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A Ruben's tube is essentially a demonstration of standing waves in air.
Numerous very small holes are drilled at lengths through the top of the tube and propane or a similar gas is fed through it. By forcing sound waves into the tube through a speaker at one end, varying areas of pressure are created. The higher flames occur at points of higher pressure (nodes) and smaller flames at lower pressure (antinodes).
I'll even show you how to control the sound with a Nintendo Wiimote so you can play god and control fire with gestures.
This is an easy physics experiment that might take a little time to assemble the parts, but the construction of which is straightforward with a fantastic reward!
REMEMBER!! Anytime you are dealing with fire, take the necessary safety precautions such as :
--Clearing the area of all flammable substances
--Using care when adjusting the propane valve
--Use ONLY in a well ventilated area
--If underage, operate ONLY under the supervision of a responsible adult
To help you remember, here's a safety haiku:
Danger! Hot Fire!
Keep Space Clear of Kids and Pets
Poor Burning Puppies
Numerous very small holes are drilled at lengths through the top of the tube and propane or a similar gas is fed through it. By forcing sound waves into the tube through a speaker at one end, varying areas of pressure are created. The higher flames occur at points of higher pressure (nodes) and smaller flames at lower pressure (antinodes).
I'll even show you how to control the sound with a Nintendo Wiimote so you can play god and control fire with gestures.
This is an easy physics experiment that might take a little time to assemble the parts, but the construction of which is straightforward with a fantastic reward!
REMEMBER!! Anytime you are dealing with fire, take the necessary safety precautions such as :
--Clearing the area of all flammable substances
--Using care when adjusting the propane valve
--Use ONLY in a well ventilated area
--If underage, operate ONLY under the supervision of a responsible adult
To help you remember, here's a safety haiku:
Danger! Hot Fire!
Keep Space Clear of Kids and Pets
Poor Burning Puppies
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Signing UpStep 1What the heck is this?
A bit of history from Wikipedia:
"August Kundt, in 1866, demonstrated an acoustical standing wave by placing seeds of lycopodium or cork dust in a tube. When a sound was made in the tube, the material inside lined up in nodes and antinodes in line with the oscillation of the wave, creating a standing wave. Later that century, Behn showed that small flames could be used as sensitive indicators of pressure. Finally, in 1905, using these two important discoveries, Heinrich Rubens, whom this experiment is named after, took a 4-metre-long tube and drilled 200 small holes into it at 2 centimeter intervals, and filled it with a flammable gas. After lighting the gas (whose flames all rose to near-equal heights), he noted that a sound produced at one end of the tube would create a standing wave, equivalent to the wavelength of the sound being made."
In many basic physics classes the Ruben's tube is used as a proof of the equation frequency = speed of sound/wavelength. Students can measure the wavelength of the standing wave (very carefully as not to burn themselves from flame maxima to maxima). Then, because the speed of sound at sea level in propane is 235 m/s, the students can attempt to guess the frequency being played into the Ruben's tube. The speed of sound in air is normally 344m/s, but because propane is almost twice as dense as air, the speed is lower in propane. (Well, not quite because it's twice as dense, but we'll leave it at that oversimplification for now.)
As the sine waves are played through the propane, they compress the propane in certain sections thereby increasing its density. This in turn increases the pressure, and because the area is at a high pressure (and air likes to flow from high to low pressure... thank you Le Chatelier) more air molecules are forced out these holes in an effort to reach equilibrium causing the flames rise higher. In areas where the propane is not as compressed, the area specific pressure is lower resulting in lower flame heights. Essentially when you are visualizing the wave with fire you are seeing a standing wave. These areas of high pressure are known as pressure nodes, and contain the highest flames (most of the time but we'll get to that in a minute) whereas the areas of relatively lower pressure are thus antinodes and yield smaller flames.
Since we know that frequency (f) equals speed (v) divided by wavelength (lamba) we are able to quantitatively determine the frequencies running through the Rubens tube. (f=v/lambda) Now, when doing this, remember that "v" is not the velocity of sound in air, (roughly 344 m/s) but rather the velocity of sound in your gas ( in this case propane, so 235 m/s). Also keep in mind that elevation and temperature affect this, but 235 is a good estimate. So, measure your wavelength from peak to peak (flame maxima) or trough to trough (flame minima), plug into the equation, and you get your frequency.
Reader Challenge: Now, you might notice an interesting effect once the gas is turned off. Yes, the flames persist if the sound is still on, no big deal. But take careful notice where the flame maixmas and minimas are. If you'll notice where the flame used to be at a high with the gas on, it is now at a low. The tubes nodes/antinodes have now switched places! Explain how this happened and you get an extra cookie!
After much digging at the college library, I was able to unearth the original journal publication by von Heinrich Rubens:
It was published on December, 8th 1904 in the Verhandlungen der Deutschen Physikalischen Gesellschaft- a German physics journal. Although I don't speak German, in my research, I was able to find out a few things. The original tube used was brass. It was four meters long, 8 centimeters wide, and had about 100 holes which were each about 2 mm wide. He used Coal Gas which was inserted on one end through a brass cap, and then covered the other end with a rubber diaphragm. Interestingly his sources of sound were bells, an organ pipe, or tuning forks.
After all this work experimenting with different tube designs blindly, and without knowing much about the tube's origins, I admittedly had a rather geeky adrenaline rush holding the actual journal in my hands and learning the origins of this project. I included 4 pictures of page scans from the journal if anyone speaks German or is further interested!
"August Kundt, in 1866, demonstrated an acoustical standing wave by placing seeds of lycopodium or cork dust in a tube. When a sound was made in the tube, the material inside lined up in nodes and antinodes in line with the oscillation of the wave, creating a standing wave. Later that century, Behn showed that small flames could be used as sensitive indicators of pressure. Finally, in 1905, using these two important discoveries, Heinrich Rubens, whom this experiment is named after, took a 4-metre-long tube and drilled 200 small holes into it at 2 centimeter intervals, and filled it with a flammable gas. After lighting the gas (whose flames all rose to near-equal heights), he noted that a sound produced at one end of the tube would create a standing wave, equivalent to the wavelength of the sound being made."
In many basic physics classes the Ruben's tube is used as a proof of the equation frequency = speed of sound/wavelength. Students can measure the wavelength of the standing wave (very carefully as not to burn themselves from flame maxima to maxima). Then, because the speed of sound at sea level in propane is 235 m/s, the students can attempt to guess the frequency being played into the Ruben's tube. The speed of sound in air is normally 344m/s, but because propane is almost twice as dense as air, the speed is lower in propane. (Well, not quite because it's twice as dense, but we'll leave it at that oversimplification for now.)
As the sine waves are played through the propane, they compress the propane in certain sections thereby increasing its density. This in turn increases the pressure, and because the area is at a high pressure (and air likes to flow from high to low pressure... thank you Le Chatelier) more air molecules are forced out these holes in an effort to reach equilibrium causing the flames rise higher. In areas where the propane is not as compressed, the area specific pressure is lower resulting in lower flame heights. Essentially when you are visualizing the wave with fire you are seeing a standing wave. These areas of high pressure are known as pressure nodes, and contain the highest flames (most of the time but we'll get to that in a minute) whereas the areas of relatively lower pressure are thus antinodes and yield smaller flames.
Since we know that frequency (f) equals speed (v) divided by wavelength (lamba) we are able to quantitatively determine the frequencies running through the Rubens tube. (f=v/lambda) Now, when doing this, remember that "v" is not the velocity of sound in air, (roughly 344 m/s) but rather the velocity of sound in your gas ( in this case propane, so 235 m/s). Also keep in mind that elevation and temperature affect this, but 235 is a good estimate. So, measure your wavelength from peak to peak (flame maxima) or trough to trough (flame minima), plug into the equation, and you get your frequency.
Reader Challenge: Now, you might notice an interesting effect once the gas is turned off. Yes, the flames persist if the sound is still on, no big deal. But take careful notice where the flame maixmas and minimas are. If you'll notice where the flame used to be at a high with the gas on, it is now at a low. The tubes nodes/antinodes have now switched places! Explain how this happened and you get an extra cookie!
After much digging at the college library, I was able to unearth the original journal publication by von Heinrich Rubens:
It was published on December, 8th 1904 in the Verhandlungen der Deutschen Physikalischen Gesellschaft- a German physics journal. Although I don't speak German, in my research, I was able to find out a few things. The original tube used was brass. It was four meters long, 8 centimeters wide, and had about 100 holes which were each about 2 mm wide. He used Coal Gas which was inserted on one end through a brass cap, and then covered the other end with a rubber diaphragm. Interestingly his sources of sound were bells, an organ pipe, or tuning forks.
After all this work experimenting with different tube designs blindly, and without knowing much about the tube's origins, I admittedly had a rather geeky adrenaline rush holding the actual journal in my hands and learning the origins of this project. I included 4 pictures of page scans from the journal if anyone speaks German or is further interested!
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Its 9 feet hight with 150 hold 2mm wide drilled ever 1.5mm in staleness steel.
For more videos and to see other revisions, http://www.tog.ie/
5 stars, my man.
the chart above from another instructable that was posted shows length versus frequency.... sorry just off from 10hr work day an not thinking right mind, but yeah what you said was what i was asking.