Rubens Tube and Propane Combustion

[stiltdancer]

I’ve constructed a Rubens Tube (

http://en.wikipedia.org/wiki/Rubens'_Tube)

and am having some trouble pushing it to do what I want.

I need some help with jetting and getting the flames to look nice. I’m having trouble finding information on jets and flame engineering.

A Rubens Tube is a length of pipe perforated along the top and sealed at both ends - one seal is attached to a small speaker, the other to a supply of a flammable gas. The pipe is filled with the gas, and the gas leaking from the perforations is lit. When the speaker is turned on, the pressure changes caused by the sound waves will cause the flames to heighten in some areas and to lower in others. I’m using a 5’ pipe with 1/16” holes drilled at ½” intervals.

My problem is that while it works great for showing standing waves, but I want to use it as more of a fire speaker. The pressures that are transmitted during music tend to blow out the flames over sections of the pipe. I’m using propane and I’m blowing too much fuel for the fuel/air mixture to stay lit at some frequencies.

I need to find a way to mix more air where the combustion is taking place. Also, I frequently get blue flames and want to find out how to make it burn in yellow flames so it shows better. I think finding a way so slow down the velocity of the propane and mixing more air in can solve my problem.

For now, I’ve ordered an equalizer/amp to that I can filter out all the higher frequencies – making it a subwoofer. The higher frequencies playing music make a lot of “noise” and I don’t get a good effect. I’ve also ordered some stainless steel wool that I’ll wrap around the tube – hopefully it will mix the propane and air better and make it less sensitive to any wind that is around.

Any ideas?

Thank you,

Sean

 

[btrueblood]

If you premix air with propane into your tube, you will have something closer to a pipe bomb, or a "spud gun". If launching your speaker on a ballistic trajectory is what you wanted to do, then fine.

"My problem is that while it works great for showing standing waves,"

Yes, that is what a Rubens Tube does.

"... but I want to use it as more of a fire speaker. The pressures that are transmitted during music tend to blow out the flames over sections of the pipe. I’m using propane and I’m blowing too much fuel for the fuel/air mixture to stay lit at some frequencies."

When the flame "goes out", does it stay out, or do the flames at those positions re-light when the frequency(ies) change again? Try turning down the volume, or adding pilot flames (fed by seperate tubing) adjacent to the holes.

 

[stiltdancer]

"If you premix air with propane into your tube, you will have something closer to a pipe bomb, or a "spud gun". If launching your speaker on a ballistic trajectory is what you wanted to do, then fine."

I thought briefly about mixing air in, but then it becomes much less safe (not just spud gun wise). Propane won't burn unless mixed with air. I don't have to worry about combustion inside the tube (or explosions) if I don't mix in air.

"When the flame "goes out", does it stay out, or do the flames at those positions re-light when the frequency(ies) change again? Try turning down the volume, or adding pilot flames (fed by seperate tubing) adjacent to the holes."

The flames tend to go out in about the middle third of the tube and have a tendency not to re-light. When I wanted to "reset" the flame, I'd turn off the music, the flame at each hole would go down very low and blue (looking like it was going to go out), then go yellow again. This process took something like 5-10 seconds.

Turning down the volume helps a lot. That's why I've decided to run a separate amp for the tube. I'll try the separate pilot lights, if I have it a bit higher off the tube, the fuel/air mixture may be enough to light. That will be a plan B.

Thanks!

 

[sbm5788]

I've constructed several revisions of the tube myself, and troubleshooting along the way, I may be of some help.

It just sounds like you're not getting enough gas into the tube. How are you regulating it? I had tried multiple regulators (none giving enough output) before modifying a torch regulator to output more. (just used a drill press)The flame should ideally be around an inch to an inch and a half high.


The best waves and response to music I've received occur when a couple of conditions are in place

The tube should be at least 2 inches in diameter- this seems to minimize the effect of larger flames closer to the speaker, and allows for a more equal distrubution of pressure. Wind of course as you mentioned is also a key factor. Even on the most still days, i've had to operate the tube in my garage to get optimal effect. Vibrations in the tubing can also be an issue for a steady light.

And regarding lower frequencies, I usually get TOO much effect from a lot of bass. I usually turn down the bass a little and focus on the midranges. Just what's worked for me. Let me know if you have other questions/problems. You can see a video of mine working here:

http://www.youtube.com/watch?v=zNolz6-i6Ps

And i'm actually selling models of them here:

http://cgi.ebay.com/ws/eBayISAPI.dl...MESE:IT&viewitem=&item=290085269125&rd=1&rd=1

Good luck!!