Picture of 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.

Karenleslie4 months ago
Also, use rubber not cardboard and a speaker roughly the same diameter of your tube.
Retired Chem Teacher
Karenleslie4 months ago
Also, use rubber not cardboard and a speaker roughly the same diameter of your tube.
Retired Chem Teacher
Karenleslie4 months ago
Try smaller diameter pipe from plumbing section and put smaller holes 1/2" or less apart.
Retired Chem Teacher
MatthewG1 year ago

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

j_john8 months ago

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 !


tmirick1 year ago

How to make the fitting for the tube on the pipe...

would be awesome to make a 2d version of this


DragonDon2 years ago
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.

Time and time again I keep seeing things that are relate to frequencies. This would seem to be one of them.

Cool stuff! And without 'dangerous experiments', our society would never have gotten off the ground. No one should stifle their curiosity! Have at it!

wonder if you could use this to tune the length of an exhaust?

Nhoj162 years ago
I was wondering how hot the pipe gets? Wouldn't the end fittings melt?
SAFan662 years ago
What is the diameter of the tube you used?
howtowithmanish (author)  SAFan662 years ago
Internal Diameter was 5 cm. External was probably 5.4 cm.
XyloCB3 years ago
Where did you get the stands from?
howtowithmanish (author)  XyloCB3 years ago
I got them welded from a factory.
razvanlost3 years ago
I have built a tube just like yours with a colleague, you can see it in action here: http://www.youtube.com/user/rubenstube101
howtowithmanish (author)  razvanlost3 years ago
Wow, that looks really good. If you liked my Instructable, then please rate it and follow me for more awesome stuff. :)
watchdog233 years ago
What size of holes are drilled along the top and does it matter what gas pressure you have?
howtowithmanish (author)  watchdog233 years ago
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
alkymist3 years ago
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.
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.
howtowithmanish (author)  alkymist3 years ago
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.
howtowithmanish (author) 3 years ago
bwelkin3 years ago
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.

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.

If you are using the balloon as the transfer media, does the gas pressure inflate the balloon?

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?

howtowithmanish (author)  bwelkin3 years ago
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.

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. :)

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. :)
msavage773 years ago
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
gratsoy3 years ago
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.
howtowithmanish (author)  gratsoy3 years ago
An Amplifier will help to increase the sound quality etc, also you can adjust bass and treble etc that way :)
mvenster3 years ago
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)
mopod3 years ago
Hi Mani, great job man! Keep up with your passion and make all Pakistanis proud. Good job on the combat robot too.
howtowithmanish (author)  mopod3 years ago
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!

howtowithmanish (author)  mopod3 years ago
You should follow me on the website :P
FreddE3 years ago
a video would of it going would be pretty sweet
howtowithmanish (author)  FreddE3 years ago
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 :)
ilpug3 years ago
great job. i really need to make one of these, seeing as i have ll the parts.
cloud_bam3 years ago
Dude... Pretty freakin cool. Slightly dangerous but what fun would an i'bble be without that?
ponyballs13 years ago
Gonna try this and I my this.