Bored at work? Build your own 3" trebuchet out of paperclips and throw balls of blu-tac up to an amazing 4 feet. WOW!!
Please excuse the number of steps. It is really easy and can be made within an hour and from bits lying around the office, hence very cheaply.
Step 1: The tools and materials list
You will need:
1 pair of pliers (needle nose would be best, where available)
1 pair of scissors (yay for scissors)
Corrugated card (approx 6"X6")
Ballast (I used a bunch of batteries from our recycling box)
Step 2: Straightening the paperclips
Use the pliers to make the paperclips as straight as possible.
Step 3: Now shape them
At the very end of four of the paperclips, make an eyelet big enough to insert an ex paperclip through (but not much bigger).
At the other end, make a dog leg. Try to make it on the same plane/axis as the eyelet.
EDIT: Ignore the dogleg. Instead bend approximately 1/2" of the non-eyeleted end at right angles (90 degrees) to the eyelet. All will become clear very soon.
Step 4: The axle
Next, shape the axle. Make it so that the distance between the hooked ends is about 2". It should be wider than your intended ballast. The V shape (U shape in this case. Needlenose pliers are best for this sort of thing) must be central on the axle.
Step 5: The arm
Make an loop in another paperclip about 1/2" from the end. At the same end make another eyelet.
Make a small hook at the other end.
Step 6: The trigger
A little hard to describe. Just look at the picture. The bump on the left is to pull. The loop on the right is there to catch the little hook on the arm.
EDIT: See the adjustment I made to the firing mechanism in the final step. It works so much better.
Step 7: The components
Here's what you should have so far.
Step 8: Assembling the parts
Take the axle and insert it through the loop in the arm (not the eyelet) so that it sits in the V. I wrapped Cellotape around the axle either side of the V just to give it some thickness (so it doesn't slide all over the place).