Make a bubble bazooka with a water shooting tube and a water bottle.

This post is in prep for a “Bubble Battle” event this coming weekend.  While I saw a lot of guns which shoot tons of small bubbles, I wanted to make something to shoot bigger bubble bombs.  So, after some brain storming, I decided I was going to stay away from electric fans.  I thought of water gun designs and the simple “water shooting tubes” inspired me as a a great simple design.  I decided I would use the one be bought last summer for the pool visits.  It should provide a good air blast and have a nice form factor for kids (and me) for any bubble battle.

So, all I’d have to do is to mount a bubble ring in front of the nozzle and I’d be done.  I decided I would try to improve the air-flow by adding an eductor.  An eductor works using the Bernoulli’s principle: as the air (fluid) increases in speed, it’s pressure drops.  So, as the jet of air goes through the eductor, you might guess that you lose air going out the side holes but instead, with the lower pressure, air is drawn in and you get a higher flow through the end resulting in more and bigger bubbles.

So, to make the eductor, I started with a used water bottle and removed the wrapper and cut of the bottom end.  I then cut three side holes to allow air to flow in.  This design hasn’t been optimized yet so I’ll update this post with improved eductors later.  Next, I cut small slits in the end to help trap bubble solution.  I taped it to the end of the water shooter and had the first trials.  While it worked, with a large diameter the small slits did not hold enough bubble solution to get a good stream of bubbles going.

photo of attachment

Water bottle with end cut off and 3 squares cut in the sides (eductor)

So, I borrowed a trick from the “giant bubble” enthusiasts (more on this topic later) and used a piece of cotton piping.  Any absorbent string or cord should do the trick.  I glued it on with 15 minute epoxy with help from my son.  So, he got to learn about mixing equal portions of resin and hardener and could tell my wife later that a chemical reaction took place to harden it.

Photo of bottle attachment with cotton piping

Cotton piping glued to end of bottle attachment (eductor) to soak up the bubble solution

After this was done, I just taped it to the end of the water shooter with black electrical tape.  I chose electrical tape because it is very stretchy and will conform to the shapes of the bottle and water shooter ends for a firm connection that can be removed later if need be.

Photo of finished assembly

Bottle attachment taped to a water shooter for finished bubble bazooka

To use, first pull back on the shooter, then dip the end into your bubble solution and let the excess drip off.   Aim and use firm but steady bursts of air to make a great stream of bubbles.  A side benefit of the eductor holes is that if you still have a bubble film after a blast, you can reload and keep the film intact for a second shot.  My neighbours kids loved it during the test trials!  Enjoy and see you at the bubble battle.

My mission through Daddy Engineer is to encourage people of all ages to enjoy engineering play.  Between work, kids and actually doing some of these projects, there’s little time left for blogging but I hope you enjoy my efforts.  Let me know what you think, your feedback and encouragement is much appreciated.

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