Homemade Reverse Crossbow

grabcad

This is a double cam reverse crossbow that I designed for a projectile motion project in my senior high school honors physics class. The goal was to design and build a device that could launch a tennis ball as far as possible. Energy is stored by using fiberglass rods inside the PVC arms.This design uses three ropes. For one rope the ends are attached to the top cams and are wound around them so the center of the rope where a pouch sits is in between the two cams.The second rope attaches to one of the bottom cams and is tied under tension to the opposite arm.The third rope is attached in a similar fashion.By pulling on the top rope, the bottom ropes will wrap around the bottom cams and pull the arms together under tension.