How to make a Ruben's Tube
11 Steps
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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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SAFan66 says: Apr 18, 2013. 7:12 AM
What is the diameter of the tube you used?
howtowithmanish (author) says: Apr 18, 2013. 7:23 AM
Internal Diameter was 5 cm. External was probably 5.4 cm.
amandaghassaei says: Nov 11, 2012. 6:37 PM
would be awesome to make a 2d version of this
XyloCB says: Apr 9, 2012. 7:24 AM
Where did you get the stands from?
howtowithmanish (author) says: Apr 9, 2012. 10:02 PM
I got them welded from a factory.
razvanlost says: Apr 4, 2012. 1:09 PM
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) says: Apr 4, 2012. 9:48 PM
Wow, that looks really good. If you liked my Instructable, then please rate it and follow me for more awesome stuff. :)
watchdog23 says: Mar 5, 2012. 11:24 AM
What size of holes are drilled along the top and does it matter what gas pressure you have?
howtowithmanish (author) says: Mar 6, 2012. 1:00 AM
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
Jan 30, 2012. 2:54 AM
Thank you, but I am 16 and unaware of a lot of school grants for women 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.
alkymist says: Sep 15, 2011. 11:46 AM
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
TallTrav says: Sep 26, 2011. 1:35 PM
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) says: Sep 15, 2011. 11:59 AM
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) says: Sep 23, 2011. 11:59 AM
http://www.instructables.com/id/How-to-Make-Sound-Come-Alive-Cymatics/
bwelkin says: Sep 16, 2011. 6:36 AM
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?

Thanks.
howtowithmanish (author) says: Sep 16, 2011. 10:47 AM
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. :)
msavage77 says: Sep 16, 2011. 10:35 AM
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
gratsoy says: Sep 15, 2011. 4:59 PM
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) says: Sep 16, 2011. 1:22 AM
An Amplifier will help to increase the sound quality etc, also you can adjust bass and treble etc that way :)
mvenster says: Sep 15, 2011. 11:56 AM
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)
mopod says: Sep 15, 2011. 7:59 AM
Hi Mani, great job man! Keep up with your passion and make all Pakistanis proud. Good job on the combat robot too.
howtowithmanish (author) says: Sep 15, 2011. 8:42 AM
Thank you :) do you live in Pakistan too?
mopod says: Sep 15, 2011. 9:46 AM
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) says: Sep 15, 2011. 9:49 AM
You should follow me on the website :P
ilpug says: Sep 11, 2011. 9:29 AM
great job. i really need to make one of these, seeing as i have ll the parts.
JarredsInstructions says: Sep 13, 2011. 5:29 AM
My jealousy is immanent.
howtowithmanish (author) says: Sep 13, 2011. 6:53 AM
Haha and why is that?
JarredsInstructions says: Sep 13, 2011. 3:08 PM
Because I wish I could have all these tools, I mostly just have a Dremel and a soldering iron.
Kinnishian says: Sep 15, 2011. 7:39 AM
I dont see any more tools than a dremel and soldering iron and knife needed in this instruct able. I think the only challenge will be attaching the pipe to the gas. This is awesome though, I'm hoping to eventually get the materials.
FreddE says: Sep 15, 2011. 6:33 AM
a video would of it going would be pretty sweet
howtowithmanish (author) says: Sep 15, 2011. 7:34 AM
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 :)
cloud_bam says: Sep 10, 2011. 7:45 PM
Dude... Pretty freakin cool. Slightly dangerous but what fun would an i'bble be without that?
ponyballs1 says: Sep 10, 2011. 1:25 PM
Gonna try this and I my this.