Pop Guns

by Bart on September 3, 2009

A few years ago Phil Dadson and I put out a book on plosive aerophones and how to make them. Plosive aerophones is the generic term for things like slap tubes, udu drums, and other instruments in which a body of air is excited by percussion or other sudden  agitation. Sometime after the book was printed, I had a sudden realization: we forgot to include POP GUNS!  Too bad, because pop guns do qualify as plosives, and their sound is one of my favorites. 

As it happens, I did include a section on pop guns, in an earlier book, Funny Noises for the Connoisseur. So if you want the full story of popguns, that’s where to look.  But for a quick start, a short primer on the topic follows here.

Here’s a sketch showing the essentials of a pop gun.

pop-gun-diagram

The idea is to have a tube with a cork lodged in one end. From the other end the player pushes a snug-fitting plunger forward. This compresses the air and forces the cork to pop out, producing the popping sound.

Notice that two corks are needed, the popping cork and the plunger cork. Both have the truncated cone shape, with the large end a little larger than the inside tube diameter, and the small end a little smaller. The plunger cork serves as the piston-plug on the end of the plunger, fitting the inside of the tube closely so as to push the air through. To get that fit, stick the cork in one end of the tube as far as it will go. Cut off the portion that is still sticking out and discard. Sand the cork remaining in the tube flush with the tube end, and then remove it from the tube (push it out from the other side by poking through with a narrow stick or dowel).

At the end where the popping cork is to be inserted, use a rat tail file or similar tool to bevel the tube edges inward. Even if you do a somewhat sloppy job of this, it seems to help the popping effect.

The string that you can see in the drawing prevents the popping cork from flying away and getting lost. It also lets you pull the cork back into popping position simply by pulling the plunger back. The string length should be a little less than the tube length.

The drawing should tell you everything else you need to know. And to give you an idea of the sound you’re after, here’s recording of pop music.

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A pop gun can produce a variety of tones, depending on how firmly the popping cork is seated, how rapidly you move the plunger, and how far you draw the plunger back before starting the forward thrust.

Another sound I get a kick out of, closely related to pop gun pops, is suction pops (think of the sound of a cork being pulled out of a bottle). Maybe in another post I’ll talk more about them.  Suction pop devices are less variable and more predictable in their sound, and it’s possible to tune suction poppers to definite pitches.   

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