[Sophia2605]

Our robot is one of the only ones I've seen that uses belts to shoot the ball. The little flipper arms at the bottom move in and out like little arms to bring the ball closer, and the two sides with rollers and belts are tensioned with surgical tubing. We also have a winch-type system on the bottom of the cradle that the ball sits in and the winch pulls the arms tighter or lets them go looser. We 3D printed about 100 rollers in total, including extras.

http://imgur.com/czqIJg6