How to Build a Catapult--Some Good Tips

When you are learning how to build a catapult, it would be well to keep the following tips in mind:

1. Start small. Big catapults need big structural parts to handle
   the counterweights and the spring tensions. The big parts are hard to
   deal with.
   
2. Big catapults require STRONG structural members,
   and typically, softwoods like pine are not good catapult building
   materials for any catapult sized to hurl projectiles larger than a
   tennis ball. I feel it is best to use steel or hardwood for those
   bigger chuckers.
3. For gravity machines (or trebuchets)
   make the pivot on which the counterweight swings as large in diameter
   as possible. I've seen thick steel rod bend and warp and become
   worthless on a single hurl. Make your pivot rod big, big, big.
   
4. Catapults
   can be dangerous. I've seen people get knocked on the head by swinging
   counterweight. Ouch! Tension and torsion springs are dangerous as well.
   They pack a lot of energy and can be dangerous.
   
5. For larger models, human powered catapults are a good place to start. They are easier to build and a lot of fun to operate.

This list was taken from the Notes from the Technology Underground blog.

Of course, building a very small catapult wouldn't pose too great a danger of injury, but it is a good idea to keep these tips in mind when making medium to large sized models.

Click here to see a catalog of catapult kits.