Cameron Silber

Physics Final Project:

The Ruben's Tube

The Ruben's Tube is a demonstration of standing waves through flames. A tube has holes cut into the top in a line. one end of the tub is sealed solid while the other has a rubber material that vibrates when a speaker is near it, creating pressure differentials inside the pipe, and moving the gas that is pumped into the tube to create flames. This creates a wave patter in the flames on top of the tube.

Materials to Construct Ruben's Tube

The Materials for this project are easily found at a local hardware store. the materials are:

  • Metal duct pipe – 3 in. x 5 ft
  • Plastic or metal end cap – 3 inches inner diameter
  • Two brass barb MIP adapters – 3/8 in. x ¼ in
  • One plastic barb tee – 3/8 in. x 3/8 in. x 3/8 in
  • Two rubber o‐rings – #10, ½ inch inner diameter
  • Two washers – ½ in. inner diameter
  • One latex hose - 10 ft. x 3/8 in. outer diameter x ¼ in. inner diameter
  • One ½ in. drill bit, capable of drilling metal 
  • One 1/8 in. drill bit, capable of drilling metal
  • One latex balloon
  • Speakers
  • Electric Drill
  • Duct tape
  • Masking tape
  • Scissors
  • Pliers
  • Permanent marker
  • Metal file


These are the instruction on how to construct the Ruben's Tube:

  1. Assemble the metal duct pipe and place a piece of duct tape down the  seam of the pipe. Cut the duct tape so that it reaches right up to the edge  of the pipe but does not wrap around it. Be sure that the duct tape is  smooth and that there are no wrinkles. The side of the tube with the duct tape will be referred to as the “bottom” of the tube, while the side  of the tube opposite the duct tape will be the “top” of the tube.
  2. A line of 1/8 inch diameter holes will be drilled along the top of the tube and will be ¾ inches apart. To  make sure that the holes are drilled in a straight line, place a piece of masking tape down the length of  the pipe with one edge of the tape along the center of the top of the pipe.
  3. Starting about 8 inches from one end of the tube, make marks every  ¾ of an inch until you get to about 8 inches from the other side of the  tube. Use the edge of the masking tape so that all of the marks are in  a straight line. There will be a total of about 59‐60 marks. Remove How to Build a Ruben’s Tube the masking tape when all of the marks have been placed.
  4. Use a 1/8 inch drill bit to drill a hole where each mark was made. Be  sure that the drill bit is precisely lined up on the mark before the hole is  drilled. Since the metal is very thin, some of the holes might have jagged  edges. A metal file or pliers may be used to clear up the holes. It is important that all of the holes are clear and round so that the flame  heights will be uniform.
  5. Two ½ inch holes will be drilled in the side of the tube for gas hoses to be  connected. Place two marks on one side of the tube, each about 18 inches from  the end of the tube. Use a ½ in. drill bit to drill a hole where each mark is  located. The two holes might have jagged edges. It is very important that the edges of these holes are as smooth and round as possible in order to ensure  that there will not be a leak.
  6. Locate the two brass barb adapters, two washers, and two o‐rings. Place a washer over  the threaded end of each adapter, and then place an o‐ring over the threaded end of  each adapter. This will be connected to the side of the pipe and is where the gas hoses will attach.
  7. Screw the threaded end of each barb adapter into the ½ inch holes. Pliers might  need to be used to tighten the barb and o‐ring down to the pipe. It is very important  that there be a tight seal between the o‐ring and metal pipe to ensure that there are no leaks. If the adapter will not thread properly, it might be that the hole needs to be  rounded out with a file or pliers.
  8. At this point all of the holes are drilled  and the hose adapters have been  installed in the side of the tube. Now one  end of the tube will be sealed with a cap  while the other will be sealed with a  flexible diaphragm.
  9. Place the cap over the crimped  end of the tube. Be sure that it  is pushed down as far as  possible on the end of the tube.  Seal the end by wrapping a  piece of duct tape around the  cap and pipe. Be sure that the  tape is smooth and has no wrinkles
  10. Locate a latex rubber balloon and use scissors to cut off  the end of the balloon. Stretch the balloon over the open  end of the tube to form the diaphragm. Be careful to  stretch the balloon tightly but not so tight that it will tear  against the edge of the tube. Use a piece of duct tape to secure the balloon to the tube.
  11. Locate the latex hose and use scissors to cut two 14 inch hose pieces. Connect  each of the 14 inch hose pieces to the barb adapters that have been installed into  the side of the tube. Ensure that the hose is connected as far up on the adapter as possible so that it has a good seal. Be sure that there are no kinks in the hose.
  12. . Locate the plastic barb tee. The two hoses that lead to the tube should be  connected to the top of the tee, while one end of the remainder of the  hose is connected to the bottom of the tee. This long length of hose will  be connected to the gas source.
  13. Construction of the Ruben’s Tube is completed. If necessary a wooden or metal stand may be built to  hold the tube. Otherwise, books can be used just as easily. The hose can be connected to a gas source  such as a propane tank or a natural has outlet in a science classroom lab table. The computer speaker can be placed in front of the diaphragm and connected to a computer. Turn on the gas and use a lighter  to light flames coming out of the holes at the top. Play single tones of different frequencies through the  speakers to produce standing waves or play music to make the flames dance with the beat. Refer to the “Ruben’s Tube Operating Instructions” for more information

Versions and Attempts

Version 1.0, Attempt 1


Building of version 1.0 proved difficult. As the first attempt at creating the Ruben's Tube, I had to work out the design and learn the construction steps for the first time. To start, the metal duct pipe was substituted for a black ABS plastic material, as PVC pipes and metal duct pipes to the length i was looking for were unavailable. I found that i had used the incorrect drill bit to make a hole for the gas and had to seal the pipe with duct tape. I later also discovered the propane gas line i had used had bad ends for my purposes. The mae threaded end that i screwed into the pipe-cap was meant to go into the regulator, and there was nothing now to connect it. Future reference , buy a male to male adapter to create solid connection.

Now that my propane line was ineffective, i had to tape the end closed, and proceeded to drill a hole for my barb MIP adapter. I only attached one to the end of the pipe, and used a full length of 20 ft. of latex hose to connect to the propane tank. I jury rigged the tank to the line with the second barb MIP connecor a washer, and a rubber o-ring gasket. After initiating a flow of propane to the Ruben Tube, i had waited for flames to ignite from the lighter. My friend assited with gas flow at the end of the 20 ft line for safety.

After a few minuets of nothing happening, i worried there was a leak somewhere in the system. After switching spots with my partner, i increased the gas flow to full open on the tank, and after a few more seconds the pipe hole finally lit. After some math i discovered that the system was way to large to be fed by a single line, 20 ft in distance from tank to system. a total area of 141.4 cubic feet of space was being filed by a single 20 ft long by 1/4 in. diameter gas line. This proved ineffective.

after the system finally built enough pressure to sustain flames of decent height, black smoke began to appear, at which point it was discovered that the black ABS pipe was melting from the flame. I worried that flashback might occur, comprimising the entire system due to this literal meltdown. At this point, i donned my gas mask, and smothered the device with a Dry-Chemical fire exstinguisher.

The official take aways from this first trial are as follows:
  • Black ABS pipe is ineffective at handleing heat from flames
  • A male to male adapter is required for the propane connection system

Finally, Version 1.0 will be officialy abandoned. I shall attempt again with metal duct pipe, although smaller and possibly harder to drill for Version 2.0.

Version 2.0


V2.0 proved incredibly more successful. Design the second time around was much easier since it was known. The used material for this was a metal duct pipe instead of ABS platic piping. The metal duct was smaller with a diameter of 2 inches, and a length of 30, half the origional length. Most of the construction steps were the same os V1.0. It took longer to drill into the metal duct than it did the ABS pipe.

Version 2.1


Test of the Lab Gas intake valves instead of propane proved to be a monumental improvement. With the better flow of gas from the nozzles in the lab, we had better control over flame height. In the beginning, we tested with full valve, giving the maximum ammount of gas flow available. After testing and measuring different tones, we had found that by decreasing the flow rate and using a smaller flame, changes in tone and waves were much more easily seen. The end result was the consensus that for best results, use a low gas flow to produce about 2-3cm high flames for the best results.

Videos and Documentation

This was the first version melting. Black smoke can be seen from the plastic melting:

This is the operation of build V2.0:

This is a problem found in build V2.0:

Here are some video demonstrations of the Rubens Tube with different forms of music:

Dubstep, and other heavy base tones prove to show the greatest change in waves and have the best effects on the Rubens Tube. High Treble songs provide higher pitches which are too finely tuned to be visualized with this version of a Rubens Tube.

500Hz Wave:


Frequency Distance from Nodes
378Hz 27cm
404Hz 28cm
440Hz 17.5cm
450Hz 22cm
460Hz 23cm
500Hz 24.5cm
514Hz 23.5cm
533Hz 29cm
550Hz 46cm


The graph demonstrates our results from measuring the distance between nodes in relation to the frequency. The bars represent our error margin in measuring the distance, as it was done by eye instead of avanced methods. Our error bars are +/- 5cm


The Rubens Tube proved successful in creating standing waves with the produced frequencies. By looking at the data table you can notice there is a trend that as we increased the frequency, then the distance between nodes also increased. This was also demonstrated visually with my graph. On the graph, you will notice bars above and below my data points. These are the error bars. The error bars demonstrate the range of error i had when measuring the distance between nodes. In future experiements, a measuring device should be used that is more accurate than just using a ruler and eye-balling it. The graph trend line helps visually confirm the previous notion that as our frequency increased, the distance between our nodes also increased.