I realize that after a long time of not blogging that I simply forgot to blog about finishing my Rubens Tube. Besides, I need to show the final piece in action. Sorry about that! Here are the first three blog posts about this. One, Two, Three.
One hole drilled for a pipe thread, the other for a 1/4" OD tube.
Step 6. Prepare the plate for the propane side. I drilled and tapped a 3/8″ NPT for the brass fitting. The other smaller hole is for a tube which I’m welding in for an attempt at a pilot light. If you’re building your first tube, you can ignore this, as it may not work well.
Welded and plumbed
Step 7. Weld the plate into place. I also had to weld my pilot tube through the plate and out through the top of the tube, so it as a bit of juggling. I then plumbed it with a brass flare fitting that mates with my propane hose. The plate isn’t very thick so it’s easy to strip out the few threads of pipe thread. Always use two wrenches to tighten/loosen the flare fittings to prevent over-torquing these relatively delicate threads. A better solution might be to braze or silver solder the flare fitting to the steel plate.
Cutting the rubber is as straightforward as it gets.
Step 8. Seal the speaker side of the tube. I use a thin rubber that is rated for exposure to propane (caution, not all rubbers are equal!). The rubber I found is Buna-N rubber that I got from McMaster Carr. It comes in a big sheet and I’ve been using the same one for all of my tubes. I poked the screw holes through the rubber so this plate can hold the rubber sheet against the flange that is welded onto the tube. The speaker is then installed over the whole package. The speaker never touches the propane. The frequencies can easily transmit through this thin rubber.
Fire at last!
Step 9. Fire it up! After sealing the flanged end with rubber, I was ready for a test. The tube may take a while to fill with propane (which is heavier than air), but eventually you can light the flames. I adjust the pressure on the propane bottle with a regulator to get a nice small, even flame across the entire tube. It’s then easy to see if you have slightly clogged holes. I usually just use a drill bit by hand to clean out clogged holes. The result speaks for itself.
I hope you enjoyed these instructions. If you have any questions, don’t hesitate to ask in the comments down below.
hello
I have a 4″ inside dia hvy steel (shedulae 40) pipe 20′ in length. or a 5″ thin wall(1/16+ wall)steel pipe witch would you recommend using. I have been wanting to make a rubens tube with it. You put only one gas port, is this enough? and only one speaker. would one speaker on each end be an improvement? did you find you needed more gas supply ports? How well did yours work? were you happy with it? what would you change?
Thank you for posting your blog
Joe
Joe, thanks for the questions! My personal feeling is that you should use the tube that will resonate the best. If you were going to build a pipe organ out of any material what would it be? That material will most likely work well for a Rubens’ Tube. Of course, a nice brass tube is expensive, so we have to use what we have. I’d go with the 5″ thin wall tube that you have. Which will be also easier to drill and carry around. I’ve found that 1 gas port is all I need. The most dynamic Rubens’ Tube flames happen at a low flame height, so it doesn’t use too much propane. Also, a second speaker won’t help with the resonating tube. So far I’ve made 4 different tubes. I’d say the one I was happiest with was the one that resonated the best. But, I think the cool sine waves are more interesting than a bass-hit poof. If you have a nicely resonating tube, you can get both easily. If not, you really only get the bass-hits. Happy Drilling!
Hello,
can you give me the specs for the Buna-N sheet? Thickness, and maybe an inventory number or direct link to the page over at McMaster, and/or any technical info you care to give. (I’m in Norway, and McMaster no longer sells to Europe, or even allows us to access their online catalog, so I’m thinking I need to get an American friend to order a sheet for me.) Alternatively, I need as much information about the rubber as I can get, so I can order something similar over here or somewhere else online.)I have been using latex, but it degenerates relatively quickly with the propane. My Ruben’s tube is similar to yours, shorter but made of relatively thick steel that can be welded.
Thank you very much for the good description of your build, and for any information you can find the time to send me.
André,
Oslo
André,
You can find out more about Nitrile rubber at the usual sources. I would go for the thinnest stuff that you can get. At McMaster that’s 1/32″. I’m sure you can find it in a 1mm thickness in Norway and that’ll work just fine. Good luck!
Where do you get the single frequency sounds inorder to visualize standing waves?
I was using a function generator that was lab surplus, but you can download software that can achieve the same result. A while back I bought AudioTest because it had a few features I needed, such as the ability to save files of the wave functions for later playback.
If you’ve got a working Rubens Tube, make a video and post it here!
So does this software run on iPhones?
There are lots of iPhone app function generators. Look ’em up!
Do you know any? Which one would you recommend?
I don’t have an iPhone, and I have my solutions, so I haven’t reviewed them. Good luck!
Thanks for your help
Do you have to have a round pipe for the tube to work properly or dose it matter
Dan Busby ,
How did you hook the cables to the tube to get the music to play?
The music is run through a normal house amplifier. I like to use a cheap 15W amp dedicated for the Rubens Tube. I run the output of the amp to the speaker on the tube just like any old speaker setup.
I am just learning about Rubens tubes, most of the others I’ve seen say not to run it for more than 20 min or so as it will over heat (they are also of lesser quality, using balloons as the membrane) how long can this one run do you think. I am looking for a permanent instillation in a picnic table for outside dinner gatherings.
The membrane I prefer to use is Buna-N. You can get varying thicknesses of it from Mcmaster-Carr. Buna-N is resistant to propane (and most other fuels), and it’s relatively cheap and easy to work with. I’ve run my tube for stretches of 8 hours at a time with no problems. Every few years you might have to swap out the membrane, but it’s really not a big deal.
Thank you sir. Is this the tube that in your experience works the best? Or do you have a tube you like better, and is there a write up of that tube somewhere? I really appreciate you sharing your knowledge, thank you so much!
Great question. In my mind steel is not the best material for a Rubens Tube. My Aluminum tube works much better. Brass would probably be awesome as well. The better the material rings when you hit it, the better it will resonate. Aluminum is more difficult to weld, but it can be done. You’ll have to make your decision based on budget, skillset, etc. Good luck! Come back and post photos.
Hi Dan,
Is it possible to remove the need for the rubber? I don’t want parts that will eventually fail and need replacing. Could the speaker be sealed in a aluminium box, with a hole drilled for power and aux cable then sealed up with glue, then welded to the pipe to put the propane in direct contact with the speaker?
Cheers,
Rowan