Gather your materials: All the materials I used are not necessary to create the catapult, many being extra accessories or editions.
DC Motors: Arrange the motors so they are in line with one another with two on one side and two on the other, with the bars attached with the motor mates facing one another. The more in line they are the better.
Attach Wire: Attach the wires to the DC Motors, you will need at least two sets that will then attach to the branch which will be connected to the battery
Figure out form of control: For my catapult I used the button attached to the slide dimmer to control the rate at which the catapult was pulled, but other forms, such as Sound Sensor, can be used for a fancier form control.
Buckle it down!: Make sure that your Little Bits will not move because instead of the DC motor pulling the catapult in, the catapult will pull the Little Bits in! I used a mounting board drilled into a wooden board in order to secure my Little Bits. I also used the 01 LED attached to the ends of my DC Motors in order to make sure they were fully connected to the mounting boards.
Create Your Weapon: I used a fair amount of duck tape and to make sure my catapult was secure, but other projects could use more rubber bands and such to make a secure and effective catapult.
Make the crank: I taped the motor mates together to make sure they would move at approximately the same rate and then attacked a string to both which eventually came together to form a loop around a paper clip that was wrapped around my catapult.
Play!: There are many different ways to succeed in making an effective catapult (or any contraption), many you may not get right away. Play around with is until you find the design that is just right for you. A feature I thought necessary was an automatic release. Putting the looped string over the paperclip allowed the catapult to release automatically when it got to a certain angle. I also used four DC Motors instead of just 1,2, or 3 for the extra pull I needed to get to my desired angle.
Hope you enjoyed my design, and of course comment if you can think of any improvements, edits, or advances to make my catapult that much better! Thanks!