# Ruben's Tube - Is a one inch OD pipe okay?

• 012anonymousx
In summary, a one inch diameter tube will work, but it may not produce clear waves. You might want to try a larger diameter pipe for better results.
012anonymousx
Hello everyone!

I'm in high school and attempting to build a ruben's tube.
I am on a very strict budget and came across free brass tubing, but the diameter is 1 inch.
All the tutorials I've seen use a diameter of at least 2inches if not more.

Will a pipe with a one inch diameter work? (at least in theory?) Or is there a real physical sciency reason that there must be a 2inch diameter.

I appreciate all the help!

I see no reason why not, the wave effect might be diminished slightly or you might get some distortion from the waves bouncing a little bit, but nothing that should make the final waveform difficult to see.
I'm going to do it with a 2" ID pipe at some point, so I'll see how it works if I ever get around to finishing the project.
Post some video when it's done!
(Oh yeah, you should try to light it with a tesla coil :p)

There could be two issues with a smaller dameter tube.

1. The gas flow velocity along the tube will be higher, assuming the same length of tube and the same size and number of holes. That might distort the standing waves a bit.

2. The resonance peaks won't be as sharp for a narrower tube. The energy loss in the gas will be mainly the boundary layer around the surface of the tube. The mass of vibrating gas is proportional to ##r^2## and the surface area is proportional to ##r##, so the amount of damping is relatively less for a wider tube.

But I don't know idea how much effect those things will have - the best way to find out would be make one and try it.

Hm, okay, so basically just perhaps the waves won't be so clear.

Yeah, I guess the best way will be to try it. I just wanted see if anyone has ever actually done or there is an actual reason so I don't waste my time.

Also, I am realizing that it'll be harder to get the holes exactly perpendicular.

I thank you all a lot for your help!

I have been trying to create a Rubens' tube with 1" black pipe myself;
due to weight & cost considerations. Thus far I have qualified success.
Currently I am only able to get a bass response near the end with the
speaker, no sinuous wave forms to speak of.

My holes are 1/16", and 1/2" apart along 4.5' of a 5' length of pipe.
I am using a helium-quality latex balloon stretched taught over the end
opposite the gas inlet, held on with a hose clamp. I have tried a plain
membrane, and one with a small disc of paperboard attached, as
recommended by some tutorials. The membrane with disc seemed to
provide a larger response to the speaker, but overall the results are
disappointing. Only about 5 inches of the 5 foot pipe are noticeably
reactive to the sound.

Any thoughts regarding troubleshooting?

P.S. I found that a standard low-pressure regulator was insufficient,
the last 15 inches of pipe had no flame. I special ordered an
adjustable high pressure regulator, and can now get all holes to light.
The adjustment also provides some control over flame height, although
much larger than 2 inches and the flames become a bit erratic.

Last edited:
I have no experience with use of reuben's tubes but 'm in the process of building a 24" er with 20" of 1/16" holes, 1" at centers. 1/2" seems a little close to me.

Packocrayons said:
I have no experience with use of reuben's tubes but 'm in the process of building a 24" er with 20" of 1/16" holes, 1" at centers. 1/2" seems a little close to me.

1/2 inch is what I saw in many tutorials, although it varies up to 2cm or 1 inch.
The proximity is so that they are close enough to relight one another if any
particular jet goes out. From experience thus far, that seems about right.
When the end gets blown out, flames reignite one jet at a time with noticeable delay.
I don't see how this should affect sound propagation, but I might try taping
up alternating holes with aluminum duct sealant tape...

## 1. What is a Ruben's Tube?

A Ruben's Tube is a physics demonstration device that uses fire to visualize standing acoustic waves in a tube. It consists of a long metal pipe with holes along its length, filled with propane gas, and attached to a speaker at one end.

## 2. How does a Ruben's Tube work?

The speaker produces sound waves that travel through the tube and cause the gas inside to vibrate. The holes along the tube allow the gas to escape and form visible flames. The height of the flames corresponds to the amplitude of the sound waves at that point, creating a visual representation of the standing waves.

## 3. Is a one inch OD pipe okay for a Ruben's Tube?

Yes, a one inch outside diameter (OD) pipe is commonly used for a Ruben's Tube. However, the length of the pipe and number of holes will also affect the quality of the demonstration. It is recommended to use a pipe that is at least 6 feet long and has at least 20 holes.

## 4. What type of gas should be used in a Ruben's Tube?

Propane gas is typically used in a Ruben's Tube because it is easily ignited and produces a visible flame. However, other flammable gases such as methane or butane can also be used.

## 5. Is a Ruben's Tube safe to use?

As with any demonstration involving fire, caution should be taken when using a Ruben's Tube. It is important to have a fire extinguisher nearby and to follow safety guidelines. It is also recommended to have a fireproof barrier between the tube and the audience. With proper precautions, a Ruben's Tube can be a safe and exciting physics demonstration.

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