Introduction: Trebuchet

About: I love K'nex, Mindstorms, Arduino, and I broke my leg at the age of 12 while tampering with the go-cart (that was about 5 years ago). That's it! =)

THIS is my first instructable, which also happens to be in a contest (the latter is more important). SO if you think it's a winner Vote for it, but it would mean more if you built it, or/and commented some constructive criticism, then voted for it.

I built this trebuchet a while ago, but since have modified it a lot. It has grown wider, stronger, more consistent, safer, ect.. The build started out as a ferris wheel, but didn't turn out, so I decided to use the good frame for this. It had a phase when it was all K'nex, with no string or rocks, and shot ten feet max (that's the last pic). Before that it had rocks for weight, and some K'nex at the end of a string as a releaser. It shot about 16 ft., but was hard to load and wasn't very consistent. The most recent version has a basket so you can use whatever you want for weight, and uses the traditional string and cloth sling (those ancients got it right the first time). The range is about 25 feet. It has wheels set permanent in lock position, helping limit the jumping that occurs when all that weight is swinging (it doesn't drive). It also has a safer release wheel, that when you turn, it releases the shot. For those who want to be ten feet away when it shoots, or just like the idea of pulling a string to shoot, you can tie a string to the wheel. (The specifics of that will be specified later)

On to the pieces list:


  • Black: 75
  • White: 95
  • Blue: 42
  • Yellow: 27
  • Red: 50
  • Grey: 39


  • Dark grey: 41
  • Orange: 31
  • Light grey: 6
  • Red: 32
  • Green: 39
  • Yellow: 79
  • White: 8


  • Standard 2 in. wheels: 4
  • Blue spacers: 32
  • Grey spacers: 36
  • Black clips: 11
  • Tan/brown clips: 9
  • Metallic-blue clips: 8
  • Yarn or string: about 22 in. (56 cm.)
  • Weight, like two K'nex motors, a bunch of rocks, or several pounds of styrofoam.

Total number of pieces: 668

I once told someone: This build is very old, I've had it for about half a year. Since then it's had 664 new pieces.

Step 1: The Bucket

Follow the notes in the pictures. This is the bucket that holds the weight. The flexi rods are the things that keep it all together when all that weight is in free fall mode. The double-plated floor is for the same reason. You could build this basket for use on whatever other rough-going machine you have.

Step 2: The Base (A)

Follow the notes. This is the central part of the base of your catapult. I had to split the base into two steps to avoid having 60 photos in one step.

Step 3: The Base (B)

Follow the notes. These are the sides of your base.

Step 4: The Frame

The frame holds the axle in place.

Step 5: The Arms & Axle

Holds the bucket and string where they should be. I wonder how well a trebuchet would work without this step?

Step 6: Putting Everything Together!

Step 7: How to Shoot

How to shoot the thing.

K'NEX Contest

Participated in the
K'NEX Contest