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

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!

Packocrayons

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)

AlephZero

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.

012anonymousx

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!

scimon

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.

Packocrayons

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.

scimon

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....