Pom-Pom Catapult

Yesterday I shared several pre-school / early elementary game ideas featuring the humble pom-pom.  One of them called for a homemade catapult.  I linked to plans for this engineering wonder at "Little Bit Funky."
Of course, I didn't follow her directions precisely - what kind of a DIY'er does that?! I thought I'd share today some of the modifications I made.
(Click to enlarge)
Why I changed things up
Several of my substitutions were based purely on the materials availability. I have wipes containers in excess since I get one with every Costco-sized box of wipes, but no shoe boxes of the right dimensions. Making a virtue of necessity, though, I decided that the plastic box gave the toy a bit of permanence, not to mention a compact means of storage since the pencil "fulcrum" can be easily slid out of the holes and folded inside.
Others were based on the fact that I don't like glue.  I realized as I was thinking through past craft projects that this is quite true. Not only is it messy and slow to set, but it has failed me too many times and I simply don't trust it.  Especially in a project like this with a lot of moving parts and relatively high pressure, I didn't want to rely on it to attach a bottle cap to a pencil, or secure two pencils at a right angle, or even attach a rubber band to the end of the spoon.  So I went out of my way to avoid it.

Materials

  • Plastic diaper wipes container, such as this Huggies one.
  • 1 Pencil
  • 1 Baby Spoon, fairly heavy.  (A disposable spoon will probably break after a few throws.)  
  • 4 rubber bands
  • 1 paper clip, the heavier the better
  • 1 bag clip (such as this one from Ikea) or a second paper clip


Tools

  • Craft Knife
  • Drill (optional, but highly recommended.) 


Procedure (in brief - definitely take a look at the Little Bit Funky tutorial for more detail)

  • Remove the lid from the wipes container.  This can be done without breaking it if you want to store the catapult inside the container later. 
  • With a permanent marker, mark a dot about 2-3 inches from the end and about 1 of an inch down on both of the long sides of the box.  Try to get the dots even with one other - the pencil should travel straight across the box. 
  • Using a craft knife, carefully cut two holes about the diameter of a pencil where your dots are marked.  These holes do Not have to be perfect.  However, they do need to be large enough to let the pencil rotate easily: extra friction here is not helpful. 
  • In the center of the short side of the box opposite the holes you just cut, cut another small hole about 1/2 inch down.  (See photo.)  This hole only needs to be big enough to allow a rubber band to pass through.  
  • If you have a drill available, use it to place a very small hole near the end of the handle of your baby spoon.  (See photo.)This is where a paperclip will attach to your rubber band. 
  • If you do not have a drill, keep reading. 
  • Using two rubber bands, connect the pencil and the baby spoon tightly at right angles. Leave at least 2 inches of spoon handle below, but make the "throwing arm" as long as possible. 
  • Join the other two rubber bands end to end.  Thread one end through the hole in the short end of the box and secure it with the plastic bag clip or a paper clip. (Using a large plastic clip makes it easier to adjust the tension of the catapult later by looping the band around a few times.)  
  • Unbend a paperclip into an "S" shape and connect one end to the rubber bands. 
  • If you've drilled a hole in your spoon, slide the other end of your paperclip through it and bend to create a loop.  (This will try its best to unbend while the catapult is "loaded.")  
  • If you have not drilled a hole, loop use another rubber band, twine, wire, or etc. around the end of the handle and secure with a drop of strong glue.  Then attach the other end of the paperclip here. Just keep in mind this is where much of the force in the device is transmitted, and is therefore most likely to slide off or otherwise break.  As an absolute last resort, attach the paperclip on the bottom side of knot of rubber bands attaching the spoon to the pencil.  This was my initial design, and it was really hard to keep it working.    
  • Finally, thread the ends of your pencil through the holes in the box, making sure that the spoon bowl faces down.  
  • Your catapult is ready to shoot!  Grasp the bowl of the spoon and pull it back until it's parallel to the bottom of the box, holding it with your thumb.  Place a pom-pom (or marshmallow, or pine cone if you're playing outside!) in the spoon, and release.  Not much distance?  Go back and adjust the tension by reducing or increasing the length of the rubber bands to get the most power possible without pulling everything apart. 
  • Uh... remember, you made this for the kids.  You'll have to give them a turn eventually!  

Comments

gingmaganda said…
thanks for this!

my son and i enjoyed constructing this for his science class :)

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