keep up the great work. The rubens tube is a visually fascinating experiment, the most fun I've had while studying wave theory I'll tell you that! :) Looking forward to seeing more instructables from you in the future!<br><br>
You should follow me on the website :P<br>
a video would of it going would be pretty sweet<br>
I made a video using a 14.1 mega-pixel camera but the quality wasn't that amazing, so i bought a cam corder and will start working with that. Thank you :)
great job. i really need to make one of these, seeing as i have ll the parts.
Dude... Pretty freakin cool. Slightly dangerous but what fun would an i'bble be without that?

About This Instructable




Bio: I am an A-Levels Student at Karachi Grammar School, Pakistan. My passion is physics and mechanics and I want to be a Mechanical Engineer in ... More »
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