How to build a tabletop catapult

From wooden dowels and rubber bands.

tabletop catapult
Ready, aim...Stan Horaczek

This weekend, Popular Science will be holding catapult competitions at World Maker Faire. We'll guide attendees through building their own miniature siege weapons from wooden dowels and rubber bands. Then we'll pit you against each other in target practice, with the winners taking home PopSci swag.

Not everyone can join us in New York, but anyone can build the same type of tabletop catapult by following these instructions (based on this project). Feel free to modify the steps if you see the opportunity to make a stronger structure.

WARNING: The wooden dowels can jump all over the place. Don't poke your eye out!

Stats

  • Time: Less than an hour
  • Cost: $15
  • Difficulty: Easy

Materials

tabletop catapult - supplies
All the supplies you need to build your catapult.Stan Horaczek
  • 12 wooden dowels, 12" long by ⅜" diameter
  • ~40 rubber bands, various sizes
  • Spoon or stemmed plastic cup
  • Ping-pong balls
  • A couple moderately heavy items for weight (optional)

Instructions

Start the arm

tabletop catapult - step 1
Step 1Stan Horaczek

Put two dowels together in a capital-T-shape. The leg of this T will become the catapult’s throwing arm, so make sure it can turn freely around the dowel.

Complete the base

tabletop catapult - step 2
Step 2Stan Horaczek

Grab three other dowels to finish framing the square base. Attach two to the top of the T (from Step 1); then use the third to connect them, forming a square.

Attach vertical rods

tabletop catapult - step 3
Step 3Stan Horaczek

At each corner of the base, affix a dowel (four total) that sticks up vertically. It’s okay if they wave around a little—the next few steps will stabilize the structure.

Brace the vertical rods

tabletop catapult - step 4
Step 4Stan Horaczek

Connect a horizontal dowel to the tops of the two vertical dowels on either side of the throwing arm. Then, between the two vertical dowels on the other side, connect a horizontal dowel a couple inches below their tops.

Complete the structure

tabletop catapult - step 5
Step 5Stan Horaczek

Lean together the structures you created in Step 4 to form a triangle, and connect their tops with rubber bands. Weigh down the square base with your moderately heavy items (optional).

Finish the arm

tabletop catapult - step 6
Step 6Stan Horaczek

Now turn your attention to the throwing arm. Wrap rubber bands around it at two points and use them to affix a second dowel that extends several inches past the end of the first, stretching the arm’s length. Use another rubber band to tie a projectile holder (either a spoon or plastic cup) at the end.

Produce tension

tabletop catapult - step 7
Step 7Stan Horaczek

Lift the arm until it touches the lower horizontal dowel from Step 4. Wrap one rubber band from one end of the horizontal dowel to the other so it holds the arm in place. This will produce the tension you need to propel your missiles.

Start shooting

tabletop catapult - step 8
Step 8Stan Horaczek

When you’re ready to shoot, put a ping-pong ball in your projectile holder, brace the base, pull back the arm, and release to fire.

Create your own design

tabletop catapult with catapult supplies
The final stepStan Horaczek

Of course, these guidelines are just a jumping-off point. If you find a way to make your ping-pong projectile fly higher, faster, and more accurately, then go ahead and modify our design. Try different projectile holders, adjust the location of the horizontal bar and the length of the throwing arm, test various spring strengths, and experiment with bracing different parts of the base.