Introduction: Propane Pop Gun

This fun toy could be customized and decorated to be a prop for a number of different costume ideas. My friends and I made a few of these to play with during a regional Burning Man event in Texas recently. We had a lot of fun with them.

This project uses methylacetylene-propadiene (MAPP), a highly flammable blend of propane gas. I'm not responsible for you or what you do with this. It shoots fire! Be careful. Continually monitor the hose for any hot spots in the hose or the bottle assembly. Shooting it continuously will increase the likelihood of melting but we were shooting ours a lot and had no problems.

From a design stand point, one of the goals in designing this was to come up with a fast and easy to assemble version. The same idea could be used to make something much more elaborate. I'm excited to see what others do with this idea.

I would like to tip my hat to Volcano Al, a fellow that I met at Burning Man this year. His Plasma Popper was my inspiration. Thanks for enduring all my questions, Al. My friends and I are having a blast with this.

As an additional safety concern, don't point this at people, especially the police. Even though there is no projectile, or any real danger unless the person is very close, this pop gun can be loud and threatening. The cops might think to shoot you before finding out that this is harmless. With that said, Have Fun!

Step 1: Supplies

Supplies

1 Bernzomatic TS4000 torch

1 can of MAPP gas or propane. Be sure you get a can that fits the torch. They are often sold together.

10’ of heavy vinyl tubing with 5/8" or 17mm ID

2 wide mouth plastic bottles (gatorade)

5’ of 2” pvc pipe

duct tape

50lb 12” zip ties

Heavy duty pruning shears

Step 2: Cut Bottles

Cut a hole in the middle of the bottom of one of the bottles just big enough to push the tubing into it without kinking the tube. The hole should not be a perfect fit but close enough to hold the tubing. Outside air is drawn into to the bottle assembly through the ill fitting seal around the tubing. This is important for getting a good pop. Cut this bottle first. If you mess it up, you can always just cut the bottom off of this one and try again with the other bottle. In my opinion, this may be the hardest step because the plastic is thicker in the center at the bottom. Take your time and be careful not to cut yourself. Don't try to do this with a knife. I used some heavy garden shears.

This step can be simplified by using only one regular plastic soda bottle. It will take a little effort but you can stretch the tubing over the opening of the bottle, then cut a hole in the bottom of the bottle. This option will save you some work but the resulting POP will not be as loud. An example of that can be seen here. https://www.youtube.com/watch?v=8KSHcGHiY0M

Step 3: Build That Nozzle

Care fully line up the mouth of each bottle and tape them together well. Wrap the tape as tight as you can get it, keeping them lined up. I found it easier to have a friend hold them together while I tapped them.

Step 4: Get Ready to Test Fire.

Before you do this step, using caution, try out the torch to get used to using it. Slide the tubing over the tip of the TS4000 about 1” past the beginning of the tip. Don’t secure it with zips just yet.

Step 5: The Tubing Goes Into the Bottle Assembly

Insert and position the tubing so that the end of the tubing is a couple of inches inside the first bottle and as centered as possible.

Step 6: Testing the System.

By this point you should have your bottles cut and assembled and the torch assembled, connected by the length of tubing. Being extra careful not to burn your face off, try it out.

Turn on the gas knob. With one hand, hold the tubing with the bottle assembly away from your body and anything flammable and the TS400 with the other hand. Push the ignition button about ¾ down and count to ten (you will hear the gas) Push the button in the rest of the way. The torch will ignite the gas in the tube and you will see a little blue ball of fire exit the tubing. It will expand in the bottle assembly with a satisfying ‘POP!’ Play around with it, change the depth that the tube goes into the bottle, experiment with timing before firing. Get a feel for how it works and what makes the best results.

Step 7: Secure the Torch to the Pipe.

Make sure the TS4000 is turned off. Zip it to one end of the pipe. Duct tape over the zips to further secure the fuel can to the pipe.

Step 8: Secure the Bottle Assembly

Zip your bottle assembly to the end of the PVC pipe. Notice how I used the grooves in the bottle. You’ll want this to be snug but not tight enough to squish the bottles. The bottle assembly works as a de Laval nozzle. Learn more about that here.

http://en.wikipedia.org/wiki/De_Laval_nozzle

Step 9: Secure the Tubing

Attach tubing to the torch with zip ties. Snug these real tight.

Notice the blue arrow and the circled area in the photo. At the torch tip connection, try to avoid this. Route the tubing so that the fire naturally chases out of the tube without encountering any sharp angles or kinks.

Depending on how you position the rest of the tube, it may cause this connection to bend a little. This can cause a hot spot that could melt. If you see this, fix it by repositioning the rest of the tube. Now secure the tubing to the pipe but don't tighten the zips too tight. No kinks or very narrow spots. You will find that the tubing will want to remain coiled. You can secure it to the pipe to make it go the way you want but I found it easy to get an interesting path using the natural curves. Just make sure that you can get the opposite end of the tubing centered in your bottle assembly.

Step 10: Variation!

Now that you have built a Propane Pop Gun, you can decorate it however you want.

I also made a double barrel pop gun. It has two separate systems made just like the single shot pop gun described in this instructible but mounted together on the same pipe. I wanted it to look more like a weapon so I wrapped the pipe and fuel cans with black tape before assembly. This double model turned out to be much heavier than I expected it to be but looks very impressive with two little fire balls instead of just one. I may put a shoulder strap on it to make it easier to handle.

Step 11: Your Cat Will Not Like This Project

This is a picture of Reynard sitting atop some catnip in a bread pan. He is proof that you can be awesome even if you were not born with a tail.

Step 12:

Remember, while this design is safe, there are some dangerous elements. Be careful. If you decide to make one, please be sure to let me know, especially if you come up with a very cool way to decorate it. This is my first Instructible and I am very happy to have finally done one. Enjoy!

Comments

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NocabN made it! (author)2017-02-07

This was a fun and easy build! Thanks Eric Rocher. Also, thanks to Nighthawkinlight, Backyard Scientist and special inspiration for Beals Science. I made a few of these, one for myself and a couple of buddies. These are a lot of fun. Of course, I made a few design tweaks of my own, but thanks to the afore mentioned people. YouTube action at this link:

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Samno911 (author)2017-01-28

Would this work in a larger chamber? I have an idea for a plasma rifle that would have a short coil of tubing, then lead into a larger 8" long 2" diameter clear pvc pipe for the chamber. Would I get a big flash? the sound isn't super important, but i was going to make a muzzle break for it so the gas could escape and oxygen could fill the chamber. Would even adding a valve that I could lightly pressurize the chamber first to make sure I had enough oxygen in there?

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twinotter (author)2016-08-04

I built one of these to your instructions after meeting Volcano All last year. I'm having a problem with the gas rarely getting to the bottle no matter how long I hold the trigger. (Up to about 30 seconds.)

I tried both combustion chamber techniques. Interestingly, the single bottle (with 1/2" drilled hole in the end) have me one good pop. It then gave a couple half hearted pops, and then nothing.

I thought perhaps gas was escaping the vent holes, but closing them up produced no flame. (I assume that they are mixing air with fuel to get the flame now.)

Ideas on why the flame would get to about a foot from the end but not fill/ignite the bottles?

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twinotter (author)twinotter2016-08-04

Additional data: I used 20 oz Gatorade bottles for one nozzle and a 20 oz mello yello bottle for the other. Tried positioning the tube at various depths into the bottle with no difference..

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twinotter (author)twinotter2016-08-04

Operator error! I held down the gas after hitting the sparker and it worked just fine!

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qdogg (author)2016-05-11

I tried this w/ a half inch ID tube, my torch tip being 1/2 inch. With 10' of tube the flame fizzled before getting to the end. I cut off a foot(not mine!) and sometimes the flame got to the end but there wasn't a loud pop. I think smaller tubing demands a shorter length. I'm gonna try cutting the length again. Seems like this could make a bottle launcher somehow...

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ExzitaM (author)2016-01-28

i was wondering if instead of using a bottle you can make a chamber of pvc. i was wanting to use this to make a mock laser rifle so if i could implement a seald and chamberd pvc pipe instead of the bottle for more customization options.

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Eric Rocher (author)ExzitaM2016-01-31

I used the bottle to provide an expansion chamber. Also, the clear plastic allows you to see the flame, which was kind of the point of this design. You could make this with PVC. I would love to see what you come up with.

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Eric Rocher (author)Eric Rocher2016-04-10

I've been thinking about this. You might try to make the expansion chamber with Lexan tube. It is a clear plastic that could make a clear rifle barrel look. If you made something, please share a photo.

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ExzitaM (author)Eric Rocher2016-01-31

alright cool I'll put up an instructable when I have completed it

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The King of Random (author)2014-11-14

Cool project! Here from NightHawkInLight!

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King of Random! I love your videos.

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Yonatan24 (author)Eric Rocher2016-01-22

You, And now almost 5,000,000 other people... (including me!)

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kittycow (author)2015-10-29

I made a propane gun using a modified implementation of this project, i was wondering if i added some electro magnets around the expansion chamber (gatorade bottle in this case) if i could turn it into plasma?

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AdamK22 (author)2015-08-05

I am planning on bringing this to Georgia's regional burn, Alchemy. However, I ran into trouble with fire suppression/safety at Transformus in North Carolina. I feel like this is a very safe contraption, but it seems unacceptable at this burn. Any suggestions on a) how to sell this to fire safety or b) how to make this safer?

I sent them:

"I have a flame effect, or kind of a flame effect. It's called a

Propane Pop Gun:

There is MAP gas at the base of a pole with plastic tube winding up

the pole with a nozzle at the end for a pop.

http://i.ytimg.com/vi/8KSHcGHiY0M/maxresdefault.jpg

https://www.instructables.com/id/Propane-Pop-Gun/

There is no LP gas in this flame effect. The flame that does happen

is nearly instantaneous through the tube, rather than most LP effects

where the flame is constant. The igniter on the MAP gas has a

pressure regulator, pressure fitting, and shutoff.

Do you think this is kosher to carry around and show off and play with

at Alchemy?"

and they responded with:

"That sort of device is not considered safe for use at Georgia burns.

The combination of flame and plastics is very dangerous. Any malfunctions could lead to significant burns and injury.

If you're interested in learning how to improve your device or make something safer, try this group on facebook:

https://www.facebook.com/groups/152104734905385/

This is a group of Flame Effects builders, and they'll happily provide you with some advice and tips. There's even a class coming up ( unscheduled right now, but keep an eye out).

Thanks for reaching out to us."

Any suggestions?

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Eric Rocher (author)AdamK222015-08-11

Their offer of education is encouraging though with this item, making it comply with code would likely change the effect as clear tubing is key. Perhaps it could be done with blown glass. In regard to using yours at a burn, it is their event and if the fire safety team says No, you will want to respect that. However, I took several to Myschievia. Before the fun started, I showed it to the fire safety team. While they initially thought that the whole idea was crazy dangerous, after seeing it in action, they allowed us to use them. You may want to try this approach. Good luck and have a great time! I've heard about Transformus. It sounds like a great burn.

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Volcano Al (author)2014-11-24

Hi Eric, this is Volcano Al. So glad you are having fun with this! Thanks for giving me credit. As you recall my popper had a metal frame with a spiral tube. I like you idea of using PVC pipe as a frame, so much easier to make. If you leave about a 1/2 inch rim around the exit hole in the second bottle you will get a louder pop.

author

Farmers use the industrial grade version to scare pests. They are called propane cannons. Standing a few feet from a Reed-Joseph unit the concussion wave hits you in the chest. They are amazing. Spent a few years experimenting with propane, pipes, collecting patents, thinking, shelved it, and gave up for a while

Getting propane to detonate is extremely "difficult". Conditions have to be just right. Thanks for sharing this with us.

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DesireeNLuvBarrett made it! (author)2015-05-14

I made it and one for my husband too! It's so cool!

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Yeah! Woot!

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Valster (author)2015-04-07

Awesome instructable, Eric!

One question. Have you experimented with different lengths of tubing?

I was thinking that I could mount the bottles to my post lantern at the end of my driveway in order to scare trick-or-treaters before they get near my door. Do you think this would work using 25-30'?

Thanks,

Steve

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Eric Rocher (author)Valster2015-04-09

The longest that I have had tried was just under 20'. It worked but to get good pops you have to hold the button and fill the line with gas longer before firing. Please let us know if you experiment further. I am interested in this application. Scaring trick-or-treaters is an important endeavor at my house.

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Valster (author)Eric Rocher2015-04-09

It may take me a while to get around to experimenting but I'll definitely get back to you when I do.

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Eric Rocher (author)Valster2015-04-09

Steve, check this scarecrow poofer out. This is a real hit in my neighborhood.

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Valster (author)Eric Rocher2015-04-09

Good one. Thanks!

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Volcano Al (author)2014-11-30

Hi Eric,

I have been trying to post for the last week with no luck. Seems to be working now. You asked if I have used a popper as a pilot for a poofer. No, but I like the idea! I would put a sheet metal flapper at the popper outlet, such that it will not block the flame but moves when fired. Hook a 12 volt micro switch to the flapper arm ( back aways and shielded from the heat) Swap the second plastic outlet bottle for a tin can (to take the heat). Hook the switch to a 12 volt pilot operated solenoid valve on the outlet of your accumulator. They need to be close so the timing will work. If this works it would be so cool! Plus you get ride of the pesky poofer pilot light.

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Eric Rocher (author)Volcano Al2014-12-08

Volcano Al, I am intrigued by the flapper/switch idea. Very cool.

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shazni (author)2014-12-08

That is awesome!

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CarmelitoAndrade (author)2014-12-07

this is super awesome !!

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Just watched the video and I gotta say that is freaking awesome. Good work. I'm excited to see further development on this as well. Might be me doing some of it. This thing (brenda mae?) rocks.

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Thanks! This is a pretty easy toy to mess around with. If you come up with something interesting, I would like to hear about it.

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Eric Rocher (author)2014-12-06

Lime 3D, thanks for the great questions.

The main reason for using the tubing in this project is the visual effect, to be able to see the fire travel the tube. Not only does it look great in the dark, it seems to defy physics, making a fun toy that much cooler.

NightHawkInLight has built a version of this with a single bottle, with the tube fitting tightly over the mouth of the bottle and the flame coming out of a hole cut into the bottom of the bottle. It works but runs a small risk of blasting the plastic bottle apart. When I tried it this way, I got good pops but not as loud as the two bottle assembly. As a side note, using two bottles

that have a smaller mouth doesn't work well. When the gas expands in the first bottle it needs room enough to escape. I blew apart my first attempt. The second bottle took off like a rocket though I thought it was secure.

As far as tuning the sound with holes on the bottle, I haven't tried that but from what I have experimented with so far, I think you would get more variation by changing the length and width of the expansion chamber by using different shaped bottles. A friend made one using gatorade bottle that were larger than the one I used here. The sound produced was deeper but not very loud. Another we made with more narrow bottles produced nice pops that were shaper in sound and pretty loud but those bottles were damaged by heat fairly quickly.

As far as using metal fittings, tubing and an expansion chamber, sure, those will work but you are stepping up the level of complexity while taking away the visual effect which in my opinion is what truly sets this project apart from other propane effects, well that and the perfect blend of air and propane that you get with the Bernzomatic torch tip. There are other ways of getting a propane explosions. A 12 volt battery powered ignition coil wired to a spark plug mounted inside an expansion chamber is one way. Controlling the gas with a solenoid propane valve is fun but difficult to jet properly. A propane 'poorer' is not going to get the pop like in this project. Adding canned O2 into the mix becomes not only more interesting but much more dangerous. Proper jetting to get the right mix of O2 and C3H8 is tough. Adding a richer mix of O2 to your propane is very explosive. If your experiments take you this direction, please be careful; the right mix can explode with a static spark.

I experiment with this stuff a lot. I'll be sure to get my next creation up soon.

Thanks again for these questions. I hope I cleared a few things up for everyone.

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lime3D (author)2014-12-06

Can you clarify a couple things?

First, are you using plastic tubing and bottles just for the visual effect? Meaning, if we wanted to make one more the the noise, would copper tubing and metal cans work? (won't melt)

Second, can you explain the bottles a little bit more? You have the tube feeding the fireball into the first bottle. Is it the fact that the fireball expands in the first bottle, then goes through the top of the bottle that makes the sound? What happens if you don't have the second bottle?

Third, you mention to keep a loose fit between the tube and hole in the bottle of the bottle to let in air. How about making a tight fit (maybe more secure on your rig), then drilling a couple of small holes in the bottle until you get the sound you want? If you end up drilling too many holes, you could then cover some with tape to 'tune' it.

I'm also sending you a private message.

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Volcano Al (author)2014-11-30

test

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samalert (author)2014-11-26

ITs great ! youtubers are flocking instructables. Welcome the the Party !

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PavelT1 (author)2014-11-19

NightHawkInLight sent me to. You got my vote.

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acewingman (author)2014-11-14

You could use multiple tubes in a Gatlin fashion to achieve rapid fire...

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rjkorn (author)2014-10-28

You should enter the first time authors contest too.

I'll vote for you....

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Eric Rocher (author)rjkorn2014-10-30

Thanks, rjkorn. I did enter.

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rjkorn (author)Eric Rocher2014-10-30

great I just voted for you....

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Eric Rocher (author)2014-10-28

Seamster, this does seem to be lacking explanation of the hose. Maybe I should edited. Thanks!

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Eric Rocher (author)2014-10-28

Thanks! Rapid fire is hindered by the need to fill the line with gas before firing. One of my pals is experimenting with rapid fire capability. I'll be sure to add details if he is successful, though rapid firing would necessitate design changes as the time between shots is important for cool down.

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to'bryant (author)2014-10-28

Very cool, can you rapid fire?

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seamster (author)2014-10-28

I was confused by the long coiled hose until I watched the videos. That's a pretty cool effect! Thanks!

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