Project: Build a Catapult

Warning: A catapult is a weapon and should be handled carefully to avoid injury.

A catapult is a device used to throw or hurl a projectile a great distance without the use of explosives.  It's meaning, derived from Greek, means "Shield piercer."  So, my son and I set out to build one of our own shield piercers, albeit a much smaller version.  Our goal: to be able to chuck flaming marshmellows (warning: chucking flaming marshmellows is dangerous and should not be done -- ever).  We got ideas for a design from various websites and books, including Backyard Ballistics by William Gurstelle.  In the end, we ended up building several different versions.  Read below for a short description of the tools, materials, and instructions needed to build a small version of a onager catapult; I've included a little video of a larger catapult that we built to use as a pitching machine.

After we finished playing around with our catapult, we decided go bigger.  So using some old pieces of 2x12s that I had laying around we created a catapult large enough to launch tennis balls a couple houses up the street.  It turns out that Catapult v2.0 also worked well as a kind of pitching machine.  Anyway, here's the video:

The only thing that's left now is to slap a couple of bicycle wheels on this thing so my son can haul it around with his PowerWheels Jeep.  I wonder how well this would launch snow balls... Anyway, do be careful when using the catapult, especially when handling the arm; when tightened up, the arm store enough potential energy that, when released, is enough to break bones or cause other injuries.  In other words, keep your hands away from the throwing arm at all times!

If making a catapult from scratch just isn't your thing, there are some easy, build-it-yourself kits from places like ThinkGeek or  Personally, I've found that my son enjoys building things as much as he does using them.

That's it for now; back to being a Daddy...


  1. Making a catapult with my son tonight. Thanks for the tips! Maybe we'll make a tennis ball launcher for our dogs...

  2. hello! can this catapult launch accurately within a specific meter(exp: 2 to 6m)

  3. hello! can this catapult launch accurately within a specific meter(exp: 2 to 6m)

  4. What makes the lever shoot forward to launch the tennis ball?

    1. Hello! The tension is created by winding up the rope that connects to the throwing arm.

    2. You can see one of the two “winders” in the right side of the catapult... it looks like a thick wooden dowel. You can wind up the rope so tightly that it can break through the wooden dowel


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