In this project, I created a flame tube, which is also known as a Rubens' tube. This device can usually be displayed in a physics classroom as a demonstration, which shows how sound waves traveling through the pipe affect the pressure of the gas and causes the flames to grow or shrink. Depending on how fast you work, this project can take a long time so I recommend starting to work on it early. Since I worked on this project with some help from my dad, it took about four to five hours to complete, test, and fix.

Step 1: Step 1: Gathering Materials

This first step took a fair amount of time because we forgot to buy some of the supplies and had to return to the stores and because we sometimes forgot what we were looking for exactly. Thankfully, some of the supplies we needed we could find at home.

You will need the following:

A galvanized pipe that is around two meters in length (about $16)
Balloons (I found mine at home but you can buy a pack for about $3)
A slab of wood that can fit the diameter of your pipe (I also found at home and the price depends on the kind of wood and size of wood you buy, based on where you buy it from)
A drill with a 2 millimeter and a 24 millimeter bit (from home but you can buy a good set for about $50)
A metal file (from home, for about $10)
Duct tape (from home, about $5)
Painter's tape (from home, about $4)
A marker (from home, about $2)
A ruler or measuring tape (from home, about $1 or $15 depending on which you use)
A hammer (from home, from $5-10)
A propane tank (as low as $4 depending on the size)
Clear tubing (about $20)
Poly tee and two elbows (about $1 each)
Polyurethane sealant (from home, for about $5-15)
A lighter (from home, about $4)

Optional:

Speaker (from home, about $5)

Step 2: Step 2: Smoothing the Edges

The second step in making your flame tube is to sand both ends of the pipe. When buying the pipe, I found the ends to be sharp enough to cut my finger on contact, which would definitely cut through the balloon that would later be attached.

Step 3: Step 3: Sealing One End

The third step is to cut a piece of wood that fits in the pipe so that you can seal on end. I found and old board of wood in my basement and traced the diameter of the pipe on it. After, I drilled holes around the traced piece and then sawed out the rest. The piece didn't fit immediately, so I used a file on the wooden piece until it fit just right. After that, I put some polyurethane sealant on the edges of the wooden piece and put it in the pipe. I then added more of the sealant on the outside of the pipe and spread it so the entire wooden piece was covered.

Step 4: Step 4: Marking and Making the Flame Holes

After the one side is sealed, you want to place painter's tape along the entire pipe. Measuring in fifteen centimeters from each end of the pipe, make a mark every two centimeters for each hole that will be made. Using a hammer and a sharp metal piece, make a dent where each hole will be. Afterwards, using a 2 millimeter drill bit, make each hole. Once this is done, you can remove the tape and sand the holes.

Step 5: Step 5: the Gas Outlet

This step is fairly simple since all you need to do is drill two holes an equal distance apart using a 25 millimeter bit. You will want to file the inside of these holes to make sure it doesn't cut through the poly elbows which will connect the gas. Now you will connect the clear tubing to the poly elbows and screw the elbows into the holes you just filed. You will want to apply and spread some sealant all around the elbows to ensure that no gas leaks from these connections. Afterwards you will want to connect both tubes to a poly tee which will lead to the gas supply. Adding tubing the the remaining end of the poly tee, you can hook up your gas supply which was a small propane tank in my case.

Step 6: Step 6: Sealing the Other End

Using scissors, cut the top portion of a balloon of. Depending on how sharp your scissors are, it may be better to use a knife. Then, seal the end of the pipe using the top portion of the balloon. Secure the balloon using duct tape, and in case you're afraid the balloon may tear at the edge of the pipe, you can add some extra duct tape to prevent leaks.

Step 7: Step 7: Testing the Tube and Improvements

The first and second time we tested our flame tube, the gas did not ignite because there wasn't enough gas flowing through the pipe. The third time we made sure there were no leaks and we opened the flow of the gas tank more to let more propane in. This time, the flames ignited. If I were to repeat this project in the future, I would probably use a larger tank of gas so that I would be able to ignite the flames more easily and I would have used better tubing so that it fit on the tee, elbows, and gas tank better, and so that it didn't bend and end up near the flames. In the end, this project turned out better than expected and if you wanted, you could attach a speaker to the balloon end of the pipe using the remaining part of the balloon and you could see how the flames react to different frequencies.